Multi-functional graphene/leather for versatile wearable electronics

Flexible wearable electronics have attracted great attention due to their extensive applications in health monitoring, intelligent clothing, etc. The substrate of most wearable electronics is commercial polymers, biopolymers, and fabrics. These substrates have some shortcomings, such as air-impermeability and being non-waterproof. Leather is a natural material with a natural hierarchical structure, which possesses the unique advantages of breathability, water resistance, and biodegradability, enabling it to be a promising substrate for wearable electronics. Although leather-based wearable electronics have been developed, it is still a challenge to integrate multiple functions in a single leather-based electronic device due to the different working mechanisms of various functions. Here, multi-functional reduced graphene oxide/leathers (RGO/leathers) for versatile wearable electronics are fabricated by vacuum filtration of GO dispersions, in situ reduction of GO/leather, and painting thermochromic ink. The RGO/leathers are characterized by low sheet resistance (90 omega (-1)), large fracture strain (91%), and air permeability, which are due to the tight intertwining and extensive hydrogen bond interaction between RGO and collagen fibers. Thus, the performances of electrical heating, output of the triboelectric nanogenerators (TENGs), and electromagnetic interference (EMI) shielding of RGO/leather are first investigated in detail. The electric-to-thermal conversion efficiency of the RGO/leather with different RGO contents is over 80%. The output of the RGO/leather-based TENG based on the contact-separation mode is stable at 80 V. Also, the EMI shielding effectiveness of RGO/leather is over 23 dB, which exceeds the target value required for commercial products. Subsequently, the wearable applications of the RGO/leather are demonstrated, such as electrically driven personal thermal management devices (kneepads), wearable dry electrodes (to collect electrophysiological signals), self-powered material identification, and EMI shielding pockets. In summary, versatile wearable electronics can be fabricated based on RGO/leather through a green and gentle approach. RGO/leather provides a new platform for the fabrication of air-permeable and sustainable wearable electronics, broadening the application prospects of natural polymer materials in wearable electronics.