Humanlike robots as platforms for Electroactive Polymers (EAP)
Author(s):
Yoseph Bar-Cohen
Show Abstract
Human-like robots, which have been a science fiction for many years, are increasingly becoming an engineering reality
thanks to many technology advances in recent years. Humans have always sought to imitate the human appearance,
functions and intelligence and as the capability progresses they may become our household appliance or even
companion. Biomimetic technologies are increasingly becoming common tools to support the development of such
robots. As artificial muscles, electroactive polymers (EAP) are offering important actuation capability for making such
machines lifelike. The current limitations of EAP are hampering the possibilities that can be adapted in such robots but
progress is continually being made. As opposed to other human made machines and devices, this technology raises
various questions and concerns that need to be addressed. These include the need to prevent accidents, deliberate harm,
or their use in crimes. In this paper the state-of-the-art and the challenges will be reviewed.
Designing components using smartMOVE electroactive polymer technology
Author(s):
Marcus Rosenthal;
Chris Weaber;
Ilya Polyakov;
Al Zarrabi;
Peter Gise
Show Abstract
Designing components using SmartMOVETM electroactive polymer technology requires an understanding of the basic
operation principles and the necessary design tools for integration into actuator, sensor and energy generation
applications. Artificial Muscle, Inc. is collaborating with OEMs to develop customized solutions for their applications
using smartMOVE. SmartMOVE is an advanced and elegant way to obtain almost any kind of movement using
dielectric elastomer electroactive polymers. Integration of this technology offers the unique capability to create highly
precise and customized motion for devices and systems that require actuation. Applications of SmartMOVE include
linear actuators for medical, consumer and industrial applications, such as pumps, valves, optical or haptic devices. This
paper will present design guidelines for selecting a smartMOVE actuator design to match the stroke, force, power, size,
speed, environmental and reliability requirements for a range of applications. Power supply and controller design and
selection will also be introduced. An overview of some of the most versatile configuration options will be presented
with performance comparisons. A case example will include the selection, optimization, and performance overview of a
smartMOVE actuator for the cell phone camera auto-focus and proportional valve applications.
Elastomeric contractile actuators for hand rehabilitation splints
Author(s):
Federico Carpi;
Andrea Mannini;
Danilo De Rossi
Show Abstract
The significant electromechanical performances typically shown by dielectric elastomer actuators make this polymer
technology particularly attractive for possible active orthoses for rehabilitation. Folded contractile actuators made of
dielectric elastomers were recently described as a simple configuration, suitable to easily implement linear contractile
devices. This paper describes an application of folded actuators for so-called hand splints: they consist of orthotic
systems for hand rehabilitation. The dynamic versions of the state-of-the-art splints typically include elastic bands, which
exert a passive elastic resistance to voluntary elongations of one or more fingers. In order to provide such splints with the
possibility of electrically modulating the compliance of the resistive elements, the substitution of the passive elastic
bands with the contractile actuators is here described. The electrical activation of the actuators is used to vary the
compliance of the system; this enables modulations of the force that acts as an antagonist to voluntary finger movements,
according to programmable rehabilitation exercises. The paper reports results obtained from the first prototype
implementations of such a type of system.
Enhancement of the electromechanical transduction properties of a silicone elastomer by blending with a conjugated polymer
Author(s):
F. Carpi;
G. Gallone;
F. Galantini;
D. De Rossi
Show Abstract
The need for high driving electric fields currently limits the diffusion of dielectric elastomer actuation in some areas of
potential application, especially in the case of biomedical disciplines. A reduction of the driving fields may be achieved
with new elastomers offering intrinsically superior electromechanical properties. So far, most of attempts in this
direction have been focused on composites between elastomer matrixes and high-permittivity ceramic fillers, yielding to
limited results. In this work, the electromechanical response of a silicone rubber (poly-dimethyl-siloxane) was improved
by blending, rather than loading, the elastomer with a highly polarizable conjugated polymer (undoped poly-hexyl-thiophene).
Very low percentages (1-6 wt%) of poly-hexyl-thiophene yielded both an increase of the dielectric
permittivity and an unexpected reduction of the tensile elastic modulus. Both these factors contributed to a remarkable
increase of the electromechanical response, which reached a maximum at 1 wt% content of conjugated polymer. This
approach may lead to the development of new types of improved dielectric elastomers for actuation.
Carbon nanotube yarns: sensors, actuators, and current carriers
Author(s):
Tissaphern Mirfakhrai;
Mikhail Kozlov;
Shaoli Fang;
Mei Zhang;
Ray H. Baughman;
John D. Madden
Show Abstract
Carbon nanotubes (CNTs) have attracted extensive attention in the past few years because of their appealing mechanical
and electronic properties. Yarns made through spinning multi-walled carbon nanotubes (MWNTs) have been reported.
Here we report the application of these yarns as electrochemical actuators, force sensors and microwires. When extra
charge is stored in the yarns, change in length. This actuation is thought to be because of electrostatic as well as quantum
chemical effects in the nanotube backbones. We report strains up to 0.7 %. At the same time, the charged yarns can
respond to a change in the applied tension by generating a current or a potential difference that is related to the applied
tension force. As current carriers, the yarns offer a conductivity of ~300 S/cm, which increases linearly with
temperature. We report a current capacity of more than 108 A/m2, which is comparable to those of macroscopic metal
wires. However, these nanotube yarns have a density (0.8 g/cm3) that is an order of magnitude lower than metallic wires.
The MWNT yarns are mechanically strong with tensile strengths reaching 700 MPa. These properties together make
them a candidate material for use in many applications including sensors, actuators and light-weight current carriers.
Characterization and modeling of conjugated polymer sensors
Author(s):
Yang Fang;
Xiaobo Tan;
Andrew Temme;
Gürsel Alici
Show Abstract
In this paper the behavior of conjugated polymers as mechanical sensors is experimentally characterized and modeled. A
trilayer conjugated polymer sensor is considered, where two polypyrrole (PPy) layers sandwich an amorphous polyvinylidene
fluoride (PVDF) layer, with the latter serving as an electrolyte tank. A theory for the sensing mechanism is proposed
by postulating that, through its influence on the pore structure, mechanical deformation correlates directly to the concentration
of ions at the PPy/PVDF interface. This provides a key boundary condition for the partial differential equation (PDE)
governing the ion diffusion and migration dynamics. By ignoring the migration term in the PDE, an analytical model is
obtained in the form of a transfer function that relates the open-circuit sensing voltage to the mechanical input. The model
is validated in experiments using dynamic mechanical stimuli up to 50 Hz.
IPMC paints
Author(s):
Il-Seok Park;
Rashi Tiwari;
Kwang J. Kim
Show Abstract
In this paper we are reporting a newely developed IPMC fabrication method, "IPMC Paint", which can be directly
sprayed onto any complex surface. In order to fabricate the IPMC paint, liquid NafionTM was used for the ionic
conducting polymer instead of the typical film/sheet type NafionTM. The viscosity of liquid NafionTM was adjusted by
adding Polyvinylpyrrolidone (PVP) to perform spray painting. Modified Nafion was sprayed onto the conducting
substrate, PolyfoilTM which acts as base electrode layer. After three times spraying, ionic polymer layer has 45 μm
thickness and 10 μm of surface roughness. Sensing tests show that IPMC paint sensor has more sensitivity (± 0.06 of
producing voltage) than that of the typical IPMC (± 0.005 of producing voltage) when dynamic bending with 10 Hz
frequency and 1.3 cm of displacement is applied to.
Micro deposition method: a novel fabrication method for ionic polymer metallic composites
Author(s):
David Griffiths;
Vishnu Baba Sundaresan;
Barbar Akle;
Pavlos Vlachos;
Don Leo
Show Abstract
A new fabrication system for Ionic Polymer Metallic Composites (IPMC) entitled Micro Deposition Method(MDM) is
introduced. The tolerances in prototyping IPMC's using available fabrication techniques does not meet the tight limits
for fabricating the polymer transducer. The MDM overcomes this limitation by using a microfluidic dispersion head that
can deposit 3 to 10 picoliters of the electrode layer dissolved in a solvent at a high throughput. The MDM in its existing
configuration can be used to fabricate micron scale polymer transducers with features 2 microns and above with high
accuracy and repeatability. A commercially available piezoelectric deposition head from an inkjet printer is modified
and used to disperse the electrode material of controlled thickness as a concept demonstration. The physical properties
of the dispersed fluid are adjusted to meet the requirements of the deposition head to fabricate the prototype. The
dispersion fluid used had a viscosity of 3.47 ±0.06 cP, a surface tension of 23.6 ±.1 mNm-1, and a conducting power
volume load set at 10%.
Ionic polymer-metal composites (IPMCs) with bimetallic Pt-Pd electrode
Author(s):
Sang-Mun Kim;
Kwang J. Kim
Show Abstract
The characteristics of Ionic polymer metal-composites, containing bimetallic Pt-Pd electrodes which had been
prepared by an electroless chemical reduction method on a polymer membrane, were investigated. Bimetallic Pt-Pd electrodes with various compositions (Pt:Pd weight ratios) were compared with those of monometallic Pt and
Pd electrodes that had been prepared under similar conditions. The surface compositions of the Pt and Pd on the
electrodes were compared using an energy dispersive X-ray spectroscopy (EDS). The crystal structures of the
electrodes were investigated by an X-ray diffraction (XRD); surface morphologies were also compared by
scanning electron microscopy (SEM) which depends on the palladium amounts. The optimal composition of the
Pt and Pd affects not only surface morphology, but also the improvement of the actuation and associated
relaxation phenomena of IPMCs.
A new force field for molecular dynamics studies of Li+ and Na+-nafion
Author(s):
Endel Soolo;
Anti Liivat;
Heiki Kasemägi;
Tarmo Tamm;
Daniel Brandell;
Alvo Aabloo
Show Abstract
Nafion is widely known as one of the most popular membrane materials for low temperature fuel cell applications.
However, the particular exchange membrane material properties make it also valuable for other applications. One of the
electroactive polymer (EAP) subclasses, ionic polymer metal composites (IPMC) commonly exploits Nafion as the ion
exchange polymer membrane. The ion conducting properties of Nafion are extremely important for IPMCs. Although,
ion conductivity depends strongly on the structural properties of the polymer matrix, there has been very little insight at
the atomistic level. Molecular dynamics simulations are one of the possibilities to study the ion conduction mechanism
at atomistic level. So far, the simulation results have been rather contradictory and very much dependent from the force
fields and polymer matrix setup used. In the present work, new force field parameters for Li+ and Na+ - nafion based on
DFT calculations are presented. The developed potentials and the force field were tested by molecular dynamics
simulations. It can be concluded that Li+ and Na+ ions are coordinated to different Nafion side-chain terminal group
(SO3-) oxygens and to very few water molecules. One cation is coordinated to three different side-chains. Oxygens of
SO3 groups and cations form complicated multi-header systems. In the equilibrium state, no cations dissociated from
side chains were found.
