Semiliquid Metal Enabled Highly Conductive Wearable Electronics for Smart Fabrics

Circularity of Smart Products and Textiles Containing Flexible Electronics: Challenges, Opportunities, and Future Directions

The integration of flexible electronics into textiles and smart products has revolutionized industries, enabling innovations such as wearable health monitors, interactive clothing, and energy-harvesting fabrics. However, the rapid growth of these technologies poses significant challenges for sustainability and circularity. This paper explores the concept of circular economy in the context of smart textiles and products containing flexible electronics. It highlights the technical, environmental, and economic challenges associated with their end-of-life management and proposes strategies to enhance circularity, including design for disassembly, advanced recycling technologies, and policy frameworks. The paper concludes with a discussion of future research directions to achieve a sustainable lifecycle for these advanced materials.

Review of Liquid Metal Fiber Based Biosensors and Bioelectronics

Liquid metal, as a novel material, has become ideal for the fabrication of flexible conductive fibers and has shown great potential in the field of biomedical sensing. This paper presents a comprehensive review of the unique properties of liquid metals such as gallium-based alloys, including their excellent electrical conductivity, mobility, and biocompatibility. These properties make liquid metals ideal for the fabrication of flexible and malleable biosensors. The article explores common preparation methods for liquid metal conductive fibers, such as internal liquid metal filling, surface printing with liquid metal, and liquid metal coating techniques, and their applications in health monitoring, neural interfaces, and wearable devices. By summarizing and analyzing the current research, this paper aims to reveal the current status and challenges of liquid metal conductive fibers in the field of biosensors and to look forward to their development in the future, which will provide valuable references and insights for researchers in the field of biomedical engineering.

Stretchable Triboelectric Nanogenerator Based on Liquid Metal with Varying Phases

Stretchable triboelectric nanogenerators (TENGs) represent a new class of energy-harvesting devices for powering wearable devices. However, most of them are associated with poor stretchability, low stability, and limited substrate material choices. This work presents the design and demonstration of highly stretchable and stable TENGs based on liquid metalel ectrodes with different phases. The conductive and fluidic properties of eutectic gallium-indium (EGaIn) in the serpentine microfluidic channel ensure the robust performance of the EGaIn-based TENG upon stretching over several hundred percent. The bi-phasic EGaIn (bGaIn) from oxidation lowers surface tension and increases adhesion for printing on diverse substrates with high output performance parameters. The optimization of the electrode shapes in the bGaIn-based TENGs can reduce the device footprint and weight, while enhancing stretchability. The applications of the EGaIn- and bGaIn-based TENG include smart elastic bands for human movement monitoring and smart carpets with integrated data transmission/processing modules for headcount monitoring/control. Combining the concept of origami in the paper-based bGaIn TENG can reduce the device footprint to improve output performance per unit area. The integration of bGaIn-TENG on a self-healing polymer substrate with corrosion resistance against acidic and alkaline solutions further facilitates its use in various challenging and extreme environments.

Stretchable Sensor Materials Applicable to Radiofrequency Coil Design in Magnetic Resonance Imaging: A Review

Wearable sensors are rapidly gaining influence in the diagnostics, monitoring, and treatment of disease, thereby improving patient outcomes. In this review, we aim to explore how these advances can be applied to magnetic resonance imaging (MRI). We begin by (i) introducing limitations in current flexible/stretchable RF coils and then move to the broader field of flexible sensor technology to identify translatable technologies. To this goal, we discuss (ii) emerging materials currently used for sensor substrates, (iii) stretchable conductive materials, (iv) pairing and matching of conductors with substrates, and (v) implementation of lumped elements such as capacitors. Applicable (vi) fabrication methods are presented, and the review concludes with a brief commentary on (vii) the implementation of the discussed sensor technologies in MRI coil applications. The main takeaway of our research is that a large body of work has led to exciting new sensor innovations allowing for stretchable wearables, but further exploration of materials and manufacturing techniques remains necessary, especially when applied to MRI diagnostics.

