Competing Roles of Hollow-Particle Ascent and Smectite Structure Formation in Drying Patterns of Aqueous Sessile Droplets
Year: 2026
Type: article
Abstract: This study examined how the volume fraction of fluorinated hectorite (Ht-F) and NaCl concentration affect the drying patterns of sessile droplets containing aluminosilicate hollow particles. Ht-F-only droplets formed low peripheral rings, whereas higher Ht-F fractions or NaCl concentrations promoted bump-like patterns. Hollow-particle-only droplets formed a well-defined core coffee-eye and a narrow peripheral ring. Ht-F addition produced extended coffee-eyes and wider rings. Hollow-particle ascent in water, observed in previous studies, provides a physical basis for interpreting central accumulation; individual vertical particle trajectories were not measured in the present drying droplets. Comparison using the apparent normalized ascent distance, Λapp, based on Stokes’ law indicated that the estimated increase in viscosity decreased Λapp and that ascent could become more influential with increasing particle size. DLVO analysis showed that increasing NaCl shortened the range of electrostatic repulsion. The core coffee-eye diameter varied nonmonotonically with NaCl concentration, suggesting that competition between interparticle interactions and particle transport may influence the extent of central accumulation. Without added NaCl, trace Ht-F was associated with a temporary coffee-eye that collapsed into a volcano-like pattern late in drying. The observed drying patterns are interpreted in terms of hollow-particle ascent, evaporation-induced outward transport, and Ht-F-induced viscosity increase and network formation. Transport and interaction calculations were used for semi-quantitative comparison based on initial conditions and simplified models.
Source: Powders
Author: Hiroshi Kimura
Institution: Gifu University
Language: English
Subfield: Computational Mechanics
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,207
OpenAlex ID: W7215730222