Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Shuwang Wu
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA; School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China
Mutian Hua
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Dong Wu
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Yichen Yan
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Xinyuan Zhu
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China
Ximin He
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA; Corresponding author
Summary: 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.
