Acoustic Stabilization and Enhanced de-Stabilization of Single Bubbles in Microfluidics and the Connection to the Acoustic Landau-Levich Coating Problem

The manipulation of liquid films over a vibrating solid substrate have been investigated for over thirty years. Applications for such systems include floatation unit operations, intense purification of water, drag delivery and cancer treatment and microfluidics.

We recently showed that the excitation of SAWs in a microfluidic channel might destabilize the micron thick film of liquid between a bubble and a solid substrate at close proximity, rendering attachment. Our results correlated very well with a model for the Landau–Levich type coating of a solid substrate by a liquid film under the action of a propagating MHz frequency SAW. We were able to show that the conditions that rendered the acoustic Landau–Levich coating film unstable in theory further supported the enhanced destabilization of the micron thick liquid film, which resulted in the fast attachment of the bubble to the substrate.

Here, we present new experimental results in which the conditions that render the acoustic Landau–Levich coating film stable in theory further supporting the stabilization of the micron liquid film between a bubble and a solid substrate. The film remains stable, resisting thinning, destabilization, and breakage, which will naturally occur in the absence of the SAW excitation.