Nanofiber-based electronic devices have attracted considerable interest owing to their conformal integration on complicated surfaces, flexibility, and sweat permeability. However, building complicated electronics on nanomesh structure has not been successful because of their inferior mechanical properties and processability. This limits their practical application. To achieve systemlevel device applications, organic field-effect transistors are one of the key components to be integrated with various sensors. Herein, a successful method for fabricating a biocompatible, ultrathin (≈1.5 µm), lightweight (1.85 g m -2 ), and mechanically durable all-nanofiber-based organic transistor is reported that can be in conformal contact with curved skin. Furthermore, it is the first development with a substrate-less nanomesh organic field effect transistor. The devices exhibit satisfactory electrical performance, including an on/off value of 3.02 × 10 4 ± 0.9 × 10 4 , saturation mobility of 0.05 ± 0.02 cm 2 V − 1 s − 1 , subthreshold slope of 1.7 ± 0.2 V dec -1 , and threshold voltage of −6 ± 0.5 V. The mechanism of crack initiation is analyzed, via simulation, to understand the deformation of the nanomesh transistors. Furthermore, active matrix integrated tactile sensors entirely on the nanomeshes is successfully demonstrated, indicating their potential applicability in the field of biomedical electronics.

Conformal integration of an epidermal device with the skin, as well as sweat and air permeability, are crucial to reduce stress on biological tissues. Nanofiber-based porous mesh structures (breathable devices) are commonly utilized to prevent skin problems. Noble metals are normally deposited on nanomesh substrates to form breathable electrodes. However, these are expensive and require high-vacuum processes involving time-consuming multistep procedures. Organic materials are suitable alternatives that can be simply processed in solution. We report a simple, cost-effective, mechanically biocompatible, and breathable organic epidermal electrode for biometric devices. Poly­(3,4-ethylenedioxythiophene):poly­(styrene sulfonate) (PEDOT:PSS) is sprayed on a nanofiber-mesh structure, treated using only heat and water to enhance its biocompatibility and conductivity, and used as the electrode. The treatment is accomplished using an autoclave, simultaneously reducing the electrical resistance and sterilizing the electrode for practical use. This research can lead to affordable and biocompatible epidermal electrodes with improved suitability for various biomedical applications.

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Polymer nanofiber-based porous structures ("breathable devices") have been developed for breathable epidermal electrodes, piezoelectric nanogenerators, temperature sensors, and strain sensors, but their applications are limited because increasing the porosity reduces device robustness. Herein, we report an approach to produce ultradurable, cost-effective breathable electronics using a hierarchical metal nanowire network and an optimized photonic sintering process. Photonic sintering significantly reduces the sheet resistance (16.25 to 6.32 Ω sq −1 ) and is 40% more effective than conventional thermal annealing (sheet resistance: 12.99 Ω sq −1 ). The mechanical durability of the sintered (648.9 Ω sq −1 ) sample is notably improved compared to that of the untreated (disconnected) and annealed (19.1 kΩ sq −1 ) samples after 10,000 deformation cycles at 40% tensile strain. The sintered sample exhibits ∼29 times less change in electrical performance compared to the thermally annealed sample. This approach will lead to the development of affordable and ultradurable commercial breathable electronics.

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