Highly strong and sensitive bilayer hydrogel actuators enhanced by cross-oriented nanocellulose networks

Temperature-responsive bilayer hydrogel actuator with anisotropic structure in mutually perpendicular directions was successfully prepared, where poly (N-isopropyl acrylamide)/cellulose nanofiber (PNIPAM/CNF) double network hydrogel was applied as the top layer, and poly (acrylamide-co-acrylic acid)/cellulose nanofiber (PAM-AA/CNF) double network hydrogel served as the bottom layer. The cross-oriented structure of the two hydrogel layers contributed to the superior actuation ability and mechanical performance of the bilayer hydrogel actuator. Consequently, the hydrogel actuator could quickly lift a weight with 70 times of their own weight with a high bending speed of 10.21 (°/s). Furthermore, the tensile strength and elongation at break of the hydrogel actuator reached 729.5 ± 21.5 KPa and (406.5 ± 11.3) % respectively. After further cross-linking by Fe 3+ , the tensile strength of the actuator reached 3.86 MPa. With excellent mechanical performance and actuation ability, the resulting bilayer hydrogel showed a promising application potential as artificial soft tissue materials and intelligent actuators. • Temperature-responsive bilayer hydrogel actuator was successfully prepared. • Both layers of the actuator were anisotropic double network hydrogels. • The orientation directions of the two hydrogel layers were mutually perpendicular. • The bending speed of the bilayer hydrogel actuator reached 10.21 (°/s). • After cross-linking by Fe 3+ , the strength of hydrogel actuators reached 3.86 MPa.