Soft Mechatronics and Wearable Systems

Metamaterials are artificially engineered structures that can exhibit unconventional properties not easily observed in nature. These unique architectures offer a robust platform for manipulating acoustic or elastic wave properties for energy localization and focusing, thus broadening their potential applications in energy harvesting and sensing. I will provide a comprehensive overview of the latest breakthroughs in the design of phononic crystals and acoustic metamaterials. These advancements promise a substantial enhancement in energy harvesting performance when these materials are integrated with piezoelectric components. In addition to wave-based metamaterials, I will summarize our recent advances in vibration energy harvesting, sensing, and energy absorption applications, facilitated by the exciting field of mechanical metamaterials. These materials feature meta-atoms that respond to external stimuli, collectively displaying extraordinary material properties like negative stiffness, Poisson's ratio, and multistability. Notably, these architectures are not constrained by dynamic wavelength dependence, offering broader design opportunities across multiple scales.

Fabric-based exosuits, for VR body haptics or to generate muscular assistance, require compliant, efficient, fast, lightweight yet high-force actuators. Much prior work has focused on pneumatic principles, an effective solution, but that needs an external pump or compressor. I will present several electrically-driven fiber-format flexible actuators developed in my lab. Making actuators shaped like fibers is key to their integration in active textiles. Our devices operate on electrostatic principles, which offers high energy density and high efficiency. I report fiber-format pumps, 2 mm in diameter and several meters in length, that generate fluid flow with no moving parts, and can be woven into fabrics, allowing both thermal management and shape change. I also report fiber-shaped electrostatic sliding stepper motors, 4 mm in diameter, that serve as long thin muscles to power gloves for VR and back-support exoskeletons. I will discuss open challenges and opportunities in making active wearables.

The current healthcare systems based on disease management are suffering from limited, delayed, and inefficient medical services, especially when confronted with the pandemic and the aging population. Health care should move from its current reactive and disease-centric system to a personalized, predictive, preventative, and participatory model with a focus on disease prevention and health promotion. Textiles have been concomitant and played a vital role in the long history of human civilization. Equipping traditional textiles with diagnostic, therapeutic, and power supply capabilities can unlock electronic textiles as a point-of-care system with incomparable wearing comfort. In this talk, I will introduce our research progress in smart textiles for biomonitoring, therapeutics, power supply, and textiles body area network for personalized health care. I will showcase the platform technologies, fabrication strategies, and clinical translation of the smart textiles.

Optogenetics is a powerful tool for unraveling neural circuitry and modulating neurophysiological processes with remarkable spatiotemporal precision. However, the transformative potential of optogenetics is hindered by the use of tethered, rigid optical fibers used for photostimulation, causing tissue damage and behavior constraints. To address these challenges, we have developed the wireless Optogenetic Deep Brain Stimulator (ODBS), enabling highly precise and reliable tether-free neuromodulation within the body. The ODBS features an innovative design incorporating stretchable interconnects, soft encapsulation, and wireless charging and control capabilities, offering a robust neurohilic interface for seamless chronic implantation and operation. The ODBS represents a significant step forward in unlocking the full potential of optogenetics. This presentation will provide an overview of our recent development of the ODBS, highlighting its potential for revolutionizing neuroscience research and therapeutic applications.

Thrombotic complications represent a challenge in small artery diseases and vascular devices. A novel in-situ piezoelectric material-based surface treatment system utilizes arterial pulsation to reduce the platelet aggregation. Negative surface charges substantially reduced the platelet aggregation to less than 2% of the surface area studied. The innovative design of piezoelectric unit was designed via numerical and computational analyses.

Recent developments in materials engineering and device architectures form the foundations for rapidly emerging classes of sensors and energy devices with mechanical characteristics that allow for conformal interfaces with the soft, curvilinear surfaces of the human body. Despite these advances, major challenges in these fields exist: wearable chemical sensors typically require complex, battery-powered electronics while the vast majority of demonstrated tissue-mounted energy storage and energy harvesting systems rely on toxic components that substantially diminish their attractiveness in bio-related applications. In this presentation I will discuss non-traditional approaches to address some of these grand challenges. I will demonstrate how seamless integration of advances in electrochemistry, soft materials, fluid mechanics, wireless electronics, and design engineering are crucial for realizing such advanced systems. Examples will include wearable sweat sensors, wound monitors, wearable and implantable biodegradable batteries.

This seminar introduces two recent progresses of self-powered flexible devices; piezo-sensors and microLED. The first part will introduce flexible inorganic piezoelectric membrane that can detect the minute vibration of membrane for self-powered acoustic sensor and blood pressure monitor. Speaker recognition has received spotlight as personalized voice-controlled interface, smart home, biometric authentication. The conventional speaker recognition was realized by a condenser type microphone, which detects sound by measuring the capacitance value between two conducting layers. The condenser type microphone, however, has critical demerits such as low sensitivity, high power consumption, low recognition rate and an unstable circuit due to the large gain amplification. Herein, we reported a machine learning-based acoustic sensor by mimicking the basilar membrane of human cochlear. Highly sensitive self-powered flexible piezoelectric acoustic sensor with a multi-resonant frequency band was employed for voice recognition. Convolutional Neural Network (CNN) were utilized for speaker recognition, resulted in a 97.5% speaker recognition rate with the 75% reduction of error rate.

In this presentation, we discuss point-of-use applications for motor skills characterization. There is no objective metric for evaluating motor skill training progress, and current assessments rely on qualitative surveys. We have fabricated an instrumented glove with pressure and motion sensors for motor characterization. This glove is useful for characterizing motor skills of people suffering from hypertonicity, a neuromuscular disorder that causes muscle stiffness/resistance and jerky movement. Analyses of force versus velocity show movement-dependent muscle resistance in a patient with hypertonicity. Through the flexible sensor systems, the shift from subjective scores to objective measurement will promote better diagnosis and dramatically improve the accuracy in tracking patient response to therapy.

The isolation of graphene in 2004 also unveiled a diverse range of graphene-like 2D materials with exceptional mechanical, thermal, and electrical properties. 2D material-based textiles have shown promise for next-generation wearable electronic textiles (e-textiles) and sustainable composite applications due to their excellent mechanical, electrical, and other performance properties. However, the realization of robust and reliable smart textiles at a mass scale remains hugely challenging due to limitations in material performance and sustainability, complex and time-consuming fabrications, poor comfortability, and durability. We have developed a highly scalable and cost-effective way of manufacturing 2D material-based textiles at commercial production rates of ∼150 m/min for fabrics and (∼1000 kg/h) for textile yarns. The graphene textiles thus produced are washable, flexible, and bendable. We then demonstrate the potential uses of such textiles for multifunctional and high-performance wearable electronics and sustainable composites applications, which will be covered in this talk.

We have examined the feasibility of our skin-wearable conformal PPG devices for measuring cardiovascular changes via pulse rate variability (PRV) and hemodynamic variable on different body sites during normal activities and under lower body negative pressures (LBNPs). For localized monitoring of PPG signals, the conformal PPG device is designed to be soft, lightweight, and mechanically complaint such that it can minimize PPG signal degradation due to motion artifacts and offer the high quality of PPG signals. Multi-site PRVs and extracted hemodynamic variables show promise for systematical assessment of cardiovascular risks and understanding localized hemodynamic changes.

