Research
Controlling droplets
Here, we study the splitting of a droplet held between the tips of two cylindrical fibers. We discover a sharp transition between two post-rupture states, navigated by changing the angle between the rods, in agreement with our bifurcation analysis. Depinning of the bridge contact line can lead to a much larger asymmetry between the volume of liquid left on each rod. This second scenario enables the near-complete transfer of an aqueous glycerol droplet between two identical vinylpolysiloxane fibers. We leverage this response in a device that uses a ruck to pass a droplet along a train of fibers, a proof-of-concept for the geometric control of droplets on deformable, architected surfaces.
Controlling droplets at the tips of fibers, Phys. Rev. Fluids 10, 073602 (2025)
Propulsion using curvature
Stresses arising from curvature mismatches can result in propulsive net forces and torques. Meniscus-climbing insects generate curvature mismatches via capillary disturbances. Inspired by such propulsion mechanisms, we consider a “surfer”– an elastic object consisting of two inextensible strips attached at their midpoints. When confined to a generic curved surface, the surfer is attracted towards elliptical or hyperbolic curves surrounding umbilical points of the surface. Further, the umbilic couples the surfer’s rotational and translational motions leading the surfer to traverse these entrapment curves when an external torque is applied. The neighborhood of umbilics are, therefore, ideal launchpads from which the surfer can deliver itself to desired locations on a surface by controlling its geometry.
Shape-shift and surf: Propulsion via bending (under preparation)