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SPIE Smart Structures + Nondestructive Evaluation event news and photos

 

SPIE Smart Structures/NDE9-13 March 2014
Town & Country Resort and Convention Center
San Diego, California, USA

 

Review the SPIE Smart Structures/ Nondestructive Evaluation week via the links below.

 

Town and Country Hotel, San Diego
Bioinspiration!
See videos of the visit
to the conference
by animal ambassadors
and staff from the San
Diego Zoo's Centre for
Bioinspiration.

Welcome! And the SSM awards go to ....

Congratulations, new Fellows!

Noncontact laser sensing

Integration for biosensing

'Soft' robotics

EAP-in-Action Session [See more photos from the EAP-in-Action Session.]

‘Fishing line and sewing thread’

Poolside for the evening

NDE awards

Permanent installations for SHM

Students and experts

Face-to-face: posters and exhibitors

Flexible materials, integrated solutions

Carbon nanotubes and flexible substrates

Dielectric elastomers for sensing

Bioinspiration, courtesy of Tipu

Reducing noise and vibration

SPIE/ASME Best Student Presentations

Best Student Papers: Bioinspiration

 


Welcome! And the SSM awards go to ....

Following a welcome, Monday's sessions opened with the first of the week's awards presentations. Symposium chair Victor Giurgiutiu of the University of South Carolina (at right below) presented 2014 Smart Structures and Materials Lifetime Achievement Awards for work in advancing the technology. Winners are:

Christopher Lynch, Victor Giurgiutiu

Christopher Lynch, University of California, Los Angeles (Lynch serves as symposium chair along with Giurgiutiu.)

Shiv Joshi, Victor Giurgiutiu

Shiv Joshi of NextGen Aeronautics

 


Congratulations, new Fellows!

New Fellows of SPIE from the Smart Structures/Nondestructive Evaluation community were introduced by SPIE Fellow Felix Wu of the University of North Texas (at right below). The three are among a total of 76 new Fellows of the Society named by SPIE this year.

Bert Müller, Felix Wu

Bert Müller (Basel University Hospital)

Norman Wereley, Felix Wu

Norman Wereley (University of Maryland, College Park)

Christopher Lynch, Felix Wu

Christopher Lynch (University of California, Los Angeles)

 


Noncontact laser sensing

Hoon Sohn, KAISTIn the first plenary talk of the week, Hoon Sohn from the Korea Advanced Institute of Science and Technology (KAIST) described the basic details of five distinct methods for noncontact sensing being studied in his labs in his plenary talk, "Noncontact Laser Sensing Technology for Structural Health Monitoring and Nondestructive Testing."

Laser ultrasonics utilizing a YAG laser excitation source partnered with a laser Doppler vibrometry (LDV) sensing arrangement and coupled with scanning mirrors enables sampling across a substrate. When combined with analytical methods which create wavefield images over time and which construct RMS energy propagation profiles, the technique enables 2mm resolution and is suitable for detection of defects with no need for prior baseline data collection.

The technique has been used to study wind turbine blades and to scan rotating objects.

By guiding the excitation beam through an optical fiber arrangement, the team has been able to adapt the method for use in monitoring pipelines inside of nuclear power plants where tolerance for high temperatures and high radiation levels is required.

A second method, laser ultrasonic modulation, involves applying distinct sinusoidal inputs to a system and studying the output response. In samples with defects such as fatigue-induced cracking, harmonics and modulations of the input frequencies result thereby providing a means for defect detection.

The team has used this technique to study aircraft fitting lugs and drop lift assemblies in automotive assembly lines.

Combining a continuous wave (CW) input laser source to scan a surface with an IR camera for viewing was the basis of the third technique, laser lock-in thermography. Use of the IR camera allows for collection of a thermal image and study of thermal diffusion effects. Surfaces that are fatigued or which are otherwise defective produce non-isotropic images in contrast to images obtained with non-defective parts.

This technique has the benefit of use with low emissivity parts. In one application, Sohn stated that cracks as small as 30-40 nanometers in width were seen on semiconductor wafers. LiDAR and LADAR techniques are also under study in Sohn's laboratories. Combining LiDAR with high frequency LDV schemes enables measurements of displacement and flatness with Sohn citing the example of flatness measurements for concrete slabs used in construction.

