Hybrid Piezoresistive 2D MoS2/PEGDA/PANI Covalent Hydrogels for the Sensing of Low-to-Medium Pressure

Wearable technologies are attracting increasing attention in the materials science field, prompting a quest for active components with beneficial functional attributes whilst ensuring human and environmental safety. Hydrogels are highly biocompatible platforms with interesting mechanical properties, which can be exploited for the construction of strain sensors. In order to improve the directionality of their strain response and combine it with electrical properties to fabricate piezoresistive devices, it is possible to incorporate various types of nanofillers within the polymeric network of the hydrogels. 2D materials are ideal nanofillers thanks to their intrinsic two-dimensional anisotropy and unique electronic properties. Herein, the covalent functionalization of 2D 1T-MoS2 is exploited to build robust hybrid cross-linked networks with a polyethylene glycol diacrylate gel (PEGDA). The conductivity of this nanocomposite is also further improved by inducing the interfacial polymerization of aniline. The resulting free-standing samples demonstrate a linear and highly reversible piezoresistive response in a pressure range compatible with that of peripheral blood, while also featuring good compatibility with human skin cells, thereby making them interesting options for incorporation into wearable strain sensors.