Continuous and unconstrained manipulation of micro-particles using phase-control of bulk acoustic waves

A method of unconstrained and continuous manipulation of micro-particles in a fluid using bulk acoustic waves is theoretically derived and experimentally demonstrated. The method is based on phase-control of standing pressure waves created by two opposing transducers. Reflections are taken into account, removing the need for complex experiments. The operating domain of this method is characterized and compared to existing techniques. In contrast to methods based on linearly adjusting the phase difference between opposing transducers, it is shown that by independently controlling the phase of each transducer, particles can be manipulated in an unconstrained manner over multiple wavelengths.