Low power sessile droplet actuation via modulated surface acoustic waves

TL;DR

This paper demonstrates that modulating high-frequency surface acoustic waves at specific frequencies can significantly reduce the power needed to move or deform sessile droplets, enhancing portable biofluid manipulation.

Contribution

It introduces a method to lower acoustic power consumption by resonantly exciting inertio-capillary modes in droplets using modulated surface acoustic waves.

Findings

Resonant excitation leads to larger droplet oscillations.

Modulation enables quicker droplet motion.

Power consumption is substantially reduced.

Abstract

Low power actuation of sessile droplets is of primary interest for portable or hybrid lab-on-a-chip and harmless manipulation of biofluids. In this paper, we show that the acoustic power required to move or deform droplets via surface acoustic waves can be substantially reduced through the forcing of the drops inertio-capillary modes of vibrations. Indeed, harmonic, superharmonic and subharmonic (parametric) excitation of these modes are observed when the high frequency acoustic signal (19.5 MHz) is modulated around Rayleigh-Lamb inertio-capillary frequencies. This resonant behavior results in larger oscillations and quicker motion of the drops than in the non-modulated case.