Whole-System Ultrasound Resonances as the Basis for Acoustophoresis in All-Polymer Microfluidic Devices

Using a previously-well-tested numerical model, we demonstrate that good acoustophoresis can be obtained in a microchannel embedded in an acoustically soft, all-polymer chip by excitation of whole-system ultrasound resonances. In contrast to conventional techniques based on a standing bulk acoustic wave inside a liquid-filled microchannel embedded in an elastic, acoustically hard material, such as glass or silicon, the proposed whole-system resonance does not need high acoustic contrast between the liquid and the surrounding solid.

Instead, it relies on the very high acoustic contrast between the solid and the surrounding air. In microchannels of usual dimensions, we demonstrate by numerical simulations the existence of whole-system resonances in an all-polymer device that supports acoustophoresis of a quality fully comparable to that of a conventional hard-walled system.

Our results open up the possibility of using cheap and easily processable polymers in a controlled manner to design and fabricate microfluidic devices for single-use acoustophoresis.