Strain-Insensitive Stretchable Fiber Conductors Based on Highly Conductive Buckled Shells for Wearable Electronics.

Based on their high applicability to wearable electronics, fiber-based stretchable electronics have been developed via different strategies. However, the electrical conductivity of a fiber electrode is severely degraded, following deformation upon stretching. Despite the introduction of conductive buckled structures to resolve this issue, there still exist limitations regarding the simultaneous realizations of high conductivity and stretchability. Here, we exploit the dense distribution of the Ag nanoparticle (AgNP) network in polyurethane (PU) to fabricate a strain-insensitive stretchable fiber conductor comprising highly conductive buckled shells via a facile chemical process. These buckled AgNPs/PU fibers exhibit stable and reliable electrical responses across a wide range (tensile strain = ∼200%), in addition to their high electrical conductivity (26,128 S/m) and quality factor (Q = 2.29). Particularly, the negligible electrical hysteresis and excellent durability (>10,000 stretching-releasing cycles) of the fibers demonstrate their high applicability to wearable electronics. Furthermore, we develop buckled fiber-based pH sensors exhibiting stable, repeatable, and highly distinguishable responses (changing pH is from 4 to 8, response time is 5-6 s) even under 100% tensile strain. The buckled AgNPs/PU fibers represent a facile strategy for maintaining the stable electrical performances of fiber electrodes across the strain range of human motion for wearable applications.

Tailored Self-Assembled Monolayer using Chemical Coupling for Indium-Gallium-Zinc Oxide Thin-Film Transistors: Multifunctional Copper Diffusion Barrier.

Controlling the contact properties of a copper (Cu) electrode is an important process for improving the performance of an amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistor (TFT) for high-speed applications, owing to the low resistance-capacitance product constant of Cu. One of the many challenges in Cu application to a-IGZO is inhibiting high diffusivity, which causes degradation in the performance of a-IGZO TFT by forming electron trap states. A self-assembled monolayer (SAM) can perfectly act as a Cu diffusion barrier (DB) and passivation layer that prevents moisture and oxygen, which can deteriorate the TFT on-off performance. However, traditional SAM materials have high contact resistance and low mechanical-adhesion properties. In this study, we demonstrate that tailoring the SAM using the chemical coupling method can enhance the electrical and mechanical properties of a-IGZO TFTs. The doping effects from the dipole moment of the tailored SAMs enhance the electrical properties of a-IGZO TFTs, resulting in a field-effect mobility of 13.87 cm2/V·s, an on-off ratio above 107, and a low contact resistance of 612 Ω. Because of the high electrical performance of tailored SAMs, they function as a Cu DB and a passivation layer. Moreover, a selectively tailored functional group can improve the adhesion properties between Cu and a-IGZO. These multifunctionally tailored SAMs can be a promising candidate for a very thin Cu DB in future electronic technology.

Electronic Drugs: Spatial and Temporal Medical Treatment of Human Diseases.

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 sites, including the gastrointestinal (GI) tract and the skin, and deliver therapeutics to enhance healing in a spatiotemporal manner. However, medical treatments often require invasive surgical procedures and implantation of medical equipment for either short or long-term use. Therefore, approaches that could minimize implantation-associated side effects, such as inflammation and scar tissue formation, while maintaining high functionality of e-drugs, are highly needed. Herein, the importance of the spatial and temporal aspects of medical treatment is thoroughly reviewed along with how e-drugs use cutting-edge technological innovations to deal with unresolved medical challenges. Furthermore, diverse uses of e-drugs in clinical applications and the future perspectives of e-drugs are discussed.

Ultrasensitive and Stretchable Conductive Fibers Using Percolated Pd Nanoparticle Networks for Multisensing Wearable Electronics: Crack-Based Strain and H2 Sensors.

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 H2 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 H2 sensing, the fiber multimodal sensors exhibit a wide sensing range of high sensitivity: -0.43% response at 5 ppm (0.0005%) H2 gas and -27.3% response at 10% H2 gas. For the first time, we demonstrate highly stretchable H2 sensors that can detect H2 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 H2 gas exposure.