Virtual Seminar"Dynamics of a viscoplastic drop on a superhydrophobic surface"Minyoung Kim


Tuesday, May 9, 2023 - 11:00




Micro/Bio/Nanofluidics (Shen) Unit would like to invite you to the seminar by Dr. Minyoung Kim on May 9 (Tuesday).
Date: May 9, 2023
Time: 11:00-11:30AM
**Zoom session

*Zoom information

Meeting ID: 980 8511 3980
Passcode: 475804


Minyoung Kim
The department of Chemical Engineering at the Pennsylvania State University


Dynamics of a viscoplastic drop on a superhydrophobic surface


While the wetting dynamics of Newtonian fluids has been extensively studied, that of non-Newtonian fluids, especially viscoplastic fluids, is less known since their multiple properties such as shear-thinning, yield stress, surface adhesion and surface tension make it difficult to understand their motions. With experimental and theoretical analysis, we discovered unique behaviors of viscoplastic drops on an inclined superhydrophobic surface: (i) rolling, sliding and sticking motions and (ii) two different rolling modes, i.e. viscous rolling and rigid-body motion. First, with the extremely low surface energy of the superhydrophobic surface, an adhesive stress at the liquid–solid interface is similar in its magnitude to gravitational stress and yield stress. Such a balance of stresses induces the clear decomposition of three basic motions according to their relative magnitudes. Additionally, we captured two distinct rolling modes, liquid-like viscous rolling and solid-like rigid-body motion, as a unique behavior of a viscoplastic fluid which has not been reported with a Newtonian fluid. At a low Deborah number (i.e. dimensionless viscoplastic relaxation time), the viscoplastic drop shows viscous rolling, similar to a Newtonian drop on an inclined surface. However, at a high Deborah number, the viscoplastic drop deforms to be more spherical and tumbles down the inclined surface, as if it were a solid body tipping over.


I am currently a PhD candidate in the department of Chemical Engineering at the Pennsylvania State University and will graduate in May 2023. Prior to my PhD, I obtained my MS degree at KAIST in Korea. Following this, I worked as a research assistant at KIST in Korea. My research has focused on wetting of non-Newtonian fluids, flow instability and vortex formation, transport phenomena in curved geometries.


Prof. Amy Shen

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