Heat detection and localization are vastly being used in navigation systems, autonomous systems in industry, medical and research. To provide a more efficient detection and localization system, feedback capability is significant. Towards that goal, simultaneous multi-mode Dielectric Elastomer Actuator (DEA) technology can be used together with MEMS technology to develop an interactive sensory system with auditory and haptic feedback. This study introduces IR sensor to detect heat in indoor environment, localizes target and calculates an approximate distance of the target from the source based on surface temperature. A YOLOV8 model is used with a custom dataset for objects and human detection based on generated thermal images. The integrated DEA control can adjust feedback autonomously based on the sensor field of view in real-time. The study shows an overall accuracy above 90% in continuous based distance estimation and an accuracy above 95% for detection and classification of heated objects while navigating.

My current research focuses on flexible and stretchable biocompatible electronics in the forms of wearable and implantable platforms. Conventional rigid systems have limitations in forming tissue interfaces due to a Young’s modulus mismatch, resulting in poor device capabilities and noise. To overcome these limitations, we have been developing flexible and stretchable electronics with a low modulus to establish intimate contact with the skin, enabling the acquisition of high-quality signals and tissue actuation. Among the various soft bio-integrated electronics that we are developing, in this talk, I will primarily introduce recent advances on soft neural interfaces for unconventional brain-machine interfaces. Specifically, I will discuss our efforts on (1) 3D neural interfaces, (2) mri compatible neural interfaces, (3) space unrestricted optogenetics, and (4) bioresorbable hybrid neural interfaces for diverse applications, including the diagnosis and treatment of disorders, paving the way for the next generation of neuroscience and medical science.

Although many people suffer from sleep disorders, most are undiagnosed, leading to impairments in health. However, the existing polysomnography method is not easily accessible, costly, and burdensome to patients, requiring specialized facilities and personnel. Here we report at-home portable wireless sleep sensors and wearable electronics with embedded machine learning and their applications in assessing sleep quality and detecting sleep apnea with multiple patients. Unlike the conventional system using numerous bulky sensors, the soft all-integrated wearable platform offers natural sleep at places users prefer. In a clinical study, the face-mounted patches that detect brain, eye, and muscle signals show comparable performance with polysomnography. When comparing healthy controls to sleep apnea patients, the wearable system can detect obstructive sleep apnea with an accuracy of 88.5%. Furthermore, deep learning offers automated sleep scoring, demonstrating portability and point-of-care usability. At-home wearable electronics could ensure a promising future supporting portable sleep monitoring and home healthcare.

This paper describes the development of various sensor solutions and energy harvesting concepts based on polypropylene ferroelectret. The use of this transducer material enables the design of particularly flexible sensor and energy harvesting solutions with an outstanding potential for the implementation of highly integrated self-powering intelligent data acquisition systems in body-worn textiles. The aim is to achieve a long-term monitoring of human physiological vital parameters, early recognition of diseases or recording mechanical stresses caused for example by vibrations that affect the health of the wearer. In addition to applications for monitoring people, some examples for the transfer of this smart textile technology to the monitoring of technical systems will be shown.

The rise in significance of wearable actuators can be attributed to their capability to offer real-time tactile feedback, multi-functionality, and above all, optimal comfort to users. While various actuator types like motor-driven tendons, pneumatics, and electromagnetics have been utilized in wearable applications, they often entail the addition of a cumbersome rigid system to the wearer, potentially leading to discomfort. Shape memory alloys (SMAs), which alter their physical form and rigidity based on temperature variance, present a viable option for wearable actuators, particularly when processed into fabric form using SMA wires. In this study, we developed an SMA-based fabric type actuator by intricately knotting SMA wires and subsequently expanding them into 2D textile form. Further, the auxetic meta-design is introduced, enhancing its adaptability to the 3D contours of human body. This auxetic-architectured SMA fabric was effectively employed as a wearable haptic device, conveying spatiotemporal feedbacks to users.

Optical fibers are one example of waveguides that can transmit multi-modal information. This information can be encoded in different optical modes in a multi-mode fiber or in different types of modes. For example, optical fibers have also recently been demonstrated to be excellent waveguide for acoustic modes. This means that sensing does not have to be performed at the location that the optical fiber is bonded to the structure, but instead Lamb waves can be converted into propagating acoustic modes in optical fibers. These modes can be transmitted to different sensor locations within the optical fiber. This presentation discusses the physical characteristics of these optical fiber acoustic modes and their use to increase the signal to noise ratio of the collection of Lamb wave information. Experimental verifications of the physical behavior of these modes using micro-laser Doppler vibrometry is also presented.

Metal additive manufacturing (AM) has experienced an explosive growth in interest within the aerospace and space sectors, but the adoption in real application has lagged interest. Process qualification (or lack thereof) is the primary reason and to date in situ sensing has failed to make a substantial impact, despite obvious utility. The primary premise of this talk is that current sensing techniques used in industry lag significantly behind what is possible and already implemented in other industries, and proper focus and division of labor between academia and industry can remedy the situation. Through this discourse we will assess whether or not current sensors used in AM are sufficient, what roadblocks may exist for academia to assist in developing solutions for industry, and how the in situ sensing community should focus their efforts for maximum impact.

Wearable sweat biosensors have the potential to provide non-invasive molecular analysis toward predictive analytics and treatment. In this talk, I will introduce our efforts in developing wearable biosensors for non-invasive molecular analysis. Such wearables can autonomously access body fluids (e.g., human sweat) across the activities and continuously measure a broad spectrum of analytes including metabolites, nutrients, hormones, and proteins. Laser engraving and inkjet printing are used to manufacture high-performance nanobiosensors at large scale and low cost. The clinical value of our wearable systems is evaluated through various human trials toward precision nutrition, stress/mental health assessment, and chronic disease management.

Wearable sweat sensors have the potential to provide valuable information related to the health and disease states of individuals. Existing sweat sensors mainly rely on biomacromolecules, such as enzymes and antibodies, as biorecognition elements to achieve specific quantification of metabolites and hormones. However, these biomacromolecules tend to degrade over time, limiting the sensors’ shelf life and compromising the sensor performance upon environmental changes, such as varying temperature and humidity. Here, we introduce a wearable plasmonic paper-based microfluidic system to continuously and simultaneously quantify sweat loss, sweat rate, and biochemicals in sweat. Plasmonic sensors based on surface-enhanced Raman spectroscopy (SERS) are label-free and can identify the analytes of interest via the chemical “fingerprint” information. We show that simple and low-cost plasmonic papers allow for detecting and quantifying biochemicals in sweat. The well-defined flow kinetics of paper microfluidic devices enable accurate quantification of sweat loss and sweat rate in real time.

Athletes frequently face risks like dehydration, fatigue, and heart issues due to high-intensity performances. Although there have been advancements in sports science training, a wearable system that can monitor multiple health parameters is crucial to prevent these conditions. Existing devices, often bulky and limited to single-parameter monitoring like heart rate, sweat, or skin hydration, focus mainly on performance. We present a multi-sensor wearable system incorporating a microfabricated, ultra-thin, flexible sensor. This system, consisting of mouthguards and chest patches, continuously monitors saliva osmolality, skin temperature, and cardiac function. It offers an athlete's hydration level and physiological stress in intense perspiration and heat conditions. The system's effectiveness in tracking physiological changes was proven in field tests, capturing significant increases in dehydration and physical strain during hour-long training sessions. This demonstration showcases the system's ability to detect rapid physiological changes, offering crucial data for mitigating athletic risks and aiding clinical decisions, ultimately improving medical care in sports.

