(314i) Acoustically-Driven Programmable Liquid Motion Using Resonance Cavities

In the field of microfluidics, device performance and utility are often overshadowed by difficulties and costs associated with operation and control. As a step toward the development of a more suitable platform for microfluidic control, we present a novel distributed pressure control scheme whereby many independently tunable pressure sources can be controlled using the energy present in acoustic waves. We demonstrate how this scheme can be utilized to perform precise droplet positioning, as well as merging, splitting, and sorting within open microfluidic networks. We further show how this scheme can be implemented for control of continuous flow systems, specifically for generation of acoustically tunable liquid gradients. Device operation hinges on a resonance-decoding and rectification mechanism by which the frequency content in a composite acoustic input is transduced into multiple independently buffered output pressures. The device consists of a bank of four uniquely tuned resonance cavities (404 Hz, 484 Hz, 532 Hz and 654 Hz respectively) each being responsible for the actuation of a single droplet, four identical flow-rectification structures, and an acoustic source. Subject to a computer generated acoustic input, cavities selectively amplify resonant tones from the input signal resulting in highly elevated local cavity pressures. Fluidic rectification structures then serve to convert the elevated oscillating cavity pressures into unidirectional flows. The resulting pressure gradients, which are used to manipulate fluids in a microdevice, are tunable over a range of approximately 0-200 Pa with a control resolution of 10 Pa.