Loach-Inspired Lubricant and Antibacterial Hydrogels with Thermochromism for Multifunctional Coatings

Hydrogels with brilliant hydrophilicity and prominent biocompatibility are among the promising coating materials with engineering applications; however, they are still facing significant challenges in terms of multifunctional integration. Herein, inspired by loach, a multifunctional hydrogel with comprehensive advantages of lubricity, bacteriostasis, thermochromism, and antifouling property is successfully constructed by introducing loach mucus. The polyacrylamide/sodium hyaluronate (PAAm/HA) network was selected as the primary framework to provide fundamental mechanical properties. By replacing the water solvent with the extracted loach mucus, we can improve the mechanical property and achieve high lubricity and bacteriostasis of the hydrogel. The hydrogel exhibits a low friction coefficient in various solvent environments and has inhibitory effects on both Gram-negative and Gram-positive bacteria. Meanwhile, the hydrogel was proven to be antifouling. Furthermore, the inclusion of dopamine not only forms stable amide bonds with the carboxyl groups on HA but also serves as an adhesive moiety to allow the hydrogel to attach to diverse substrates, thus improving the hydrophilicity and lubrication of the target substrate. Besides, the crystallization properties of gluconate at low temperatures enable the hydrogel to undergo a thermochromic transparent-opaque transition. This work opens up an avenue for the rational design of multifunctional hydrogel coatings, which can be used for drag reduction in medical devices and privacy protection in smart windows.