Stretchable Fibers with Highly Conductive Surfaces and Robust Electromechanical Performances for Electronic Textiles

One-dimensional conductive fibers that can simultaneously accommodate multiple deformations are crucial materials to enable next-generation electronic textile technologies for applications in the fields of healthcare, energy harvesting, human-machine interactions, etc. Stretchable conductive fibers (SCFs) with high conductivity on their external structure are important for their direct integration with other electronic components. However, the dilemma to achieve high conductivity and concurrently large stretchability is still quite challenging to resolve among conductive fibers with a conductive surface. Here, a three-layer coaxial conductive fiber, which can provide robust electrical performance under various deformations, is reported. A dual conducting structure with a semisolid metallic layer and a stretchable composite layer was designed in the fibers, providing exceptional conductivity and mechanical stability under mechanical strains. The conductive fiber achieved an initial conductivity of 2291.83 S cm-1 on the entire fiber and could be stretched up to 600% strains. With the excellent electromechanical properties of the SCF, we were able to demonstrate different electronic textile applications including physiological monitoring, neuromuscular electrical stimulation, and energy harvesting.

Versatile Liquid Metal/Alginate Composite Fibers with Enhanced Flame Retardancy and Triboelectric Performance for Smart Wearable Textiles

Liquid metal (LM) shows the superiority in smart wearable devices due to its biocompatibility and electromagnetic interference (EMI) shielding. However, LM based fibers that can achieve multifunctional integrated applications with biodegradability remain a daunting challenge. Herein, versatile LM based fibers are fabricated first by sonication in alginate solution to obtain LM micro/nano droplets and then wet-spinning into LM/alginate composite fibers. By mixing with high-concentration alginate solution (4-6 wt.%), the LM micro/nano droplets stability (colloidal stability for > 30 d and chemical stability for > 45 d) are not only improved, but also facilitate its spinning into fibers through bimetallic ions (e.g., Ga3+ and Ca2+ ) chelation strategy. These resultant fibers can be woven into smart textiles with excellent flexibility, air permeability, water/salt resistance, and high temperature tolerance (-196-150 °C). In addition, inhibition of smoldering result from the LM droplets and bimetallic ions is achieved to enhance flame retardancy. Furthermore, these fibers combine the exceptional properties of LM droplets (e.g., photo-thermal effect and EMI shielding) and alginate fibers (e.g., biocompatibility and biodegradability), applicable in wearable heating devices, wireless communication, and triboelectric nanogenerator, making it a promising candidate for flexible smart textiles.

Liquid Metal Fibers with a Knitted Structure for Wearable Electronics

Flexible conductive fibers have shown tremendous potential in diverse fields, including health monitoring, intelligent robotics, and human-machine interaction. Nevertheless, most conventional flexible conductive materials face challenges in meeting the high conductivity and stretchability requirements. In this study, we introduce a knitted structure of liquid metal conductive fibers. The knitted structure of liquid metal fiber significantly reduces the resistance variation under tension and exhibits favorable durability, as evidenced by the results of cyclic tensile testing, which indicate that their resistance only undergoes a slight increase (<3%) after 1300 cycles. Furthermore, we demonstrate the integration of these liquid metal fibers with various rigid electronic components, thereby facilitating the production of pliable LED arrays and intelligent garments for electrocardiogram (ECG) monitoring. The LED array underwent a 30 min machine wash, during which it consistently retained its normal functionality. These findings evince the devices' robust stable circuit functionality and water resistance that remain unaffected by daily human activities. The liquid metal knitted fibers offer great promise for advancing the field of flexible conductive fibers. Their exceptional electrical and mechanical properties, combined with compatibility with existing electronic components, open new possibilities for applications in the physiological signal detection of carriers, human-machine interaction, and large-area electronic skin.