Application of feedforward dynamics compensation in ionic-polymer metal composite actuators
Author(s):
Yingfeng Shan;
Kam K. Leang
Show Abstract
Ionic-polymer metal composites are innovative materials that offer combined sensing and actuating ability in
lightweight and flexible package. As such, they have been exploited in robotics and a wide variety of biomedical
devices, for example, as fins for propelling aquatic robots and as an injector for drug delivery. One of the
main challenges of IPMC-based actuators is precision control of their movements, especially at high operating
speed (frequency) because of dynamic effects. As the frequency increases, the dynamics cause vibration which
leads to significant tracking error. A model-based feedforward controller is applied to control the position of a
custom-made Nafion-based IPMC actuator. The feedforward controller was designed to account for the linear
dynamics, and the feedforward input was computed by considering the magnitude of the input signal and the
tracking precision. To account for unmodeled effects not captured by the linear model, a feedback controller
was integrated with the feedforward controller. The feedback controller provides robustness. Experimental
results show a significant improvement in the tracking performance using feedforward control. In particular, the
feedforward controller resulted in over 75% improvement in the tracking error compared to the case without
dynamic compensation. Then by adding a proportional-integral feedback controller, the tracking error was less
than 10% at 18 Hz scan frequency.
A distributed model of IPMC
Author(s):
A. Punning;
U. Johanson;
M. Anton;
M. Kruusmaa;
A. Aabloo
Show Abstract
This paper presents a distributed model of an IPMC (Ionomeric Polymer-Metal Composite). Unlike other
electromechanical models of an IPMC, the distributed nature of our model permits modelling the non-uniform bending
of the material. Instead of modeling solely the tip deflection of the material, we model the changing curvature. Our
model of the IPMC describes the actuator or sensor as a distributed one-dimensional RC transmission line. The behavior
of the IPMC at its each particular position in time-domain is described by a system of Partial Differential Equations.
(PDE). The parameters of the PDE-s have a clear physical interpretation: the conductivity of the electrodes, the
pseudocapacitance of the arising double-layer at the boundary of the electrodes, the electric current caused by electrode
reactions etc. The electromechanical coupling between the electrical parameters and the bending motion is implemented
by means of distribution of electric current along the material in a time domain. The distributed nature of the model
permits predicting the non-uniform bending of the IPMC actuators in time domain or to reconcile the output of an IPMC-based
position sensor with its shape. Taking into account several nonlinear parameters, the model is consistent with the
experimental results even when the inflexion of the actuator or sensor is large or the water electrolysis appears.
Extensional ionomeric polymer conductor composite actuators with ionic liquids
Author(s):
Sheng Liu;
Minren Lin;
Qiming Zhang
Show Abstract
Although the Ionic Polymer-Metal Composite (IPMC) actuators developed up to date are in the form of bending
actuators, development of extensional actuators based on IMPC is highly desirable from practical applications and
fundamental understanding points of view. This talk presents the design, fabrication and characterization of a recent
work on an extensional Ionic Polymer-Metal Composite actuator. The extensional actuator consists of the Nafion
ionomer as the matrix and the sub-micron size RuO2 particles as the conductive filler for the conductor/ionomr
composites. In this investigation, several ionic liquids (IL) were investigated. For a Nafion/RuO2 composite with 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) IL, it was found that as the ions are driven into the
ionomer/RuO2 composite (the composite under negative voltage), an extensional strain of 0.9% was observed; while as
the ions were expelled from the ionomer/RuO2 composite (under positive voltage), a contraction of -1.2% was observed.
The results indicate that multiple ions are participating in charge transport and actuation process. In this paper, we also
discuss several design considerations for future extensional actuators with fast response, much improved strain and stress
level. Especially an actuator based on multilayer configuration can significantly increase the electric field level in the
actuator and consequently significantly improve the actuator speed. The extensional actuator investigated here provides a
unique platform to investigate various phenomena related to ion transport and their interaction with the
ionomer/conductor matrix to realize high electromechanical performance.
A scalable dynamic model for ionic polymer-metal composite actuators
Author(s):
Zheng Chen;
Xiaobo Tan
Show Abstract
Ionic polymer-metal composites (IPMCs) have built-in sensing and actuation capabilities which make them attractive in
many biomedical and biological applications. In this paper a physics-based but control-oriented dynamic model is proposed
for IPMC actuators. The modeling work starts from the governing partial differential equation (PDE) that describes the
charge redistribution dynamics under external electrical field, electrostatic interactions, ionic diffusion, and ionic migration
along the thickness direction. It is further extended by incorporating the effect of distributed surface resistance. The
electrical impedance model is obtained by deriving the exact solution to the governing PDE in the Laplace domain. By
assuming a linear electromechanical coupling, an actuation model which relates bending displacement to voltage input
is derived. The model is represented as an infinite-dimensional transfer function, which is amenable to model reduction
and real-time control design while capturing fundamental physics. It thus bridges the traditional gap between the physics-based
perspective and the system-theoretic perspective on modeling of IPMC materials. The model is expressed in terms
of fundamental material parameters and dimensions of the IPMC, and is therefore geometrically scalable. The latter has
been further confirmed in experiments.
A correlation between extensional displacement and architecture of ionic polymer transducers
Author(s):
Barbar J. Akle;
Andrew Duncan;
Donald J. Leo
Show Abstract
Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain
and a moderate stress at low applied voltages (<5V). Bending actuators have limited engineering applications due to the
low forcing capabilities and the need for complicated external devices to convert the bending action into rotating or
linear motion desired in most devices. Recently Akle and Leo reported extensional actuation in ionic polymer
transducers. In this study, extensional IPTs are characterized as a function of transducer architecture. In this study 2
actuators are built and there extensional displacement response is characterized. The transducers have similar electrodes
while the middle membrane in the first is a Nafion / ionic liquid and an aluminum oxide - ionic liquid in the second. The
first transducer is characterized for constant current input, voltage step input, and sweep voltage input. The model
prediction is in agreement in both shape and magnitude for the constant current experiment. The values of α and β used
are within the range of values reported in Akle and Leo. Both experiments and model demonstrate that there is a
preferred direction of applying the potential so that the transducer will exhibit large deformations. In step response the
model well predicted the negative potential and the early part of the step in the positive potential and failed to predict the
displacement after approximately 180s has elapsed. The model well predicted the sweep response, and the observed 1st
harmonic in the displacement further confirmed the existence of a quadratic in the charge response. Finally the
aluminum oxide based transducer is characterized for a step response and compared to the Nafion based transducer. The
second actuator demonstrated electromechanical extensional response faster than that in the Nafion based transducer.
The Aluminum oxide based transducer is expected to provide larger forces and hence larger energy density.
Frequency response of anisotropic ionic polymer metal composites (IPMC) transducers
Author(s):
Boyko L. Stoimenov;
Jonathan Rossiter;
Toshiharu Mukai;
Kinji Asaka
Show Abstract
The emergence of soft polymer actuators brings a great deal of excitement in the robotics and biomedical engineering
community because of the possibilities to easily mimic the motion of living organisms and ability to manipulate living
tissue and cells without damaging it. Some of the applications of soft polymer actuators, such as micropumps, require
them to operate at high frequency and large displacement, which usually achieved near resonance. It would be beneficial
for the designer, if he could easily tailor the frequency response and the resonance frequency to suit the operating
conditions. We propose such an effective method of modification of the frequency response of ionic polymer metal
composite (IPMC) actuators by introducing an anisotropic roughness on their surface.
The effect of IPMC parameters in electromechanical coefficient based on equivalent beam theory
Author(s):
Halime Didem Çilingir;
Yusuf Menceloglu;
Melih Papila
Show Abstract
"Effective" electromechanical coupling coefficient for IPMC by equivalent bimorph beam model is studied. The
collective effect of the membrane thickness and operating voltage is demonstrated by using a design of experiment of
three and four levels of the two factors, respectively. Experiments and finite element analyses using MSC.NASTRAN
are used to evaluate the tip displacement and the coupling coefficient for which approximations as function of the
thickness and voltage are constructed. Initial curvature of the strips before electrical excitation is also shown to be a
factor in "effective" coupling coefficient. A correction factor approach is proposed to include the effect of the preimposed
curvature.
Accomplishments and future trends in the field of electroactive polymers
Author(s):
Aleksandra M. Vinogradov
Show Abstract
The paper provides a summary review of the accomplishments and challenges in the field of electroactive polymers
(EAP). It consists of three parts. The first part outlines the main classes of EAP, their properties and applications. Efforts
to enhance the functional performance of EAP are discussed. The second part summarizes the development and use of
electroactive polymer based composites. Challenges, opportunities and future research directions in the field are
discussed in the third part. The issues of particular interest concern accurate material characterization of electroactive
polymers, their time dependent behavior, constitutive modeling, and cyclic loading effects that determine the long-term
functionality, integrity and durability of electroactive polymers. Research efforts in these focus areas are necessary to
ensure effective integration of EAP in multifunctional material systems.
Polyaniline nanofibers as a novel electrode material for fault-tolerant dielectric elastomer actuators
Author(s):
Tuling Lam;
Henry Tran;
Wei Yuan;
Zhibin Yu;
SoonMok Ha;
Richard Kaner;
Qibing Pei
Show Abstract
Polyaniline nanofibers (Pani nanofibers) have exhibited high performance and fault tolerant properties for dielectric
elastomer actuator devices. Electrodes comprised of uniformly sprayed Pani nanofibers in thicknesses 0.7 μm, 1.1 μm,
1.3 μm, and 1.5 μm have shown the following high strains: 65% in area for 0.7 μm electrodes at 3 kV, 97% in area for
1.1 μm thick electrodes at 3.5 kV, 84% in area for 1.1 μm thick electrodes at 3 kV, and 114.% in area for 1.5 μm thick
electrodes at 3.5 kV. Optimal performance was achieved with actuators with electrodes 1.1 μm thick, which
demonstrated self-healing properties at 3 kV. These actuators displayed a preserved strain of 91% after the clearing and
sustained a 93% area strain for 10 minutes at 3 kV. Devices with 1.1 μm thick electrodes were also able to perform 700
actuation cycles over a total duration of 75 minutes with a pulsed half-sinusoidal voltage of 3 kV. Mechanical
compliance tests performed on a film with a 1.1 μm thick Pani nanofiber electrode reveals that the electrode material
does not significantly alter the mechanical properties of the film. The estimated Young's modulus was found to be 32
MPa for the film with the electrode and 31 MPa for the film itself.