Changes in biophysical movements are among the earliest vital signals for worsening health and are the most predictive of a concerning clinical outcome for patients. Among the different biophysical parameters to detect, changes in respiration and breathing rate are particularly relevant, as variations at rest almost always indicate some form of worsening pathology. Despite the fact that breathing rate is a relatively simple phenomenon, its detection can be tedious and often requires a long monitoring period in highly specialized laboratories or is often left to the health practitioner for manual recordings. In this poster presentation, we present the design and development of a wearable and flexible breathing sensor with remote connectivity that can immediately detect changes in breathing patterns in real-time with high accuracy and precision.

Compliant vibrating soft actuators made with dielectric elastomer actuators are successfully assembled with mechanical energy harvesters, which operate a few hundred volts. The TENG-DEA module as a sensor-actuator fusion is applicable to wearable haptic systems, which are self-powering as well as sensing mechanical touches. The modules provide a solution for compliant and lightweight energy-generating, sensing and actuation functions to wearable haptic systems.

There are two basic types of dispersal mechanisms in natural seeds: (1) Parachute-like seeds, such as dandelions, employ parachute-like structures equipped with fine, filamentous appendages that create air resistance; and (2) Maple seeds can autorotate in the air, utilizing mechanisms reminiscent of helicopters to generate lift, thus prolonging their airborne time. Our research demonstrates the feasibility of engineering passive flying soft robots through the combination of smart materials (liquid crystalline elastomers) with tailored aerodynamic designs. We have created two wind-assisted fliers, parachute-like flier and spinning one, inspired by dandelion seed and maple rotary seed, respectively. We report the fine-tune of the soft fliers’ structure by change of external stimuli, i.e., light and humidity, light control of the take-off and landing. We also demonstrate possibility to integrate onboard materials sensors for remote sensing (optical reflection, humidity, pH, etc).

Shape-morphing magnetic materials that can implement various 3D structures have great potential in the fields of 3D electronics and soft robotics. Despite the recent advancements, existing magnetoactive shape-programmable materials lack abilities to reprogram multiple configurations within a single system and to maintain the morphed state securely without external magnetic stimuli. Here, we report a magnetic shape-morphing platform(mSMP) that can realize complex 3D geometries through the combination of thermal and magnetic stimuli under an intricate preprogrammed magnetization profile. This composite consists of low melting point alloy(LMPA) droplets with magnetic particles within a polymer matrix. Owing to stiffness modulation by phase transition of LMPA, mSMP firmly retains its deformed shapes with cooling to provide the reliability of device operation. Furthermore, it enables rapid reversible shape transformations and possesses reprogrammable magnetization capabilities, allowing multi-morphological reconfiguration. This innovative mSMP is expected to bring out a novel 3D magnetic structural programming strategy, contributing to the development of 3D electronics and soft robots.

Bio-inspired electro-ionic artificial muscles are considered suitable for biomimetic soft robotic applications. However, their slow response time, low blocking force, and limited durability have prevented their application in soft robotics. Here, we report soft electro-ionic artificial muscles based on 3D dendritic nickel cobalt sulfide nanorods grown on graphene electrodes. Importantly, both the phase transition from nickel-cobalt oxide to nickel-cobalt sulfide and the use of a graphene template influence the tuning of the electrical and electrochemical properties of the composite electrodes. The ionic artificial muscles with the electrodes exhibit significantly improved bending displacement and durable response to both AC and DC input signals without phase delay or distortion. These significant enhancements in the performance of artificial muscles have allowed us to demonstrate bioinspired soft locomotive robots. Therefore, these artificial muscles have the potential to expand the soft electronics industry in next-generation human-machine interfaces

In this paper, a novel soft origami tripod structure that is scalable and controllable using electrohydraulic actuators is proposed. The parallel designed structure consists of three origami legs connecting the top and bottom plates. The tripod is activated with self-unfolding legs when electrohydraulic actuators are swelled by applied voltage. Each leg has the classic origami pattern waterbomb, which serves as a spherical joint. When the actuator is activated, the legs are stretched, lifting the top plate of the soft tripod in various directions. That is, the tripod has multimodal shape morphing, including linear and tilting motions with only three electrohydraulic actuators.

This research delves into an innovative approach to layer jamming, where the jamming structure serves a dual purpose: jamming and pressure sensing. The tunable stiffness technique empowers soft grippers to manage both their grip strength and rigidity. To bolster stiffness control, a piezoresistive sensor is integrated, monitoring changes in resistance during gripping operations. This is achieved by stacking multiple thin layers of MWCNT-polyurethane acrylate material within an elastomer envelope, forming the gripper's jamming structure and pressure sensor. The sensor fabrication combines Direct Ink Writing and Digital Light Projection printing methods, while the gripper itself is crafted from Polydimethylsiloxane and Ecoflex. Utilizing resistance value shifts from the sensor, we optimize gripping performance. Experimental validations confirm the efficacy of the sensing and layer jamming approaches. Precise gripper stiffness control is achieved through data gleaned from the sensor's force measurements. Furthermore, this study illuminates potential applications in healthcare and the wearable technology industry.

In this study, we present an innovative approach to significantly enhance the performance of cellulose-based actuators particularly thermo-hygroscopic ones, known for their ability to change shape based on water absorption and heat. Cellulose paper, with its high hygroscopic expansion coefficient and low thermal expansion coefficient, is an ideal candidate for thermo-hygroscopic actuators. Our study suggests enhancing thermo-hygroscopic properties of cellulose paper by incorporating hydrophobic nanostructures through a scalable hydrothermal process. This approach significantly increases surface area, water absorption capacity, and light absorption efficiency. Consequently, it leads to improved hygroscopic volume changes and enhanced actuation performance. Leveraging these properties, the hybrid cellulose-vanadium oxide nanowire (VONW) paper increases actuation deformation by nearly 70% and triples actuation speed during cooling—a critical challenge in thermo-hygroscopic actuators. Moreover, the cellulose-VONW actuator exhibits an impressive increase, up to 200%, in force generation under light stimulation, surpassing conventional paper actuators.

Functional carbon materials are the key to a clean, safe, and sustainable working environment and advanced energy-related devices because they can be reused, recycled, and repurposed. However, effort is necessary to make them ideal candidates for such applications. In this study, we introduce a novel approach by designing covalent-organic frameworks (COFs) and metal-organic frameworks (MOFs) with contrasting electrical and electrochemical properties, aiming to achieve highly desirable electrochemical soft actuators. A careful structural investigation is carried out to determine the structure–property relationship, while the fascinating properties of them are validated by real-field demonstrations. The proposed functional carbon materials exhibit exceptional actuation properties, thereby representing a significant advancement for complex robotic interactions.

We have demonstrated a diaphragm-type valve can amplify electrostatic actuation and attenuate pressure applied onto the diaphragm, which is sandwiched by a pair of electrodes. When a voltage is applied, the electrostatic attraction induces a zipping motion of the diaphragm. The actuation of the valve can seal an air chamber and maintain its internal pressure at a high level, which drives an elastomer membrane to form a bump. If the voltage falls below a certain threshold, air bypasses the diaphragm to the atmosphere and causes a sharp drop of the inter pressure. By manipulating pressure, the valve can control the movement of the membrane and the stimulation to the skin. Structures are 3D printed, coated with electrodes, and integrated to realize actuators with 1 cm3 in volume. The fabricated membrane of 3 mm in diameter and 0.1 mm in thickness forms a bump of 0.5 mm in height under a pressure of 10 kPa, which requires a voltage of >472 V to maintain. While the voltage is lower than 472 V, the pressure drops and the membrane moves down. Once a voltage of >814 V is applied, it seals the chamber and forms the bump again. Therefore, haptic actuation can be generated as desired.

