Strong rotating flow in stationary droplets in low power budget using wire electrode configuration.

We explore a simple strategy of generating strong rotating flow in a stationary surface-droplet, using an intricate interplay of local electrical and thermal fields. Wire electrodes are employed to generate on-spot heating without necessitating any elaborate micro-fabrication, which causes strong local gradients in electrical properties to induce mobile charges into the droplet. Applying a low voltage (∼10 V), strong rotational velocity of the order of mm/s can be achieved in the system, within the standard operating ranges of operating and geometrical parameters. Further, altering the diameter of the electrode, vortices can be tuned locally or globally in low power budget, without incurring any droplet oscillations. These results may turn out to be of immense consequence in enhancing micromixing in a plethora of droplet based applications ranging from thermal management to medical diagnostics to be potentially employed in resource-limited settings.