Self-clearable carbon nanotube electrodes for improved performance of dielectric elastomer actuators
Author(s):
Wei Yuan;
Liangbing Hu;
Soonmok Ha;
Tuling Lam;
George Grüner;
Qibing Pei
Show Abstract
Dielectric elastomer actuators which consist of an electrode/dielectric elastomer/electrode sandwich structure show
greater than 100% electromechanical strain performance when high electrical field is applied. The strain in the dielectric
elastomer film occurs due to attraction of opposite charges across the dielectric film and repulsion of similar charges on
each compliant electrode. Structural defects present in these elastomers such as gel particles, uneven thickness, and stress
concentration may cause dielectric breakdown, leading to premature failure during continuous or repeated actuations.
Dielectric breakdown consequently reduces production yield and device lifetime. Carbon nanotubes (CNTs) have been
introduced as compliant electrodes for dielectric elastomers. Higher than 100% electromechanical strain was obtained
with ultrathin CNT electrodes due to the high aspect ratio and the high electrical conductivity of the nanotubes. These
ultrathin CNT electrodes also exhibit fault-tolerance in dielectric elastomers through the local degradation of CNTs
during dielectric breakdown. The degraded areas electrically isolate the defects, while keeping the rest of the elastomer
active. The "self-clearing" electrodes significantly increase the lifetime of the dielectric elastomers, making the dielectric
elasomer actuator much more reliable.
Cellular ferroelectrets for electroactive polymer hybrid systems: soft matter integrated devices with advanced functionality
Author(s):
Reinhard Schwödiauer;
Ingrid Graz;
Martin Kaltenbrunner;
Christoph Keplinger;
Petr Bartu;
Gerda Buchberger;
Christoph Ortwein;
Siegfried Bauer
Show Abstract
Thin polymer foams with a closed cell void-structure can be internally charged by silent or partial discharges
within the voids. The resulting material, which carries positive and negative charges on the internal void surfaces
is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic
materials. The soft foams are strongly piezoelectric in the 3-direction, but show negligible piezoelectric response
in the transverse direction. This, together with a very low pyroelectric coefficient, make ferroelectrets highly
suitable for flexible electroactive transducer element which can be integrated in thin bendable organic electronic
devices. Here we describe some fundamental characteristics of cellular ferroelectrets and present a number of
promising examples for a possible combination with various functional polymer systems. Our examples focus on
flexible ferroelectret field-effect transistor systems for large-area sensor skins and microphones, flexible large-array
position detectors (touchpad), and stretchable large-array pressure sensors.
A dielectric electroactive polymer generator-actuator model: modeling, identification, and dynamic simulation
Author(s):
Curtis M. Ihlefeld;
Zhihua Qu
Show Abstract
Dielectric electroactive polymer membranes have been shown to have capabilities both as actuators and generators.
Recent models of actuators have shown input to output dynamics that link the electrical energy input to
the acceleration of a mass. Models such as these are useful for implementing closed loop control systems and
will be necessary in the future for the construction of robust and fault tolerant controls. On the other hand,
explanations of the generator behavior of dielectric EAP devices tend to ignore full dynamics. In this paper it is
demonstrated that an EAP actuator model with full electrical-mechanical dynamics can be used as a generator
model with the generator input force equivalent to the actuator disturbance force. Since the generator and
actuator models are equivalent, it can be shown how disturbance inputs can cause energy surges back toward the
electrical input. Simulations and experimental results are provided of a device model that describes generation
and actuation.
Feasibility studies for a bionic propulsion system of a blimp based on dielectric elastomers
Author(s):
Silvain Michel;
Alex Bormann;
Christa Jordi;
Erick Fink
Show Abstract
After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically
inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the
envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in
the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state
horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which
consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a
slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary
active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed.
Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in
preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.
An experimentally validated model of a dielectric elastomer bending actuator
Author(s):
Benjamin O'Brien;
Emilio Calius;
Shane Xie;
Iain Anderson
Show Abstract
This paper presents an experimentally validated, nonlinear finite element model capable of predicting the blocked force
produced by Dielectric Elastomer Minimum Energy Structure (DEMES) bending actuators. DEMES consist of pre-stretched
dielectric elastomer (DE) films bonded to thin frames, the complex collapse of which can produce useful
bending actuation. Key advantages of DEMES include the ability to be fabricated in-plane, and the elimination of bulky
pre-stretch supports which are often found in other DE devices.
Triangular DEMES with 3 different pre-stretch ratios were fabricated. Six DEMES at each stretch ratio combination
were built to quantify experimental scatter which was significant due to the highly sensitive nature of the erect DEMES
equilibrium point. The best actuators produced approximately 10mN blocked force at 2500V.
We integrate an Arruda-Boyce model incorporating viscoelastic effects with the Proney series to describe the stress-strain
response of the elastomer, and a Neo-Hookean model to describe the frame. Maxwell pressure was simulated using
a constant thickness approximation and an isotropic membrane permittivity was calculated for the stress state of the
DEMES membrane.
Experimental data was compared with the model and gave reasonable correlation. The model tended to underestimate the
blocked force due to a constant thickness assumption during the application of Maxwell stress. The spread due to
dielectric constant variance is also presented and compared with the spread of experimental scatter in the results.
A dielectric elastomer actuator with self-sensing capability
Author(s):
Nguyen Huu Chuc;
Doan Vu Thuy;
Jonggil Park;
Duksang Kim;
Jachoon Koo;
Youngkwan Lee;
Jae-Do Nam;
Hyouk Ryeol Choi
Show Abstract
In this paper we present a dielectric elastomer actuator, which has the ability to sense the force acting on it
without any additional sensing device. Basic physical behaviors of the dielectric elastomer are experimentally
investigated and it is noted that the impedance of the dielectric elastomer varies depending on external forces
acting on it. Based on that concept, we propose the principle of a self-sensing actuator according to experimental
result. In addition, a multi-stacked actuator with self-sensing capability is realized to validate its feasibility.
Ion-implanted compliant and patternable electrodes for miniaturized dielectric elastomer actuators
Author(s):
Samuel Rosset;
Muhamed Niklaus;
Venjamin Stojanov;
Arnaud Felber;
Philippe Dubois;
Herbert R. Shea
Show Abstract
This article presents metal ion implantation as an alternative technique to fabricate compliant electrodes for
small-size dielectric elastomer actuators. When reducing the size of these actuators to below 1 cm, the ability
to pattern the electrodes is added to the need for compliance. Metal ion implantation on Polydimethylsiloxane
(PDMS) layers allows the creation of conductive and compliant electrodes, which can be easily defined by
photolithography or with a shadow mask. Mechanical testing show that implantation has a limited impact on
the PDMS' properties, with a Young's modulus increase of 50%-200% depending on the dose. Uniaxial stretching
tests show that conductivity is conserved for strains up to 50% and present no hysteresis. Dielectric breakdown
tests were conducted for Au and Pd implantations, which exhibited high breakdown fields (> 100V/μm), similar
to non-implanted PDMS layers. Other advantages of ion implanted electrodes include transparency and a
negligible mass. Buckling mode diaphragm actuators were fabricated with ion-implanted electrodes and exhibited
out-of-plane displacements up to 7% of their lateral dimensions.
Study on core free rolled actuator based on soft dielectric EAP
Author(s):
Gabor M. Kovacs;
Soon Mok Ha;
Silvain Michel;
Ron Pelrine;
Qibing Pei
Show Abstract
The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times around a spring core in
order to form a multilayer actuator system with unidirectional actuation. The freestanding rolled configuration enables
the use of the DE film for muscle like linear actuators with a broad application potential. The stress state of the pre-strained
acrylic film in the rolled configuration and the required stiff core can cause several serious problems concerning
lifetime, size and efficiency of the actuator.
In order to obtain an acceptable specific actuator performance and lifetime the pre-stretching stress has to be essentially
reduced or even eliminated. This can be achieved by the interpenetrating polymer network (IPN) process newly
developed at the UCLA. Thereby a trifunctional methacrylate monomers is introduced into the highly pre-strained
acrylic films and subsequently curing the monomers to form an interpenetrating elastomeric network. The as obtained
interpenetrating polymer network (IPN) can effectively support the pre-strain of the acrylic film and consequently
eliminate the need for external pre-strain-supporting structures.
In this study a new rolled actuator design is presented based on the IPN post treated VHB material. Due to the stress free
state of the wrapped film no spring core is necessary. As a result a significantly longer lifetime and better specific
volume efficiency of the actuator has been achieved at lower unidirectional elongation when activated.
Introductorily, the specific problems on conventional rolled actuators are discussed and the aims for core free rolled
actuators are specified. Then some structural design parameters are addressed in order to achieve a slight shape and
reliable working principle. In the main part of the study the manufacturing process of the actuators and some
measurement results and experiences are discussed in detail.
Coupled chemo-electro-mechanical simulation of polyelectrolyte gels as actuators and sensors
Author(s):
Thomas Wallmersperger;
Dirk Ballhause;
Bernd Kröplin;
Margarita Günther;
Zhangman Shi;
Gerald Gerlach
Show Abstract
Polyelectrolyte gels are ductile elastic electroactive materials. They consist of a polymer network with charged
groups and a liquid phase with mobile ions. Changing the chemical or electric conditions in the gel-surrounding
solution leads to a change of the chemo-electro-mechanical state in the gel phase: diffusion and migration of ions
and solvent between the gel and solution phases trigger the swelling or shrinkage of the polymer gel. In case
of chemical stimulation (change of pH or salt concentration), a swelling ratio of up to 100% may be obtained.
Due to this large swelling ratio the gels exhibit excellent actuatoric capabilities. In this paper, a polyelectrolyte
gel placed in a solution bath is investigated. The actuatoric and sensoric capabilities are described by a chemo-electro-mechanical model. The chemical field is represented by a convection-migration-diffusion equation while
the electric field is described by a quasi-static Laplace equation. For the mechanical field a partial differential
equation of first order in time is applied. Inertia effects are neglected due to the relatively slow swelling/shrinkage
process. On the one hand, the coupling between the chemo-electrical and the mechanical field is realised by the
differential osmotic pressure stemming from the concentration differences between gel and solution. On the
other hand, the mechanical deformation influences the concentration of the bound charged groups in the gel.
The three fields are solved simultaneously by applying the Newton Raphson method using finite elements in
space and finite differences in time. The developed model is applicable for both, hydrogel actuators and sensors.
