Scaling and mechanism of droplet array formation on a laser-ablated superhydrophobic grid

Bahador Farshchian; Javad R. Gatabi; Steven M. Bernick; Gwan Hyoung Lee; Ravindranath Droopad; Namwon Kim

doi:10.1016/j.colsurfa.2018.03.026

Scaling and mechanism of droplet array formation on a laser-ablated superhydrophobic grid

Bahador Farshchian, Javad R. Gatabi, Steven M. Bernick, Gwan Hyoung Lee, Ravindranath Droopad, Namwon Kim

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

Superhydrophobic grid patterns were ablated on a hydrophobic polydimethylsiloxane (PDMS) substrate using a nanosecond pulsed laser. The substrate with a wettability contrast (superhydrophobic-hydrophobic) was vertically immersed in a pool of water and withdrawn at different speeds to form droplet arrays spontaneously. The size of droplets was tuned by controlling the withdrawal speed (S_w), which resulted in different contact line speeds on non-irradiated cell (NIC) and laser-irradiated grid (LIG) areas with different surface properties of no-slip and partial-slip conditions, respectively. The ratio of the contact line speeds on NIC and LIG areas (S_NIC/S_LIG) decreased exponentially with the withdrawal speed, leading to formation of larger droplets on NIC. A geometric scaling model predicted the size of droplets formed on NIC arrays over a range of contact line speeds on NIC and LIG, the ratio of the contact line speeds, the withdrawal speed, and the size of NIC.

Original language	English
Pages (from-to)	49-55
Number of pages	7
Journal	Colloids and Surfaces A: Physicochemical and Engineering Aspects
Volume	547
DOIs	https://doi.org/10.1016/j.colsurfa.2018.03.026
Publication status	Published - 2018 Jun 20

Bibliographical note

Publisher Copyright:
© 2018 Elsevier B.V.

All Science Journal Classification (ASJC) codes

Surfaces and Interfaces
Physical and Theoretical Chemistry
Colloid and Surface Chemistry

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10.1016/j.colsurfa.2018.03.026

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abstract = "Superhydrophobic grid patterns were ablated on a hydrophobic polydimethylsiloxane (PDMS) substrate using a nanosecond pulsed laser. The substrate with a wettability contrast (superhydrophobic-hydrophobic) was vertically immersed in a pool of water and withdrawn at different speeds to form droplet arrays spontaneously. The size of droplets was tuned by controlling the withdrawal speed (Sw), which resulted in different contact line speeds on non-irradiated cell (NIC) and laser-irradiated grid (LIG) areas with different surface properties of no-slip and partial-slip conditions, respectively. The ratio of the contact line speeds on NIC and LIG areas (SNIC/SLIG) decreased exponentially with the withdrawal speed, leading to formation of larger droplets on NIC. A geometric scaling model predicted the size of droplets formed on NIC arrays over a range of contact line speeds on NIC and LIG, the ratio of the contact line speeds, the withdrawal speed, and the size of NIC.",

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AU - Farshchian, Bahador

AU - Gatabi, Javad R.

AU - Bernick, Steven M.

AU - Lee, Gwan Hyoung

AU - Droopad, Ravindranath

AU - Kim, Namwon

PY - 2018/6/20

Y1 - 2018/6/20

N2 - Superhydrophobic grid patterns were ablated on a hydrophobic polydimethylsiloxane (PDMS) substrate using a nanosecond pulsed laser. The substrate with a wettability contrast (superhydrophobic-hydrophobic) was vertically immersed in a pool of water and withdrawn at different speeds to form droplet arrays spontaneously. The size of droplets was tuned by controlling the withdrawal speed (Sw), which resulted in different contact line speeds on non-irradiated cell (NIC) and laser-irradiated grid (LIG) areas with different surface properties of no-slip and partial-slip conditions, respectively. The ratio of the contact line speeds on NIC and LIG areas (SNIC/SLIG) decreased exponentially with the withdrawal speed, leading to formation of larger droplets on NIC. A geometric scaling model predicted the size of droplets formed on NIC arrays over a range of contact line speeds on NIC and LIG, the ratio of the contact line speeds, the withdrawal speed, and the size of NIC.

AB - Superhydrophobic grid patterns were ablated on a hydrophobic polydimethylsiloxane (PDMS) substrate using a nanosecond pulsed laser. The substrate with a wettability contrast (superhydrophobic-hydrophobic) was vertically immersed in a pool of water and withdrawn at different speeds to form droplet arrays spontaneously. The size of droplets was tuned by controlling the withdrawal speed (Sw), which resulted in different contact line speeds on non-irradiated cell (NIC) and laser-irradiated grid (LIG) areas with different surface properties of no-slip and partial-slip conditions, respectively. The ratio of the contact line speeds on NIC and LIG areas (SNIC/SLIG) decreased exponentially with the withdrawal speed, leading to formation of larger droplets on NIC. A geometric scaling model predicted the size of droplets formed on NIC arrays over a range of contact line speeds on NIC and LIG, the ratio of the contact line speeds, the withdrawal speed, and the size of NIC.

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Scaling and mechanism of droplet array formation on a laser-ablated superhydrophobic grid

Abstract

Bibliographical note

All Science Journal Classification (ASJC) codes

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