Ultrasonic manipulation of microparticles and cells using microfluidic devices

Critical to the development of lab-on-a-chip (LOC) devices is the ability to accurately manipulate microparticles and cells within microfluidic volumes. In real fluid samples, the analyte of interest usually coexists in low concentration amongst a myriad of other constituents, resulting in the need for pre-analytical preparation procedures. Consequently, much research attention has been directed towards concentrating and/or isolating the analyte of interest from the other constituents within microfluidic volumes. The central theme of this thesis is the ultrasonic manipulation of particles and cells within microfluidic systems. Acoustically driven mechanisms for particle and cell manipulation are particularly advantageous as these techniques generally exhibit high throughput, have negligible physiological effects on cells, and are highly portable. Comprising both experimental and theoretical investigations, the studies presented herein focus on the selective concentration and isolation of one particle type from another. Both bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices provide physical platforms for the microfluidic manipulation techniques. Specifically, three related studies are included: (1) selective particle concentration and isolation within a droplet, (2) particle and cell clustering at air–liquid interfaces, and (3) selective particle trapping using oscillating bubbles. These studies illustrate the intricate interplay of physics between fluid drag and acoustic forcing on the particles, where parameters such as frequency, particle size and device geometry have been exploited to achieve such results. Furthermore, these findings demonstrate the possibility and benefits of using acoustic actuation methods as a platform for microfluidic LOC devices.