Article: Liu, TS; Xu, XJ; Nadermann, N; He, ZP; Jagota, A; Hui, CY; “Interaction of Droplets Separated by an Elastic Film”, Langmuir, 33 (1): 75-81
Abstract: The Laplace pressure of a droplet placed on one side of an elastic thin film can cause significant deformation in the form of a bulge on its opposite side. Here, we show that this deformation can be detected by other droplets suspended on the opposite side of the film, leading to interaction between droplets separated by the solid (but deformable) film. The interaction is repulsive when the drops have a large overlap and attractive when they have a small overlap. Thus, if two identical droplets are placed right on top of each other (one on either side of the thin film), they tend to repel each other, eventually reaching an equilibrium configuration where there is a small overlap. This observation can be explained by analyzing the energy landscape of the droplets interacting via an elastically deformed film. We further demonstrate this idea by designing a pattern comprising a big central drop with satellite droplets. This phenomenon can lead to techniques for directed motion of droplets confined to one side of a thin elastic membrane by manipulations on the other side.
Funding Acknowledgement: U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-FG02-07ER46463]
Funding Text: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-07ER46463. We would also like to acknowledge the assistance of Theodore Lee of Liberty High School in Bethlehem, PA, with the experiments. We are grateful to Prof. Pedro Reis of the Massachusetts Institute of Technology for introducing us to the elastomeric material used to fabricate our samples.