On acoustic particle and cell manipulation in microfluidic systems

Abstract: The combination of laminar flows in microfabricated channels and acoustic forces induced in ultrasonic standing wave fields offers new possibilities for advanced particle and cell manipulation in lab-on-a-chip applications as well as in relatively high throughput applications. Acoustic particle manipulation systems can be used e.g. to separate, wash, sort, trap or distribute particles in microfluidic networks. This doctoral thesis starts by reviewing the fundamental fields of study needed to realize such systems and to understand their potential impact. Next, the design, fabrication, operation and performance of a number of systems, based on system design principle termed the "Lund method", are described. The developed methods comprise a toolbox of generic particle handling methods that can be combined or used separately to handle biological and non-biological particles in liquid suspension. The toolbox is applied to solve various blood component handling tasks, e.g. separation of lipid particles and other contaminating substances from red blood cells and preparation of blood components. The results imply that it is possible to save thousands of people from brain damage caused by lipid particles each year, to reduce the strain on the blood banks significantly and to offer new methods for routine blood component handling. Several other important areas of application, where micrometer sized particles are routinely handled, can also be identified. Microscale acoustic particle manipulation technology is still in its infancy but, based on the findings presented in this thesis and by other researchers, it can be anticipated that new laboratory and industrial standards may very well emerge from the current research.