A novel eco- and user-friendly graphene/leather-based composite for real-time mechano-monitoring of human motion

Up to now, flexible wearable sensors have played a significant role in mimicking the comprehensive functions of human sensing as an essential part of the realization of human-machine interactions and artificial intelligence. However, most electronic devices are made of polymer-based materials, which have poor biodegradability and are harmful to the environment. Inspired by natural hair squama structure, a high conductivity, biodegradable, and biocompatible flexible sensor was designed for detecting human physiological signals. The graphene/leather-based composite was leeched onto oil-tanned leather prepared without the involvement of chromium ions, then scalable adsorption assisted coating was used to construct a piezoresistive sensor. With the micro-to-nano hierarchical three-dimensional structure of natural leather, the novel conductive oil-tanned leather (COL) exhibited a high specific surface area for a piezoresistive effect and excellent conductivity (80 kΩ·sq−1), high sensitivity (28.96 kPa−1 under compressing condition and 52.10 under stretch condition). Meanwhile, favorable biodegradability and biocompatibility could be achieved. Moreover, the relatively mature and fully integrated commercial wearable sensors are mostly wired transmission and expensive. The piezoresistive COL sensor can not only be used to monitor physiological signals, but can also be connected to a wireless module to obtain real-time monitoring data of plantar pressure. Furthermore, the sensor can control the light of LED to achieve human-machine interaction. This wearable intelligent sensor can not only solve the problem that traditional sensors are toxic to the environment but also has broad applications in health-monitoring technology.