A final technique discussed was laser-based power and data transmission involving modulating input laser intensity to provide input waveforms to a piezoelectric transducer excitation and detection scheme for applications such as impedance measurements.

Sohn noted that these methods do face challenges in terms of safety, laser beam alignment, and surface complexity but said that he expects noncontact sensing to capture its share of structural health monitoring and nondestructive testing applications because of the resolution it can provide, the opportunity for rapid deployment given the limited hardware required, and the ability of the techniques to function in harsh environments.

SPIE Smart Structures and Nondestructive Evaluation plenary audience

 


Integration for biosensing

Gianaurelio Cuniberti, TU DresdenIn his plenary talk, "Laser-Induced Switching of Si Nanowire-based BioFET's," Gianaurelio Cuniberti of the Technische Universität Dresden described research integrating electronics, biotechnology and microfluidics.

Nanowires offer the opportunity to make and study devices that are not readily achievable with other methods. Through combining aspects of material science with biotechnology, Cuniberti's team is able to create novel bioanalytical devices with high sensitivity and unique performance.

Cuniberti described a droplet-based microfluidic scheme coupled with arrays of silicon nanowires made into FET's functionalized using NiSi2. This type of hybrid structure forms the basis of a biosensing device, and sweeping the transistor current-voltage curves allows for detection of analytes.

As a proof-of concept example, Cuniberti discussed results obtained using a pH sensor made with this scheme.

In another application, coating the Si nanowires with porphyrin results in a light-sensitive circuit. Sweeping the transistor I-V curves generates varying output signatures depending upon the concentration of the porphyrin and the presence or absence of light.

By adapting a multi-disciplinary approach and combining nanoelectronics with microfluidics in a novel fashion, Cuniberti and his team have demonstrated that it is possible to produce powerful sensing and analytical approaches for biotechnology applications.

 


'Soft' robotics

In a keynote talk of soft robotics in the Electroactive Polymer Actuators and Devices (EAPAD) conference, Robert Shepherd, currently at Cornell University, described work done with collaborators during his time in the Whitesides group at Harvard.

Shepherd defined “soft” robotics as referring to mechanical stress levels at which machines are deformed but which are safe to humans. Much of Shepherd’s work is focused on the materials used in robots and the use of elastomers to both stretch and sense.

Among several examples and use cases. Shepherd described injecting a material with chemiluminescent dye to allow use of the robot in low light conditions. Hybridizing or combining the soft robot with traditional "hard" robots allows for greater capability as demonstrated with a "marsupial" robot, which used a wheeled hard robot with a four-legged soft robot to enable rapid motion over terrain followed by deployment of the soft robot to retrieve a target.

Using silicones allows for greater temperature tolerances and the ability to lift heavier objects. To increase actuation speed, methods such as combustion were investigated and demonstrated with an untethered jumping robot. Incorporating fibers into the material matrix helps to add puncture resistance and self-sealing response for robots in harsh environments.

Moving forward, Shepherd’s team is looking at 3D printing of devices such as soft actuators to position solar cells. Shepherd’s talk and the many examples he cited from his time in the Whitesides group clearly demonstrates the capability and flexibility of this branch of robotics.

 


EAP-in-Action Session

Another highlight of Day One was the annual EAP-in-Action Session and Demonstrations, which drew nine participating organizations from both industry and academia. Chaired by SPIE Fellow Yoseph Bar-Cohen of the Jet Propulsion Lab, the event provides the opportunity for conference attendees to see demonstrations of the latest applications and capabilities of electroactive polymer (EAP) materials. The results demonstrated clearly indicated the diverse applications available to these materials and the progression from university lab research to industrial use.

Included in this year's program was work done by a group led by Ray Baughman at the University of Texas at Dallas making artificial muscles. The group presented several findings including the use of 150 micron diameter structures woven from fishing line which can lift 50 grams and which can be scaled up by twisting into a 2.45 mm assembly capable of lifting 15 kilograms. A structure constructed of sewing thread coated with silver was capable of 60,000 rpm and a thermally actuated structure made out of twisted yarn was demonstrated to handle in excess of 75 MPa stress.

