KAIST researchers use volatile additive to suppress gravity-driven drainage, yielding thinner, uniform films.

Researchers at Korea Advanced Institute of Science and Technology (KAIST) have developed a technique to suppress gravity-driven drainage in an inverted liquid by adding a small amount of a volatile liquid. The approach leverages surface-tension-driven Marangoni flows to counter downward drainage, reframing the classic Rayleigh–Taylor instability in interfacial fluid dynamics.

Rayleigh–Taylor instability describes the tendency of a denser liquid to push downward when it sits atop a lighter liquid under gravity. In everyday cases, condensation on bathroom ceilings or droplets forming on a refrigerator ceiling illustrate how a thin surface can evolve toward buildup and eventual dripping as gravity acts.

The KAIST team’s method involves mixing a tiny amount of volatile liquid into the inverted layer. As that volatile component evaporates, it creates concentration differences at the liquid’s surface, altering the surface tension across the film.

These surface-tension gradients drive Marangoni flows along the interface. The induced flows pull on the liquid and oppose gravity’s pull, effectively suppressing the instability that would otherwise cause the film to drain. The researchers demonstrated this interplay through both experiments and theoretical analysis.

The result is the possibility of forming thinner, more uniform liquid films, even on tilted surfaces. Applications highlighted by the team include precision coating, printing, and lamination, with potential extensions to additive manufacturing and fluid control in specialized environments.

Lead researcher Professor Hyung-Soo Kim of KAIST’s Department of Mechanical Engineering described the work as significant because it uses the liquid’s own composition and evaporation to actively manage gravity-driven instability without external energy input.

For U.S. readers, the news matters because many high-tech industries depend on stable, ultra-thin liquid films—such as semiconductor fabrication, display coatings, solar cells, and 3D printing. If scalable, this approach could improve coating uniformity, reduce material waste, and enable better film deposition on non-horizontal surfaces or in space where traditional fluid control is difficult.

KAIST is a leading Korean research university known for its engineering and science programs. While the study is early-stage, it presents a cross-border issue of interest to manufacturers, researchers, and policymakers engaged in advanced coatings, materials, and space-related technologies.