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What is the effect of droplet size on the contact angle on hydrophobic and hydrophilic surfaces?

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The effect of droplet size on the contact angle varies depending on the surface's hydrophobicity. On hydrophobic surfaces, the drop size has a weak dependence on the contact angle for deionized water drops, with the effect being strongest for nearly hydrophobic surfaces like PC . Conversely, on hydrophilic surfaces, such as those studied in molecular dynamics simulations, the contact angle shows significant dependence on droplet size, with a notable increase of up to 10° as the droplet size decreases. This effect is attributed to the curved water-vapor interface and a generalized line tension with contact angle dependence . Understanding these dynamics is crucial for evaluating the wetting characteristics of droplets on different surfaces and can provide insights into surface hydrophobicity and wetting behavior.

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Journal Article•DOI Influence of contact angle on droplet parameters in ellipsoidal wettability model 31 May 2023-Surface topography	Contact angle is inversely proportional to droplet-solid contact radius and area, and directly proportional to droplet projected area. Droplet size affects contact angle on both hydrophobic and hydrophilic surfaces.
Journal Article•DOI Going beyond the standard line tension: Size-dependent contact angles of water nanodroplets. Matej Kanduč 01 Nov 2017-Journal of Chemical Physics 57 Citations	Droplet size significantly affects contact angle on hydrophilic surfaces, increasing up to 10° with smaller droplets, while the effect is weaker and reversed on hydrophobic surfaces.
Journal Article•DOI Influence of contact angle on droplet parameters in ellipsoidal wettability model Zehua Xu, Yanbin Zhang, Xiaosen Wang, Kangshuai Li, Qiang He - Show less +4 more 19 May 2023-Surface topography	Droplet size affects contact angle; it is inversely proportional to droplet-solid contact radius and area, and directly proportional to droplet projected area on both hydrophobic and hydrophilic surfaces.
Proceedings Article•DOI Size effect on surface tension and contact angle between protein solution and silicon compound, pc, and pmma substrates 01 Jan 2023	Drop size has a weak effect on contact angle for deionized water on all substrates, but a stronger effect for protein drops, especially on hydrophobic PC substrates.
Journal Article•DOI The Size Effect on Contact Angles and Dynamic Behaviors of Droplets on Microcolumn and Microstrip Array Surfaces Hai Liang Du, Sheng Hua Zhao, Zhichao Ma, Jize Liu, Guolin Xiao, Weizhi Li, Yue Nan Jiang, Hongwei Zhao, Luquan Ren - Show less +8 more 19 Jan 2022-Advanced Engineering Materials 3 Citations	Droplet size affects contact angles on microcolumn and microstrip array surfaces; larger droplets have higher contact angles due to increased adhesion, impacting dynamic behaviors like bouncing.

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