Researchers are developing a master glove with haptic feedback to control robot hands for precise object manipulation. This technology ensures the robot applies the right amount of force when grasping objects, preventing damage or insufficient grip. A 3D-printed robot hand with DYNAMIXEL motors was used, and reinforcement learning determined the optimal grip force through grasping experiments with haptic feedback. The results demonstrate the successful and stable grasping of various objects, especially soft ones, by the robot hand using this method.

Graphene nanoplatelets (GNP) films possess superior electrical and thermal properties, making them suitable for modern electronic devices. However, the GNP film preparation via green manufacturing, oxidation, and exfoliation methods is costly and shows poor mechanical strength. In this work, the GNP-based flexible films are directly 3D printed via direct ink writing technique. Different concentrations (10, 20, 30, and 40wt%) of GNP are exfoliated in the NC suspension (8.15 wt%) followed by direct ink writing technique. The 3D printed films are dried in cleanroom conditions (relative humidity: 45% and temperature: 25oC). Tensile properties and electrical conductivity of the 3D printed GNP-NC films are investigated. A simple, economical, scalable, and effective approach to printing flexible conductive materials with outstanding mechanical properties will open a new horizon for flexible electronics.

Electronic devices for monitoring and controlling falls are currently classified into three categories: manual, automatic or intelligent. Manual devices are those characterized by being activated by mechanical activation, arising from the physical action of the user, in the face of a possible fall or emergency risk situation, and they cannot be activated with the use of the hands by individuals with reduced motor capacity, people with cognitive restrictions or bedridden individuals due to a serious immobilizing illness. Automatic devices are presented as an evolution, when compared to manual ones, since they allow the use of sensors to monitor the individual and are independent of the user's condition, or his will to carry out the monitoring. On the other hand, intelligent electronic devices, object of study of this research that was developed in a hospital environment, in addition to having all the previous advantages of the automatic device, can recognize the individual's behavior through artificial intelligence, indicating the time spent per position, trend of movements and imminence of risk conditions and/or subject to pressure sores while bedridden.

Existing wireless neural implants are limited by their predefined modalities and functionalities, necessitating extensive time and resources for modifications to cater to diverse neuroscience needs. In response, we introduce miniaturized modular wireless neural devices with one-touch magnetic replacement of neural interface modalities and functionalities. Comprising two integral components – an implantable neural probe with a magnetic female adapter and a replaceable wireless functional control module with a magnetic male adapter – these devices offer high versatility. The neural probes can integrate diverse modalities such as optical stimulation, electrical stimulation, and drug delivery. The wireless modules can be effortlessly assembled and disassembled from the implanted neural probe in freely behaving animals, enabling facile replacement of functional modalities and/or recharging of batteries/drugs. This innovation empowers neuroscientists to seamlessly configure customized neural devices with diverse functionalities, eliminating the need for additional time or expense for new developments.

Biomechanical energy harvesters are gaining growing interest with the advancement of technology and their great potential to power smart wearable systems. Smart wearable electronics is one of the most suitable energy harvesting applications because wearable sensor applications for health monitoring require minimal energy consumption, as many research articles on health monitoring sensors highlight ultra-low power, seamless, compact, and skin-conformable health monitoring sensors. Herein, this study suggests a simple biomechanical energy harvesting device to adopt a mechanical regulator to convert a mechanical motion input into a continuous rotary motion. By using a hybrid rotary energy harvester consisting of both an electromagnetic generator and a triboelectric nanogenerator, a balloon-type energy harvesting device enables the rotary mechanical motion conversion which could be efficiently harnessed. The electrical characterization and parametric analysis to influence the output performance of the hybrid energy harvester were systematically conducted. The energy harvesting device can pave the way for the application for the smart wearable systems.

In this work, an equivalent unit cell model is designed to predict the behavior of loop-linked actuator sheets. Linear constitutive equations were used to observe the actuation of highly nonlinear shape memory alloys material, used for soft actuators. The deformation in the form of strain is studied while applying the electric field and incorporating the material properties using a user-defined material subroutine (UMAT). The model accurately replicates the deformation of basic loop patterns, validating its potency for SMA-textile-based actuator design.

Traditional force sensors are costly, and require constant power, limiting their applications. To overcome these challenges, some researches introduced triboelectric nanogenerator (TENG). However the surface charge of the contacting surface can heavily affect the data of TENG force sensors. In this work the pantograph-structured triboelectric nanogenerator (PS-TENG) is proposed. The PS-TENG converts vertical motion to horizontal motion, reducing tribocharge effects. Lubricant oil enhances mechanical durability and electrical output by minimizing friction and filling air gaps between triboelectric surfaces. The PS-TENG developed in this study demonstrates a strategy for TENG based force sensors to enhance its output and durability.

Carbon nanotube (CNT) yarns exhibit significant potential in yarn actuators and energy storage devices. The nano-bundles and micro gap channels macroscopically absorb the mechanical stress and microscopically provide electrochemical reacting surface area. However, their chemical inertness remains a major challenge. We propose an effective CNT yarn functionalizing method, electrochemical oxidation. Applying an electrical potential to CNT yarns immersed in an electrolyte facilitates the holistic and homogeneous oxidation of the entire yarn. As a result, the yarn achieves torsional stroke of about 960 turns/m and areal capacitance of 73 mF/cm2.

Triboelectric nanogenerators (TENGs) are a promising technology for harvest sound input. However, increasing the total electrical output of sound TENGs a challenge. We propose a capacitor-based sound triboelectric generator (CS-TENG) to enhance the electrical output of TENGs by accumulating more charges using a capacitor structure on its electrodes. In addition, CS-TENG shows high mechanical durability by avoiding contact between the vibrating diaphragm and the electrode. This negative charge then induces a positive charge on the aluminum electrode through electrostatic induction. The CS-TENG produces a peak open-circuit voltage of 14.24 V and a peak closed-circuit current of 0.87 μA when it is subjected to a sound pressure of 90 dB at 200 Hz. This shows that the CS-TENG is capable of generating a significant amount of electrical energy from sound. Furthermore, CS-TENG can monitor, analyze, and classify various sounds to improving pedestrian safety as a real-time detection sensor from hazardous situations.

Introduced in 1970s, Spinal Cord Stimulator (SCS) devices have played a crucial role in managing a wide range of chronic pains. Currently, two primary types of leads, namely cylindrical and paddle leads, are widely used for pain management. While both types effectively alleviate pain, cylindrical leads, due to their small size, are susceptible to movement and migration, leading to device displacement. On the other hand, paddle leads offer a larger surface area and secure placement but require a relatively large incision for device placement. To address these limitations of existing SCS devices, a new SCS device has been developed that contains a low-profile, deployable, and retrievable design. A prototype SCS has been successfully designed, fabricated, and tested in vitro. This innovative device features a laser-trimmed mesh nitinol structure serving as the deployable backbone, an ultrathin ePTFE membrane isolating the conductive backbone from the electrodes, and platinum strips for the electrodes. Stainless-steel wires have been utilized to seamlessly integrate an external battery pack with the electrodes for efficient electrical potential delivery.

Electro-ionic soft actuators have the advantages of being possible to drive at low voltage and to operate in the air by using ionic liquid. However, they have a disadvantage of slow response. This paper proposes to accelerate electro-ionic soft actuators by feedforward control. Feedforward control can automatically generate online pulse-shaped input signals from any reference signals and is easy to implement. The experimental results show that the feedforward control can automatically generate control inputs for any references and achieve 2 times faster than the no-control case. In addition, it was found that the control performance was significantly degraded when a voltage limit was set to protect the actuator.

