Self-adhesive and contractile silk fibroin/graphene nano-ionotronic skin for strain sensing of irregular surfaces.

Nanofiber-based artificial skin has shown promise for application in flexible wearable electronics due to its favorable breathability and comfortable wearability. However, the electrospinning method commonly used for nanofiber preparation suffers from poor spinning performance when used for ionotronic solutions. Moreover, the resulting membrane usually lacks self-adhesive and self-adapting properties when it is attached to an irregular subject, which greatly hinders its practical usage. Herein, a self-adhesive and contractile silk fibroin/graphene nano-ionotronic skin was successfully prepared using a high-yield electro-blowing technique. The electro-blowing technique was able to effectively overcome the instability of the spinning jet and raise the feed rate to at least 5 ml h-1. The high Ca2+content provided the fabricated nano-ionotronic skin with humidity-induced stretchability and robusticity. More importantly, the ionotronic skin also possessed a self-adhesive property and was able to contract to adapt to irregular surfaces. Additionally, an analytical piezoresistive model was successfully built to predict the response of the sensors to stress. Furthermore, due to its stable conductivity, sensitivity, and self-adapting property, the obtained nano-ionotronic skin can be used for body monitoring, for example, for bending of the arm and hand gestures. The design and manufacture concept proposed in this work might inspire the development of high-yield ionotronic nanofibers and the design of self-adapting artificial skin.