Acoustophoretic particle manipulation in hybrid solid/gel resonators

This study presents a proof of concept to demonstrate the ability ultrasounds perform acoustophoretic processes in hybrid millifluidic resonators that include channels laterally embedded extremely soft media with physical properties close those liquids. In our experiments, particles are driven by acoustic radiation forces toward hydrodynamic/acoustic equilibrium positions similar way produced conventional microfluidic solid structures; 20 um-sized polystyrene beads immersed deionized water flow channelized throughout an aqueous-based gel between inlet and outlet resonant chamber while being exposed at frequency 1.54 MHz. The liquid channel formed irregular walls variable geometry defined sample injection pressure. Particles collect rapidly along central line equidistant from walls, regardless whether they parallel or not, as observed for different geometries cross-sectional dimensions. Only when stops, pressure nodes established 2D spatial distribution. These results break paradigm structures essential elements support acoustophoresis, demonstrating produce these without consolidated structure. It opens door bioprinting applications.