Recent developments in force assistance wearable robot technology have opened up innovative applications in muscle strengthening, rehabilitation, and elderly lifestyle support. This trend is driven by the fusion of wearable robot advancements and machine learning algorithms. Research on IMU sensor-based user movement and posture analysis is on the rise, enhancing behavior and posture understanding for wearable robot performance improvement. These robots, designed to support and strengthen user muscles when needed, are primarily attached to the body. This study focuses on real-time extraction of posture information, including walking intention and various movements, using machine learning and deep learning applied to IMU data. Experimental results confirm the potential for more accurate user behavior and posture recognition, promising enhanced wearable robot functionality.

Electronic skin is a flexible wearable device that is usually used in fields such as motion recognition and health monitoring. the strain sensor is one of the important components of electronic skin and is used to monitor the motion status of human joints. In this study, we constructed an electrochemical system with two counter-arranged coiled carbon nanotube yarns and encapsulated them in silicone rubber to develop a multidirectional strain sensor. It can simultaneously sense the magnitude and direction of strain applied to the sensor without the need for an external power supply. Therefore, it can be used for electronic skin to identify the joint movement direction and degree of the wrist for a long time, and is expected to be applied in the fields of sports science and medicine.

In this research, fiber-type reprogrammalbe poly(n-isopropylacrylamide)/polycaprolactone composited actuator is showed. Being composited poly(n-isopropylacrylamide) with polycaprolactone gave shape memory properties to the hydrogel. Shape memory properties made the hydrogel actuator actuate which did not depend on its own structure ahd shape. Therefore, this poly(n-isopropylacrylamide)/polycaprolactone composite actuator showed deformation of reversible torsional, tensile, and bending actuation in the same structure. Moreover, the programmed actuation could be erased and other type of actuation could be reprogrammed.

Implantable energy harvesters hybridize to improve performance in the in vivo environment. Despite the increase in performance of the hybrid harvesters, the increasing volume and weight of the harvesters is a challenge. Because the environment inside the body is narrow and harsh, technology is needed to increase performance while reducing the weight and volume of the harvesters. Herein, we demonstrated a hybrid electrochemical energy harvester that can obtain biochemical energy and mechanical energy in a single electrochemical cell. This hybrid energy harvester generated high performance to weight ratio in biofluid. This hybrid energy harvester generated high performance to weight ratio in biofluid based on sum of energy from redox reaction with glucose and energy from stratching. In addition, this hybrid electrochemical energy harvester with fiber type can achieve improved performance in a small size and lightweight, so it has the potential to be a power source for implantable device.

Outdoor workers, such as construction workers, are exposed to the risk of heat-related illnesses (HRIs) due to prolonged heat stress and heavy labor. Heat-related illnesses include heat stroke, heat exhaustion, heavy dehydration, and the like, which can lead to highly dangerous accidents on work sites. Thus, the prevention of HRIs is crucial. To address this, we developed wireless biopatches that can measure various physiological signals in real time, ensuring the worker's convenience. The biopatch directly monitors electrocardiogram (ECG), 3-axis acceleration, skin impedance, photoplethysmography (PPG), and skin temperature. It is designed as a rigid-flex system to ensure mechanical reliability and maintain conformal contact with the skin. The biopatch does not impede the workers' tasks with its small form factor. The developed biopatch was attached to the subject’s chest, allowing continuous physiological signal collection in real-time over a full working period, displayed on a mobile phone via Bluetooth. These physiological signals can serve as biomarkers for diagnosing HRIs. With this approach, the biopatch shows a high potential for preventing HRIs in outdoor workers.

The development of micro-batteries is very important for the progression of micro-mechatronics and wearable devices. These miniature power sources, known for their compact design and efficient energy storage, play an essential role in extending the operating life and improving the portability of wearable technologies. Researchers are actively exploring innovative materials, electrode designs, and manufacturing techniques to maximize energy density while minimizing size. These micro-battery advancements are vital in integrating micromechatronics and wearable devices into costomer needs, contributing to the evolution of compact and efficient electronic systems. To facilitate the production of all-solid-state micro-batteries, National Nanofab Center(NNFC) have developed specialized equipment and utilized this equipment to create high-stability all-solid-state batteries. These advancements enable technology to meet the ever-growing demand for smaller, more powerful, and long-lasting energy solutions.

Surface Acoustic Wave (SAW) sensors were employed for the Chemical Warfare Agents (CWAs) detection due to their notable advantages which includes high sensitivity, swift responsiveness, reversibility, ease of production, and compact size. In this study, a SAW sensor coated with Polyhedral Oligomeric Silsesquioxane 1,1,1,3,3,3-hexafluoro-2-propanol (POSS-HFIP) based sensing material was used to detect three CWAs which includes Tabun, Sarin, and Mustard gas along with their simulants. The results demonstrated a frequency shift of around 2.26 to 3.88 kHz for Tabun and Sarin at a concentration of 0.1 mg/m³, and Mustard gas at 1.0 mg/m³

Effective control of triboelectricity through the development of materials is vital for the safety of electronic devices and human well-being. However, a lack of foundational research on the triboelectricity mechanism has led to limited material development. Here, we verified the effect of deformation on triboelectric behavior to gain a comprehensive understanding of the triboelectrification phenomenon. Theoretical findings show that deformation led to a shift in the energy level related to electron-accepting properties, enhancing the tribonegative attributes of tribonegative materials. Conversely, the energy level contributing to the electron-donating properties was increased, causing a waning in the tribopositive property of the tribopositive materials. Furthermore, experimental results align with our theoretical findings, showing that increased deformation boosts the output of tribonegative materials and diminishes the output of tribopositive materials. Our insights pave the way for improved control of triboelectricity and rejuvenate the development of previously stagnant triboelectric materials.

The goal of the present work is to create a miniature 2D light scanning device without any moving parts using integrated electro-optic (EO) liquid crystal (LC) material. The design is based on changing the propagation direction of a light beam when it is incident to an electro-optic medium with a voltage-controlled index of refraction. To achieve 2D beam steering and scanning, the device is designed in two stages. For horizontal beam steering, a LC prism (thickness = 10 um) created between two glasses is used to deflect beam by refraction due to change in refractive index of LC. For vertical beam steering, a virtual prism is created between two glasses by offsetting top and bottom electrodes. When electric field is applied to the electrodes, LC directors create a virtual prism due to physical offset between top and bottom electrode help to achieve beam deflection in vertical direction.

In the field of soft robotics, flexible sensors offer real-time health and state awareness within wearable electronics. This research presents the design, fabrication, and calibration of a highly compliant artificial wearable sensor tailored for soft haptic robotics applications. The wearable sensor comprises a bio-inspired network consisting of distributed piezoelectric sensors encapsulated within a latex skin capable of detection of multi-axis strains and contact pressure. The bio-inspired architecture of the proposed sensor network amplifies the network's coverage area by tenfold from its manufactured footprint when subjected to stretching. An innovative auxetic polar expansion tool is developed to integrate the multi-axis sensor circuit into the latex skin. During the fabrication process, a 3D-printed silicone mold is employed to cure the dried latex skin with the embedded sensor network. The experimental results demonstrate the appropriateness of these sensors in strain and pressure sensing. The characteristic modulus of the skin prototype is approximately 10 kPa, and the sensor remains operational up to strains of approximately 230%.

