Ultraelastic Yarns from Curcumin-Assisted ELD toward Wearable Human-Machine Interface Textiles

Ionic aggregates induced room temperature autonomous self-healing elastic tape for reducing ankle sprain

Traditional kinesiology tape (KT) is an elastic fabric tape that clinicians and sports trainers widely use for managing ankle sprains. However, inadequate mechanical properties, adhesive strength, water resistance, and micro-damage generation could affect the longevity of the tape on the skin during physical activity and sweating. Therefore, autonomous room-temperature self-healing elastomers with robust mechanical properties and adequate adhesion to the skin are highly desirable to replace traditional KT. Ionic aggregates were introduced into the polymer matrix via electrostatic attraction between polymer colloid and polyelectrolyte to achieve such elastic tape. These ionic aggregates act as physical crosslink points to enhance mechanical properties and dissociate at room temperature to provide self-healing functions. The obtained elastic tape possesses a tensile strength of 3.7 MPa, elongation of 940 %, toughness of 16.6 MJ∙m-3, and self-healing efficiency of 90 % for 2 h at room temperature. It also exhibits adequate reversible adhesion on the skin via van der Waals force and electrostatic interaction in both dry and wet conditions. The new elastic tapes have great potential in biomedical engineering for preventing and rehabilitating ankle sprain.

Sonochemical Synthesis of Natural Polyphenolic Nanoparticles for Modulating Oxidative Stress

Natural polyphenolic compounds play a vital role in nature and are widely utilized as building blocks in the fabrication of emerging functional nanomaterials. Although diverse fabrication methodologies are developed in recent years, the challenges of purification, uncontrollable reaction processes and additional additives persist. Herein, a modular and facile methodology is reported toward the fabrication of natural polyphenolic nanoparticles. By utilizing low frequency ultrasound (40 kHz), the assembly of various natural polyphenolic building blocks is successfully induced, allowing for precise control over the particle formation process. The resulting natural polyphenolic nanoparticles possessed excellent in vitro antioxidative abilities and in vivo therapeutic effects in typical oxidative stress models including wound healing and acute kidney injury. This study opens new avenues for the fabrication of functional materials from naturally occurring building blocks, offering promising prospects for future advancements in this field.

High-Performance Hydrogel Sensors Enabled Multimodal and Accurate Human-Machine Interaction System for Active Rehabilitation

Human-machine interaction (HMI) technology shows an important application prospect in rehabilitation medicine, but it is greatly limited by the unsatisfactory recognition accuracy and wearing comfort. Here, this work develops a fully flexible, conformable, and functionalized multimodal HMI interface consisting of hydrogel-based sensors and a self-designed flexible printed circuit board. Thanks to the component regulation and structural design of the hydrogel, both electromyogram (EMG) and forcemyography (FMG) signals can be collected accurately and stably, so that they are later decoded with the assistance of artificial intelligence (AI). Compared with traditional multichannel EMG signals, the multimodal human-machine interaction method based on the combination of EMG and FMG signals significantly improves the efficiency of human-machine interaction by increasing the information entropy of the interaction signals. The decoding accuracy of the interaction signals from only two channels for different gestures reaches 91.28%. The resulting AI-powered active rehabilitation system can control a pneumatic robotic glove to assist stroke patients in completing movements according to the recognized human motion intention. Moreover, this HMI interface is further generalized and applied to other remote sensing platforms, such as manipulators, intelligent cars, and drones, paving the way for the design of future intelligent robot systems.

Porous Conductive Textiles for Wearable Electronics

Over the years, researchers have made significant strides in the development of novel flexible/stretchable and conductive materials, enabling the creation of cutting-edge electronic devices for wearable applications. Among these, porous conductive textiles (PCTs) have emerged as an ideal material platform for wearable electronics, owing to their light weight, flexibility, permeability, and wearing comfort. This Review aims to present a comprehensive overview of the progress and state of the art of utilizing PCTs for the design and fabrication of a wide variety of wearable electronic devices and their integrated wearable systems. To begin with, we elucidate how PCTs revolutionize the form factors of wearable electronics. We then discuss the preparation strategies of PCTs, in terms of the raw materials, fabrication processes, and key properties. Afterward, we provide detailed illustrations of how PCTs are used as basic building blocks to design and fabricate a wide variety of intrinsically flexible or stretchable devices, including sensors, actuators, therapeutic devices, energy-harvesting and storage devices, and displays. We further describe the techniques and strategies for wearable electronic systems either by hybridizing conventional off-the-shelf rigid electronic components with PCTs or by integrating multiple fibrous devices made of PCTs. Subsequently, we highlight some important wearable application scenarios in healthcare, sports and training, converging technologies, and professional specialists. At the end of the Review, we discuss the challenges and perspectives on future research directions and give overall conclusions. As the demand for more personalized and interconnected devices continues to grow, PCT-based wearables hold immense potential to redefine the landscape of wearable technology and reshape the way we live, work, and play.

