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Evaporation of Binary-Mixture Liquid Droplets: The Formation of Picoliter Pancakelike Shapes

Pahlavan, Amir A.; Yang, Lisong; Bain, Colin D.; Stone, Howard A.

Evaporation of Binary-Mixture Liquid Droplets: The Formation of Picoliter Pancakelike Shapes Thumbnail


Authors

Amir A. Pahlavan

Howard A. Stone



Abstract

Small multicomponent droplets are of increasing importance in a plethora of technological applications ranging from the fabrication of self-assembled hierarchical patterns to the design of autonomous fluidic systems. While often far away from equilibrium, involving complex and even chaotic flow fields, it is commonly assumed that in these systems with small drops surface tension keeps the shapes spherical. Here, studying picoliter volatile binary-mixture droplets of isopropanol and 2-butanol, we show that the dominance of surface tension forces at small scales can play a dual role: Minute variations in surface tension along the interface can create Marangoni flows that are strong enough to significantly deform the drop, forming micron-thick pancakelike shapes that are otherwise typical of large puddles. We identify the conditions under which these flattened shapes form and explain why, universally, they relax back to a spherical-cap shape toward the end of drop lifetime. We further show that the formation of pancakelike droplets suppresses the “coffee-ring” effect and leads to uniform deposition of suspended particles. The quantitative agreement between theory and experiment provides a predictive capability to modulate the shape of tiny droplets with implications in a range of technologies from fabrication of miniature optical lenses to coating, printing, and pattern deposition.

Journal Article Type Article
Acceptance Date Jun 7, 2021
Online Publication Date Jul 7, 2021
Publication Date Jul 9, 2021
Deposit Date Sep 6, 2021
Publicly Available Date Sep 6, 2021
Journal Physical Review Letters
Print ISSN 0031-9007
Electronic ISSN 1079-7114
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 127
Issue 2
Article Number 024501
DOI https://doi.org/10.1103/physrevlett.127.024501
Public URL https://durham-repository.worktribe.com/output/1241559

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Copyright Statement
Reprinted with permission from the American Physical Society: Pahlavan, Amir A., Yang, Lisong, Bain, Colin D. & Stone, Howard A. (2021). Evaporation of Binary-Mixture Liquid Droplets: The Formation of Picoliter Pancakelike Shapes. Physical Review Letters 127(2): 024501 © 2021 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.






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