Non-Swelling and Anti-Fouling MXene Nanocomposite Hydrogels for Underwater Strain Sensing

Flexible wearable sensors are of interest for underwater applications such as aquatic robots and marine exploration. Non-swelling hydrogels would be a preferable candidate for underwater sensing with stable sensing performance. Herein, hydrogels comprised of MXene and polyhydroxyethyl methacrylate (PHEMA) are designed and manufactured. Owing to the synergistic effect of phase separation zones and hydrophilic/hydrophobic interaction, MXene/PHEMA hydrogels exhibit non-swelling performance in various liquid media (e.g., water, seawater) and effectively avoid the adhesion of proteins and bacteria. In addition, MXene/PHEMA hydrogels exhibit a large sensing range (more than 400%), high tensile strength (0.54 MPa), and skin-compliance modulus (120 kPa). Furthermore, the resulted hydrogel-based sensors possess superior sensibility (4.42 at 150–450% strain), fast responsiveness (200 ms), and durable sensing ability (over 1000 cycles). The hydrogel-based sensors can accurately monitor human motions (both large and subtle motions) in air and in various liquid media. Benefiting from the non-swelling and anti-fouling ability, the hydrogels could maintain high mechanical strength and cyclic stability after being immersed in water for 30 days, and precisely detect the movement of human and shark models underwater. It is conceivable that non-swelling and anti-fouling MXene/PHEMA hydrogels provide a feasible material to construct electronic skins for various harsh liquid environments.