Wetting Dynamics of a Water Droplet on Micropillar Surfaces with Radially Varying Pitches

Kumar, Manish and Bhardwaj, Rajneesh and Sahu, Kirti Chandra (2020) Wetting Dynamics of a Water Droplet on Micropillar Surfaces with Radially Varying Pitches. Langmuir, 36 (19). pp. 5312-5323. ISSN 0743-7463

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The wetting dynamics of a sessile droplet on square micropillar substrates with radially varying pitches, prepared on silicon wafers using a photolithography technique, is investigated experimentally. Two configurations are considered, namely, substrates with radially increasing pitch and radially decreasing pitch. The droplet initially placed at the center experiences a wettability gradient because of the variation in pitch of the micropillar substrate leading to complex wetting dynamics. We observed that the droplet remains in the Cassie-Baxter state in the case of a radially increasing pitch and exhibits a higher contact angle than that on a smooth surface during its spreading stage. In contrast, the droplet experiences the Wenzel condition in the case of a radially decreasing pitch and assumes a lower contact angle relative to that observed on a smooth surface. The wetted diameter of the droplet in the radially decreasing pitch configuration is found to be smaller than that observed in the radially increasing pitch configuration. Our study also reveals that increasing the size of the pillars increases the wetted diameter of the droplet in both configurations. Theoretical models developed using the Cassie-Baxter and Wenzel states for the radially increasing and radially decreasing pitches satisfactorily predict the experimental behaviors.

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IITH Creators:
IITH CreatorsORCiD
Sahu, Kirti Chandrahttp://orcid.org/0000-0002-7357-1141
Item Type: Article
Uncontrolled Keywords: Contact angle,Drops,Dynamics,Silicon wafers,Substrates
Subjects: Chemistry
Chemical Engineering
Chemical Engineering > Fluid Mechanics
Divisions: Department of Chemical Engineering
Depositing User: . LibTrainee 2021
Date Deposited: 06 May 2021 07:00
Last Modified: 06 May 2021 07:00
URI: http://raiith.iith.ac.in/id/eprint/7767
Publisher URL: http://doi.org/10.1021/acs.langmuir.0c00697
OA policy: https://v2.sherpa.ac.uk/id/publication/7789
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