Numerical results of swelling and bending are given for chemically and electrically stimulated polymer gels. In
this paper we show the differences between the chemo-electric and the fully coupled chemo-electro-mechanical
formulation for polymer gels in different solution baths. The inverse (sensor-) effect is demonstrated by the
influence of the mechanical deformation on the gel, which results in a change of the chemical and electrical
unknowns in the gel. The validity of the employed numerical model is shown by a comparison of the obtained
results with experimental measurements.
Redox level-dependent impedance model for conjugated polymer actuators
Author(s):
Yang Fang;
Xiaobo Tan;
Gürsel Alici
Show Abstract
The reduction-oxidation (redox) level of a conjugated polymer has significant impact on its electro-chemo-mechanical
properties, such as conductivity, impedance, and Young's modulus. A redox level-dependent impedance model is developed
in this paper by including the dynamics of ion diffusion, ion migration, and redox reactions. The model, in the form
of a transfer function, is derived through perturbation analysis around a given redox level. Experimental measurements
conducted under different redox conditions correlate well with the model prediction and thus validate the proposed model.
This work, for the first time, incorporates the effect of redox level into the dynamics of conjugated polymers, and facilitates
the future use of nonlinear control methods for the effective control of these materials.
A theory of large deformation in soft active materials
Author(s):
Zhigang Suo;
Xuanhe Zhao;
Wei Hong;
Jinxiong Zhou;
William H Greene
Show Abstract
Soft active materials have many important applications. We develop a theory of large deformation in a family
of soft active materials known as dielectric elastomers. We show that the Maxwell stress is not applicable to deformable
dielectrics in general, and that the effect of electric field on deformation is material specific. Based on available
experimental data, we construct for a class of model materials, which we call ideal dielectric elastomers, a free-energy
function comprising contributions from stretching and polarizing. We show that the free-energy function is typically
non-convex, causing the pull-in instability of dielectric elastomers.
An advanced finite element model of IPMC
Author(s):
D. Pugal;
H. Kasemägi;
M. Kruusmaa;
A. Aabloo
Show Abstract
This paper presents an electro-mechanical Finite Element Model of an ionic polymer-metal composite (IPMC) material. Mobile counter ions inside the polymer are drifted by an applied electric field, causing mass imbalance inside the material. This is the main cause of the bending motion of this kind of materials. All foregoing physical effects have been considered as time dependent and modeled with FEM. Time dependent mechanics is modeled with continuum mechanics equations. The model also considers the fact that there is a surface of platinum on both sides of the polymer backbone. The described basic model has been under developement for a while and has been improved over the time. Simulation comparisons with experimental data have shown good harmony. Our previous paper described most of the basic model. Additionally, the model was coupled with equations, which described self-oscillatory behavior of the IPMC material. It included describing electrochemical processes with additional four differential equations. The Finite Element Method turned out to be very reasonable for coupling together and solving all equations as a single package. We were able to achieve reasonably precise model to describe this complicated phenomenon. Our most recent goal has been improving the basic model. Studies have shown that some electrical parameters of an IPMC, such as surface resistance and voltage drop are dependent on the curvature of the IPMC. Therefore the new model takes surface resistance into account to some extent. It has added an extra level of complexity to the model, because now all simulations are done in three dimensional domain. However, the result is advanced visual and numerical behavior of an IPMC with different surface characteristics.
Modelling electroactive polymer (EAP) actuators: electro-mechanical coupling using finite element software
Author(s):
F. Rosenblatt;
J. F. Morrison;
L. Iannucci
Show Abstract
Controlling turbulence is a major aim for many engineering disciplines. Decades of research, have shown that the large
frictional drag in turbulent flows is attributed to the existence of near-wall coherent structures. Turbulence control is
therefore likely to be achieved by manipulating these coherent structures. The challenge this presents is to find actuators
that are functional at the spatial scales of those coherent structures (10 μm to 0.1 mm) and their temporal scale (100
kHz). Recent advances in MEMS technology have made possible the construction of such actuators. Electroactive
polymers (EAP) provide excellent performance, are lightweight, flexible, and inexpensive. Therefore EAPs, and in
particular dielectric elastomers (DEAs), provide many potential applications as micro-actuators. The modelling and
simulating of EAP actuators are a cost-effective way of providing a better understanding of the material itself in order to
optimise designs. A technique to accurately model DEA materials, taking into account its non-linearities as well as its
large deformations, is being developed in this study.
Overview on energy harvesting and storage systems (EHSS) for future AF vehicles
Author(s):
Minoru Taya;
Chunye Xu;
Morio Nagata
Show Abstract
Energy harvesting and storage systems (EHSS) for future AF vehicles are reviewed with emphasis on thermoelectics,
organic materials, specifically, dye-sensitized solar cells and polymer batteries. The organic solar cells include solid-state
organic solar cells and dye-sensitized solar cells (DSSC). The advantages of using such organic EHSS for AF vehicles
are their specific performance, its scalability to larger skin area and low-temperature processing route, thus cost-effective
however, there are several technical challenges preventing us to develop the organic EHSS in a speedy way.
Electrolyte for laminated polymer lithium rechargeable battery
Author(s):
Chunye Xu;
Chao Ma;
Minoru Taya
Show Abstract
Proposed thin film battery is comprised of a polymer-lithium ion cell material with barrier-layer packaging and
mechanical reinforcing layers. A semi-solid/ solid electrolyte and a mesoporous polymer separator are sandwiched in
between of anode and cathode. A composite film with a carbon nanotube (CNT) network serves as the anode and a
mesoporous transitional metal oxide LixCoO2 as the cathode, where porous metal sheets serve as the current collector.
The CNT network fabrics have high in-plane tensile strength. LiCoO2 is used as the cathode, because the Co atoms do
not migrate to Li layers, so that cathode does not generate flammable gases during charging that create safety problems.
Merit of this study is using the porous metal sheet, which is flexible, lightweight, low electric resistance, high strength
and strong stability in alkaline solution. This paper presented development of electrolyte for laminated polymer lithium
rechargeable battery. Two-type electrolytes, semi-solid and solid, were attempted; high ionic conductivity of Li ion
electrolytes was achieved.
Innovative power generators for energy harvesting using electroactive polymer artificial muscles
Author(s):
Seiki Chiba;
Mikio Waki;
Roy Kornbluh;
Ron Pelrine
Show Abstract
The type of electroactive polymer known as dielectric elastomers has shown considerable promise for a variety of
actuator applications and may be well suited for harvesting energy from environmental sources such as ocean waves or
water currents. The high energy density and conversion efficiency of dielectric elastomers can allow for very simple and
robust "direct drive" generators. Preliminary energy harvesting generators based on dielectric elastomers have been
tested. A generator attached to a rotating waterwheel via a crankshaft produced 35 mJ per revolution in a laboratory test
with an actual water flow. A generator that harvests the energy of ocean waves for purposes of supplying power to ocean
buoys (such as navigation buoys) was tested at sea for two weeks. This buoy-mounted generator uses a proof-mass to
provide the mechanical forces that stretch and contract the dielectric elastomer generator. The generator operated
successfully during the sea trials. Wave conditions were very small during this test. Although the device did not produce
large amounts of power, it did produce net power output with waves as small as 10 cm peak-to-peak wave height. Both
the waterwheel and buoy-mounted generators will be scaled up to produce larger amounts of power. The use of
significantly larger amounts of dielectric elastomer material to produce generator modules with outputs in the kilowatt
range is being investigated for application to ocean wave power systems.
Dielectric polymer: scavenging energy from human motion
Author(s):
Claire Jean-Mistral;
Skandar Basrour;
Jean-Jacques Chaillout
Show Abstract
More and more sensors are embedded in human body for medical applications, for sport. The short lifetime of the
batteries, available on the market, reveals a real problem of autonomy of these systems. A promising alternative is to
scavenge the ambient energy such as the mechanical one. Up to now, few scavenging structures have operating
frequencies compatible with ambient one. And, most of the developed structures are rigid and use vibration as
mechanical source. For these reasons, we developed a scavenger that operates in a large frequency spectrum from quasi-static
to dynamic range. This generator is fully flexible, light and does not hamper the human motion. Thus, we report in
this paper an analytical model for dielectric generator with news electrical and mechanical characterization, and the
development of an innovating application: scavenging energy from human motion. The generator is located on the knee
and design to scavenge 0.1mJ per scavenging cycle at a frequency of 1Hz, enough to supply a low consumption system
and with a poling voltage as low as possible to facilitate the power management. Our first prototype is a membrane with
an area of 5*3cm and 31µm in thickness which scavenge 0.1mJ under 170V at constant charge Q.
Improving the electrical conductivity by forming Ni powder chains in a shape-memory polymer filled with carbon black
Author(s):
Xin Lan;
Wei Min Huang;
Na Liu;
Sy Phee;
Jin Song Leng;
Shan Yi Du
Show Abstract
We demonstrate a simple approach to significantly reduce the electrical resistivity of thermo-responsive shape-memory
polymers (SMPs), so that they can be easily triggered for shape recovery by Joule heating at a low electrical voltage.
After adding a small amount of Ni micro particles into a polyurethane SMP filled with carbon black (CB), the electrical
resistivity is slightly reduced. However, if these Ni particles are aligned into chains (by applying a low magnetic field on
SMP/CB/Ni solution and then drying to fix the conductive chains), the drop of electrical resistivity is significant. This
kind of SMP composites is suitable for cyclic operation as only micro/nano particles are used. A sample (40×15×1mm)
with 10vol% of CB and 0.5vol% of chained Ni can be heated to 80°C for shape recovery at 30 V (1.2 W) of power. This
approach is generic and applicable for producing other conductive polymers.
Design of dye-sensitized solar cells with new light-harvesting dyes
Author(s):
Morio Nagata;
Mutsumi Kimura;
Minoru Taya
Show Abstract
Phthalocyanine dyes are well known for their intense absorption in the red and near-IR regions. We synthesized novel
phthalocyanines for dye-sensitized solar cell (DSSC). Those dyes can absorb in the red and near-IR regions and adsorb
onto the surface of TiO2. Using such phthalocyanines as working electrode with TiO2, DSSCs were assembled and its
photocurrent-voltage and IPCE characteristics have been studied and compared. Light energy conversion efficiency of
DSSCs depended on the structures of phthalocyanine, the co-adsorbent, and the electrolytes. Furthermore, multi-dye
type DSSC was investigated, which mixed a phthalocyanine and a carotenoid derivative. The conversion efficiency of
the multi-dye DSSC increased compared with the DSSC which used single dye.