A second group, under the lead of Jin Gong of Yamagata University, demonstrated shape memory gels activated by hot (50C) water. Gong's group is working on combining this material in a 3D printing setup to enable additive manufacturing approaches to varifocal lenses, artificial organs and intraocular implants for cataract treatment.

A group from EPFL demonstrated a three-phase dielectric elastomer actuator (DEA) motor scheme at the heart of their rolling robot while a team from the Bristol Robotics Lab using a DEA-based whisker sensor with adaptive control illustrated that this technology can learn and correct in sense and move scenarios.

Representing the University of Tartu, Indrek Must and Friedrich Kaasik shared their bio-inspired low-voltage autonomous robot made with ionic polymer, and Helmut Schlaak of the Technische Universität Darmstadt described the functioning of a DEA for use on tactile surfaces such as a computer mouse.

Industry was well-represented at the forum as well.

Vivitouch shared their latest EAP stacked actuator for gaming and entertainment applications, and Ras Labs described their recent work in low voltage EAP materials for synthetic muscles while StretchSense, a spin-out from the Biomimetics Lab at the University of Auckland, discussed stretchable capacitive sensors.

Yosi Bar-Cohen at EAP-in-Action session

EAP conference chair Yoseph Bar-Cohen (at microphone, above) announced participants in the EAP-in-Action session; below a sample of the demonstrations. See more photos in the EAP-in-Action gallery.

EAP-in-Action demonstration

EAP-in-Action demonstration

EAP-in-Action demonstration

 


'Fishing line and sewing thread'

In an invited talk in the EAPD conference, Carter Haines of Ray Baughman's labs at the University of Texas at Dallas provided technical perspective on a system the team demonstrated in the EAP-in-Action session on Monday "Carbon-based torsional and tensile artificial muscles driven by thermal expansion: artificial muscles from fishing line and sewing thread" [9056-13].

Taking the approach of making fiber-based actuators that mimic natural muscle, the group began their work several years ago working with carbon nanotubes and transitioned that learning to materials more commonly available.

Along the way they discovered that commercially available polymer fibers, which are designed for strength, are excellent sources for material containing oriented polymer chains and, in turn, for building artificial muscles. Haines shared results demonstrating that polymer fibers can be operated thermally, achieve >30% stroke and lift loads 100X heavier than what a similar length and weight of natural muscle can achieve.

Unlike NiTi systems, the polymer fiber systems operate with little or no hysteresis and have demonstrated millions of cycles in lab testing. A key element to the functionality demonstrated by the fibers is the introduction of coils to the geometry, which enables >30% tensile contraction when thermally actuated.

Weaving the fibers to form braids can provide a pathway to such diverse applications as lifting heavy loads at high speeds and temperature sensitive textiles.

The group will present additional findings regarding their exciting research including their work on hydrothermal muscles later during the conference.

 


Poolside for the evening

Attendees enjoyed a poolside welcome reception Monday evening on the hotel patio.

SPIE Smart Structures/NDE reception

SPIE Smart Structures/NDE reception

SPIE Smart Structures/NDE reception

SPIE Smart Structures/NDE reception

SPIE Smart Structures/NDE reception

 


NDE awards

The first order of business on Tuesday was presentation of the Nondestructive Evaluation Lifetime Achievement Awards, for contributions advancing the field. Symosium chair Victor Giurgiutiu made the presentations to:

Nobuo Takeda, Victor Giurgiutiu

Nobuo Takeda, University of Tokyo

 Peter Cawley, Victor Giurgiutiu

Peter Cawley, Imperial College London

 


Permanent installations for SHM

Peter CawleyThe transition from periodic inspection to full-time monitoring is a key trend in the field, noted Peter Cawley of Imperial College London in his plenary talk "Transition from Nondestructive Testing (NDT) to Structural Health Monitoring (SHM): Potential and Challenges" on Tuesday.

Historically, the cost of transducers and instrumentation made ongoing monitoring cost prohibitive, but the availability of inexpensive equipment and wireless networks have made permanent installations more attractive.

