Multi-wavelength ultrasonic standing wave device for non-invasive cell manipulation and characterisation

Ultrasonic standing wave manipulation has many promising applications in cell biology, such as noncontact investigation of cell and tissue mechanics. In this paper, recent progress in developing a high frequency resonant chamber using a lithium niobate transducer is presented. This device is designed to sit on a petri dish or microscope slide, with the propagation direction parallel to the dish surface, in a configuration compatible with an optical microscope. It comprises a high frequency ultrasonic transducer with a low acoustic impedance transducer mounting, a polished reflector, and a set of precision spacers between the reflector and transducer. The prototype device demonstrates the feasibility of trapping microparticles with ultrasound radiation forces in multiple trapping sites, and the short wavelength reduces the separation of trapping sites to the same order as the cell dimensions. The basic design of device was validated with one dimensional modelling and finite element simulation. Experimental results of trapping 10 μm polystyrene beads correspond to simulated pressure distributions showing multiples of half-wavelength standing waves.