Inflated dielectric elastomer actuator for eyeball's movements: fabrication, analysis and experiments
Author(s):
Yanju Liu;
Liang Shi;
Liwu Liu;
Zhen Zhang;
Jinsong Leng
Show Abstract
Bio-mimetic actuators are inspired to the human or animal organ and they are aimed at replicating actions exerted by the
main organic muscles. We present here an inflated dielectric Electroactive Polymer actuator based on acrylic elastomer
aiming at mimicing the ocular muscular of the human eye. Two sheets of polyacrylic elastomer coated with conductive
carbon grease are sticked to a rotatable backbone, which function like an agonist-antagonist configuration. When
stimulating the two elastomer sheets separately, the rotatable
mid-arc of the actuator is capable of rotating from -50° to
50°. Experiments shows that the inflated actuator, compared with uninflated one, performs much bigger rotating angle
and more strengthened. Connected with the actuator via an elastic tensive line, the eyeball rotates around the
symmetrical axes. The realization of more accurate movements and emotional expressions of our native eye system is the
next step of our research and still under studied. This inflated dielectric elastomer actuator shows as well great potential
application in robofish and adaptive stucture.
Bio-inspired tactile sensor with arrayed structures based on electroactive polymers
Author(s):
Jin Wang;
Chunye Xu;
Minoru Taya;
Yasuo Kuga
Show Abstract
Ionic polymer metal composites based on Nafion and Flemion have attracted great attention as an newly developed
actuator and sensor materials due to their good performance, such as light weight, good flexibility, low actuation voltage,
large strain, good sensitivity. Previous investigations were mostly focused on actuation performance. Recently, we
reported some work on flexible tactile sensors based on Flemion ionic polymer metal composites. In this work, we
expanded the previous single-dome tactile sensor into a three by three arrayed structure. The correlated substrate and
signal collective lines were designed. Several mechanical-electrical relationships on different test domes were obtained
when different mechanical input pulses were applied. According to the experiment results, this tactile sensor arrays could
achieve good special resolution. By further improving signal circuits, a flexible large-area sensing system could be
achieved based on this material. Flemion based ionic polymer metal composites would be a good candidate for
bio-related sensors especially for artificial derma applications.
An adaptive control method for dielectric elastomer devices
Author(s):
Todd A. Gisby;
Emilio P. Calius;
Shane Xie;
Iain A. Anderson
Show Abstract
The future of Dielectric Elastomer Actuator (DEA) technology lies in miniaturizing individual elements and utilizing
them in array configurations, thereby increasing system fault tolerance and reducing operating voltages. An important
direction of DEA research therefore is real-time closed loop control of arrays of DEAs, particularly where multiple
degrees-of-freedom are desirable.
As the number of degrees-of-freedom increases a distributed control system offers a number of advantages with respect
to speed and efficiency. A low bandwidth digital control method for DEA devices is presented in this paper. Pulse Width
Modulation (PWM) is used as the basis for a current controlled DEA system that allows multiple degrees-of-freedom to
be controlled independently and in parallel using a single power supply set to a fixed voltage. The amplitude and the
duty cycle of the PWM signal control the current flow through a high speed, high voltage opto-coupler connected in
series with a DEA, enabling continuous control of both the output displacement and speed. Controlling the current in
real-time results in a system approaching a stable and robust constant charge system.
Closed loop control is achieved by measuring the rate of change of the voltage across the DEA in response to a step
change in the current input generated by the control signal. This enables the capacitance to be calculated, which in
combination with the voltage difference between the electrodes and the initial dimensions, enables the charge, strain state
and Maxwell pressure to be inferred. Future developments include integrating feedback information directly with the
control signal, leaving the controller to coordinate rather than control individual degrees-of-freedom.
Potential of thermally expandable polymers with embedded skeletons for actuator applications
Author(s):
Gih-Keong Lau;
Johannes F. L. Goosen;
Trinh Chu Duc;
Fred van Keulen
Show Abstract
This paper presents an overview of a new type of thermal
micro-actuators using thermally expandable polymers with embedded skeletons. Embedding a stiff skeleton enhances the actuation capability of the thermally expandable polymer. Consequently, the skeleton-reinforced polymers feature a large maximum actuation stress
(often above 100 MPa) and a moderate maximum strain (often above 1%) besides a faster thermal response. In addition, the present composite design has room for performance improvement by tuning the volume fraction of the polymeric expander or selecting a proper expander material. Furthermore, the micro-actuators can be taylored for different motion characteristics, using various skeleton shapes. Finally, we discussed the possible applications using the present actuators.
The application of polypyrrole trilayer actuators in microfluidics and robotics
Author(s):
Rudolf Kiefer;
Xerxes Mandviwalla;
Rosalind Archer;
Sungkono Surya Tjahyono;
Han Wang;
Bruce MacDonald;
Graham A. Bowmaker;
Paul A. Kilmartin;
Jadranka Travas-Sejdic
Show Abstract
Trilayer actuators were constructed using polypyrrole (PPy) films doped with dodecylbenzene sulfonate (DBS). Identical
5-20 μm PPy/DBS films were grown on either side of a 110 μm poly(vinylidene fluoride) (PVDF) membrane to serve as
working and counter electrodes with respect to each other. The performance of the trilayer actuator was tested using
potential step experiments between -0.8 and +0.8 V at different frequencies (0.03 to 10 Hz) and trilayer lengths (1 to 2.5
cm), and the extent of deflection was measured using a CCD camera. Satisfactory deflections in the range of 1-3 mm
were observed for 10 μm thick PPy layers on trilayers 1.5 to 2.5 cm in length when operated at 1-5 Hz for over 40,000
cycles. The trilayer actuators were examined in a fluidics channels, and mathematical modelling using finite element
analysis was used to predict overall fluid movement and flow rates. The trilayers were also used to construct a 'fish-tail'
positioned at the back of a self-driven robotic fish.
An electroactive polymer based concept for vibration reduction via adaptive supports
Author(s):
Kai Wolf;
Tobias Röglin;
Frerk Haase;
Torsten Finnberg;
Bernd Steinhoff
Show Abstract
A concept for the suppression of resonant vibration of an elastic system undergoing forced vibration coupled to
electroactive polymer (EAP) actuators based on dielectric elastomers is demonstrated. The actuators are utilized to vary
the stiffness of the end support of a clamped beam, which is forced to harmonic vibration via a piezoelectric patch. Due
to the nonlinear dependency of the elastic modulus of the EAP material, the modulus can be changed by inducing an
electrostrictive deformation. The resulting change in stiffness of the EAP actuator leads to a shift of the resonance
frequencies of the vibrating beam, enabling an effective reduction of the vibration amplitude by an external electric
signal. Using a custom-built setup employing an aluminum vibrating beam coupled on both sides to electrodized strips of
VHB tape, a significant reduction of the resonance amplitude was achieved. The effectiveness of this concept compared
to other active and passive concepts of vibration reduction is discussed.
Plastic Muscles as lightweight, low voltage actuators and sensors
Author(s):
Matthew Bennett;
Donald Leo;
Andrew Duncan
Show Abstract
Using proprietary technology, Discover Technologies has developed ionomeric polymer transducers that are capable of
long-term operation in air. These "Plastic MuscleTM" transducers are useful as soft distributed actuators and sensors and
have a wide range of applications in the aerospace, robotics, automotive, electronics, and biomedical industries.
Discover Technologies is developing novel fabrication methods that allow the Plastic MusclesTM to be manufactured on
a commercial scale.
The Plastic MuscleTM transducers are capable of generating more than 0.5% bending strain at a peak strain rate of over
0.1 %/s with a 3 V input. Because the Plastic MusclesTM use an ionic liquid as a replacement solvent for water, they are
able to operate in air for long periods of time. Also, the Plastic MusclesTM do not exhibit the characteristic "back
relaxation" phenomenon that is common in water-swollen devices.
The elastic modulus of the Plastic MuscleTM transducers is estimated to be 200 MPa and the maximum generated stress
is estimated to be 1 MPa. Based on these values, the maximum blocked force at the tip of a 6 mm wide, 35 mm long
actuator is estimated to be 19 mN. Modeling of the step response with an exponential series reveals nonlinearity in the
transducers' behavior.
Cellulose-chitosan blended electroactive paper actuator
Author(s):
Zhijiang Cai;
Yi Chen;
Jaehwan Kim
Show Abstract
Cellulose based Electro-Active Paper (EAPap) has been reported as a smart material that has merits in terms of
lightweight, dry condition, biodegradability, sustainability, large displacement output and low actuation voltage.
However, its actuator performance is sensitive to humidity: its maximum bending performance was shown at high
humidity condition. To overcome this drawback, we introduce an EAPap made with cellulose and chitosan blend.
Cellulsoe-chitosan blend films with varied mixing ratio were prepared by dissolving the polymers in trifluoroacetic acid
as a co-solvent followed by spincoating onto glass substrates.
A bending EAPap actuator is made by depositing thin gold electrodes on both sides of the cellulose-chitosan films. The
performance of the EAPap actuator is evaluated in terms of free bending displacement with respect to the actuation
frequency, activation voltage, humidity level and content of chitosan. The actuation principle is also discussed.
The development of electrically driven mechanochemical actuators that act as artificial muscle
Author(s):
Lenore Rasmussen;
Lewis Meixler;
Don Harper;
Kimun Park
Show Abstract
Ras Labs, LLC, is committed to producing a variety of electroresponsive smart materials that are strong,
resilient, and respond quickly and repeatedly to electrical stimuli. By effectively combining the synthetic
expertise of Ras Labs with the plasma expertise of the Princeton University Plasma Physics Laboratory
(PPPL), Ras Labs is actively developing superior electroresponsive materials and actuators. One of the
biggest challenges is the interface between the embedded electric electrodes and the electroresponsive
material because of the pronounced movement of the electroresponsive material. If the electroresponsive
material moves very quickly, the electric lead is often left behind and thus becomes detached. Preliminary
experiments explored the bonding between these electroresponsive materials with plasma treated metals
provided by PPPL. The results were encouraging, with much better bond strengths in the plasma treated
metals compared to the untreated control. Ras Labs expanded upon improving the attachment of the
embedded electric leads to the electroresponsive materials in these actuators using plasma treatment and
other treatments to non-corrosive metal leads at PPPL. Water drop contact angle tests were performed on
plasma treated stainless steel and titanium. The strength of the metal-polymer interface was determined at
TRI/Princeton using modified T-peel tests on samples of electroresponsive material sandwiched between
plasma treated stainless steel and titanium foils. Based on the water drop contact angle tests and the T-peel
tests, nitrogen plasma treatment of titanium produced the best metal-polymer interface. Metallic plasma
treatment allowed for the embedded electric leads and the electroresponsive material to work and move as a
unit, with no detachment, by significantly improving the interface between the electric leads and the
electroresponsive material.
