Tough Adhesive, Antifreezing,\nand Antidrying Natural\nGlobulin-Based Organohydrogels for Strain Sensors

Abstract

Hydrogels are often used to fabricate strain sensors;\nhowever,\nthey also suffer from freezing at low temperatures and become dry\nduring long-time storage. Encapsulation of hydrogels with elastomers\nis one of the methods to solve these problems although the adhesion\nbetween hydrogels and elastomers is usually low. In this work, using\nbovine serum protein (BSA) as the natural globulin model and glycerol/H₂O as the mixture solvent, BSA/polyacrylamide organohydrogels\n(BSA/PAAm OHGs) were prepared by a facile photopolymerization approach.\nAt the optimal condition, BSA/PAAm OHG demonstrated not only high\ntoughness but also tough adhesion properties, which could strongly\nadhere to various substrates, such as glass, metals, rigid polymeric\nmaterials (even poly­(tetrafluoroethylene), i.e., PTFE), and soft elastomers.\nMoreover, BSA/PAAm OHG was flexible and showed tough adhesion at −20\n°C. The toughening mechanism and the adhesive mechanism were\nproposed. On being encapsulated by poly­(dimethylsiloxane) (PDMS),\nit illustrated good antidrying performance. After introducing a conductive\nfiller, the encapsulated BSA/PAAm OHG could be used as a strain sensor\nto detect human motions. This work provides a better understanding\nof the adhesive mechanism of natural protein-based organohydrogels.