Stretchable interconnects with invariable conductivity and complete elasticity, which return to their original shape without morphological hysteresis, are attractive for the development of stretchable electronics. In this study, a polydimethylsiloxane‐coated multifilament polyurethane‐based helical conductive fiber is developed. The stretchable helical fibers exhibit remarkable electrical performance under stretching, negligible electrical and mechanical hysteresis, and high electrical reliability under repetitive deformation (10 000 cycles of stretching with 100% strain). The resistance of the helical fibers barely increases until the applied strain reaches the critical strain, which is based on the helical diameter of each fiber. According to finite element analysis, uniform stress distribution is maintained in the helical fibers even under full stretching, owing to the fibers' true helix structure. In addition, the stretchable helical fibers have the ability to completely return to their original shapes even after being fully compressed in the vertical direction. Cylinder‐shaped connecting pieces made using 3D printing are designed for stable connection between the helical fibers and commercial components. A deformable light‐emitting diode (LED) array and biaxially stretchable LED display are fabricated using helical fibers. A skin‐mountable band‐type oximeter with helical fiber‐based electrodes is also fabricated and used to demonstrate real‐time detection of cardiac activities and analysis of brain activities.

Advances in electronic textiles (E-textiles) for next-generation wearable electronics have originated from making a balance between electrical and mechanical properties of stretchy conductive fibers. Despite such progress, the trade-off issue is still a challenge when individual fibers are woven and/or stretched undesirably. Time-consuming fiber weaving has limited practical uses in scalable E-textiles. Here, a facile method is presented to fabricate ultra-stretchable Ag nanoparticles (AgNPs)/polyurethane (PU) hybrid conductive fibers by modulating solvent diffusion accompanied by in situ chemical reduction and adopting a tough self-healing polymer (T-SHP) as an encapsulation layer. First, the controlled diffusivity determines how formation of AgNPs is spatially distributed inside the fiber. Specifically, when a solvent with large molecular weight is used, the percolated AgNP networks exhibit the highest conductivity (30 485 S cm −1) even at 300% tensile strain and durable stretching cyclic performance without severe cracks by virtue of the efficient strain energy dissipation of T-SHP encapsulation layers. The self-bondable properties of T-SHP encapsulated fibers enables self-weavable interconnects. Using the new integration, mechanical and electrical durability of the self-bonded fiber interconnects are demonstrated while stretching biaxially. Furthermore, the self-bonding assembly is further visualized via fabrication of a complex structured E-textile.

The need for wearable electronic devices continues to grow, and the research is under way for stretchable fiber-type sensors that are sensitive to the surrounding atmosphere and will provide proficient measurement capabilities. Currently, one-dimensional fiber sensors have several limitations for their extensive use because of the complex structures of the sensing mechanisms. Thus, it is essential to miniaturize these materials with durability while integrating multiple sensing capabilities. Herein, we present an ultrasensitive and stretchable conductive fiber sensor using PdNP networks embedded in elastomeric polymers for crack-based strain and H 2 sensing. The fiber multimodal sensors show a gauge factor of ∼2040 under 70% strain and reliable mechanical deformation tolerance (10,000 stretching cycles) in the strain-sensor mode. For H 2 sensing, the fiber multimodal sensors exhibit a wide sensing range of high sensitivity: −0.43% response at 5 ppm (0.0005%) H 2 gas and −27.3% response at 10% H 2 gas. For the first time, we demonstrate highly stretchable H 2 sensors that can detect H 2 gas under 110% strain with mechanical durability. As demonstrated, their stable performance allows them to be used in wearable applications that integrate fiber multimodal sensors into industrial safety clothing along with a microinorganic light-emitting diode for visual indication, which exhibits proper activation upon H 2 gas exposure.

pharmaceutical drug delivery and healthcare systems. E-drugs are biocompatible electronic devices capable of identifying specific biological analytes (e.g., glucose, enzymes, and other biomolecules), [1,2] environmental stimuli (e.g., strain, pressure, and external temperature), and electrophysiological signals (e.g., electrocardiograms (ECG), electromyograms (EMG), and electroencephalography (EEG)) to monitor health status and deliver therapeutic treatments in a controlled manner via wireless prompts. [3][4][5] Owing to their innovative functions and technologies, e-drugs have been widely adopted in pharmaceutical and medical research to monitor and treat chronic diseases, which are still considered difficult to cure. Conventional pharmaceutical treatments or medical procedures for chronic diseases encounter a major obstacle in patient compliance, as they involve regular drug intake or treatments. [6] For example, patients with diabetes are recommended to collect blood samples to measure their glucose levels twice a day. However, the International Diabetes Management Practice Study reported that only 29.7-38.5% of patients with type-2 diabetes in Asia, Eastern Europe, and Latin America self-monitor their glucose levels, which hinders effective management of their condition. [7] As a strategy to improve patients' adherence to drug intake and treatments, electronic devices capable of continuously monitoring biological signal levels and therapeutic response via wireless applications have been demanded by the markets.The fundamental differences between electronics and biological tissues have emerged as a challenge in the development of an advanced generation of e-drugs. For instance, soft biological tissues have a low modulus of elasticity, which is typically less than 100 kPa, and high moisture content. By contrast, conventional electronics are generally made of electronic materials such as metals and silicone, which are stiff, with modulus greater than 80 GPa, dry, and static. [8] This mechanical and physical mismatch between human tissues and electronics causes adverse clinical outcomes. Major consequences include inflammatory responses induced by the micromotion of the implant, during and after implantation, as well as scar tissue and fibrotic encapsulation, which substantially compromises the performance and lifetime of e-drugs. [9,10] Recent advances in diagnostics and medicines emphasize the spatial and temporal aspects of monitoring and treating diseases. However, conventional therapeutics, including oral administration and injection, have difficulties meeting these aspects due to physiological and technological limitations, such as long-term implantation and a narrow therapeutic window. As an innovative approach to overcome these limitations, electronic devices known as electronic drugs (e-drugs) have been developed to monitor real-time body signals and deliver specific treatments to targeted tissues or organs. For example, ingestible and patch-type e-drugs could detect changes in biomarkers at the target s...

Implantable neural probes are a crucial part of brain-machine interfaces that serve as direct interacting routes between neural tissues and machines. The neural probes require both mechanical and electrical properties to acquire high-quality signals from individual neurons with minimal tissue damage. However, overcoming the trade-off between flexibility and electrical property is still challenging. Herein, a fiber neural probe, composed of core polymer and Au nanoparticles (AuNPs) on the outer shell, is fabricated by absorbing Au precursor following in situ chemical reduction with a variation of percolating and leaching time. The proposed fiber exhibits excellent electrical properties, with an electrical conductivity of 7.68 × 10 4 S m −1 and an impedance of 2.88 × 10 3 Ω at 1 kHz, as well as a Young's modulus of 170 kPa, which is comparable to that of brain tissue (≈100 kPa). Additionally, the AuNPs fiber neural probe demonstrates extremely stable in vivo electrophysiological signal recordings for four months with reduced foreign body responses at the tissue-probe interface. Furthermore, this innovative approach encourages a new paradigm of long-term recording in the fields of neuroscience and engineering to better understand brain circuits, develop bioelectronic devices, and treat chronic disorders.