Simple preparation of redox induced shape memory and self-healable ionic liquid based gels for flexible strain sensors

Abstract

The aim of this work is to fabricate the stretchable, redox-driven shape memory, and self-healable gels sensors using one-step self-assembling method at ambient temperature. The mixed aqueous solution of poly (vinyl alcohol) (PVA), ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate), and phytic acid (PA) can transfer to PVA/IL/PA gels due to the multiple hydrogen bonds and electrostatic interaction among the three different molecules. The gel exhibits outstanding redox-driven shape memory fixity in trivalent iron ion solution and reversible recovery in ascorbic acid solution, respectively. The reversible breakage and recombination of hydrogen bonds and electrostatic interaction endows the PVA/IL/PA gels excellent mechanical properties and self-healing effect. The optimum tensile strength and elongation at break (EB) of gels are 1.56 MPa and 368%, respectively. The EB and self-healing efficiency of the healed gel can reach up to 161.91% and 74%, which are competitive in ion gels. Moreover, the gel can be used as flexible strain sensors, which exhibit good performance in monitoring human activities and voice recognition. This study will provide one green and universal approach in fabricating multi-functional gels, which show promising applications in the field of tissue engineering, sensors and actuators, and soft electronic materials etc.