Cell agglomeration using guided surface acoustic waves through a couplant layer

Abstract

Cell agglomeration has been useful and crucial for tissue engineering, cell culturing, and drug testing, such as for cancer drug development. However, most of the methods require specific and complex experimental setups and the resulting agglomerates are generally slow or of poor quality. We propose a microfluidic device using surface acoustic waves (SAWs), a contact-free means, in the application of cell engineering. It is composed of a piezoelectric substrate, 127.86 deg Y-rotated X-propagating lithium niobate, and a focused interdigital transducer to generate focused surface waves with a resonant frequency at 100 MHz. An aluminum guiding layer is deposited on top of the substrate to overcome the beam steering and lateral diffraction problems due to the anisotropy nature of the piezoelectric material, further trapping the wave to a small region of a few wavelengths. The SAWs generated travel into a thin layer of liquid and diffract at the Rayleigh angle, so that the acoustic radiation is coupled and propagates into the superstrate, which can be a bio-friendly container culturing cells. The localized acoustic streaming induced from the radiation carries and accumulates the cells to the center of the recirculation. Our data show that the agglomeration can form in less than 20 s, and the separation between the living yeast cell agglomeration islands can be as small as △x = 720 μm. This device is proven to be an effective, reliable, and easy-to-handle approach for cell manipulation, independent of the culturing container.