Superhydrophilic coatings with intricate nanostructure based on biotic materials for antifogging and antibiofouling applications

Methods for creating unique superhydrophilic interfaces by means of layer-by-layer (LbL) assembly have been demonstrated, and such interfaces have been used extensively in a variety of practical applications. Further, fabricating multifunctional superhydrophilic coatings using low-cost, nontoxic, environment-friendly, and plentiful materials from biological resources is highly desirable. Herein, superhydrophilic coatings with a highly jagged surface morphology were synthesized based on the electrostatic-interaction- or hydrogen-bonding-based LbL assembly of the biotic materials chitosan (CHI) and rice husk ash (RHA) nanosilica, which are abundantly available in nature. The synthesized multilayered (CHI/RHA nanosilica)_n films were highly transparent and resisted fogging, frosting, and biofouling. Specifically, given the water-absorbing capability of the films, they showed excellent antifogging and antifrosting properties even under aggressive fogging and frosting conditions. Further, the as-prepared superhydrophilic multilayered films, which had a rough surface structure at the micro- and nanoscale, showed potential in reducing the attachment of proteins and various microorganisms, significantly preventing the phenomenon of biofouling in stagnant liquids. Hence, this work provides a new route for assembling superwetting coatings from cost-effective natural materials for use in industrial applications.