Development and Optimization of 3D-Printed Flexible Electronic Coatings: A New Generation of Smart Heating Fabrics for Automobile Applications

Textile-based Joule heaters in combination with multifunctional materials, fabrication tactics, and optimized designs have changed the paradigm of futuristic intelligent clothing systems, particularly in the automobile field. In the design of heating systems integrated into a car seat, conductive coatings via 3D printing are expected to have further benefits over conventional rigid electrical elements such as a tailored shape and increased comfort, feasibility, stretchability, and compactness. In this regard, we report on a novel heating technique for car seat fabrics based on the use of smart conductive coatings. For easier processes and integration, an extrusion 3D printer is employed to achieve multilayered thin films coated on the surface of the fabric substrate. The developed heater device consists of two principal copper electrodes (so-called power buses) and three identical heating resistors made of carbon composites. Connections between the copper power bus and the carbon resistors are made by means of sub-divide the electrodes, which is critical for electrical-thermal coupling. Finite element models (FEM) are developed to predict the heating behavior of the tested substrates under different designs. It is pointed out that the most optimized design solves important drawbacks of the initial design in terms of temperature regularity and overheating. Full characterizations of the electrical and thermal properties, together with morphological analyses via SEM images, are conducted on different coated samples, making it possible to identify the relevant physical parameters of the materials as well as confirm the printing quality. It is discovered through a combination of FEM and experimental evaluations that the printed coating patterns have a crucial impact on the energy conversion and heating performance. Our first prototype, thanks to many design optimizations, entirely meets the specifications required by the automobile industry. Accordingly, multifunctional materials together with printing technology could offer an efficient heating method for the smart textile industry with significantly improved comfort for both the designer and user.

Smart Eutectic Gallium-Indium: From Properties to Applications

Eutectic gallium-indium (EGaIn), a liquid metal with a melting point close to or below room temperature, has attracted extensive attention in recent years due to its excellent properties such as fluidity, high conductivity, thermal conductivity, stretchability, self-healing capability, biocompatibility, and recyclability. These features of EGaIn can be adjusted by changing the experimental condition, and various composite materials with extended properties can be further obtained by mixing EGaIn with other materials. In this review, not only the are unique properties of EGaIn introduced, but also the working principles for the EGaIn-based devices are illustrated and the developments of EGaIn-related techniques are summarized. The applications of EGaIn in various fields, such as flexible electronics (sensors, antennas, electronic circuits), molecular electronics (molecular memory, opto-electronic switches, or reconfigurable junctions), energy catalysis (heat management, motors, generators, batteries), biomedical science (drug delivery, tumor therapy, bioimaging and neural interfaces) are reviewed. Finally, a critical discussion of the main challenges for the development of EGaIn-based techniques are discussed, and the potential applications in new fields are prospected.

A new 3D, microfluidic-oriented, multi-functional, and highly stretchable soft wearable sensor

Increasing demand for wearable devices has resulted in the development of soft sensors; however, an excellent soft sensor for measuring stretch, twist, and pressure simultaneously has not been proposed yet. This paper presents a novel, fully 3D, microfluidic-oriented, gel-based, and highly stretchable resistive soft sensor. The proposed sensor is multi-functional and could be used to measure stretch, twist, and pressure, which is the potential of using a fully 3D structure in the sensor. Unlike previous methods, in which almost all of them used EGaIn as the conductive material, in this case, we used a low-cost, safe (biocompatible), and ubiquitous conductive gel instead. To show the functionality of the proposed sensor, FEM simulations and a set of designed experiments were done, which show linear (99%), accurate (> 94.9%), and durable (tested for a whole of four hours) response of the proposed sensor. Then, the sensor was put through its paces on a female test subject's knee, elbow, and wrist to show the potential application of the sensor as a body motion sensor. Also, a fully 3D active foot insole was developed, fabricated, and evaluated to evaluate the pressure functionality of the sensor. The result shows good discrimination and pressure measurement for different foot sole areas. The proposed sensor has the potential to be used in real-world applications like rehabilitation, wearable devices, soft robotics, smart clothing, gait analysis, AR/VR, etc.

