TY - JOUR
T1 - Discontinuous dewetting dynamics of highly viscous droplets on chemically heterogeneous substrates
AU - Jiang, Jiatong
AU - Jackson, Frankie
AU - Tangparitkul, Suparit
AU - Wilson, Mark C.T.
AU - Harbottle, David
N1 - Funding Information:
J. J. thanks the China Scholarship Council (Scholarship # 201906440066) for supporting this research. The authors would like to acknowledge the experimental assistance of Mr. Rob Simpson (School of Chemical and Process Engineering, University of Leeds) who provided guidance on using the confocal laser scanning microscope and Mr. Hongqian Wei (School of Mechanical Engineering, Beijing Institute of Technology) who co-developed the MATLAB code.
Funding Information:
J. J. thanks the China Scholarship Council (Scholarship # 201906440066) for supporting this research. The authors would like to acknowledge the experimental assistance of Mr. Rob Simpson (School of Chemical and Process Engineering, University of Leeds) who provided guidance on using the confocal laser scanning microscope and Mr. Hongqian Wei (School of Mechanical Engineering, Beijing Institute of Technology) who co-developed the MATLAB code.
Publisher Copyright:
© 2022 Elsevier Inc.
PY - 2023/1/1
Y1 - 2023/1/1
N2 - Hypothesis: Droplet spreading on heterogeneous (chemical/structural) surfaces has revealed local disturbances that affect the advancing contact line. With droplet dewetting being less studied, we hypothesize that a receding droplet can be perturbed by localized heterogeneity which leads to irregular and discontinuous dewetting of the substrate. Experiments: The sessile drop method was used to study droplet dewetting at a wettability boundary. One-half of a hydrophilic surface was hydrophobically modified with either i) methyloctyldichlorosilane or ii) clustered macromolecules. A Lattice Boltzmann method (LBM) simulation was also developed to determine the effect of contact angle hysteresis and boundary conditions on the droplet dynamics. Findings: The two surface treatments were optimized to produce comparable water wetting characteristics. With a negative Gibbs free energy on the hydrophilic-half, the oil droplet receded to the hydrophobic-half. On the silanized surface, the droplet was pinned and the resultant droplet shape was a distorted spherical cap, having receded uniformly on the unmodified surface. Modifying the surface with clustered macromolecules, the droplet receded slightly to form a spherical cap. However, droplet recession was non-uniform and daughter droplets formed near the wettability boundary. The LBM simulation revealed that daughter droplets formed when θR > 164°, with the final droplet shape accurately described by imposing a diffuse wettability boundary condition.
AB - Hypothesis: Droplet spreading on heterogeneous (chemical/structural) surfaces has revealed local disturbances that affect the advancing contact line. With droplet dewetting being less studied, we hypothesize that a receding droplet can be perturbed by localized heterogeneity which leads to irregular and discontinuous dewetting of the substrate. Experiments: The sessile drop method was used to study droplet dewetting at a wettability boundary. One-half of a hydrophilic surface was hydrophobically modified with either i) methyloctyldichlorosilane or ii) clustered macromolecules. A Lattice Boltzmann method (LBM) simulation was also developed to determine the effect of contact angle hysteresis and boundary conditions on the droplet dynamics. Findings: The two surface treatments were optimized to produce comparable water wetting characteristics. With a negative Gibbs free energy on the hydrophilic-half, the oil droplet receded to the hydrophobic-half. On the silanized surface, the droplet was pinned and the resultant droplet shape was a distorted spherical cap, having receded uniformly on the unmodified surface. Modifying the surface with clustered macromolecules, the droplet receded slightly to form a spherical cap. However, droplet recession was non-uniform and daughter droplets formed near the wettability boundary. The LBM simulation revealed that daughter droplets formed when θR > 164°, with the final droplet shape accurately described by imposing a diffuse wettability boundary condition.
KW - Daughter droplet generation
KW - Droplet dewetting
KW - Heterogeneous surfaces
KW - Highly viscous oil
KW - Lattice Boltzmann method
KW - Wettability boundary
UR - https://www.scopus.com/pages/publications/85138396730
U2 - 10.1016/j.jcis.2022.09.064
DO - 10.1016/j.jcis.2022.09.064
M3 - Article
AN - SCOPUS:85138396730
SN - 0021-9797
VL - 629
SP - 345
EP - 356
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
IS - Part B
ER -