Biomimetic Wearable Sensors: Emerging Combination of Intelligence and Electronics

Owing to the advancement of interdisciplinary concepts, for example, wearable electronics, bioelectronics, and intelligent sensing, during the microelectronics industrial revolution, nowadays, extensively mature wearable sensing devices have become new favorites in the noninvasive human healthcare industry. The combination of wearable sensing devices with bionics is driving frontier developments in various fields, such as personalized medical monitoring and flexible electronics, due to the superior biocompatibilities and diverse sensing mechanisms. It is noticed that the integration of desired functions into wearable device materials can be realized by grafting biomimetic intelligence. Therefore, herein, the mechanism by which biomimetic materials satisfy and further enhance system functionality is reviewed. Next, wearable artificial sensory systems that integrate biomimetic sensing into portable sensing devices are introduced, which have received significant attention from the industry owing to their novel sensing approaches and portabilities. To address the limitations encountered by important signal and data units in biomimetic wearable sensing systems, two paths forward are identified and current challenges and opportunities are presented in this field. In summary, this review provides a further comprehensive understanding of the development of biomimetic wearable sensing devices from both breadth and depth perspectives, offering valuable guidance for future research and application expansion of these devices.

Asymmetric Multienergy-Coupled Radiative Warming Textiles for Personal Thermal-Moisture Management

In order to address the requirements for warmth and energy conservation in cold climates, the development of personal thermal management textiles that regulate local human thermal comfort has emerged as a promising solution in recent times. Nevertheless, existing warming textile strategies often rely on a singular energy source, exhibit inadequate air/moisture permeability, and lack adaptability to dynamic and intricate climate variations. Herein, a novel multienergy-coupled radiative warming Janus textile has been effectively designed and fabricated via screen printing and foam finishing. Taking advantage of the synergistic effects of directional water transport capability of polyester-covered cotton (with a directional water-transport index of R = 577.5%), high mid-infrared radiant reflection (at 60%), electrothermal conversion of copper coating (with a sheet resistance of 0.01 Ω sq-1), and strong solar absorption of the nanoporous structure TA@APTES@Fe(III)@CNT (TAFC) coating (at 98.5%), the Janus fabric exhibits exceptional performance in expelling out one-way sweat/moisture (R = 329.3%) and solar heating (86.9 °C)/Joule heating (226.4 °C at 3.0 V)/heat retention (2.4 °C higher than that of cotton fabric). Furthermore, the fabric is also provided with exceptional mechanical, washing, flame-retardant, and antibacterial performance. This research holds the potential to revolutionize the development and production of warming textiles by incorporating desirable sweat/moisture permeability and multienergy-coupled heating.

Destructive-Treatment-Free Rapid Polymer-Assisted Metal Deposition for Versatile Electronic Textiles

Highly conductive, durable, and breathable metal-coated textiles are critical building block materials for future wearable electronics. In order to enhance the metal adhesion on the textile surface, existing solution-based approaches to preparing these materials require time-consuming presynthesis and/or premodification processes, typically in the order of tens of minutes to hours, on textiles prior to metal plating. Herein, we report a UV-induced rapid polymer-assisted metal deposition (r-PAMD) that offers a destructive-treatment-free process to deposit highly conductive metals on a wide variety of textile materials, including cotton, polyester, nylon, Kevlar, glass fiber, and carbon cloth. In comparison to the state of the arts, r-PAMD significantly shortens the modification time to several minutes and is compatible with the roll-to-roll fabrication manner. Moreover, the deposited metals show outstanding adhesion, which withstands rigorous flexing, abrasion, and machine washing tests. We demonstrate that these metal-coated textiles are suitable for applications in two vastly different fields, being wearable and washable sensors, and lithium batteries.

