An ultrafast thermal-responsive, shape memory and solvent-driven Fe3+-alginate/poly(N-isopropyl acrylamide)-based hydrogel actuator

In recent years, stimulus-responsive hydrogels have been extensively researched in the field of actuators due to their capacity to undergo significant deformation in response to various external stimuli. However, it is difficult for the existing hydrogel actuators to meet the requirements of simple preparation, fast response speed and shape memory function, which greatly limits their further application. In the present study, a multi-functional Fe3+-sodium alginate/poly(N-isopropyl acrylamide) interpenetrating network (IPN) hydrogel with ultrafast thermal response, shape memory function and solvent-driven behavior was prepared via a simple method. The creation of Fe3+-carboxylate coordination within the hydrogel network, coupled with ultraviolet (UV) photodissociation, was employed to achieve shape memory properties. Moreover, the local gradient of the hydrogel could be precisely programmed by manipulating the UV irradiation time and position. As a result, the obtained gradient hydrogels possessed excellent temperature-driven and solvent-driven properties which could not only carry out 4 s fast grasping of objects in 70 degrees C water, but also achieve 2D to 3D complex deformation in methanol aqueous solution. This work provided a new manufacturing method and application prospect for the development of novel intelligent hydrogel actuators.