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    Impacting Droplet Can Mitigate Dust from PDMS Micro-Post Array Surfaces

    Year: 2021

    Journal: Coatings, Volume 11, NOV

    Authors: Abubakar, Abba Abdulhamid; Yilbas, Bekir Sami; Yakubu, Mubarak; Al-Qahtani, Hussain; Hassan, Ghassan; Adukwu, Johnny Ebaika

    Organizations: Deanship of Scientific Research at King Fahd University of Petroleum and Minerals (KFUPM) [DF 201016]; King Abdullah City for Atomic and Renewable Energy

    Keywords: micro-post arrays; hydrophobic; droplet impact; dust mitigation

    In this paper, the impact mechanisms of a water droplet on hydrophobized micro-post array surfaces are examined and the influence of micro-post arrays spacing on the droplet behavior in terms of spreading, retraction, and rebounding is investigated. Impacting droplet behavior was recorded using a high-speed facility and flow generated in the droplet fluid was simulated in 3D geometry accommodating conditions of the experiments. Micro-post arrays were initially formed lithographically on silicon wafer surfaces and, later, replicated by polydimethylsiloxane (PDMS). The replicated micro-post arrays surfaces were hydrophobized through coating by functionalized nano-silica particles. Hydrophobized surfaces result in a contact angle of 153 & DEG; & PLUSMN; 3 & DEG; with a hysteresis of 3 & DEG; & PLUSMN; 1 & DEG;. The predictions of the temporal behavior of droplet wetting diameter during spreading agree with the experimental data. Increasing micro-post arrays spacing reduces the maximum spreading diameter on the surface; in this case, droplet fluid penetrated micro-posts spacing creates a pinning effect while lowering droplet kinetic energy during the spreading cycle. Flow circulation results inside the droplet fluid in the edge region of the droplet during the spreading period; however, opposing flow occurs from the outer region towards the droplet center during the retraction cycle. This creates a stagnation zone in the central region of the droplet, which extends towards the droplet surface onset of droplet rebounding. Impacting droplet mitigates dust from hydrophobized micro-post array surfaces, and increasing droplet Weber number increases the area of dust mitigated from micro-post arrays surfaces.
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