We report the reduction in the wire resistance of gold nanomesh electrodes caused by interconnecting mesh electrodes. The porous-structured electrodes show high resistance because of the high junction resistance between electrodes. For the wiring of wearable sensors, the resistance of conductive wiring needs to be minimal. Therefore, it is necessary to reduce the resistance of nanomesh conductors by interconnecting electrodes. We fabricated the interconnected nanomesh conductors in the following steps. We heat pressed electrospun poly(vinyl alcohol) (PVA) fiber sheets at 180 °C (near the melting point of PVA), and then deposited the gold layer. We attached the nanomesh conductors to a target substrate by dissolving the PVA layer with spraying water. The electrodes were electrically connected to each other, which decreased the wire resistance by 76% and the sheet resistance from 3.18 to 1.27 Ω/sq. Furthermore, the interconnected structures improved stretchability of nanomesh conductors from 25 to 80%. The decreased resistance helps operate wearable devices by maintaining the same electrical properties when the wire length is increased.

structures in two or three dimensions. This method enables the stretching of hard and non-stretchable materials (such as, metals [2,[30][31][32] and plastics [1,4,33] ). Deformable structures, such as serpentine, [2,34] mesh, [29,35] kirigami-shapes, [1,6,36] or helix/spring structures, [26,30,31,[37][38][39][40][41][42] can be fabricated by deposition, [2,35] lift-off, [36] laser cutting, [1,37] pre-stretching, [30,38,39] or molding methods. [40][41][42] In particular, the spring structure is stretchable and resilient, enabling electronic devices to be highly stretchable and durable. [42] In addition to stretchable conductors, [42] accurate strain and bending sensors [9] have been reported using inductance changes in coil structures. Devices with liquid metals have better cyclic electrical characteristics than those with rigid metallic materials such as, copper nanowires [40] and silver nanoparticles. [42] Further, a helix-structured device with a metal wire wrapped around a nylon fiber enabled the estimation of pressure by inductance changes in compression. [43] 3D printers have enabled the fabrication of complex 3D structures with structural deformation [44,45] or internal channels. [9,46,47] They can also utilize soft materials such as, elastomers and gels. Therefore, soft spring-type electronic devices have been developed with combinations of electronic materials as well. [9,47] For example, a spring-type device composed of silicone rubber and liquid metal as the core and shell, respectively, exhibited highly stable electrical characteristics in cyclic deformations. [9] However, achieving the desired deformable properties, such as ≈400% stretchability, is challenging when 3D objects are composed of only soft materials, because the resulting devices cannot maintain their structures owing to self-weight deformation. For instance, a spring structure cannot be maintained without a supporting rod inside the coil owing to the deformation caused by its weight. The presence of the supporting rod limits the extent of stretching because the radius of the coil decreases with stretching. Therefore, spring structures with soft material as the shell and liquid metal as the core have achieved almost 100% stretching. [9] Moreover, the supporting rod disturbs the compression of only the spring section. Hence, sensors that measure pressure based on the deformation of the spring structure have not been realized in soft materials.

Thin parylene coating suppressed the negative temperature coefficient (NTC) effect of polymer thermistors with a positive temperature coefficient (PTC) while maintaining the PTC characteristics.

The functional support and advancement of our body while preserving inherent naturalness is one of the ultimate goals of bioengineering. Skin protection against infectious pathogens is an application that requires common and long-term wear without discomfort or distortion of the skin functions. However, no antimicrobial method has been introduced to prevent cross-infection while preserving intrinsic skin conditions. Here, we propose an antimicrobial skin protection platform copper nanomesh, which prevents cross-infectionmorphology, temperature change rate, and skin humidity. Copper nanomesh exhibited an inactivation rate of 99.99% for Escherichia coli bacteria and influenza virus A within 1 and 10 min, respectively. The thin and porous nanomesh allows for conformal coating on the fingertips, without significant interference with the rate of skin temperature change and humidity. Efficient cross-infection prevention and thermal transfer of copper nanomesh were demonstrated using direct on-hand experiments.

Flexible sensors enable on-skin and in-body health monitoring, which require flexible thermal protection circuits to prevent overheating and operate the devices safely. Here, ultrathin fiber-mesh polymer positive temperature coefficient (PTC) thermistors via electrospinning are developed. The fiber-type thermistors are composed of acrylate polymer and carbon nanofibers. The fibrous composite materials are coated with a parylene to form a core-sheath structure, which improves the repeatability of temperature characteristics. Approximately 5 μm thick fiber-type thermistors exhibit an increase in the resistance by three orders of magnitude within ≈2 °C and repeatable temperature characteristics for up to 400 cycles. The mesh structure enables the thermistor layer to be ultra-lightweight and transparent; the mesh-type thermistor operates with a fiber density of 16.5 μg cm −2 , whose fiber layer has a transmittance of more than 90% in the 400-800 nm region. By fabricating the mesh thermistor on a 1.4 μm thick substrate, the thermistor operates without degradation when wrapped around a 280 μm radius needle. Furthermore, the gas-permeable property is demonstrated by fabricating the fibrous thermistor on a mesh substrate. The proposed ultrathin mesh polymer PTC thermistors form the basis for on-skin and implantable devices that are equipped with overheat prevention.