Multifunctional electronic skin with waterproof strain sensing and ultra-stretchable triboelectric energy harvesting

Abstract

Wearable flexible strain sensors and single-electrode triboelectric nanogenerators (TENGs) have emerged as promising building blocks for smart electronic skin applications. However, only a few studies have succeeded in integrating both technologies into a single device while maintaining stable and reliable performance. Here, we present a simple and scalable fabrication approach using spraying, electrostatic spinning, and vacuum filtration to develop a multifunctional system comprising a water-resistant strain sensor and a stretch-insensitive TENG. The strain sensor is constructed from carboxylated carbon nanotubes (CNTs-COOH), fluorinated alkyl silane-modified Ti₃C₂T_x (FAS-MXene), and a flexible polydimethylsiloxane (PDMS). The TENG consists of a film made of polyvinylpyrrolidone-modified CNTs (PVP-CNTs), Ti₃C₂T_x (MXene), and electrospun thermoplastic polyurethane nanofibres (TPU) as an electrode. When employed as a strain sensor, the device demonstrates high sensitivity, a wide sensing range (0% to 100% strain), excellent water resistance, and outstanding durability (5,000 cycles at 50% strain). These properties are achieved through MXene surface chemical modification and a unique microcrack structure developed under strain. As a highly stretchable TENG, the device exhibits remarkable stability, with minimal changes in relative resistance (0.03 at 20% strain) even after 5,700 cycles, owing to the strong adhesion forces generated by hydrogen bonding interactions between the porous TPU film, PVP-CNTs, and MXene. The integrated device enables simultaneous strain sensing and self-powering capabilities, offering a versatile platform for applications such as health monitoring, encrypted information transmission, and object recognition. The low cost and ease of mass fabrication of this electronic skin mark a significant advancement towards future multifunctional wearable technologies.