By way of example, Cawley discussed point measurement procedures in use today at refineries. These manual thickness measurements are conducted during shutdowns and suffer from poor repeatability performance (typically on the order of +/-1mm) and high access costs.

Replacing this method with an ongoing scheme requires a robust sensor, which can operate in conditions where temperatures reach 600C for extended periods of time. Using a permanently attached waveguide arrangement isolates the transducer and allows for such ongoing monitoring. Frequent data collection then becomes a value-added function allowing for accurate monitoring and tracking of corrosion rates and enabling new capability such as monitoring inhibitor effectiveness.

In the space of area management, guided-wave inspection allows monitoring length of pipelines by exciting and monitoring response from the torsional mode and nearby flexural modes. Defects such as corrosion patches demonstrate non-symmetric reflection patterns enabling detection.

The presence of permanent installations and ongoing monitoring naturally leads to questions on how to monitor and reliably identify changes in structures. Simple baseline subtraction methods may be insufficient since residuals can overwhelm the signature being sought.

To address this issue, Cawley suggested generalized likelihood ratio (GLR) methods as one technique to analyze data collected over time.  GLR allows the investigator to trade off of the probability of detection, the probability of false positives and the amount of data collected.

An example using GLR techniques to detect defects of various depths at different locations in a curved pipeline layout demonstrated the power of the method.

Summing up, Cawley said that permanent installations for structural health monitoring is proving to be a viable alternative to periodic nondestructive testing. The frequent collection of data inherent in the method enables better sensitivity and higher confidence in defect detection. Significant research opportunities remain but permanently installed arrangements are now a reality.

 


Students and experts

Tuesday afternoon's well-attended Lunch with the Experts afforded students a chance to network with experts to learn more about career paths and opportunities.

Student Lunch with Experts

 


Face-to-face: posters and exhibitors

A poster reception combined with evening exhibition hours provided attendees with an oppotunity to talk face-to-face with researchers and suppliers about new research as well as new applications.

Smart Structures/NDE poster exhibition reception

Smart Structures/NDE poster exhibition reception

Smart Structures/NDE poster exhibition reception

 


Flexible materials, integrated solutions

Karlheinz BockSocietal challenges such as expanding city populations and growing energy consumption require increasingly clever and integrated solutions, said Wednesday plenary speaker Karlheinz Bock of Fraunhofer EMFT. Smart structures that can sense and react to changes in the environment are one solution path, and flexible substrates allow for open form factors that enable integration of functionality into everyday objects.

In "Heterointegration of smart systems in foil," Bock cited the automotive industry, where compliant materials would allow integration of antennas onto the vehicle surface, and the life sciences, where such materials could produce smart skins for medical monitoring.

Solutions will involve overlapping applications and hence modular system integration. Bock described both homogeneous-single foil-and heterogeneous-multiple foils and materials-approaches to integration.

In both schemes, roll-to-roll processing enables the use of flexible materials at production rates and volumes.

In the case of homogeneous integration, Bock demonstrated 20 micron line/space printing capability on materials such as PET, PEN and polyimide. Applications discussed included a double-sided coplanar waveguide and printing of carbon paste resistors.

Heterogeneous integration enables more sophisticated devices and makes use of materials such as silicon, thinned to 20 micron thickness to enable flexibility, to add functionality. Bock described a thin chip foil package incorporating silicon integrated circuitry and taking advantage of the wetting properties of the polymer films to self-align glues to contact pads achieving accuracies better than one micron.

Additional stacking of foils moves the applications into the 3D space as was demonstrated with a multi-foil device integrating antennas, batteries, sensors, photovoltaic cells and integrated circuits. In the life sciences field, adding microfluidics devices allows for lab-on-chip applications to be explored, while in the safety field, adding detection modules facilitates chemical sensing applications for such things as airborne contaminants.

 


Carbon nanotubes and flexible substrates

In the keynote presentation "Printing nanotube/nanowire for flexible microsystems" [9060-31], Jin-Woo Choi of Louisiana State University discussed work in his labs pairing carbon nanotube (CNT) devices with flexible substrates, demonstrating how nanotechnology, flexible materials, and fairly traditional patterning schemes can be combined to produce unique results.