Smart sunglasses with tunable shade
Author(s):
Chao Ma;
Minoru Taya;
Chunye Xu
Show Abstract
This paper discusses the design, fabrication and characterization of lens for smart sunglasses based on electrochromic
devices. The prepared electrochromic device was fabricated with ITO coated PET plastic. The working EC material film
was poly [3,3-dimethyl-3,4-dihydro-2H-thieno [3,4-b][1,4]dioxepine] (PProDOT-Me2), while the counter layer of the
device was vanadium oxide titanium oxide (V2O5/TiO2) composite film, which serves as an ion storage layer. A solution
type electrolyte as the ionic transport layer was sandwiched between the working and counter layers. The lens exhibited
tuneable shade in visible light wave length, with a maximum contrast ratio at 580nm.
Design and position control of AF lens actuator for mobile phone using IPMC-EMIM
Author(s):
Sung-Joo Kim;
Chul-Jin Kim;
No-Cheol Park;
Hyun-Seok Yang;
Young-Pil Park;
Kang-Ho Park;
Hyung-Kun Lee;
Nak-Jin Choi
Show Abstract
IPMC-EMIM (Ionic Polyer Metal Composites + 1-ethyl-3- methyl imidazolium trifluromethane sulfonate, EMIM-Tfo)
is fabricated by substituting ionic liquid for water in Nafion film, which improves water sensitiveness of IPMC
and guarantees uniform performance regardless of the surrounding environment. In this paper, we will briefly
introduce the procedure of fabrication of IPMC-EMIM and proceed to introduce the Hook-type actuator using IPMC-EMIM
and application to AF Lens actuator. Parameters of Hook-type actuator are estimated from experimental data.
In the simulation, The proposed AF Lens Actuator is assumed to be a linear system and based on estimated parameters,
PID controller will be designed and controlled motion of AF Lens actuator will be shown through simulation.
Fast bender actuators for fish-like aquatic robots
Author(s):
S. T. McGovern;
G. M. Spinks;
B. Xi;
G. Alici;
V. Truong;
G. G. Wallace
Show Abstract
Small, highly-mobile "swimming" robots are desired for underwater monitoring operations, including pollution
detection, video mapping and other tasks. Actuator materials of all types are of interest for any application where space
is limited. This constraint certainly applies to the small-scale swimming robot, where multiple small actuators are
needed for forward/backward propulsion, steering and diving/surfacing. A number of previous studies have
demonstrated propulsion of floating objects using IPMC type polymer actuators [1-3] or piezoceramic actuators [4, 5].
Here, we show how propulsion is also possible using a multi-layer polypyrrole bimorph actuator. The actuator is based
on our previously published work showing very fast resonance actuation in polypyrrole bending-type actuators [6].
The bending actuator is a tri-layer structure, in which the gold-PVDF (porous poly(vinylidene fluoride) membrane)
substrate was coated on both sides with polypyrrole layers to form an electrochemical cell. Polypyrrole films on gold
coated PVDF were grown galvanostatically at a current density of 0.10 mA/cm2 for 12 hours from propylene carbonate
(PC) solution containing 0.1 M Li+TFSI-, 0.1 M pyrrole and 1% (w/w) water. The polypyrrole deposited PVDF was
thoroughly rinsed with acetone and stored in 0.1 M Li+TFSI- / PC solution. The edges of the bulk film were trimmed
off and the bending actuators were prepared as rectangular strips typically 2mm wide and 25 mm long.
These actuators gave fast operation in air (to 90 Hz), and were utilised as active flexural joints on the tail fin of a fishshaped
floating "boat". The actuators were attached to a simple truncated shaped fin and the deflection angle was
analysed in both air and liquid for excitation with +/- 1V square wave at a range of frequencies. The mechanical
resonance of the fin was seen to be 4.5 Hz in air and 0.45 Hz in PC, which gave deflection angles of approximately 60°
and 55° respectively.
The boat contained a battery, receiver unit and electronic circuit attached to the actuator fin assembly. Thus, the boat
could be operated by remote control, and by varying the frequency and duty cycle applied to the actuator, the speed and
direction of the boat could be controlled. The boat had a turning circle as small as 15 cm in radius and a maximum
speed of 2m/min when operating with a tail frequency of approximately 0.7 Hz. The efficiency of the flapping tail fin
was analysed and it was seen that operation at this frequency corresponded with a Strouhal number in the optimal range.
Development of a dry actuation conducting polymer actuator for micro-optical zoom lenses
Author(s):
Baek-Chul Kim;
Hyunseok Kim;
H. C. Nguyen;
M. S. Cho;
Y. Lee;
Jae-Do Nam;
Hyouk Ryeol Choi;
J. C. Koo;
H.-S. Jeong
Show Abstract
The objective of the present work is to demonstrate the efficiency and feasibility of NBR (Nitrile Butadiene Rubber)
based conducting polymer actuator that is fabricated into a micro zoon lens driver. Unlike the traditional conducting
polymer that normally operates in a liquid, the proposed actuator successfully provides fairly effective driving
performance for the zoom lens system in a dry environment. And this paper is including the experiment results for an
efficiency improvement. The result suggested by an experiment was efficient in micro optical zoom lens system. In
addition, the developed design method of actuator was given consideration to design the system.
Application of ionic polymer-metal composites for auto-focusing compact camera modules
Author(s):
Hyung-Kun Lee;
Nak-Jin Choi;
Sunkyung Jung;
Sunyoung Lee;
Hewon Jung;
Jae Wook Ryu;
Kang-Ho Park
Show Abstract
Step-motor, piezo, liquid lens and voice coil motor (VCM) have been thought as good candidates for actuators in auto-focusing
compact camera module (CCM). Currently, VCMs take possession of big place in auto-focusing CCM market.
However, VCMs have limitations in developing thin, low-power CCMs. Therefore, ionic polymer-metal composites
(IPMCs) could be thought as one of the best candidates in developing auto-focusing CCM due to their well-known
characteristics such as low-power consumption and large displacement. It is required that fast bending response (20
μm/20 ms) and large blocking force (800 mgf) should be achieved for the practical applications of IPMCs in developing
auto-focusing CCM. Here, we present the method for increasing IPMC's bending response and displacement by
anisotropic plasma treatment. Furthermore, we demonstrate the fabrication of a prototype of CCM actuated by IPMC
and its remarkable low power consumption.
Nonlinear dynamic characteristics of dielectric elastomer membranes
Author(s):
Jason W. Fox;
Nakhiah C. Goulbourne
Show Abstract
The dynamic response of dielectric elastomer membranes subject to time-varying voltage inputs for various initial
inflation states is investigated. These results provide new insight into the differences observed between quasi-static and
dynamic actuation and presents a new challenge to modeling efforts. Dielectric elastomer membranes are a potentially
enabling technology for soft robotics and biomedical devices such as implants and surgical tools. In this work, two key
system parameters are varied: the chamber volume and the voltage signal offset. The chamber volume experiments
reveal that increasing the size of the chamber onto which the membrane is clamped will increase the deformations as
well as cause the membrane's resonance peaks to shift and change in number. For prestretched dielectric elastomer
membranes at the smallest chamber volume, the maximum actuation displacement is 81 microns; while at the largest
chamber volume, the maximum actuation displacement is 1431 microns. This corresponds to a 1767% increase in
maximum pole displacement. In addition, actuating the membrane at the resonance frequencies provides hundreds of
percent increase in strain compared to the quasi-static strain. Adding a voltage offset to the time-varying input signal
causes the membrane to oscillate at two distinct frequencies rather than one and also presents a unique opportunity to
increase the output displacement without electrically overloading the membrane. Experiments to capture the entire
motion of the membrane reveal that classical membrane mode shapes are electrically generated although all points of the
membrane do not pass through equilibrium at the same moments in time.
Optimization of active electrodes for novel ionomer-based ionic polymer transducers
Author(s):
Andrew J. Duncan;
Stephen A. Sarles;
Donald J. Leo;
Timothy E. Long;
Barbar J. Akle;
Matthew D. Bennett
Show Abstract
This study expands the number of novel synthetic ionomers specifically designed for performance as ionic polymer
transducers (IPT) membranes, specifically employing a highly branched sulfonated polysulfone. Control of the synthetic
design, characterization, and application of the novel ionomer is intended to allow fundamental study of the effect of
polymer branching on electromechanical transduction in IPTs. Fabrication methods were developed based upon the
direct application process (DAP) to construct a series of stand-alone electrodes as well as full IPTs with corresponding
electrode compositions. Specifically, the volumetric ratio of RuO2 conducting particles to the novel ionomeric matrix
was varied from 0 - 45 vol % in the electrodes. Electrical impedance spectroscopy was employed to determine the
electrical properties and their variation with electrode composition separate from and in the IPT. A percolation threshold
was detected for increased ionic conductivity of the stand-alone electrodes and the full IPTs based on increased loading
of conducting particles in the electrodes. An equivalent electrical circuit model was applied to fit the impedance data and
implicated interfacial and bulk effects contributing differently to the electrical properties of the electrodes and IPT as a
whole. The fabricated IPT series was further tested for bending actuation in response to applied step voltages and
represents the first demonstration of IPTs constructed with the DAP process using 100 % novel ionomer in all
components. The percolation behavior extended to the bending actuation responses for strain and voltage-normalized
strain rate and is useful in optimizing IPT components for maximum performance regardless of the ionomer employed.
Tunable transmission grating based on dielectric elastomer actuators
Author(s):
Manuel Aschwanden;
David Niederer;
Andreas Stemmer
Show Abstract
Optical gratings are used for light steering, wavelength separation, and filtering. So far, tunable diffraction gratings were
based on relatively stiff materials allowing only a limited spatial tuning range. In this paper, we describe a technology for
the implementation of shape changing, electrically adjustable, transmissive optical elements. To achieve large shape
changes, soft optical materials and dielectric elastomer actuators (DEAs) are combined. The discussed optical
transmission gratings operate with high transmission (> 90 %), good optical quality, high damage threshold
(> 93 kW/cm2), are polarization independent, and achieve very large, continuous changes in their main optical properties
(7.5 % in-plane compression of the active optical region). Further, the excellent properties of the novel optical
components are highlighted by the implementation of a low cost, objective launched, total internal reflection
fluorescence (TIRF) microscope that can be switched from epifluorescence operation to TIRF mode by simply applying
a voltage to a DEA tuned diffractive transmission grating.
Self-sensing of dielectric elastomer actuator
Author(s):
Kwangmok Jung;
Kwang J. Kim;
Hyouk Ryeol Choi
Show Abstract
In this paper, we introduce a novel, self-sensing technique for dielectric elastomer (DE) actuators which will adequately
measure the in-situ impedance variation of the DE under a deformation. A standard signal processing technique was
introduced to accurately mix and extract actuating and sensing signals. Although the technique is limited to the
actuation-bandwidth of several tens of Hz, its practical use for applications and tests is attractive. With the proposed
technique, the self-sensing actuation system was effectively demonstrated without using auxiliary sensors. The proposed
technique is useful for many attractive robotic applications including space-limited micro-actuation systems and multi-DOF systems that use hyper redundant manipulators.
