Highly Stretchable and Strong Poly (Vinyl Alcohol)-Based Hydrogel for Reprogrammable Actuator Applications

Abstract

Actuators are biomimetic devices inspired by behaviors of different creatures. Among different kinds of materials, hydrogel is considered as a suitable choice for fabrication of actuators because of its similarity to biological tissues and multi-stimuli responsiveness. For hydrogel actuators, 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. Therefore, imparting reprogrammability to actuator with homogeneous materials to achieve complex shape configuration is a convenient and cost-effective method for multimode deformation. Nevertheless, there have been rarely such actuators that meet the requirement above yet. 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, as a hydrophilic polymer and an amphiphilic surfactant, forms the hydrogel substrate and helps disperse the hydrophobic PVA-SA-AN into the hydrogel. TA, which formed hydrogen bonds with PVA and PVA-SA-AN, provides 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 further demonstrated. We believe that the proposed design strategy can provide a facile and low-cost way to develop high-performance reprogrammable hydrogel actuators.

Keywords: poly (vinyl alcohol), Mechanical property, reprogrammable, hydrogel actuator