Thermal Transfer-Enabled Rapid Printing of Liquid Metal Circuits on Multiple Substrates

Low-cost, rapid patterning of liquid metal on various substrates is a key processing step for liquid metal-based soft electronics. Current patterning methods rely on expensive equipment and specific substrates, which severely limit their widespread applications. Based on surface adhesion adjustment of liquid metal through thermal transferring toner patterns, we present a universal printing technique of liquid metal circuits. Without using any expensive processing steps or equipment, the circuit patterns can be printed quickly on thermal transfer paper using a desktop laser printer, and a toner on the thermal transfer paper can be transferred to various smooth substrates and polymer-coated rough substrates. The technique has yielded liquid metal circuits with a minimum linewidth of 50 μm fabricated on various smooth, rough, and three-dimensional substrates with complex morphology. The liquid metal circuits can maintain their functions even under an extreme strain of 800%. Various circuits such as LED arrays, multiple sensors, a flexible display, a heating circuit, a radiofrequency identification circuit, and a 12-lead electrocardiogram circuit on various substrates have been demonstrated, indicating the great potential of such a technique to rapidly achieve large-area flexible circuits for wearable health monitoring, internet of things, and consumer electronics at low cost and high efficiency.

Durability Study of Thermal Transfer Printed Textile Electrodes for Wearable Electronic Applications

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 10⁴ S/cm), high adhesion (≥1750 N/m), good abrasion/washing resistance, high patterning resolution (∼40 μm), and good electromechanical performance up to 50% strain. To demonstrate the potential applications, we developed textile-based radio frequency identification (RFID) tags for remote identification and a large-sized heater for wearable thermotherapy. More importantly, the solvent-free thermal transfer printing technology developed in this paper enables people to DIY interesting flexible electronics on clothes with daily tools, which can promote the commercial application of smart textile-based electronics.

E-textile based modular sEMG suit for large area level of effort analysis

We present a novel design for an e-textile based surface electromyography (sEMG) suit that incorporates stretchable conductive textiles as electrodes and interconnects within an athletic compression garment. The fabrication and assembly approach is a facile combination of laser cutting and heat-press lamination that provides for rapid prototyping of designs in a typical research environment without need for any specialized textile or garment manufacturing equipment. The materials used are robust to wear, resilient to the high strains encountered in clothing, and can be machine laundered. The suit produces sEMG signal quality comparable to conventional adhesive electrodes, but with improved comfort, longevity, and reusability. The embedded electronics provide signal conditioning, amplification, digitization, and processing power to convert the raw EMG signals to a level-of-effort estimation for flexion and extension of the elbow and knee joints. The approach we detail herein is also expected to be extensible to a variety of other electrophysiological sensors.

A New Class of Electronic Devices Based on Flexible Porous Substrates

With the advent of the Internet of Things era, the connection between electronic devices and humans is getting closer and closer. New-concept electronic devices including e-skins, nanogenerators, brain-machine interfaces, and implantable medical devices, can work on or inside human bodies, calling for wearing comfort, super flexibility, biodegradability, and stability under complex deformations. However, conventional electronics based on metal and plastic substrates cannot effectively meet these new application requirements. Therefore, a series of advanced electronic devices based on flexible porous substrates (e.g., paper, fabric, electrospun nanofibers, wood, and elastic polymer sponge) is being developed to address these challenges by virtue of their superior biocompatibility, breathability, deformability, and robustness. The porous structure of these substrates can not only improve device performance but also enable new functions, but due to their wide variety, choosing the right porous substrate is crucial for preparing high-performance electronics for specific applications. Herein, the properties of different flexible porous substrates are summarized and their basic principles of design, manufacture, and use are highlighted. Subsequently, various functionalization methods of these porous substrates are briefly introduced and compared. Then, the latest advances in flexible porous substrate-based electronics are demonstrated. Finally, the remaining challenges and future directions are discussed.

