Tendon-inspired anti-freezing tough gels

Sidi Duan; Shuwang Wu; Mutian Hua; Dong Wu; Yichen Yan; Xinyuan Zhu; Ximin He

doi:10.1016/j.isci.2021.102989

Tendon-inspired anti-freezing tough gels

iScience. 2021 Aug 17;24(9):102989. doi: 10.1016/j.isci.2021.102989. eCollection 2021 Sep 24.

Authors

Sidi Duan¹, Shuwang Wu^{1

2}, Mutian Hua¹, Dong Wu¹, Yichen Yan¹, Xinyuan Zhu², Ximin He¹

Affiliations

¹ Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
² School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.

Abstract

Hydrogels have gained tremendous attention due to their versatility in soft electronics, actuators, biomedical sensors, etc. Due to the high water content, hydrogels are usually soft, weak, and freeze below 0°C, which brings severe limitations to applications such as soft robotics and flexible electronics in harsh environments. Most existing anti-freezing gels suffer from poor mechanical properties and urgently need further improvements. Here, we took inspirations from tendon and coniferous trees and provided an effective method to strengthen polyvinyl alcohol (PVA) hydrogel while making it freeze resistant. The salting-out effect was utilized to create a hierarchically structured polymer network, which induced superior mechanical properties (Young's modulus: 10.1 MPa, tensile strength: 13.5 MPa, and toughness: 127.9 MJ/m³). Meanwhile, the cononsolvency effect was employed to preserve the structure and suppress the freezing point to -60°C. Moreover, we have demonstrated the broad applicability of our material by fabricating PVA hydrogel-based hydraulic actuators and ionic conductors.

Keywords: biomimetics; materials property; polymers.