Electro-osmotic Actuators from Cellulose Nanocrystals and Nanocomposite Hydrogels

Electroactive biopolymer hydrogels have potential applications as soft actuators for biomedicine and robotics. Both free-standing films of biosourced cellulose nanocrystals (CNCs) and nanocomposite hydrogels comprising CNCs and hydrophilic polymers behave as anionic polymer actuators in response to an electric field. CNCs were incorporated into non-electroresponsive polyacrylamide to yield nanocomposite materials with greater field-induced bending responses and longer lifetimes than purely CNC films. The actuation rate of CNC–polyacrylamide nanocomposite hydrogels in ionic solution can be tuned by the amount of sulfate-bearing CNCs incorporated into the hydrogel and the density of sulfate groups on CNC surfaces to produce vast nanocomposite actuators (9° s–1 bending speed).