Capillary Balancing: Designing Frost-Resistant Lubricant-Infused Surfaces.

William S Y Wong,Katharina I Hegner,Abhinav Naga,Valentina Donadei,Lukas Hauer,Doris Vollmer

doi:10.1021/acs.nanolett.0c02956

William S Y Wong, Katharina I Hegner + Show 4 more

Open Access

https://doi.org/10.1021/acs.nanolett.0c02956

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Abstract

Slippery lubricant-infused surfaces (SLIPS) have shown great promise for anti-frosting and anti-icing. However, small length scales associated with frost dendrites exert immense capillary suction pressure on the lubricant. This pressure depletes the lubricant film and is detrimental to the functionality of SLIPS. To prevent lubricant depletion, we demonstrate that interstitial spacing in SLIPS needs to be kept below those found in frost dendrites. Densely packed nanoparticles create the optimally sized nanointerstitial features in SLIPS (Nano-SLIPS). The capillary pressure stabilizing the lubricant in Nano-SLIPS balances or exceeds the capillary suction pressure by frost dendrites. We term this concept capillary balancing. Three-dimensional spatial analysis via confocal microscopy reveals that lubricants in optimally structured Nano-SLIPS are not affected throughout condensation (0 °C), extreme frosting (−20 °C to −100 °C), and traverse ice-shearing (−10 °C) tests. These surfaces preserve low ice adhesion (10–30 kPa) over 50 icing cycles, demonstrating a design principle for next-generation anti-icing surfaces.

Highlights

Frost formation occurs whenever cold surfaces interact with warmer and more humid environments.[1−4] In Nature, frosting is far more prevalent than icing and can be even more detrimental
To assess the influence of capillary balancing on condensationfrosting (Figure 1), microstructured slippery liquid-infused porous surfaces (SLIPS) (Micro-SLIPS, 18 μm, μS, Figure 1a,b, Figure S1) are investigated alongside asproposed nanostructured SLIPS composed of nanointerstitials (Nano-SLIPS, 30 nm, nS, Figure 1c,d)
The severe problem of lubricant depletion in SLIPS during frosting and icing can be prevented if the interstitial spacing of the infused surface is smaller than that between frost dendrites

Summary

■ INTRODUCTION

Frost formation occurs whenever cold surfaces interact with warmer and more humid environments.[1−4] In Nature, frosting is far more prevalent than icing and can be even more detrimental. Anti-icing and anti-frosting properties of these coatings are potentially ruined after a single frosting event.[16−18] To the best of our knowledge, the understanding and control of frost-induced lubricant depletion is still unresolved To solve this standing problem and to prevent frost-induced depletion in SLIPS, it is important to correlate the characteristic length scales between the surface and the frost. SLIPS should provide a stabilizing capillary pressure, PnS that exceeds the capillary-induced suction pressure posed by frost dendrites, Pice. We term this design principle “capillary balancing”. The capillary pressure stabilizing the smallest interstitially spaced NanoSLIPS (30 nm) dominates over the capillary suction pressure of the frost dendrites, resulting in a stabilized lubricant layer. Our design principle successfully achieved frost-resistant antiicing surfaces, showing a consistently low ice adhesion (N) per unit area (m2) of between 10 and 30 kPa over 50 icing cycles

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES