Liquid-bridge mediated droplet switch: A tristable capillary system

Abstract

The double-droplet switch is the simplest example of a system of capillary surfaces ͑liquid/gas interfaces at small scales͒ that demonstrates bistability. A liquid bridge placed between the droplets allows the nonlinear response to be mediated by a pressure p o maintained outside the bridge. Response diagrams that give droplet volumes versus p o are constructed through computations. The combination of the nonlinear pV responses of the bridge and the droplet switch reveals regions with markedly different behaviors depending on the control parameters. The response diagrams show regions with high sensitivity to p o , behavior dominated by the double-droplet response, and also regions with low sensitivity to p o , where the bridge response dominates. Stability is determined following the Poincaré approach with illustration using nonequilibrium energy contours ͑"landscapes"͒. The computations predict regions of hysteresis with three stable equilibria. When imperfections arising from contact-circle movement at the boundaries are included, five simultaneously stable equilibria and double hysteresis loops are predicted.

Robust electrical contacts integrating a liquid metal bridge for mechanical switches

“…Two Galinstan droplets are deposited and wetted on the surface of two aligned copper electrodes. Approaching two droplets anchored on solid plates gradually leads to their coalescence and a capillary LM bridge surface is determined primarily by Galinstan's surface tension [19]. As introduced in [20], when subjected to a gravity field parallel to the bridge axis, the liquid bridge could be defined by the following dimensionless parameters: the slenderness, defined as the ratio of gap separation to disk diameter, Λ = L/(2R), the dimensionless volume of liquid,V = V/(πR 2 L), defined as the ratio of the physical volume V to the volume of a cylinder of the same L and R, and the Bond number, B = ρgR 2 /γ, where ρ and γ are respectively density (6400 kg m −3 ) and surface tension (0.533 N m −1 ) of Galinstan [21], g the axial acceleration.…”