Hydro-elastic pump inspired by snail feeding
The apple snail Pomacea canaliculata exhibits a unique feeding mechanism to collect food particles floating at the water-air interface: while under water, it positions part of its flexible foot parallel to the water surface and generates rhythmic undulations. These undulations trigger a flow near the free surface that brings the food particles towards the mouth. Inspired by this feeding mechanism, I am currently developing an actuation mechanism that drives liquid flow by undulating a thin, flexible structure placed beneath the liquid surface. We have found that the undulating sheet pumps a thin layer of liquid near the interface that drags any floating particle along with it. The flux of liquid, which is a direct measurement of the pump efficiency, varies non-linearly with the speed of sheet undulations, and is a direct consequence of hydro elastic coupling, and dictates the far-field particle trajectories.
Active swimmers at a crowded interface
Self propelling floaters that utilize Marangoni effect to move at an interface exhibit intriguing collective dynamics such as flocking, self assembly, and synchronous oscillations. In this project, we explore how these active swimmers propel through an interface that is uniformly packed with passive particles. Interestingly, the active hydrodynamics of the swimmer lead to phase separation at the interface into a jammed part and an unjammed part. Constrained to move within the unjammed portion of the interface, the swimmer exhibits petal-like orbits which are qualitatively similar to the apsidal precession in celestial mechanics.
Soft wetting & surface elasticity
Functionality of soft, polymeric solids crucially rely on their surface properties. In particular, the wettability of a soft surface is a key property since it dictates the interaction of liquid drops with it. My research has demonstrated that these solids possess an intricate surface elasticity which governs the contact angle of liquid drops deported onto the surface. A detailed understanding this surface mechanics potentially open up routes to design soft surfaces that switch between hydrophilic and hydrophobic states on demand by sequential deformation.
Elastocapillary interactions beyond the 'cheerios effect'
Most of us have noticed that paperclips, breakfast cereals, and small bubbles tend to float in clusters on a liquid surface. This phenomenon is a classical example of capillary interaction governed by surface tension of the liquid. If we replace the liquid with a bowl of soft solid e.g. jello and place tiny liquid drops on top of it, the drops starts to interact. We found that the nature of this interaction purely depend upon size of the underlying substrate. For a very thick substrate, droplets attract and coalesce, whereas very thin substrates lead to a repulsive interaction between the droplets. This 'inverted cheerios effect' could potentially lead to the design of self cleaning soft surfaces and smart fabrics.
Snapping, curling, bending of soft, slender structures
Soft, slender structures bend, crease, snap, and wrinkle in response to a wide range of external stimuli like pH, humidity, electric field or swelling. These large yet reversible deformations offer an exciting pathway towards soft, designer materials. My interest is to investigate the fundamental dynamics of these deformations, and how liquid flow can alter the dynamics these structures. As such, my work has revealed how fast a curved strip snaps between two stable configurations that are far apart within milliseconds, how two curling fibers transport a water drop in a ratchet like mechanism, and how a structure transitions from global bending to local creasing when swelled in a solvent.