Progress in Flexible Electronic Textile for Heating Application: A Critical Review

Intelligent textiles are predicted to see a 'surprising' development in the future. The consequence of this revived interest has been the growth of industrial goods and the improvement of innovative methods for the incorporation of electrical features into textiles materials. Conductive textiles comprise conductive fibres, yarns, fabrics, and finished goods produced using them. Present perspectives to manufacture electrically conductive threads containing conductive substrates, metal wires, metallic yarns, and intrinsically conductive polymers. This analysis concentrates on the latest developments of electro-conductivity in the area of smart textiles and heeds especially to materials and their assembling processes. The aim of this work is to illustrate a potential trade-off between versatility, ergonomics, low energy utilization, integration, and heating properties.

Customizable, conformal, and stretchable 3D electronics via predistorted pattern generation and thermoforming

Recently, three-dimensional electronics (3DE) is attracting huge interest owing to the increasing demands for seamless integration of electronic systems on 3D curvilinear surfaces. However, it is still challenging to fabricate 3DE with high customizability, conformability, and stretchability. Here, we present a fabrication method of 3DE based on predistorted pattern generation and thermoforming. Through this method, custom-designed 3DE is fabricated through the thermoforming process. The fabricated 3DE has high 3D conformability because the thermoforming process enables the complete replication of both the overall shape and the surface texture of the 3D mold. Furthermore, the usage of thermoplastic elastomer and a liquid metal–based conductive electrode allows for high thermoformability during the device fabrication as well as high stretchability during the device operation. We believe that this technology can enable a wide range of new functionalities and multiscale 3D morphologies in wearable electronics.

Highly Sensitive and Stretchable c-MWCNTs/PPy Embedded Multidirectional Strain Sensor Based on Double Elastic Fabric for Human Motion Detection

Owing to the multi-dimensional complexity of human motions, traditional uniaxial strain sensors lack the accuracy in monitoring dynamic body motions working in different directions, thus multidirectional strain sensors with excellent electromechanical performance are urgently in need. Towards this goal, in this work, a stretchable biaxial strain sensor based on double elastic fabric (DEF) was developed by incorporating carboxylic multi-walled carbon nanotubes(c-MWCNTs) and polypyrrole (PPy) into fabric through simple, scalable soaking and adsorption-oxidizing methods. The fabricated DEF/c-MWCNTs/PPy strain sensor exhibited outstanding anisotropic strain sensing performance, including relatively high sensitivity with the maximum gauge factor (GF) of 5.2, good stretchability of over 80%, fast response time < 100 ms, favorable electromechanical stability, and durability for over 800 stretching-releasing cycles. Moreover, applications of DEF/c-MWCNTs/PPy strain sensor for wearable devices were also reported, which were used for detecting human subtle motions and dynamic large-scale motions. The unconventional applications of DEF/c-MWCNTs/PPy strain sensor were also demonstrated by monitoring complex multi-degrees-of-freedom synovial joint motions of human body, such as neck and shoulder movements, suggesting that such materials showed a great potential to be applied in wearable electronics and personal healthcare monitoring.

Recent Development in Liquid Metal Materials

Liquid metals (LM) have shown a very broad development prospect over the past decades. This review article focuses on the latest research dedicated to liquid metal materials and their applications in five significant areas: stretchable conductive composite, intelligent sensing electronic skin, catalysis, 3D printing material, and driving machines. The fabrication, specific properties and application of stretchable liquid metal-polymer composites that can be used as self-healing materials have been summarized. Liquid metal deposition printing technology, liquid phase 3D printing, suspension 3D printing technology, micro-contact printing technology, and in vivo 3D printing molding technology have also been reviewed. Furthermore, the application of liquid metal catalyst in aldehyde reaction, photocatalysis, and electrocatalysis have been discussed. We have shown that electricity, magnetism, sound, light and heat could stimulate the movement of liquid metal. Through this comprehensive overview of the latest research, the main practical application, development, and mechanism of liquid metal were summarized and described. The future development of liquid metal technology was prospected, thus providing a strong basic research support for the further development of LM materials and their applications.

