A sticky, thermal tolerant, tough BP@PVP ionogel for epidermal sensors

By exploring liquid-phase exfoliation in an imidazolium ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), with the help of a two-step ultrasonic process, the high-yield few-layered black phosphorus (BP) flake with a thickness of 1.3–1.75 nm and a lateral size of 300–900 nm has been obtained. Afterwards, a transparent BP@PVP ionogel has been prepared through the photoinitiated polymerization of N-vinylpyrrolidone (NVP) in [BMIM]PF6 including BP flakes (0.2 mg g−1). The imidazole-containing polyvinylpyrrolidone (PVP) network structure endowed the BP@PVP ionogel with the ability to adhere to diverse surfaces and superior mechanical performance, including high tensile strength (≈1.43 MPa), large elongation (≈19 times), and high toughness (≈1868 MJ m−3). The BP@PVP ionogel can be assembled into a flexible and tough epidermal sensor to precisely monitor the diverse human body motions in real time; importantly, the sensor can tolerate a high temperature (100 °C) over 72 hours without any protection. The sensitive performance, robust interfacial adhesion, and thermal tolerance provide the BP@PVP Ionogel with potential for application in healthcare monitoring or human-computer user interfaces.