Droplet fluid infusion into a dust layer in relation to self-cleaning

Hassan, Ghassan; Yilbaş, Bekir Sami; Al‐Qahtani, Hussain

doi:10.1039/d0ra05700b

“…The coefficient of liquid spreading ( ) over dust surface is governed by , here is the surface free energy of dust, is interfacial tension between dust-droplet fluid, and is droplet fluid surface tension. The spreading coefficient for droplet fluid (water) is estimated as S = 21.95 mJ/m 2 , which is consistent with the early work 42 . Hence, water droplet spreads over dust surfaces.…”

Section: Resultssupporting

confidence: 88%

“…Dust composition shows that dust has salt compounds, which can dissolve in water 41 . The droplet fluid (water) infusion over dust remains critical for dust particles to be picked up by rolling droplet fluid 42 . In this case, the coefficient of droplet liquid spreading over the dust surface needs to remain greater than zero for droplet fluid infusion.…”

Section: Resultsmentioning

confidence: 99%

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Abubakar

¹

,

Yilbaş

²

,

Al‐Qahtani

³

et al. 2021

Sci Rep

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Water droplet rolling motion over the hydrophobized and optically transparent micro-post array surfaces is examined towards dust removal pertinent to self-cleaning applications. Micro-post arrays are replicated over the optically transparent polydimethylsiloxane (PDMS) surfaces. The influence of micro-post array spacing on droplet rolling dynamics is explored for clean and dusty surfaces. The droplet motions over clean and dusty micro-post array surfaces are monitored and quantified. Flow inside the rolling droplet is simulated adopting the experimental conditions. Findings reveal that micro-post gap spacing significantly influences droplet velocity on clean and dusty hydrophobized surfaces. Air trapped within the micro-post gaps acts like a cushion reducing the three-phase contact line and interfacial contact area of the rolling droplet. This gives rise to increased droplet velocity over the micro-post array surface. Droplet kinetic energy dissipation remains large for plain and micro-post arrays with small gap spacings. A Rolling droplet can pick up dust particles from micro-post array gaps; however, few dust residues are observed for large gap spacings. Nevertheless, dust residues are small in quantity over hydrophobized micro-post array surfaces.

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“…Although silicon oil and water could spread over the dust particle surface, because of positive spreading coefficient (S), energy dissipation, due to viscous effect on the particle surface and gravitational pull over the particle height, slows down the liquid infusion on the surface [31]. Liquid infusion over dust surface was associated with the Joos' law [32]. The liquid energy used during the infusion was related to the Ohnesorge number (Oh = µ/ √ ρaγ L ), where a represents the particle size [33].…”

Section: Dust Removal From Oil Surface and Droplet Dynamicsmentioning

confidence: 99%

Sliding Water Droplet on Oil Impregnated Surface and Dust Particle Mitigation

Bahatab

¹

,

Yilbaş

²

,

Abubakar

³

et al. 2021

Molecules

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Self-cleaning of surfaces becomes challenging for energy harvesting devices because of the requirements of high optical transmittance of device surfaces. Surface texturing towards hydrophobizing can improve the self-cleaning ability of surfaces, yet lowers the optical transmittance. Introducing optical matching fluid, such as silicon oil, over the hydrophobized surface improves the optical transmittance. However, self-cleaning ability, such as dust mitigation, of the oil-impregnated hydrophobic surfaces needs to be investigated. Hence, solution crystallization of the polycarbonate surface towards creating hydrophobic texture is considered and silicon oil impregnation of the crystallized surface is explored for improved optical transmittance and self-cleaning ability. The condition for silicon oil spreading over the solution treated surface is assessed and silicon oil and water infusions on the dust particles are evaluated. The movement of the water droplet over the silicon oil-impregnated sample is examined utilizing the high-speed facility and the tracker program. The effect of oil film thickness and the tilting angle of the surface on the sliding droplet velocity is estimated for two droplet volumes. The mechanism for the dust particle mitigation from the oil film surface by the sliding water droplet is analyzed. The findings reveal that silicon oil impregnation of the crystallized sample surface improves the optical transmittance significantly. The sliding velocity of the water droplet over the thick film (~700 µm) remains higher than that of the small thickness oil film (~50 µm), which is attributed to the large interfacial resistance created between the moving droplet and the oil on the crystallized surface. The environmental dust particles can be mitigated from the oil film surface by the sliding water droplet. The droplet fluid infusion over the dust particle enables to reorient the particle inside the droplet fluid. As the dust particle settles at the trailing edge of the droplet, the sliding velocity decays on the oil-impregnated sample.

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“…38 The droplet fluid (water) infusion over dust remains critical for dust particles to be picked up by rolling droplet fluid. 39 In this case, the coefficient of droplet liquid spreading over the dust surface needs to remain greater than zero for droplet fluid infusion. The coefficient of liquid spreading ( − ) over dust surface is governed by − = − − − , here is the surface free energy of dust, − is interfacial tension between dust-droplet fluid, and is droplet fluid surface tension.…”

Section: Droplet Dynamics and Dust On Surfacementioning

confidence: 99%

“…The spreading coefficient for droplet fluid (water) is estimated as S = 21.95 mJ/m 2 , which is consistent with the early work. 39 Hence, water droplet spreads over dust surfaces. Droplet fluid infusion over dust takes place in two stages.…”

Section: Droplet Dynamics and Dust On Surfacementioning

confidence: 99%

Water Droplet Can Mitigate Dust from Hydrophobized Micro-Post Array Surfaces

Abubakar

¹

,

Yilbas

²

,

Al‐Qahtani

³

et al. 2021

Preprint

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Water droplet rolling motion over the hydrophobized and optically transparent micro-post array surfaces is examined towards dust removal pertinent to self-cleaning applications. Micro-post arrays are replicated over the optically transparent polydimethylsiloxane (PDMS) surfaces. The influence of micro-post array spacing on droplet rolling dynamics is explored for clean and dusty surfaces. The droplet motions over clean and dusty micro-post array surfaces are monitored and quantified. Flow inside the rolling droplet is simulated adopting the experimental conditions. Findings reveal that micro-post gap spacing significantly influences droplet velocity on clean and dusty hydrophobized surfaces. Air trapped within the micro-post gaps acts like a cushion reducing the three-phase contact line and interfacial contact area of the rolling droplet. This gives rise to increased droplet velocity over the micro-post array surface. Droplet kinetic energy dissipation remains large for plain and micro-post arrays with small gap spacings. A Rolling droplet can pick up dust particles from micro-post array gaps; however, few dust residues are observed for large gap spacings. Nevertheless, dust residues are small in quantity over hydrophobized micro-post array surfaces.

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Droplet fluid infusion into a dust layer in relation to self-cleaning

Abstract: Wettability of a droplet liquid on a dusty hydrophobic plate is considered and the fluid infusion into the dust layer is studied pertinent to dust removal from the hydrophobic surfaces via rolling/sliding droplets.

Cited by 9 publications

References 34 publications

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Water droplet can mitigate dust from hydrophobized micro-post array surfaces

Sliding Water Droplet on Oil Impregnated Surface and Dust Particle Mitigation

Water Droplet Can Mitigate Dust from Hydrophobized Micro-Post Array Surfaces

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