Smart multi-stimuli responsive single- and bilayer hydrogels with combined shape memory and actuating properties for self-healable circuits and sensors

The combination of shape memory and actuating properties has recently been an exciting topic in smart material science, broadening their applications. Herein, we prepared single- and bilayer hydrogels using polyvinyl alcohol, crosslinked poly (aminated glycidyl methacrylate- acrylamide- acrylic acid), and poly (N-isopropyl acrylamide) to the combination of shape memory and actuating behavior. Single- and bilayer hydrogels represented good shape memory properties in response to temperature, solvents (DMF and ethanol), and electrolyte environment (NaCl, CuCl2, and FeCl3 solutions). The actuating behavior in response to temperature, electrolytes, and the electrical field was observed in the bilayer form. Also, the hydrogels were well applied as a temperature-responsive gripper. The hydrogels are electrically conductive and self-healable in single-layer form, allowing them to be part of self-healing circuits. Temperature electrical sensing is another application of these single-layer hydrogels.