Elastic Fibers/Fabrics for Wearables and Bioelectronics

Wearables and bioelectronics rely on breathable interface devices with bioaffinity, biocompatibility, and smart functionality for interactions between beings and things and the surrounding environment. Elastic fibers/fabrics with mechanical adaptivity to various deformations and complex substrates, are promising to act as fillers, carriers, substrates, dressings, and scaffolds in the construction of biointerfaces for the human body, skins, organs, and plants, realizing functions such as energy exchange, sensing, perception, augmented virtuality, health monitoring, disease diagnosis, and intervention therapy. This review summarizes and highlights the latest breakthroughs of elastic fibers/fabrics for wearables and bioelectronics, aiming to offer insights into elasticity mechanisms, production methods, and electrical components integration strategies with fibers/fabrics, presenting a profile of elastic fibers/fabrics for energy management, sensors, e-skins, thermal management, personal protection, wound healing, biosensing, and drug delivery. The trans-disciplinary application of elastic fibers/fabrics from wearables to biomedicine provides important inspiration for technology transplantation and function integration to adapt different application systems. As a discussion platform, here the main challenges and possible solutions in the field are proposed, hopefully can provide guidance for promoting the development of elastic e-textiles in consideration of the trade-off between mechanical/electrical performance, industrial-scale production, diverse environmental adaptivity, and multiscenario on-spot applications.

Textile Strain Sensor Enhancement by Coating Metal Yarns with Carbon-Filled Silicone

Flexible and stretchable strain sensors are an important development for measuring various movements and forces and are increasingly used in a wide range of smart textiles. For example, strain sensors can be used to measure the movements of arms, legs or individual joints. Thereby, most strain sensors are capable of detecting large movements with a high sensitivity. Very few are able to measure small movements, i.e., strains of less than 5%, with a high sensitivity, which is necessary to carry out important health measurements, such as breathing, bending, heartbeat, and vibrations. This research deals with the development of strain sensors capable of detecting strain of 1% with a high sensitivity. For this purpose, a total of six commercially available metallic yarns were coated with a carbon-containing silicone coating. The process is based on a vertical dip-coating technology with a self-printed 3D coating bath. Afterwards, the finished yarns were interlooped and stretched by 1% while electrical resistance measurements were carried out. It was shown that, although the coating reduced the overall conductivity of the yarns, it also improved their sensitivity to stress. Conclusively, highly sensitive strain sensors, designed specially for small loads, were produced by a simple coating set-up and interlooping structure of the sensory yarns, which could easily be embedded in greater textile structures for wearable electronics.

Helical Fiber Strain Sensors Based on Triboelectric Nanogenerators for Self-Powered Human Respiratory Monitoring

Respiration is a major vital sign, which can be used for early illness diagnosis and physiological monitoring. Wearable respiratory sensors present an exciting opportunity to monitor human respiratory behaviors in a real-time, noninvasive, and comfortable way. Among them, fiber-shaped triboelectric nanogenerators (FS-TENGs) are attractive for their comfort and high degree of freedom. However, the single-electrode FS-TENGs cannot respond to their own tensile strains, and the coaxial double-electrode FS-TENGs show low sensitivity to strain due to structural limitations. Here, a type of helical fiber strain sensor (HFSS) is developed, which can respond to tiny tensile strains. In addition, a smart wearable real-time respiratory monitoring system is developed based on the HFSSs, which can measure some key breathing parameters for disease prevention and medical diagnosis. An intelligent alarm can automatically call a preset mobile phone for help in response to respiratory behavior changes. This work provides an effective helical structure for fabricating highly sensitive strain sensors based on FS-TENGs and develops wearable self-powered real-time respiratory monitoring systems.

Functionalized Fiber-Based Strain Sensors: Pathway to Next-Generation Wearable Electronics

Wearable strain sensors are arousing increasing research interests in recent years on account of their potentials in motion detection, personal and public healthcare, future entertainment, man-machine interaction, artificial intelligence, and so forth. Much research has focused on fiber-based sensors due to the appealing performance of fibers, including processing flexibility, wearing comfortability, outstanding lifetime and serviceability, low-cost and large-scale capacity. Herein, we review the latest advances in functionalization and device fabrication of fiber materials toward applications in fiber-based wearable strain sensors. We describe the approaches for preparing conductive fibers such as spinning, surface modification, and structural transformation. We also introduce the fabrication and sensing mechanisms of state-of-the-art sensors and analyze their merits and demerits. The applications toward motion detection, healthcare, man-machine interaction, future entertainment, and multifunctional sensing are summarized with typical examples. We finally critically analyze tough challenges and future remarks of fiber-based strain sensors, aiming to implement them in real applications.

