Acoustic levitation device for probing biological cells with high-frequency ultrasound

High-frequency ultrasound has been shown to be sensitive to changes in the cell cytoskeletal makeup during a variety of biological processes. It can therefore be used to study cellular responses such as T-cell activation and cancer metastasis. To date, obtaining cytoskeletal properties with high-frequency ultrasound has required the use of monolayer cell cultures. Ultrasonic signals from these cultures can be problematic due to the interference of reflections from the culture-plate well. The cell structure is also often deformed from its native state due to adhesion to the culture plate. The objective of this study was to develop an acoustic levitation device that creates a monolayer of cells suspended in a fluid in order to simulate their environment in vivo. By using a 250 kHz transducer, standing waves were generated in a suspension of polyethylene microspheres (53–63μm diameter) in distilled H2O. Microspheres formed layers at the standing-wave nodes. Varying the shape of the transducer voltage waveform had a significant effect on layer thickness, with a square waveform creating thinner, more distinct layers than a sine waveform due to steeper pressure gradients at the nodes. Future work will entail creating a monolayer suspension of biological cells that can be probed with high-frequency ultrasound.