ACOUSTIC FORCE DISTRIBUTION IN RESONATORS FOR ULTRASONIC PARTICLE SEPARATION

The effectiveness of particle - liquid separation by ultrasonic radiat ion forces depends on the acoustic energy density distribution in the standing-wavefield. The energy distribution lit an ultrasonic particle -separation device was analyzed to assist continued optimization and d esign efforts. Measurements of the energy-density distribution in the liquid using a microscope-based imaging system were compared to laser interferometer measurements of the velocity-amplitude distribution on the transducer and reflector surfaces of the ultrasonic separator. The energy density followed the same trend as the surface velocity, being highest near the resonator center and approaching zero near the walls . The energy density gradients and local gridlike reflector-amplitude variation had characteristic lengths of 1.4 mm. These results suggest that the energy-density distribution in the liquid is a defined functi on of the dimensions, imposed boundary conditions and physical propert ies of the reflector and transducer. This understanding provides a pra ctical basis for developing a mathematical model of cell aggregation a nd retention, potentially enabling the design of resonators with prede termined energy density distributions for specific particle aggregatio n, separation, and fractionation applications.