Choi described three different methods of fabrication, their advantages and disadvantages, and devices manufactured with each technique.

The group typically used chloroform both as their dispersion agent for the CNTs and the solvent for their choice of a flexible material, PDMS. Using a microcontact printing method resulted in a resolution of 200 microns for line/space pairs.

A precision screen printing technique provided better resolution, sub-20 micron feature sizes, and the ability to print arbitrary patterns. Using this technique, Choi's lab manufactured strain sensors which demonstrated 63% resistance change with strain up to 42%.

They also demonstrated pressure sensors capable of detecting less than 10 Pa differential pressure. The use of inkjet printing allows for simultaneous deposition of multiple materials and more sophisticated devices. In this instance sodium dodecyl sulfate (SDS) was used to disperse the CNTs, and the team had to optimize the SDS:CNT ratio to minimize sheet resistance and counter the tendency of SDS to wrap around the CNTs. The team was able to achieve a sheet resistance of 132 Ω/□ and used this arrangement to construct electrochemical sensors.

 


Dielectric elastomers for sensing

Dielectric elastomers are known for their use as actuators, but Holger Böse of the Fraunhofer-Institut für Silicatforschung ISC proposed another idea in his invited talk on "Novel dielectric elastomer sensors for compression load detection" [9056-39]. He suggested taking advantage of them in sensing applications and in particular using them to measure changes in capacitance.

Doing so in circumstances in which the materials expand is relatively straightforward, but the situation changes when materials are under compression since silicone, the material central to this study, is nearly incompressible.

Böse described two designs of sensor mats which overcome this limitation. Both take advantage of interlocking meshes separated by elastomer material.

In the first case, electrodes are placed on the intervening elastomer, whereas in the second case, electrodes are placed on the surfaces of the meshes themselves. In the first design, a 9 mm elastomer film was placed between 100 mm x 100 mm square mats containing the interlocking mesh pattern. Compression of the system resulted in a linear change in capacitance up to a 400 N load; a capacitance change from 6.7 nF to 13 nF was observed. In a three-cycle test, some hysteresis was observed but the system demonstrated good repeatability.

In similar testing on the second design using a similar form factor, a change in capacitance from 0.5 nF to 12 nF was seen. This configuration benefits from the higher permittivity of the elastomer material serving as the filler between the interlocking meshes thereby resulting in larger changes in capacitance under similar loads. Temperature dependence of the sensor design was studied in thermal cycle testing, and the capacitance was seen to return to its original, pre-test value.

Durability was also analyzed and a test system showed no measurable change in capacitance after 400,000 cycles involving stretching by 100% of the initial area. This work demonstrates another use for these materials and fills an important void and need in applications for automobile passenger safety and medical patient care.

 


Bioinspiration, courtesy of Tipu

Tipu, San Diego Zoo tamandua
Tipu, a tamandua (lesser anteater), an Animal
Ambassador at the San Diego Zoo, took part
in a bioinspiration demonstration.

Following in the claw tracks of such luminaries as Laveau, a caiman, and Shaman, a great horned owl, was Tipu, a tamandua (more commonly known as a lesser anteater), providing a focal point for a panel discussion on "Biomimicry, Bioinspiration and the San Diego Zoo." This annual event in the "Bioinspiration, Biomimetics, and Bioreplication" conference seeks to give engineers and scientists a closer look at nature and promote discussion on biomimetry and the role of bioinspiration in research, science, and technology.

Lesser anteaters like Tipu can be found in Central and South America. In zoos, they have life expectancies of 20 years so Tipu, at age 14, is entering the golden years of his life.

With physical attributes such as a 16-inch tongue with barbules perfect for extracting ants and termites from mounds, potent scent glands to deter predators and mark territory, and nails that can destroy concrete, Tipu was nonetheless content to snack on honey while staff from the San Diego Zoo explained the Animal Ambassador program. In addition to helping scientists who are looking to the biota for inspiration, one of the program's goals is to inspire the public to think more about the natural world in our daily lives.

