Tough, antibacterial and self-healing ionic liquid/multiwalled carbon nanotube hydrogels as elements to produce flexible strain sensors for monitoring human motion

Hydrogel wearable sensors with multifunctional characteristics are highly desirable in the development of the current environment. Besides the constant concern of high conductivity and good mechanical properties, antibacterial properties and self-healing capability are also essential to hydrogel strain sensors. Herein, inspired by the purslane, the multifunctional hydrogel sensors (p(AAm/DMLB)/IL-LPs/c-MWCNTs) were mainly constructed by the copolymerization of dimethylaminoethyl methacrylate (DMLB) and polyacrylamide p(AAm) without adding external antimicrobial agents in a facile strategy. The results exhibited DMLB could contribute not only the antimicrobial properties, but also interact with the carboxyl-functionalized multi-walled carbon nanotubes (c-MWCNTs) and ionic liquid (IL)-latex particles (LPs) by hydrogen bond cross-linking and physical entanglement, respectively, which significantly enhanced the mechanical strength and resilience of the hydrogel sensors. Notably, without adding inorganic salt, the obtained hydrogel sensors owned a wide spectrum of sensory properties and high strain sensitivity (gauge factor = 12.71 at 100–1100%, quick response = 500 ms) owing to the synergistic effect between IL and c-MWCNTs. Moreover, the hydrogel sensors exhibited anti-piercing for efficient energy dissipation, together with self-healing properties. Therefore, the integration of self-healing, conductive and antibacterial hydrogel-based strain sensors will display broad application in sophisticated intelligence, soft robotics, bionic prosthetics, personal health care, and other fields using inexpensive, green, and easily available biomass.