An All‐Nanofiber‐Based Substrate‐Less, Extremely Conformal, and Breathable Organic Field Effect Transistor for Biomedical Applications

Abstract 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 system‐level 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 × 10⁴ ± 0.9 × 10⁴, saturation mobility of 0.05 ± 0.02 cm² 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.