Saline tolerant tough-yet-strong fiber-reinforced gel-nacre for soft actuator

Abstract

Fiber-reinforced hydrogel (FrH) possesses the capability as flexible structural materials. The state-of-the-art FrH left a number of key issues untouched, including interfacial effects and the tolerance against salt disturbance. Herein, we report a saline-tolerant and strong-yet-tough FrH. This is achieved by infiltrating gel-nacre matrix into a polyaramid fabric via a multiscale reinforcement at the interface. The incorporation of strong yet geometrically compliant fabric skeleton into saline-induced shrinking gel-nacre matrix with mechanical superiority resolves the swelling mismatch between swollen hydrogel and rigid fiber, relieving the trade-off property between strength and toughness. Such integration leads to a tight interfacial binding between both components, where fabricated FrH can sustain its structure up to 5 months in artificial sea water yet exhibit superior tough-yet-strong mechanical performances, i.e., ultimate fracture strength of 111.6 MPa, toughness of 383.3 MJ/m3, and fracture energy of 195.8 kJ/m2. The prototype of a bilayer petalage-like actuator that reversibly transfers from 2D to 3D structure in water and saline driving by osmotic pressure gradient was demonstrated. These inspiring results open the door for developing flexible, tough yet stable materials for applications in salty environments including soft robots, energy absorption structural materials, etc.