Substrate-Independent, Mechanically Tunable, and Scalable Gelatin Methacryloyl Hydrogel Coating with Drag-Reducing and Anti-Freezing Properties

Hydrogel coatings have aroused tremendous research interest due to their excellent biocompatibility, lubricity, and flexibility. However, most hydrogel coatings are limited by their low mechanical strength and large-scale applications on diverse substrates. Herein, a mechanically tunable gelatin methacryloyl-based hydrogel coating is developed via a scalable ultraviolet-curing strategy combined with post-immersion treatment in a sodium citrate–water–glycerol solution. Notably, the hydrogel coating shows mechanically tunable properties by changing the soaking time or the concentration of sodium citrate. The compression modulus of the hydrogel is enhanced by 15 times after 120 min of soaking in sodium citrate–water–glycerol. Besides, the anti-freezing property endows the hydrogel coating with low-temperature (e.g., −40 °C) flexibility. The hydrogel coating is transparent with a transmittance of over 80% within the visible light region and exhibits long-term stability (over 60 days at 25 °C and 40% relative humidity). Moreover, the obtained hydrogel coating shows good lubrication properties with a friction coefficient of less than 0.01. The fabricated hydrogel coating can be potentially used in engineering applications where mechanically tunable properties, anti-freezing, lubrication, and excellent light transmittance are required.