Liquid metal-based nanocomposite materials: fabrication technology and applications

Research on liquid metals has been steadily garnering more interest in recent times, especially in flexible electronics applications because of their properties like possessing high conductivity and being liquid state at room temperature. The unique properties afforded by such materials at low temperatures can compensate for the limitations of stretchable electronic devices, particularly robustness and their fluidic property, which can enhance the flexibility and deformation of these devices. Therefore, interest in liquid-metal nanoparticles and liquid metals with nanocomposites has enabled research into their fabrication technologies as well as utilisation in fields such as chemistry, polymer engineering, computational modelling, and nanotechnology. In particular, in flexible and stretchable electronic device applications, the research attention is focused on the fabrication methodologies of liquid-metal nanoparticles and liquid metals containing nanocomposites. This review attempts to summarise the available stretchable and flexible electronics applications that use liquid-metal nanoparticles as well as liquid metals with nanomaterial additives.

Liquid Metal Based Flexible and Implantable Biosensors

Biosensors are the core elements for obtaining significant physiological information from living organisms. To better sense life information, flexible biosensors and implantable sensors that are highly compatible with organisms are favored by researchers. Moreover, materials for preparing a new generation of flexible sensors have also received attention. Liquid metal is a liquid-state metallic material with a low melting point at or around room temperature. Owing to its high electrical conductivity, low toxicity, and superior fluidity, liquid metal is emerging as a highly desirable candidate in biosensors. This paper is dedicated to reviewing state-of-the-art applications in biosensors that are expounded from seven aspects, including pressure sensor, strain sensor, gas sensor, temperature sensor, electrical sensor, optical sensor, and multifunctional sensor, respectively. The fundamental scientific and technological challenges lying behind these recommendations are outlined. Finally, the perspective of liquid metal-based biosensors is present, which stimulates the upcoming design of biosensors.

Liquid metal-integrated ultra-elastic conductive microfibers from microfluidics for wearable electronics

Liquid metal (LM) has shown potential values in different areas. Attempts to implement LM are tending to develop new functions and make it versatile to improve its performance for practical applications. Here, we present an unprecedented LM-integrated ultra-elastic microfiber with distinctive features for wearable electronics. The microfiber with a polyurethane shell and an LM core was continuously generated by using a sequenced microfluidic spinning and injection method. Due to the precise fluid manipulation of microfluidics, the resultant microfiber could be tailored with tunable morphologies and responsive conductivities. We have demonstrated that the microfiber could act as dynamic force sensor and motion indicator when it was embedded into elastic films. In addition, the values of the LM-integrated ultra-elastic microfiber on energy conversions such as electro-magnetic or electro-thermal conversions have also been realized. These features indicate that LM-integrated microfiber will open up new frontiers in LM-integrated materials and the wearable electronics field.

Self-Chargeable Flexible Solid-State Supercapacitors for Wearable Electronics

Flexible supercapacitors (SCs) always face the charging issue when they are used in some special situations (e.g., wilderness island) that cannot provide electricity, which would limit the continuous energy supply for the attached wearable electronics. Herein, a self-chargeable flexible solid-state supercapacitor (FSSSC) was creatively constructed by sandwiching a piezoelectric polyvinyl alcohol/potassium hydroxide/barium titanate electrolyte between symmetric NiCo₂O₄@activated carbon cloth electrodes. By virtue of the efficient synergy of each component in the FSSSC, the device exhibits integrated merits with excellent flexibility, satisfactory electrochemical properties, and considerable self-charging capability through synchronously collecting and converting mechanical energy (e.g., repeated bending) into storable electrochemical energy in a persistent way. When the devices are serially connected and self-charged, they can be used to drive typical electronics with normal working. Such a unique material and device design enables the FSSSC with combined capabilities such as energy-harvesting and conversion and storage device for self-powered wearable electronics.

