Desublimation Frosting on Nanoengineered Surfaces

TL;DR

This study investigates how nanoengineered surface textures influence frost formation from vapor, revealing that certain nanoroughness can promote or inhibit frost growth at very low temperatures, with implications for designing icephobic surfaces.

Contribution

It provides a comprehensive experimental analysis of frost nucleation mechanisms on nanostructured surfaces within the sublimation domain, highlighting the effects of surface morphology on frost formation.

Findings

Nanoroughness increases frost probability on silicon at low temperatures.

Nanoscale textures with radii near the critical nucleation radius promote frost growth.

Desublimation is not the dominant frost pathway below -46°C on silicon.

Abstract

Ice nucleation from vapor presents a variety of challenges across a wide range of industries and applications including refrigeration, transportation, and energy generation. However, a rational comprehensive approach to fabricating intrinsically icephobic surfaces for frost formation-both from water condensation (followed by freezing) and in particular from desublimation (direct growth of ice crystals from vapor)-remains elusive. Here, guided by nucleation physics, we investigate the effect of material composition and surface texturing (atomically smooth to nanorough) on the nucleation and growth mechanism of frost for a range of conditions within the sublimation domain (0 C to -55C; partial water vapor pressures 6 to 0.02 mbar). Surprisingly, we observe that on silicon at very cold temperatures-below the homogeneous ice solidification nucleation limit (< -46 C)-desublimation does not become the favorable pathway to frosting. Furthermore we show that surface nanoroughness makes frost formation on silicon more probable. We experimentally demonstrate at temperatures between -48 C and -55 C that nanotexture with radii of curvature within one order of magnitude of the critical radius of nucleation favors frost growth, facilitated by capillary condensation, consistent with Kelvin's Equation. Our findings show that such nanoscale surface morphology imposed by design to impart desired functionalities-such as superhydrophobicity-or from defects, can be highly detrimental for frost icephobicity at low temperatures and water vapor partial pressures (< 0.05 mbar). Our work contributes to the fundamental understanding of heterogeneous phase transitions well within the equilibrium sublimation domain and has implications for applications such as travel, power generation, and refrigeration.