Moderators Gabriel Miller of the San Diego Zoo and Akhlesh Lakhtakia of Pennsylvania State University helped field questions -- including several from student representative Veronica Sardo, a Penn State undergraduate -- for a panel including Joseph Jakes of the U.S. Forest Service, Tony Prescott of the University of Sheffield, Georg Studor from NASA Johnson Space Center, Mato Knez of CIC nanoGUNE Consolider, and Akira Saito of Osaka University.

Several themes emerged including the need for collaboration and communication between scientists and engineers from different fields to share information and to more effectively and efficiently solve problems. Lakhtakia closed out the session by reminding the audience that researchers need to engage others on these types of topics. Although we are scientists, he said, we are also citizens and have a responsibility to ourselves, to fellow citizens, and to nature to educate our communities on these concepts.

Bioinspiration panel

Akhlesh Lakhtakia (above, with microphone) poses a question for the panel; below, Tipu with Kristina Seitz, Senior Education Guide with the San Diego Zoo.

Tipu, San Diego Zoo tamandua, and Kristina Seitz

 


Reducing noise and vibration

Roger OhayonRoger Ohayon, Professor (Emeritus) at Conservatoire National des Arts et Métiers, demonstrated the power of bringing computational methods to study complex problems in Thursday's plenary talk on "Intelligent adaptive fluid-structure interaction systems."

Using computational schemes including finite element discretization and reduced order models, Ohayon and his collaborators study the dynamic behavior of complex coupled systems for such purposes as vibration and noise reduction.

In the aerospace industry, for example, the analysis is applicable to studying behavior involving engine vibrations, atmospheric turbulence, thrust fluctuations, and equipment motion.

Ohayon provided several examples of how to reduce complex fluid-structural systems into constituent systems, which more readily lend themselves to analysis. The methods were then applied to problems of practical importance, and Ohayon compared computational output to experimental results.

Reducing cabin noise in a helicopter resulted in studies of a new composite material panel which performed well in the laboratory; however, in the field, although vibration performance was improved, noise reduction was minor, suggesting that the field excitation modes are more complex than what can be easily realized in a lab setting.

Other examples discussed included active twist rotor blades for helicopters, vibration reduction at launcher/payload interface, and active flutter control.

Ohayon concluded with the observation that a number of open problems exist that should stimulate continued work and progress in this area.

 


SPIE/ASME Best Student Presentations

SPIE/ASME Best Student Presentation Awards for 2014 were presented by Darren Hartl of Texas A&M University (at right with winners below).

Majid Tabesh, Darren Hartl

First place was won by Majid Tabesh (Texas A&M University) for "Modeling size effect in the SMA response: a gradient theory" [9058-2].

Justin Scheidler, Darren Hartl

Second place was won by Justin Scheidler (Ohio State University) for "Stiffness tuning of FeGa structures manufactured by ultrasonic additive manufacturing" [9059-7].

Chandrayee Basu, Darren Hartl

Third place was won by Chandrayee Basu (University of California, Berkeley) for "Affordable and personalized lighting using inverse modeling and virtual sensors" [9061-103].

 


Best Student Papers: Bioinspiration

Best Student Paper Awards for 2014 were presented at the Bioinspiration, Biomimetics, and Bioreplication conference by Yoseph Bar-Cohen of the Jet Propulsion Lab (at right with winners below).

Hongbin Fang, Yoseph Bar-Cohen

First place was won by Hongbin Fang (University of Michigan) for "Design and experimental gait analysis of a multi-segment in-pipe robot inspired by earthworm's peristaltic locomotion" [9055-16].

Anansa Ahmed, Yoseph Bar-Cohen

Second place was won by Anansa Ahmed (Nanyang Technological University) for "Bio-inspired magnet-polymer (Magpol) actuators" [9055-23].

Ashok Kancharala, Yoseph Bar-Cohen

Third place was won by Ashok Kancharala (Virginia Polytechnic Institute and State University) for "Influence of bending mode shape and trailing edge deflection on propulsive performance of flexible heaving fins using digital image correlation" [9055-26].

 


Town and Country Hotel, San Diego

See you next year: 8-12 March 2015, Town & Country Resort and Convention Center, San Diego!