Ultra‐Lightweight, Highly Permeable, and Waterproof Fibrous Organic Electrochemical Transistors for On‐Skin Bioelectronics

Abstract Recently emerged on‐skin electronics with applications in human–machine interfaces and on‐body healthy monitoring call for the development of high‐performance skin‐like electrodes and semiconducting polymers. The development of waterproof and breathable membranes that can provide a high level of protection for human skins and a comfortable contact between electronics and skin are the pressing demands for on‐skin electronics. However, major challenges remain, such as the limited mechanical durability and permeability of gas and liquid, hindering long‐term stability and reusability. Herein, a fibrous electrolyte containing polymer matrix and ionic liquid, which is highly robust, breathable, waterproof, and conformal with human skin is reported. Serving as fibrous substrate and electrolyte of organic electrochemical transistors (OECTs), a high transconductance of ≈0.8 mS, stability over pulsing and time (≈1000 cycles and 30 days) are achieved. The softness of fibrous OECTs enables a comfortable contact after attaching to human skin, which can reduce the interfacial impedance to achieve a high‐quality local amplification of the electrocardiography signals (signal‐to‐noise ratio of 21.7 dB) even in skin squeezed state or after one week. These results indicated that our fibrous OECTs have huge potential for versatile on‐skin electronics such as non‐invasive medical monitoring, soft sensors, and textile electronics.