KAIST develops energy-free method to stabilize gravity-driven liquid films on inclined surfaces
KAIST researchers say they have developed a way to control gravity-driven liquid flow on tilted or curved surfaces by mixing a small amount of volatile liquid into an inverted liquid film. The approach could improve precision coating, electronic circuit printing, additive manufacturing processes, and fluid control in space or other harsh environments.
On inclined surfaces, a thin liquid layer tends to spread and then break apart under gravity, a phenomenon tied to what engineers call gravity or Rayleigh–Taylor instability. The KAIST team reinterpreted this interfacial instability in fluid dynamics terms and proposed a method to counteract it without applying external energy.
Their strategy involves adding a tiny quantity of a volatile liquid to the inverted liquid. As the volatile component evaporates, it creates a concentration gradient along the liquid surface, producing a surface-tension gradient. This gradient drives Marangoni flows that oppose the downward pull of gravity, effectively stabilizing the film.
Experiments showed that under certain conditions the liquid film remained intact despite gravity, while in other cases droplets did not detach from the surface. The researchers also observed a regime where the liquid film oscillated periodically. All of these behaviors occurred without any external energy input, relying solely on natural evaporation and composition changes.
The researchers say the method could enable much thinner, more uniform liquid coatings for precise coating, printing, and layered manufacturing processes. Beyond terrestrial manufacturing, the technique could extend to fluid control in space or other environments where gravity complicates liquid handling.
KAIST’s Department of Mechanical Engineering conducted the work, led by Professor Kim Hyung-su, with researchers Choi Min-woo and Jeon Hye-jun. The findings were announced on the KAIST website on the 12th and published online January 29 in the journal Advanced Science.
For U.S. readers, the work matters because it points to a passive, energy-free route to stabilize thin liquid films used in semiconductor manufacturing, display and sensor coatings, and high-precision 3D printing. It also touches on liquid management challenges in microgravity, which are central to future space missions and fabrication techniques in orbit. The study adds to fundamental fluid dynamics while offering a potential avenue to improve reliability and uniformity in critical coating and printing processes.