Frequency response of polypyrrole trilayer actuator displacement
Author(s):
Stephen John;
Gursel Alici;
Christopher Cook
Show Abstract
Conducting polymer trilayers are attractive for use in functional devices, given low actuation voltages, operation in air
and potentially useful stresses and strains; however, their dynamic behavior must be understood from an engineering
perspective before they can be effectively incorporated into a design. As a step towards the identification of the actuator
dynamics, frequency response analysis has been performed to identify the magnitude and phase shift of displacement in
response to a sinusoidal voltage input. The low damping of the trilayer operating in air and the use of a laser
displacement sensor has allowed the frequency response to be continuously identified up to 100Hz, demonstrating a
resonant peak at 80Hz for a 10mm long actuator. Two linear transfer function models have been fitted to the frequency
response of the trilayer displacement (i) a 3rd order model to represent the dynamics below 20Hz and (ii) a higher
complexity 6th order model to also include the resonant peak. In response to a random input signal, the 3rd order model
coarsely follows the experimental identified displacement, while the 6th order model is able to fully simulate the real
trilayer movement. Step responses have also been obtained for the 3rd and 6th order transfer functions, with both models
capable of following the first 4 seconds of experimental displacement. The application of empirical transfer function
models will facilitate accurate simulation and analysis of trilayer displacement, and will lead to the design of accurate
positional control systems.
Porous conductive polyblends of polyaniline in poly(methyl methacrylate)
Author(s):
Aaron D. Price;
Hani E. Naguib
Show Abstract
The conductive polymer polyaniline is typically blended with conventional industrial thermoplastics in order to
obtain an electrically conductive polymer blend with adequate mechanical properties. Processing these polyblends
into foams yields a porous conductive material that exhibits immense application potential such as dynamic
separation media and low-density electrostatic discharge protection. In the current study, the morphology
of a thermally-processable blend consisting of an electrically conductive polyaniline-dodecylbenzene sulfonic acid
complex and poly(methyl methacrylate) is explored using a two-phase batch foaming setup. The effect of blend composition and processing parameters on the resulting cellular morphology is investigated. Finally, the impact of the underlying microstructure on the frequency dependent electrical conductivity is elucidated.
A double-sided electret polymer film-based electrostatic actuator
Author(s):
Wen-Ching Ko;
Jia-Lun Chen;
Wen-Jong Wu;
Chih-Kung Lee
Show Abstract
A solution made from blending cycloolefin copolymer (COC) and polystyrene (PS) was proposed to create a
double-sided electret polymer film. This electret polymer was then sandwiched to form an electret-metal-electret
structure by using the MEMS processes. The upper and lower polymer layers were found to both enhance charge
storage capacity significantly and to improve the machining property. It was identified that lower concentration of PS
led to sphere-like morphology distributed uniformly within the COC/PS blends, which created better electret properties
than that of pure COC or pure PS polymers. In addition, it was also found that these COC/PS blends have better
adhesion to both metal and polymers. A series of processes developed to optimize this line of new electret polymers for
actuator development are detailed. The recipe of this new material and the associated fabricating process to develop an
electret loudspeaker are also detailed. In comparison, the pros and cons of this speaker system versus a typical
electrostatic loudspeaker or a headphone, which require both bulky and expensive DC-to-DC converters, are detailed as
well.
Electromechanical simulation of cellulose based biomimetic electro-active actuator
Author(s):
Sangdong Jang;
Heung Soo Kim;
Jaehwan Kim;
Prathap Basappa
Show Abstract
Electro-active paper (EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It
is made by cellulose that is very abundant material in nature. This material is fascinating with its biodegradability,
lightweight, large displacement, high mechanical strength and low actuation voltage. It has been reported that ionic and
piezoelectric effects play a dominant roll in the actuation mechanism. However, the electromechanical actuation
mechanisms are not clearly established yet. This paper presents the modeling of the actuation behavior of water infused
cellulose samples and their composite dielectric constant calculated by Maxwell- Wagner theory. Electro-mechanical
forces are calculated using Maxwell stress tensor method. Also, bending deflection is evaluated from simple beam model
and compared with experimental observation.
Novel electro-active polymer actuator based on ionic networking membrane of PSMI-incorporated PVDF
Author(s):
Jun Lu;
Sang-Gyun Kim;
Sunwoo Lee;
Il-Kwon Oh
Show Abstract
There is growing interest in searching for new smart materials, which responds to external stimuli by changes in shape or
size and can be utilized in biomimetic motions. To develop artificial muscles with improved performance, a novel
electro-active polymer actuator was prepared by employing the newly-synthesized ionic networking membrane of poly
(styrene-alt-maleimide) (PSMI)-incorporated poly (vinylidene fluoride) (PVDF). Scanning electron microscope (SEM)
and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were
formed on the surfaces of the actuator fabricated through the electroless-plating technique as well as within its polymer
matrix. Under constant voltage excitation, the tip displacement of the actuator constructed with the ionic network
membrane was several times larger than that of its Nafion(R) counterpart of similar thickness without straightening-back.
Under the stimulus of alternating-current voltage, the newly-developed actuator displayed an excellent harmonic
performance, and the measured mechanical displacement was comparable to that of the Nafion(R)-based actuator. The nice
electromechanical response, especially the large tip displacement, is attributed to two factors: the inherent large ionic-exchange
capacity and the unique hydrophilic nanochannels of the ionic networking membrane. The actuator of PSMI-incorporated
PVDF has some advantages over the most widely-used traditional Nafion-based actuator by diversifying
niche applications in biomimetic motion, and the present study may possibly open a new avenue for the design and
fabrication of the electro-active polymer with unique functional properties.
Self healing properties of Cu-Pt coated ionic polymer actuators
Author(s):
Urmas Johanson;
Andres Punning;
Maarja Kruusmaa;
Alvo Aabloo
Show Abstract
Composite actuators consisting of sheets of the solid polymer electrolyte (similar to Nafion(R)) with Cu2+ counter-ions
inserted and coated with platinum and copper metal layers (so-called Ionomeric Polymer-Metal Composites; IPMCs)
have been synthesised and their electromechanical performance upon actuation has been monitored. Resistance
measurements on the electrodes show that the electrical conductivity of the membranes metal surface increases on the
cathode side during the actuation process, contradictory to the situation when Cu is absent from the metal coating. This
phenomenon is explained by the subsequent reduction of Cu2+ ions on the cathode upon actuation; Cu layer growth in
this side prevents it from cracking and decreases its electrode resistance. The phenomenon opens up for longer life-times
for Cu-based IPMCs. However, additional problems with Cu layer oxidation and Cu dendrite growth on the electrodes
should be considered.
A multilink manipulator with IPMC joints
Author(s):
Andres Hunt;
Andres Punning;
Mart Anton;
Alvo Aabloo;
Maarja Kruusmaa
Show Abstract
IPMC (Ionic Polymer Metal Composite) is a class of electroactive polymers (EAP) that bend when electric field is
applied to the material. From our theoretical studies of the material it appears that IPMC can be modelled as a lossy
transmission line. From simulations it appears that IPMC reaction time depends on length of the strip used. Also the
shorter the transmission line the less complex it is to model. We have also mechanically modeled an IPMC. It appears
that the output force does not depend on length on IPMC but on width. Also the shape unpredictability is the larger the
longer the strip is. Based on these results the concept of a short IPMC with rigid extension was created. From
simulations and experiments it was seen that there exists a certain length of IPMC at which output force and deflection
angle remain close to those of a long IPMC while precision increases. Also, the material becomes easier to model and its
short-term stability appears to be sufficient to be controlled. A manipulator was built to verify IPMC compatibility as
links, tested for accuracy and compared with a long sheet of IPMC. The manipulator appeared to be 314% more accurate
and twice as fast compared to the long strip of an IPMC and thus confirming the usability of the described design.
Electrochemomechanical behaviour of free standing PEDOT films in organic and aqueous electrolytes
Author(s):
Rudolf Kiefer;
Paul A. Kilmartin;
Graham A. Bowmaker;
Jadranka Travas-Sejdic
Show Abstract
The actuation properties of free standing films of poly-3,4-ethylenedioxythiophene (PEDOT) prepared from propylene
carbonate (PC) solutions of tetrabutylammonium trifluromethanesulfonate have been studied in a range of aqueous and
organic (PC) solvent electrolytes. The following electrolyte salts were investigated: TBACF3SO3, LiCF3SO3, TBAPF6,
NaPF6, NaDBS and TMACl. The best actuation performance was achieved in TMACl (aq.) with >4 % strain, 0.18 % s-1
strain rate and a low creep of 2.3 % after 50 cycles using potential step experiments. The PEDOT film morphology was
significantly changed from an open sub-micron pore polymer network to a morphology with fewer and less open pores when the solvent was changed from PC to water.
Sensor response of polypyrrole trilayer benders as a function of geometry
Author(s):
Stephen John;
Gursel Alici;
Geoffrey Spinks;
John D. W. Madden;
Gordon G. Wallace
Show Abstract
Trilayer polypyrrole benders are capable of generating voltages and currents when applied with an external force or
displacement, demonstrating potential as mechanical sensors. Previous work has identified the effects of dopant and
electrolyte on the sensor output, and a 'deformation induced ion flux' model was proposed. The current work aims to
identify the change in sensor response with input amplitude and bender geometry as a function of frequency. The
current and charge output from the trilayer benders were found to increase proportionally with input displacement and
bender strain for multiple input frequencies, indicating linearity. Sensitivities of the current and charge output have also
been calculated in response to strain, and are found to increase as the volume of the conducting polymer is increased.
Some guidelines for sensor geometry are then suggested, using the identified sensitivities as a guide.
High-precision characterization of dielectric elastomer stack actuators and their material parameters
Author(s):
Marc Matysek;
Peter Lotz;
Klaus Flittner;
Helmut F. Schlaak
Show Abstract
Stacked dielectric elastomer actuators (DEA) act as solid state actuators. Modeling such an electromechanical system
demands the knowledge about the mechanical and electrical parameters of the used materials as well as the real static
and dynamic behavior.
In elastomer actuators the electrical properties of the materials might change with applied mechanical stress or applied
voltage as it is known from some materials (e. g. polyacryl). Therefore, we examined the PDMS used in stacked
dielectric elastomer actuators regarding such dependencies. We present results from testing the permittivity of two
different silicones (Elastosil P7670, Wacker Silicones; RTV410, Bayer) versus mechanical stress, frequency of the
driving voltage, film thickness and curing temperature.
