"Sweat-Driven" MXene Composites with Energy-Storage and Thermal-Management Multifunctions: A Platform for Versatile Electronic Skins.

Abstract

Most exogenous electronic skins (e-skins) currently face challenges of complex structure and poor compatibility with the human body. Utilizing human secretions (e.g., sweat) to develop e-skins is an effective solution strategy. Here, a new kind of "sweat-driven" e-skin is proposed, which realizes energy-storage and thermal-management multifunctions. Through the layer-by-layer assembly of MXene-carbon nanotube (CNT) composite with paper, lightweight and versatile e-skins based on supercapacitors and actuators are fabricated. Long CNTs wrap and entangle MXene nanosheets, enhancing their long-distance conductivity. Furthermore, the CNT network overcomes the structural collapse of MXene in sweat, improving the energy-storage performance of e-skin. The "sweat-driven" all-in-one supercapacitor with a trilayer structure is patternable, which absorbs sweat as electrolyte and harnesses the ions therein to store energy, exhibiting an areal capacitance of 282.3 mF cm-2 and a high power density (2117.8 µW cm-2). The "sweat-driven" actuator with a bilayer structure can be driven by moisture (bending curvature of 0.9 cm-1) and sweat for personal thermal management. Therefore, the paper serves as a separator, actuating layer, patternable layer, sweat extractor, and reservoir. The "sweat-driven" MXene-CNT composite provides a platform for versatile e-skins, which achieve the interaction with humans and offer insights into the development of multifunctional wearable electronics.