The thermoelectric generator (TEG) is commonly used to harvest or scavenge the remnant energy from waste heat sources, such as automotive exhaust systems, cooling line of power plants, ocean temperature difference, human body, and industrial processes. The performance of TEG depends on the thermoelectric material and its structural configuration. To obtain the maximum power from TEG module, the optimal design of heat exchanger is required to realize the full potential of power generating system. The internal structure of heat exchanger plays a critical role to determine the efficiency of TEG by enhancing heat transfer between the hot and cold sides of the TEG module. We studied the effect of internal fin structure in heat exchanger with hot water feeding condition to obtain the best performance of TEG module array by using computational simulations and compared with the experimental results.

To improve the current SMP actuator, we propose a novel approach: fabricating a cost-effective sponge tubular carbon nanotube shape memory polymer (ST-CNT/SMP). Unlike conventional methods utilizing chemical vapor deposition (CVD), which compromises the advantageous sponge structure, our process introduces a simple scaffolding material and accelerates solidification. The presentation will cover background, fabrication details, and mechanical characterization of this innovative composite, with demonstrations showcasing multidirectional movement of the actuator.

Chronic stress induces structural changes in the brain and elevates cardiovascular risk. Assessing stress levels via galvanic skin response linked to eccrine sweat gland activity requires a steady skin-electrode interface, which may result in unintended disconnection and noise in the data. In this study, we have developed a non-invasive flexible optical sensor employing multiple wavelengths (460 nm, 660 nm, and 960 nm) photoplethysmography (PPG) data to classify stress events from emotional stimuli. By capitalizing on the differential water absorption of light in the visible and near-infrared spectrum, our sensor effectively correlates with sweat gland activity during stress events. We use a cold pressor test protocol to assess the sensor’s stress event classification performance. Using six reflected mode PPG datasets from the index finger of two participants, we trained support vector model (SVM) and random forest models (RFC). SVM accuracy reached 93%, 91%, and 97% when trained with only nir-to-blue, only red-to-blue, and both, while RFC accuracy was 93%, 91%, and 95%, respectively. Thus we classify stress through sweat absorption for seamless integration into wearable tracker.

The talk will begin with a brief introduction of structural health monitoring (SHM) which has been attracting intensive attention since early 1990s. An essential difference between sensor centric SHM and nondestructive evaluation (NDE) will be highlighted. Advances in smart sensors powered by energy harvesting via ambient vibrations will be exemplified by two practical case studies. Recent advances in computer vision based SHM techniques using optical non-contact sensors with machine learning to detect impact loading and barely visible impact damage (BVID) in composite panels will be discussed in details. Finally, the digital twin framework under digital transformation and artificial intelligence (AI) is gaining potential to pave the way for future aircraft health monitoring.

Electroactive polymers cover a broad spectrum of actuation properties. Conjugated polymers (CP) can be electrochemically doped and undoped at low voltages. Dielectric elastomers (DE) require high voltage to output large force and high strain. Side-chain crystallizable polymers (SCP) exhibit three orders of magnitude change in stiffness during the reversible melting and recrystallization of the side chains. SCP behave like the DE at the soft state, and can thus be explored for bistable actuation. SCP also exhibit other important properties resulted from the phase change. These material research and device exploration undertaken at our Soft Materials Research Lab will be presented.

Currently, many technology innovations have advanced piezoelectric materials and composites toward a broad range of biomedical applications. In this talk, I introduce our most recent development of piezoelectric materials and composites that are particularly designed for implantable nanogenerator applications. First, I present our wafer-scale approach to creating piezoelectric biomaterial thin films based on γ glycine crystals. The self-assembled sandwich film structure enabled both strong piezoelectricity and largely improved flexibility. Then, new ferroelectric composites are presented as a new material used in 3D printing for directly manufacturing of piezoelectric architectures with tunable piezoelectric and mechanical properties. Toward the end, development of implantable nanogenerator devices are introduced, including biocompatibility, degradability and packaging. This type of devices enables new capability of in vivo charging and electrostimulations, which revolutionaries the design and implementation of many biomedical therapeutics.

Tribomaterials are important not only for improving the output performance of energy harvesting devices but also for extending their applications. In general, the static surface charges are created by the contact electrification, in which the driving force is possibly related to the difference of the surface chemical potential. However, as limited by the surface potential difference, the charge density generally cannot reach an ultimate high level to approach, commonly ~ tens of uC/m2. Here, we present facile strategies to maximize the charge density via sophisticated materials design as well as the potential applications such as filters for polluted air, microbial disinfection, and energy harvesting devices.

In the field of energy harvesting and sensing technologies, triboelectric nanogenerators (TENGs) have emerged as a promising platform for self-powered sensors. However, user convenience is often overlooked during the material and design selection process. User-friendliness relies not only on material flexibility but also on the sensitivity of the force-to-signal relationship in TENG applications. This study aims to address this gap by tailoring material properties to enhance user experience specifically. We investigated the electrical and mechanical properties of various filler materials, utilizing styrene-ethylene-butylene-styrene (SEBS) as a stretchable polymer base. The resulting self-standing membranes were evaluated for comfort, durability, and adaptability, while maintaining functional effectiveness under low external force. These findings lay the groundwork for designing user-centric, self-powered sensing systems based on TENGs.

Bioresorbable bioelectronics, with their natural degradation properties, hold significant potential to eliminate the need for surgical removal. Despite notable achievements, two major challenges hinder their practical application in medical settings. Firstly, they necessitate sustainable energy solutions with biodegradable components via biosafe powering mechanisms. More importantly, reliability in their function is undermined by unpredictable device lifetimes due to the complex polymer degradation kinetics. Here, we propose an on-demand bioresorbable neurostimulator to address these issues, thus allowing for clinical operations to be manipulated using biosafe ultrasound sources. Our ultrasound-mediated transient mechanism enables i) electrical stimulation through transcutaneous ultrasound-driven triboelectricity and ii) rapid device elimination using high-intensity ultrasound without adverse health effects. Furthermore, we perform neurophysiological analyses to show that our neurostimulator provides therapeutic benefits for both compression peripheral nerve injury and hereditary peripheral neuropathy.

Electrospun polymeric piezoelectric fibers have considerable potential for shape-adaptive mechanical energy harvesting and self-powered sensing in biomedical, wearable, and industrial applications. However, their unsatisfactory piezoelectric performance remains an issue to be overcome. While strategies for increasing the crystallinity of electroactive β phases have thus far been the central focus in realizing enhanced piezoelectric performance, controlling the fiber surface morphology and yarn structuring can also be promising alternatives. Here, we summarize a collection of advances that push the boundaries to achieve a drastic enhancement of self-powered sensing and multifunctional biomedical wound healing performance by tailoring both material and structural properties of electrospun piezoelectric polymer fibers and yarns at multi-scales.

In the recent years triboelectric energy harvesting has gained a lot of research attention, and numerous triboelectric harvester designs have been proposed. We introduce a novel triboelectric energy harvesting architecture, where animal hair is used as the active material with a high positive charge affinity. To induce the triboelectric effect, animal hair is then brought into contact with polytetrafluoroethylene which in turn has a high negative charge affinity. In our approach, the electrodes are built as an array of individual charge collecting pins, which protrude into and interweave with the animal hair and skin and act as the net charge collector. The generators are built with two different approaches: a) by using 3D-printed structures with miniature electrode arrays and b) by using conductive fabrics arranged in a specific laminated structure. These are then tested in the laboratory in interaction with different animal hair materials with a novel methodology based on using a robotic manipulator test bed.

