Highly stretchable and strong poly (vinyl alcohol)-based hydrogel for reprogrammable actuator applications

Abstract

Hydrogel is considered as a suitable choice for fabrication of actuators because of its similarity to biological tissues and multi-stimuli responsiveness. However, it is necessary to address the limit resulted from the traditional bilayer structure that leads to interface issue or permanent gradient structure that leads to unchangeable deformation mode. Herein, a highly-stretchable and reprogrammable PVA-based hydrogel actuator is reported. The actuator was fabricated through a freezing-thawing treatment of the blend of PVA, mono (9-anthracene methyl) succinate grafted PVA (PVA-SA-AN), tannic acid (TA) and cetyltrimethyl-ammonium bromide (CTAB) followed with UV irradiation. According to the scheme, PVA forms the hydrogel substrate and helps disperse the hydrophobic PVA-SA-AN into the hydrogel. TA forms hydrogen bonds with PVA and PVA-SA-AN, providing enhancement to the mechanical properties of the hydrogel. CTAB further disperses the anthracene groups so that the UV-induced reversible dimerization/cleavage can endow the hydrogel with the function of water-driven actuation as well as reversible programmability. The improved mechanical properties and the reprogrammable actuation performance are demonstrated. We believe that the proposed design strategy can provide a facile and low-cost way to develop high-performance reprogrammable hydrogel actuators.