On-chip ultrasonic manipulation of micro-particles using flexural vibration of a glass substrate

With development of biotechnology, manipulation and separation techniques of small particles such as cells and DNA are required in the field of life sciences. This report investigates on-chip manipulation of micro-particles in channels using ultrasound. The chip consists of a rectangular glass substrate having a cross-shaped channel and four PZT transducers attached to four corners on the glass substrate. The configuration of the glass substrate and the transducers were determined by the finite element analysis to generate the flexural vibration mode on the chip efficiently. The channel is filled with ethanol, and silicon carbide micro-particles with an average diameter 50 μm were immersed in the channel. By applying the in-phase input voltages of 75 V_pp at 225 kHz to the four transducers, the flexural vibration mode with the wavelength of 13.0 mm was excited on the glass substrate, and the particles can be trapped at the nodal lines of a standing wave in the channel generated by the flexural vibration. By controlling the driving phase difference between two pairs of the transducers, the vibrational distribution of the chip can be changed and the trapped particles can be manipulated.