Silk fibroin/Ag nanowire-based multifunctional sensor for wearable self-powered wireless multi-sensing microsystems

Wearable sensing devices play an increasingly important role in advancing the rapid development of the Internet of Things (IoT) and artificial intelligence (AI), and a smart sensing network based on wide-distributed sensing nodes has become an appealing trend. However, monolithic integration of multiple sensing functions is still a critical issue for sensing nodes. Herein, we present a flexible multifunctional sensor based on a silk fibroin/silver nanowire (SF/AgNW) composite film. Mask spray coating technology is optimized to prepare the functional sensing layer with a cross-linked AgNW network structure inside. The association of the SF/AgNW composite film and the cross-linked AgNW network structure endows the developed sensor with pressure sensing characteristics and temperature sensing characteristics. Furthermore, by in-depth analysis of the coupling law between the input variables and the resistance changes, the sensor is successfully extended to realize the functions of finger proximity detection and human breathing monitoring. Additionally, the sensor is successfully confirmed to possess remarkable mechanical reliability and sensing characteristic stability by a systematic experiment. More importantly, to highlight the practical feasibility of the proposed sensor, an all-in-one self-powered wireless multi-sensing microsystem is constructed based on the developed sensor, a high-performance triboelectric-piezoelectric-electromagnetic hybrid generator (TPEHG), and system circuits. With the TPEHG as the only power source, the microsystem is successfully demonstrated to realize continuous self-powered work and sense environmental variables through the developed sensor. Meanwhile, the obtained sensing data are transmitted to a mobile phone in real time at 1 Hz. The multiple sensing characteristics of the sensor and the autonomous features of the microsystem give them outstanding potential and value in the smart IoT field, especially in constructing a distributed smart sensing network.