3D dual network effect of alkalinized MXene and hBN in PVA for wearable strain/pressure sensor applications

Next-generation wearable electronic devices rely on electronic skin for its high flexibility, wearability, and ability to monitor vital health signs. Despite these advantages, developing flexible strain sensors for full-range human activity detection remains challenging. A solution involves thread-based motion sensors seamlessly integrated into clothing. This study employs a synergistic dual three-dimensional network using hydroxyl-functionalized MXene (MXOH) and hexagonal boron nitride (hBN) to modify poly(vinyl alcohol) (PVA) hydrogels, showcasing promising advancements in wearable technology. The hydrogel, incorporating MXOH with its larger lateral size and hBN with its smaller lateral size, forms a robust 3D network that reinforces the percolation network of MXOH nanosheets. This strategic combination ensures stability in the conductive pathway, minimizing electrical hysteresis during mechanical stress. The completion of the 3D network in PVA, facilitated by hBN, significantly enhances electrical conductivity due to the ion conduction properties of hBN. Moreover, the incorporation of non-conductive hBN nanosheets amplifies overall conductivity compared to MXOH alone, contributing to network stability. Rheological tests demonstrate the pronounced impact of increasing hBN weight percentage on the storage modulus, indicating the formation of a 3D network upon percolation. Additionally, MXOH and hBN exhibit self-healing characteristics through hydrogen bonding with the PVA chain, with hBN displaying higher mobility and faster self-healing compared to MXOH. These hydrogel-based flexible sensors exhibit mechanical stability and responsiveness across a wide pressure range (0 to 80 kPa) and find versatile applications in touch screens, thread-based motion sensors, and wearable electronics, promising transformative advances in handwriting-to-digital translation and smart textile technologies.