Description
As the number of cancer cases rise around the world, the study of CSC’s has never been needed more to speed up the cancer detection process. Prior research worked in the field of microfluidics for cell trapping. This approach utilized a used a herringbone chip design to induce a turbulent flow in a series of microfluidic channels to trap cells against the walls of the channels. This thesis presents a multi-physics approach to increase the efficiency of cell capture. This thesis proposes an acoustophoresis based microfluidic method for rare cell isolation. Acoustophoresis allows for the free flow manipulation of a variety of cells based on the cells’ physical properties such as compressibility and size. Acoustophoresis works by inducing a surface standing acoustic wave (SSAW) through a piezoelectric substrate by applying an alternating voltage to a set of identical, parallel interdigital transducers (IDT’s). The preferred piezo is a 4 inch diameter, 128° Y-cut, Lihium Niobate substrate because of its high piezo-electric constant. The IDT design determines the wavelength of the induced wave. The chosen design utilizes a 40μm finger width with a 80μm spacing between fingers. The finger overlap, or aperture, is 15mm. This is the working length of the wave. The IDT’s are then stimulated with a 5 volt peak-to-peak, 16.5 MHz AC signal from a signal generator, thus, creating a SSAW in between the two pairs of IDT’s. The square microfluidic channel is placed symmetrically between the two IDT’s so the SSAW pressure node is centered in the channel. As particles flow through the channel, the acoustic force is supposed to overcome the fluidic force of the flowing medium and cause the particle to stop. However, through simulation, it is discovered that for this system design, the applied 5 volts is not enough for the acoustic force to overcome the fluidic forces. Through this work, a comprehensive simulation method was developed that explains the relationship between the acoustic and fluidic forces. Closed form solution was then used to find the root cause of why the device did not behave as expected.
