Microscopic receding contact line dynamics on pillar and irregular superhydrophobic surfaces.

Yong Han Yeong,Ilker S Bayer,Eric Loth,Athanasios Milionis

doi:10.1038/srep08384

Yong Han Yeong, Ilker S Bayer + Show 2 more

Open Access

https://doi.org/10.1038/srep08384

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Abstract

Receding angles have been shown to have great significance when designing a superhydrophobic surface for applications involving self-cleaning. Although apparent receding angles under dynamic conditions have been well studied, the microscopic receding contact line dynamics are not well understood. Therefore, experiments were performed to measure these dynamics on textured square pillar and irregular superhydrophobic surfaces at micron length scales and at micro-second temporal scales. Results revealed a consistent “slide-snap” motion of the microscopic receding line as compared to the “stick-slip” dynamics reported in previous studies. Interface angles between 40–60° were measured for the pre-snap receding lines on all pillar surfaces. Similar “slide-snap” dynamics were also observed on an irregular nanocomposite surface. However, the sharper features of the surface asperities resulted in a higher pre-snap receding line interface angle (~90°).

Highlights

Receding angles have been shown to have great significance when designing a superhydrophobic surface for applications involving self-cleaning
I nspired by organisms in nature such as the lotus leaf[1] and water strider legs[2], superhydrophobic surfaces feature remarkable water repellency which are widely known to be governed by a combination of roughness at the micro/nano scale and low surface energy[3,4,5]
It has been comprehensively agreed by researchers that the sole use of contact angle (CA) is insufficient to describe the wettability of the surface[8,9,10,11,12], especially within the context of practical applications of superhydrophobic surfaces such as self-cleaning

Summary

Introduction

Receding angles have been shown to have great significance when designing a superhydrophobic surface for applications involving self-cleaning. I nspired by organisms in nature such as the lotus leaf[1] and water strider legs[2], superhydrophobic surfaces feature remarkable water repellency which are widely known to be governed by a combination of roughness at the micro/nano scale and low surface energy[3,4,5] These two parameters reduce the area of contact between the solid-liquid interface as well as its molecular attraction to trap pockets of air between the surface asperities, resulting in a Cassie-Baxter wetting state[6]. The understanding of receding line dynamics at the microscopic level could potentially lead to a more successful optimization and implementation of superhydrophobic surfaces in these applications

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