Electrical stimulation has emerged as a therapeutic approach for accelerating the healing of wound. Piezoelectric materials, characterized by their ability to generate electrical potential differences when applied to mechanical stress, have shown great potential in this regard. Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), an important engineering piezoelectric polymer, exhibits biocompatibility, high piezoelectric properties, and chemical stability. Electrospinning is a promising way for fabricating P(VDF-TrFE) fibers with enhanced electroactive β-phase contents of P(VDF-TrFE) through in-situ poling effects and mechanical stretching.In this work, we tailor P(VDF-TrFE) fiber porous structures to mimic the structure of extracellular matrix (ECM) and furthermore, enhance electrical stimulation for accelerating wound healing. Moreover, the wound healing process is often hindered by bacterial infections. To address this concern, our strategy is to incorporate antibacterial zinc oxide (ZnO) nanoparticles into PVDF-TrFE electrospun fibers. We conduct in vitro wound healing assays and evaluate the antibacterial properties of our multifunctional piezoelectric fibers..

Our study emphasizes tailoring ceramic suspensions for optimizing the 3D printability of Digital Light Processing (DLP) 3D printing. Barium titanate (BTO) has emerged as an eco-friendly piezoelectric ceramic alternative to lead titanates. Utilizing DLP, an advanced 3D printing method, we can fabricate complex 3D-printed ceramic architectures. In contrast to pure resin suspension, one of the most significant issues in ceramic DLP printing is the poor layer-by-layer adhesion owing to reduced photocuring. In this work, we control BTO ceramic particle sizes and additives for optimal ceramic suspension, leading to improved rheological properties, increased packing density, and reduced light scattering. Furthermore, the final ceramics exhibit enhanced dielectric and ferroelectric properties after heat-treating the 3D-printed green bodies using specifically designed profiles for de-binding and sintering. These optimized 3D-printed BTO architectures show potential for self-powered sensing, energy harvesting, and ultrasound transducers applications.

Dysphagia, prevalent among Parkinson's and stroke patients, hinders proper eating, impacting their quality of life and potentially leading to fatal outcomes if untreated. Currently, Videofluoroscopic Swallowing Study (VFSS) is the gold standard for diagnosis but requires specialized facilities and trained staff. While many wearable devices have been developed to ease these burdens, none could reliably detect specific dysfunctions like silent aspiration without VFSS. We present a multimodal wearable swallowing monitor incorporating machine learning for automatic dysfunction assessment and silent aspiration diagnosis. The device, featuring a kirigami pattern, is directly mounted on the neck for continuous, high-fidelity monitoring of electromyograms and swallowing sounds. The built-in machine learning algorithm classifies various swallowing patterns, including silent aspiration. Clinical trials with stroke patients underscored the device's significance, matching the VFSS in detecting swallowing disorders. This wearable technology holds promise for advancing dysphagia healthcare and post-stroke rehabilitation therapy.

Cystic fibrosis (CF) is a genetic disorder that primarily affects the respiratory, digestive, and reproductive systems. Approximately 30,000 children and adults in the United States suffer from cystic fibrosis and about 1,000 new cases of cystic fibrosis are diagnosed each year in the U.S. Despite the existing methods available for diagnosing and monitoring cystic fibrosis patients, a rapid, efficient and cost-effective system is needed to diagnose and monitor the treatment process cystic fibrosis. Here, we propose a flexible, mass-producible, and effective TENG based wearable sensor for diagnosing and monitoring cystic fibrosis patients that effectively extracts power from body motion through flexible sensors. With the sweat test and fitness workouts being the most common methods for diagnosing and treating cystic fibrosis patients respectively, this sensor uses the ion concentration in sweat to diagnose cystic fibrosis patients and uses the varying sweat concentration of the patient for activity tracking.

Perioperative ECG monitoring plays a crucial role in ensuring patient safety and care during anesthesia and surgical procedures. The general electronics setup for electrocardiogram (ECG) monitoring in the operating room relies on wired connections to the anesthesia machine, which poses limitations in mobility and can lead to potential interruptions during patient transportation. Moreover, the gel and adhesive electrodes can result in skin irritation and sensitivity reactions. Herein, we introduce a novel approach—a smart adhesive-based wireless device—for perioperative ECG monitoring, offering wireless connectivity, eliminating the need for gel electrodes, and boasting a minimal form factor that seamlessly integrates into the perioperative setting. The wireless prototype demonstrated significant benefits in improving efficiency in ECG measurement and reducing medical errors during patient transfer.

Implantable vascular sensors can offer advantageous alternatives to the existing invasive and repetitive procedures that provide incomplete views of vascular health. However, device manufacturability, alongside strict requirements of size, mechanics, and sensing capability, have hindered the development of implantable vascular sensors. Here, we design and fabricate implantable, flexible vascular electronic systems using a multi-material, electronic stent and soft, printed sensors for wireless monitoring of vascular health. The sensing system is compatible with conventional endovascular surgery, operates via inductive coupling, and is demonstrated with monitoring of pressure, flow, and arterial stiffness. Overall, the studies of device fabrication and sensor design offer promising strategies to create flexible vascular electronics.

Nanocellulose has aroused extensive interests in materials engineering and design owing to its great potential in fabricating robust architectures for diverse applications and functionalities. On the other hand, the sensitivity of cellulose to water results in the deterioration of strength, durability, and functionality thus unsuitable for advanced applications. To address this challenge, we present an efficient, sustainable and scalable strategy to convert cellulose into an advanced biomaterial by integration with a green hydrogen bonded slurry. The resultant cellulose hybrid slurry was cast and cured to fabricate strong and tough biofilms. The hydrogen bonded slurry was revealed to promote tight rapping of the nanofibers resulting to a compact structure with an enhanced performance. The dry and wet tensile characteristics of the cellulose hybrid biofilms (375.1 MPa and 160.0 MPa) were much improved compared to the neat cellulose film. The hybrid biofilms also possess excellent UV shielding characteristics, hydrophobicity and a unique antioxidant activity. Of particular interest, the hybrid biofilms can be readily recycled or biodegraded at end of life, hence promoting a circular

In this study, we present the mechano-luminescence-optoelectronic (MLO) strip capable of DC-based strain sensing. The conceptual design of the MLO strip was presented and the MLO strip prototype was fabricated to measure tensile strains in a distributed manner. The MLO strip has three MLO-based sensor nodes along the strip. The MLO is composed of two functional constituents – the mechano-luminescent (ML) copper-doped zinc sulfide (ZnS:Cu)-embedded polydimethylsiloxane (PDMS) (ZnS:Cu-PDMS) micro-composites and the mechano-optoelectronic (MO) poly(3-hexylthiophene) (P3HT-based thin films. The ML and MO functional constituents were assembled and encased using the PDMS in a strip mold to complete the preparation of the MLO strip prototype. The MLO strip prototypes were subjected to cyclic tensile loadings while measuring DC output from the sensor nodes in the MLO strip.

The convergence of wearable technology and healthcare monitoring has revolutionized personalized health monitoring through real-time data acquisition and analysis. To fully unleash the potential of wearable sensors, developing a soft, disposable, and flexible platform that can easily interface with the epidermis is required. Leveraging printing technologies in flexible sensor fabrication offers a platform that is easily customizable, highly scalable, and disposable, all while possessing notable attributes such as speed, high throughput, and cost-effectiveness. Printed organic electrochemical transistors (OECTs) are one of the prominent candidates for flexible and wearable sweat sensing due to their inherent properties, including signal amplification and the ability to mitigate challenges in miniaturization, and complexities in interfacing with electronic readout due to their high input impedance. Here, we present an epidermal wearable chemical sensing patch for sweat ions analysis fabricated using inkjet printing and direct 3D writing. This real-time monitoring of sweat analytes will ensure timely medication and enhance the experience of personalized healthcare monitoring.

Personalized healthcare is undergoing a revolution with wearable sensors that continuously monitor biomarkers, notably sweat-based ones. However, powering these devices sustainably has been challenging. We introduce a solution using a flexible perovskite solar cell (FPSC) for autonomous sweat sensors. Our FPSC wearable efficiently harvests ambient light energy, ensuring continuous monitoring even in low activity. A standout feature is its 31% power conversion efficiency in indoor light, achieved by incorporating α-methylbenzylamine (MBA) into the perovskite. Additionally, the FPSC endures bending, enhancing its suitability for wearables. Tested in real-world scenarios, our device consistently analyzed sweat biomarkers, highlighting the potential of solar-driven sensors in advancing personalized healthcare.

Telerehabilitation technologies can deliver physical therapy to patients’ homes, yet, remote assessment of their motor performance by healthcare professionals remains underdeveloped. Presently, therapists need to work with technicians who process and analyze motion data. Automation of remote motor assessment could benefit from machine learning algorithms that detect impaired movements. Here, we investigate the viability of this approach with data from ten healthy subjects who interact with a low cost telerehabilitation system we previously developed. Our preliminary findings set the grounds for automated motion analysis in telerehabilitation.

Global climate change is increasing the frequency of cold events, which can threaten health and increase the demand for energy. Having sun as the heat and body radiation as warmth preservation source, the need to save energy is mitigated through personal thermal management (PTM). Herein, we report a self-powered woven Kevlar fiber (WKF)-based flexible PTM device with a porous Ag@MoxFe1-xSe nanostructure (NS) between a substrate of WKF and Ti3C2 MXene film dispersed in polydimethylsiloxane (PDMS).

Stroke survivors commonly experience long-term motor impairment, which limits their engagement in activities of daily living. Haptic desktop robots such as the Novint Falcon can provide programmable haptic therapy to effectively recover fine-motor skills in the wrist. However, it is presently not possible to measure users’ wrist angles from data acquired by these robots for remote assessment. To maintain practical use of haptic robots in telerehabilitation, we propose a set-up where patients strap a smartphone to their forearm and manipulate the haptic robots. We develop a machine learning algorithm to infer the wrist angle toward automatic motion analysis.

Electronics that can seamlessly integrate with soft organs could have significant impact in medical diagnostic, therapeutics. However, seamless integration is a grand challenge because of the distinct nature between electronics and human body. Conventional electronics are rigid and planar, made out of rigid materials. Human body are soft, deformable, comprised of biological materials, organs and tissues. This talk will introduce our solution to address the challenge through the recent development rubbery electronics, which is constructed all based on elastic rubber electronic materials of semiconductors, conductors and dielectrics, which possesses tissue-like softness and mechanical stretchability to allow seamless integration with soft deformable tissues and organs. Rubbery electronic materials (semiconductors, conductors, dielectrics) and device innovations set the foundation. This presentation will describe the development the recent advances of rubbery electronics and rubbery bioelectronics. As a platform technology, rubbery electronics could address many challenges in biomedical research and clinical studies.

Herein, we synthesized four sensing materials namely N-MWCNT, N-MWCNT/CMC, N-MWCNT/PANI, and N-MWCNT/PPy, and characterized them using FTIR, XRD, XPS, SEM, and TEM. Then, we studied the effect of polymers such as CMC, PANI, and PPy on the N-MWCNT for the detection of DMMP with a concentration ranging from 2–10 ppm. The results showed that N-MWCNT alone possesses the lowest sensitivity towards 10 ppm DMMP molecules. When the polymers were added to the N-MWCNT, the results showed enhancement in the sensitivity towards the DMMP molecules. The order of highest sensitivity is N-MWCNT/CMC > N-MWCNT/PANI > N-MWCNT/PPy > N-MWCNT.

The practical wearable electronics applications of stretchable conductive nanocomposites have been hindered by mechanical and electrical irreversibility. Here we report a resistive-type nanocomposite strain sensor, demonstrating excellent reversibility (30% strain, 3000 cycles). The sensor element consists of flower-shaped silver nanoparticles (AgNFs) embedded in a stretchable polyurethane (PU) matrix. The thin petals of AgNFs construct efficient percolation network with neighboring AgNFs. The nanocomposite sensor shows high sensitivity (gauge factor 32.08) and impressive mechanical and electrical reversibility. The recent progress in our lab will also be introduced. Reference: [1] Compos. Sci. and Tech., 221, 109305 (2022).

Efficient thermal management of wearable electronic devices is necessary for human comfort. Here we report leakage-free healable phase change thermal interface materials for efficient heat removal [1]. The matrix material is synthesized by covalent functionalization of octadecanol on a polymer backbone, preventing leakage at high temperatures. The silver flakes and silver nanoparticle functionalized multi-walled carbon nanotubes are employed as conductive fillers, resulting in high thermal conductivity (43.4 Wm-1K-1) and low total thermal resistance (30.5 mm2KW-1) [1]. The reversible hydrogen bonding provides a nearly complete healing efficiency. Excellent healing and heat dissipation demonstrations are also carried out [1]. The recent progress in our laboratory will also be introduced. Reference: [1] Advanced Materials 2023, 35, 2300956.

A miniaturized and plant-wearable chlorophyll meter for rapid, non-destructive, in situ, and long-term chlorophyll monitoring is developed. The reflectance-based chlorophyll sensor with 1.5 mm thickness and 0.2 g weight (1000 times lighter than the commercial chlorophyll meter), includes a light emitting diode (LED) and two symmetric photodetectors (PDs) on a flexible substrate, and is patched onto the leaf upper epidermis with a conformal light guiding layer.

This study was conducted to explore the impact of bending angle, radius, and number of bending cycles on the performance of solid polymer electrolyte (SPE) capacitors. The bending angle, radius, and cycles were carefully controlled. The results showed that the bending angle had the greatest impact on the capacitors’ performance, with higher bending angles leading to a decrease in specific capacitance. This finding shows that when designing flexible electronic devices with SPE based capacitors, the bending parameters should be carefully considered to ensure optimal performance and longer lifespan.

This study proposed a high intensity and single-mode cross-fishnet grating based single-electron near infrared (NIR) free -electron laser (FEL). We have numerically investigated the achievable laser emission from a single electron and atop a nano-grating silicon waveguide in order to envision a chip-size free-electron laser as a potent research tool, for the first time. A single 45-keV electron generates 1.14 μm laser-like radiation at the Bragg resonance of a 31 μm long silicon grating with a 250-nm thickness and 1.23- μm period. The FEL is capable of producing a high intensity Electric field of 7.45×〖10〗^(-10) V/m, and magnetic field of 6.0×〖10〗^(-12) A/m. Besides, the FEL can generate a single-mode emission of radiation at 0.2629 PHz. This research suggests that electrons might interact with the structure more effectively by utilizing methods from both electron beam physics and nanophotonic design to create high-brightness photon sources for potential applications in the NIR wavelengths. It would also be fascinating to look deeper into the possibility of single-photon sources for quantum optics in nano-grating generated by a single keV electron.