Highly Selective Metal-Organic Framework Textile Humidity Sensor

The increase in demand and popularity of smart textiles brings new and innovative ideas to develop a diverse range of textile-based devices for our daily life applications. Smart textile-based sensors (TEX sensors) become attractive due to the potential to replace current solid-state sensor devices with flexible and wearable devices. We have developed a smart textile sensor for humidity detection using a metal-organic framework (MOF) as an active thin-film layer. We show for the first time the use of the Langmuir-Blodgett (LB) technique for the deposition of a MIL-96(Al) MOF thin film directly onto the fabrics containing interdigitated textile electrodes for the fabrication of a highly selective humidity sensor. The humidity sensors were made from two different types of textiles, namely, linen and cotton, with the linen-based sensor giving the best response due to better coverage of MOF. The TEX sensor showed a reproducible response after multiple cycles of measurements. After 3 weeks of storage, the sensor showed a moderate decrease in response. Moreover, TEX sensors showed a high level of selectivity for the detection of water vapors in the presence of several volatile organic compounds (VOCs). Interestingly, the selectivity is superior to some of the previously reported MOF-coated solid-state interdigitated electrode devices and textile sensors. The method herein described is generic and can be extended to other textiles and coating materials for the detection of toxic gases and vapors.

Soft electromagnetic actuators

Rigid electromagnetic actuators serve our society in a myriad of ways for more than 200 years. However, their bulky nature restricts close collaboration with humans. Here, we introduce soft electromagnetic actuators (SEMAs) by replacing solid metal coils with liquid-metal channels embedded in elastomeric shells. We demonstrate human-friendly, simple, stretchable, fast, durable, and programmable centimeter-scale SEMAs that drive a soft shark, interact with everyday objects, or rapidly mix a dye with water. A multicoil flower SEMA with individually controlled petals blooms or closes within tens of milliseconds, and a cubic SEMA performs programmed, arbitrary motion sequences. We develop a numerical model supporting design and opening potential routes toward miniaturization, reduction of power consumption, and increase in mechanical efficiency. SEMAs are electrically controlled shape-morphing systems that are potentially empowering future applications from soft grippers to minimally invasive medicine.

Control of thermal deformation with photonic sintering of ultrathin nanowire transparent electrodes

Development of electronic devices on ultrathin flexible plastic substrates is of great value in terms of portability, cost reduction, and mechanical flexibility. However, because thin plastic substrates with low heat capacity can be more easily damaged by thermal energy, their use is limited. Highly flexible nanowire (NW) transparent conductive electrodes on ultrathin (∼10 μm) low cost polyethylene terephthalate (PET) substrates are fabricated. The control of intense pulsed light (IPL) irradiation process parameters to induce NW welding for maximum conductivity and minimal thermal damage of the PET substrate is explored. For this purpose, trends in temperature variation of NW thin films irradiated by IPL under various operating conditions are numerically analyzed using commercial software. Simulations indicate that irradiating light operated at a higher voltage and for a shorter time, and use of multiple pulses of low frequency can reduce thermal deformation of the PET substrate. Furthermore, we experimentally confirm that NW transparent electrodes can be successfully fabricated with less thermal deformation of the ultrathin plastic substrate when light is irradiated under well-controlled conditions derived from the simulation. The highly flexible NW transparent conducting electrode exhibits excellent mechanical flexibility to withstand severe deformation and can be successfully implemented in flexible organic light-emitting diodes (OLEDs).