Bio-inspired flexible electronics for smart E-skin

"Learning from nature" provides endless inspiration for scientists to invent new materials and devices. Here, we review state-of-the-art technologies in flexible electronics, with a focus on bio-inspired smart skins. This review focuses on the development of E-skin for sensing a variety of parameters such as mechanical loads, temperature, light, and biochemical cues, with a trend of increased integration of multiple functions. It highlights the most recent advances in flexible electronics inspired by animals such as chameleons, squids, and octopi whose bodies have remarkable camouflage, mimicry, or self-healing attributes. Implantable devices, being overlapped with smart E-skin in a broad sense, are included in this review. This review outlines the remaining challenges in flexible electronics and the prospects for future development for biomedical applications. STATEMENT OF SIGNIFICANCE: This article reviews the state-of-the-art technologies of bio-inspired smart electronic skin (E-skin) developed in a "learning-mimicking-creating" (LMC) cycle. We emphasize the most recent innovations in the development of E-skin for sensing physical changes and biochemical cues, and for integrating multiple sensing modalities. We discuss the achievements in implantable materials, wireless communication, and device design pertaining to implantable flexible electronics. This review will provide prospective insights integrating material, electronics, and mechanical engineering viewpoints to foster new ideas for next-generation smart E-skin.

Highly Dispersed, Adhesive Carbon Nanotube Ink for Strain and Pressure Sensors

Carbon nanotubes (CNT) with prominent electrical and mechanical properties are ideal candidates for flexible wearable devices. However, their poor dispersity in solvents greatly limits their applications as a conductive ink in the fabrication of wearable sensors. Herein, we demonstrate a kind of CNT-based conductive dispersion with high dispersity and adhesiveness using cellulose derivatives as the solvent, in which γ-aminopropyl triethoxy silane as a cross-linking agent reacts with cellulose to form copolymer networks, and simultaneously it also acts as an initiator to induce the self-polymerization of dopamine. Based on the conductive CNT ink, we also demonstrated textile-based strain sensors by stencil printing and sponge-based pressure sensors by the dipping method. The textile-based strain sensors could respond to external stimuli promptly. Then, the strain sensors were encapsulated via polydimethylsiloxane with the expansion of working ranges from less than 20 to nearly 70%. The encapsulated textile sensors exhibited excellent sensing performance as wearable strain sensors to monitor human motions including smile, throat vibration, finger folding, wrist bending, and elbow twisting. The sponge sensors hold high sensitivity and excellent durability as well. The conductive CNT-based ink provides an alternative idea in the development of flexible wearable devices.

Crack Suppression in Conductive Film by Amyloid-Like Protein Aggregation toward Flexible Device

A fatal weakness in flexible electronics is the mechanical fracture that occurs during repetitive fatigue deformation; thus, controlling the crack development of the conductive layer is of prime importance and has remained a great challenge until now. Herein, this issue is tackled by utilizing an amyloid/polysaccharide molecular composite as an interfacial binder. Sodium alginate (SA) can take part in amyloid-like aggregation of the lysozyme, leading to the facile synthesis of a 2D protein/saccharide hybrid nanofilm over an ultralarge area (e.g., >400 cm2 ). The introduction of SA into amyloid-like aggregates significantly enhances the mechanical strength of the hybrid nanofilm, which, with the help of amyloid-mediated interfacial adhesion, effectively diminishes the microcracks in the hybrid nanofilm coating after repetitive bending or stretching. The microcrack-free hybrid nanofilm then shows high interfacial activity to induce electroless deposition of metal in a Kelvin model on a substrate, which noticeably suppresses the formation of microcracks and consequent conductivity loss during the bending and stretching of the metal-coated flexible substrates. This work underlines the significance of amyloid/polysaccharide nanocomposites in the design of interfacial binders for reliable flexible electronic devices and represents an important contribution to mimicking amyloid and polysaccharide-based adhesive cements created by organisms.

Biosignal-Based Human-Machine Interfaces for Assistance and Rehabilitation: A Survey

As a definition, Human–Machine Interface (HMI) enables a person to interact with a device. Starting from elementary equipment, the recent development of novel techniques and unobtrusive devices for biosignals monitoring paved the way for a new class of HMIs, which take such biosignals as inputs to control various applications. The current survey aims to review the large literature of the last two decades regarding biosignal-based HMIs for assistance and rehabilitation to outline state-of-the-art and identify emerging technologies and potential future research trends. PubMed and other databases were surveyed by using specific keywords. The found studies were further screened in three levels (title, abstract, full-text), and eventually, 144 journal papers and 37 conference papers were included. Four macrocategories were considered to classify the different biosignals used for HMI control: biopotential, muscle mechanical motion, body motion, and their combinations (hybrid systems). The HMIs were also classified according to their target application by considering six categories: prosthetic control, robotic control, virtual reality control, gesture recognition, communication, and smart environment control. An ever-growing number of publications has been observed over the last years. Most of the studies (about 67%) pertain to the assistive field, while 20% relate to rehabilitation and 13% to assistance and rehabilitation. A moderate increase can be observed in studies focusing on robotic control, prosthetic control, and gesture recognition in the last decade. In contrast, studies on the other targets experienced only a small increase. Biopotentials are no longer the leading control signals, and the use of muscle mechanical motion signals has experienced a considerable rise, especially in prosthetic control. Hybrid technologies are promising, as they could lead to higher performances. However, they also increase HMIs’ complexity, so their usefulness should be carefully evaluated for the specific application.

