Water drop-surface interactions as the basis for the design of anti-fogging surfaces: Theory, practice, and applications trends

Abstract

Glass-and polymer-based materials have become essential in the fabrication of a multitude of elements, including eyeglasses, automobile windshields, bathroom mirrors, greenhouses, and food packages, which unfortunately mist up under typical operating conditions. Far from being an innocuous phenomenon, the formation of minute water drops on the surface is detrimental to their optical properties (e.g., light-transmitting capability) and, in many cases, results in esthetical, hygienic, and safety concerns. In this context, it is therefore not surprising that research in the field of fog-resistant surfaces is gaining in popularity, particularly in recent years, in view of the growing number of studies focusing on this topic. This review addresses the most relevant advances released thus far on anti-fogging surfaces, with a particular focus on coating deposition, surface micro/nanostructuring, and surface functionalization. A brief explanation of how surfaces fog up and the main issues of interest linked to fogging phenomenon, including common problems, anti-fogging strategies, and wetting states are first presented. Anti-fogging mechanisms are then discussed in terms of the morphology of water drops, continuing with a description of the main fabrication techniques toward anti-fogging property. This review concludes with the current and the future perspectives on the utility of anti-fogging surfaces for several applications and some remaining challenges in this field.

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…Fogging on the surface of safety glasses, eyeglasses, cold windshields, photovoltaic cell, and other substrates frequently occurs and may cause detrimental effects on daily life and problems for many technological applications . This problem can be effectively solved by controlling the interaction between liquids and substrates ( Figure a).…”

“…On superhydrophobic surfaces such as water‐repellent lotus leaf, due to the micro‐/nanoscale structure, the nucleated water droplets would not be able to wet the surface, forming a typical Cassie state. Therefore, the unstable water droplets can easily roll off the surfaces instead of pinning on the surfaces to form fog . Inspired by green bottle fly eye (Figure b), Kim et al prepared ZnO microspheres with the similar structure.…”

“…In addition, micro‐/nanostructured surfaces fabricated by hydrophilic building blocks can exhibit superhydrophilicity and prevent fogging . Because of the strong affinity between superhydrophilic substrate and water droplets, condensed droplets would spread out to form a scattering‐free water film rather than gather as separated droplets (Figure a) . With inspiration from Morpho menelaus terrestris butterfly wing scales, Niu et al fabricated a monolayer SiO 2 film with multiscale hierarchical pagoda structures (MHPSs) on a glass substrate.…”

Preparation of superhydrophilic nanosilica/polyacrylate hard coatings on plastic substrate for antifogging and frost‐resistant applications

“…[1][2][3][4][5][6][7][8][9][10] Good performance of such AFF coatings on glass and metals (Al and Cu) has been achieved. This phenomenon is known as fogging or frosting depending on whether the surface temperature is lower than the dew or frost point of water.…”

“…Fogging/frosting occurs frequently in our daily life. 1,2,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] There is great demand for effective AFF surfaces to maintain visibility and transparency in relatively moist environments. To avoid its formation, it is useful to apply an antifog/frost resistant (termed AFF, hereinafter) layer on the surface of use, particularly when the surface is hydrophobic and susceptible to deposition of moisture droplets.…”