The resulting movement of a stacked actuator is not a single displacement of the elements but a rather complex bulk
deformation. Therefore, a planar displacement measurement system is necessary. Laser displacement sensors offer the
possibility of a two-sided measurement. This allows to determine the actual thickness variation even if the actuator array
moves out of plane. The setup includes a prestretching device to clamp the actuators symmetrically and to simulate an
uniaxial load. The realized measurement setup has an effective vertical measurement range of 10 mm, a resolution of
100 nm at a sample rate of 20 kHz. This allows the static and dynamic displacement measurement of planar actuators.
Dielectric elastomer actuators using improved thin film processing and nanosized particles
Author(s):
Peter Lotz;
Marc Matysek;
Pia Lechner;
Monika Hamann;
Helmut F. Schlaak
Show Abstract
Stacked dielectric elastomer actuators are fabricated by an automated process using spin coating of uncured elastomers.
To improve the performance of these multilayer actuators we present two different ways. To reduce the driving voltage it
is desirable to fabricate dielectric films with a thickness below 20 μm. This can be achieved by high speed spin coating
of an uncured elastomer. Analyzing the automated process reveals nine principal process parameters. An adequate design
of experiment reduces the number of necessary tests to an acceptable value. With these results we are able to spin thin
films with a thickness of less than 5 μm and a thickness variation of about 3%.
Secondly, we examine the influence of nanosized particles of metal oxide powder on the permittivity of the elastomer
film. Three different materials, namely aluminiumoxide, titaniumdioxide and bariumtitanate with a bulk permittivity of
about 10, 100, 1000, respectively, are used to increase the overall permittivity of the composite. To predict the resulting
performance of an elastomer actuator the figure of merit Κ is introduced.
Frequency response characteristics of IPMC sensors with current/voltage measurements
Author(s):
Kentaro Takagi;
Norihiro Kamamichi;
Boyko Stoimenov;
Kinji Asaka;
Toshiharu Mukai;
Zhi-Wei Luo
Show Abstract
This paper discusses a model of IPMC sensors and the characteristics of the frequency responses. There are
two different methods of measurements, the current sensing and the voltage sensing, which exhibit completely
different frequency responses each other. A simple model based on Onsager's equation is shown in order to
explain the experimental results of the current sensing. The voltage sensing model is derived by the equivalent
transform of the voltage and the current sources. In contrast to the constant gain of the charge response, the
characteristics of the voltage response are directly related to the impedance dynamics. In the experiments, the
frequency responses of the charge/current sensing and the voltage sensing for two species of counter ion are
measured. The ratio of the obtained frequency responses and the measured impedance are also compared to
validate the voltage sensing model. Though the theoretical prediction of the sensor coefficient does not match
the experimental one, the structure of the model agrees with the experimental data.
Preisach modeling of IPMC-EMIM actuator
Author(s):
Chul-Jin Kim;
Hyun Woo Hwang;
No-Cheol Park;
Hyun-Seok Yang;
Young-Pil Park;
Kang-Ho Park;
Hyung-Kun Lee;
Nak-Jin Choi
Show Abstract
The IPMC-EMIM actuator is an improved IPMC actuator to replace the water by stable ionic liquids (1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EtMeIM][TA])). Just as a general IPMC actuator which uses the
solvent of water has hysteresis, so do the IPMC-EMIM actuator exhibits hysteresis like other smart materials such as
piezoceramics (PZT), magnetostrictive materials, and shape memory alloys (SMA). Hysteresis can cause it to be
unstable in closed loop control. The Preisach Model has been used to model the hysteretic response arising in PZT and
SMA. Noting the similarity between IPMC-EMIM and other smart materials, we apply the Preisach model for the
hysteresis in the IPMC-EMIN actuator. This paper reviews the basic properties of the Preisach model and confirms
that the Preisach model of IPMC-EMIM actuator is possible.
Preisach modeling of dielectric elastomer EAP actuator
Author(s):
HyunWoo Hwang;
Chul-Jin Kim;
Sung Joo Kim;
Hyunseok Yang;
No Cheol Park;
Young-Pil Park
Show Abstract
DE EAP(Dielectric Elastomer ElectroActive Polymer) has advantages in its weight, ease of fabrication and low
power consumption. There are many efforts applied to various field in recent ten years. But the present modeling is not
enough to appear its characteristics because of its hysteresis. In this paper, we propose modeling of DE EAP with
Preisach Model that is used in order to model the hysteretic response arising in PZT and SMA. The modeling of DE
EAP with Presach model is verified by experiment with various DE EAP actuators.
Molecular dynamics studies of interpenetrating polymer networks for actuator devices
Author(s):
Daniel Brandell;
Heiki Kasemägi;
Johann Citérin;
Frédéric Vidal;
Claude Chevrot;
Alvo Aabloo
Show Abstract
Molecular Dynamics (MD) techniques have been used to study the structure and dynamics of a model system of an
interpenetrating polymer (IPN) network for actuator devices. The systems simulated were generated using a Monte
Carlo-approach, and consisted of poly(ethylene oxide) (PEO) and poly(butadiene) (PB) in a 80-20 percent weight ratio
immersed into propylene carbonate (PC) solutions of LiClO4. The total polymer content was 32%, in order to model
experimental conditions. The dependence of LiClO4 concentration in PC has been studied by studying five different
concentrations: 0.25, 0.5, 0.75, 1.0 and 1.25 M. After equilibration, local structural properties and dynamical features
such as phase separation, coordination, cluster stability and ion conductivity were studied. In an effort to study the
conduction processes more carefully, external electric fields of 1×106 V/m and 5×106 V/m has been applied to the
simulation boxes. A clear relationship between the degree of local phase separation and ion mobility is established. It is
also shown that although the ion pairing increases with concentration, there are still significantly more potential charge
carriers in the higher concentrated systems, while concentrations around 0.5-0.75 M of LiClO4 in PC seem to be
favorable in terms of ion mobility. Furthermore, the anions exhibit higher conductivity than the cations, and there are
tendencies to solvent drag from the PC molecules.
Classification and selection of actuator technologies with consideration of stimuli generation
Author(s):
Alan Poole;
Julian D. Booker
Show Abstract
With the aim of discovering, designing and developing a novel actuator, existing technologies are broken down into
components. These are the material or phenomena that provide mechanical power, the type of stimulus required to
"excite" the technology and the geometrical arrangement, or configuration of the technology to manifest as an actuator.
To date, a number of attempts have been made to classify and compare actuators. Existing comparisons typically use
active material performance as a source for actuator data, even though a material alone is not active. A stimulus
generation must be present for an active material to be used as an actuator and the addition of local stimulus generation
can severely affect the performance of an actuator. Little or no attempt to classify different actuation technologies and
configurations with consideration of the nature and provision of stimulus has been made. By classification of stimulus
and actuator configuration, many further research areas are identified. The structured actuator categorisation along with a
fundamental view of the requirements of an actuator forms the basis of an engineering biased selection strategy.
Electric field around a dielectric elastomer actuator in proximity to the human body
Author(s):
Anita C. McKenzie;
Emilio P. Calius;
Iain A. Anderson
Show Abstract
Dielectric elastomer actuators (DEAs) are a promising artificial muscle technology that will enable new kinds of
prostheses and wearable rehabilitation devices. DEAs are driven by electric fields in the MV/m range and the dielectric
elastomer itself is typically 30μm in thickness or more. Large operating voltages, in the order of several kilovolts, are
then required to produce useful strains and these large voltages and the resulting electric fields could potentially pose
problems when DEAs are used in close proximity to the human body. The fringing electric fields of a DEA in close
association with the skin were modelled using finite element methods. The model was verified against a known analytic
solution describing the electric field surrounding a capacitor in air. The agreement between the two is good, as the
difference is less than 10% unless within 4.5mm of the DEA's lateral edges. As expected, it was found that for a DEA
constructed with thinner dielectric layers, the fringe field strength dropped in direct proportion to the reduction in applied
voltage, despite the internal field being maintained at the same level. More interestingly, modelling the electric field
around stacked DEAs showed that for an even number of layers the electric field is an order of magnitude less than for
an odd number of layers, due to the cancelling of opposing electric fields.
High electromechanical performance of electroelastomers based on interpenetrating polymer networks
Author(s):
Soon Mok Ha;
Il Seok Park;
Michael Wissler;
Ron Pelrine;
Scott Stanford;
Kwang J. Kim;
Gabor M. Kovacs;
Qibing Pei
Show Abstract
The electromechanical performance of interpenetrating polymer networks (IPN) in which one elastomer network is
under high tension balanced by compression of the second network, were investigated. Uniaxial stress relaxation
analysis confirmed significant decrease in viscoelasticity in comparison with 3M VHB films, the primary component
network in the IPN films. In dynamic mechanical analysis, the IPN composite showed a higher mechanical efficiency,
suggesting delayed relaxation of the acrylic chains in the presence of IPN formation. This improvement was found to be
dependant on the contents of poly(TMPTMA). Actuation performance without mechanical prestrain showed that these
IPN electroelastomers had demonstrated high elastic strain energy density (3.5 MJ/m3) and a high electromechanical
coupling factor (93.7%). These enhanced electromechanical performances indicate that IPN electroelastomer should be
suitable for diverse applications.
Architecture for the semi-automatic fabrication and assembly of thin-film based dielectric elastomer actuators
Author(s):
M. Randazzo;
R. Buzio;
G. Metta;
G. Sandini;
U. Valbusa
Show Abstract
One problem related to the actuation principle of macroscopic dielectric elastomer actuators is the high voltage required,
typically in the Kilovolt range, that imposes particular care in the insulation of the whole actuator from the surrounding
environment. This high actuation voltage, however, can be drastically reduced if a thin film of dielectric elastomer is
used. Despite this, the manufacture of a macroscopic stack-like actuator, starting from thin films of dielectric elastomer
can present many manufacture difficulties, like the handling and the assembly of the films, the power distribution to
hundreds or thousands of layers, the presence of defects in one single layer that can cause the complete failure of the
whole actuator. In this paper, a fast, semi-automatic process is proposed for the manufacture of modular units of
dielectric elastomer, each of them consisting of many layers of rolled thin dielectric film. All the manufactured units are
independent and take their power from a lateral, compliant supply rail that contacts the sides the electroded layers. This
design is very suitable for industrial production: each module can be independently tested and then assembled in a
complete macroscopic actuator composed by an unlimited number of these modules. The simple assembly methodology
and the semi-automatic manufacture process described in this paper allows the fabrication of multilayer stacked devices,
that can be used both as contractile or expanding actuators.