Dewetting Fingering Instability in Capillary Suspensions: Role of Particles and Liquid Bridges

TL;DR

This paper explores how particles and liquids influence fingering instability during dewetting in capillary suspensions, revealing complex interactions that affect pattern formation and stability.

Contribution

It provides new insights into the roles of microparticles, nanoparticles, and secondary liquids in dewetting instability of capillary suspensions.

Findings

Microparticles increase finger length due to particle interactions.

Secondary fluid reduces fingering length by forming a strong network.

Nanoparticles induce early cavitation and enhance instability.

Abstract

This study investigates the fingering instability that forms during stretching of capillary suspensions with and without added nanoparticles. The dewetting process is observed using a transparent lifted Hele-Shaw cell. The liquid bridge is stretched under constant acceleration, and the resulting instability patterns are recorded using two high-speed cameras. Finger-like structures, characteristic of the Saffman-Taylor instability are observed. The total length of the dendrites and the intersecting number of branches are quantified. We reveal the roles of microparticles, nanoparticles, and the secondary liquid during the fingering instability. The addition of microparticles to pure liquid enhanced finger length due to increased particle interactions and nucleation sites for bubbles. The addition of secondary fluid reduces fingering length by forming a strong interparticle network. Incorporation of nanoparticles induces an early onset of cavitation and enhances fingering instability. However, nanoparticles make the capillary suspensions' overall microstructure more homogeneous, reduce the sample variation in fingering patterns, and promote the even distribution of gel on both slides during splitting. These findings highlight the complex interactions governing dewetting in capillary (nano)suspensions. This knowledge has potential applications in microfluidics, 3D printing, and thin-film coatings, where controlling dewetting is crucial.