Curcumin: Modern Applications for a Versatile Additive

The recent development of several methods for extracting curcumin from the root of the plant Curcuma longa has led to intensified research on the properties of curcumin and its fields of application. Following the studies and the accreditation of curcumin as a natural compound with antifungal, antiviral, and antibacterial properties, new fields of application have been developed in two main directions—food and medical, respectively. This review paper aims to synthesize the fields of application of curcumin as an additive for the prevention of spoilage, safety, and quality of food. Simultaneously, it aims to present curcumin as an additive in products for the prevention of bacterial infections and health care. In both cases, the types of curcumin formulations in the form of (nano)emulsions, (nano)particles, or (nano)composites are presented, depending on the field and conditions of exploitation or their properties to be used. The diversity of composite materials that can be designed, depending on the purpose of use, leaves open the field of research on the conditioning of curcumin. Various biomaterials active from the antibacterial and antibiofilm point of view can be intuited in which curcumin acts as an additive that potentiates the activities of other compounds or has a synergistic activity with them.

Fully Fabric-Based Triboelectric Nanogenerators as Self-Powered Human-Machine Interactive Keyboards

Combination flexible and stretchable textiles with self-powered sensors bring a novel insight into wearable functional electronics and cyber security in the era of Internet of Things. This work presents a highly flexible and self-powered fully fabric-based triboelectric nanogenerator (F-TENG) with sandwiched structure for biomechanical energy harvesting and real-time biometric authentication. The prepared F-TENG can power a digital watch by low-frequency motion and respond to the pressure change by the fall of leaves. A self-powered wearable keyboard (SPWK) is also fabricated by integrating large-area F-TENG sensor arrays, which not only can trace and record electrophysiological signals, but also can identify individuals' typing characteristics by means of the Haar wavelet. Based on these merits, the SPWK has promising applications in the realm of wearable electronics, self-powered sensors, cyber security, and artificial intelligences.

Significant Reduction of Interfacial Thermal Resistance and Phonon Scattering in Graphene/Polyimide Thermally Conductive Composite Films for Thermal Management

The developing flexible electronic equipment are greatly affected by the rapid accumulation of heat, which is urgent to be solved by thermally conductive polymer composite films. However, the interfacial thermal resistance (ITR) and the phonon scattering at the interfaces are the main bottlenecks limiting the rapid and efficient improvement of thermal conductivity coefficients (λ) of the polymer composite films. Moreover, few researches were focused on characterizing ITR and phonon scattering in thermally conductive polymer composite films. In this paper, graphene oxide (GO) was aminated (NH₂-GO) and reduced (NH₂-rGO), then NH₂-rGO/polyimide (NH₂-rGO/PI) thermally conductive composite films were fabricated. Raman spectroscopy was utilized to innovatively characterize phonon scattering and ITR at the interfaces in NH₂-rGO/PI thermally conductive composite films, revealing the interfacial thermal conduction mechanism, proving that the amination optimized the interfaces between NH₂-rGO and PI, reduced phonon scattering and ITR, and ultimately improved the interfacial thermal conduction. The in-plane λ (λ _||) and through-plane λ (λ _⊥) of 15 wt% NH₂-rGO/PI thermally conductive composite films at room temperature were, respectively, 7.13 W/mK and 0.74 W/mK, 8.2 times λ _|| (0.87 W/mK) and 3.5 times λ _⊥ (0.21 W/mK) of pure PI film, also significantly higher than λ _|| (5.50 W/mK) and λ _⊥ (0.62 W/mK) of 15 wt% rGO/PI thermally conductive composite films. Calculation based on the effective medium theory model proved that ITR was reduced via the amination of rGO. Infrared thermal imaging and finite element simulation showed that NH₂-rGO/PI thermally conductive composite films obtained excellent heat dissipation and efficient thermal management capabilities on the light-emitting diodes bulbs, 5G high-power chips, and other electronic equipment, which are easy to generate heat severely.