Abstract
Microfluidic-based microparticles manipulation, such as patterning, enrichment and separation of cells and polymer beads, become a very promising technique for biomedical analysis. Acoustophoresis, the particles movement in acoustic field, with the advantages of good biocompatibility and low power consumption, has recently emerged as a promising non-invasive method for microparticles manipulation. A considerable number of studies on acoustic microfluidic devices have been reported, involving the mechanism, design and characterization of them. However, there is still gap between the conceptions and practical exploitation of acoustophoresis for microparticles manipulation. For example, few of studies has achieved acoustic properties based microparticles separation, though it is of great importance in biomedical analysis. Moreover, the acoustofluidic devices are still at a high price thus making it hard to be widely commercialized. In addition, the acoustic radiation force is dependent on particle size, raising difficulties on manipulation of sub-micron particles on which the acoustic radiation force is relatively weak. In this thesis, surface acoustic wave, a type of acoustic wave propagating along substrate surface, is used to realize microparticle manipulations. Compared with other types of acoustic wave actuation methods (e.g. bulk acoustic wave), surface acoustic wave has the advantages of good integration with other microfluidic components, high frequency of acoustic field and flexibility in localizing the acoustic field. In the studies presented in this thesis, surface acoustic wave based devices are used to (1) assemble and pattern nanomaterials, (2, 3) separate microparticles based on their size or mechanical properties and (4) sort cell samples by their fluorescence labeling. (5) Designs for lower cost and better performance of the devices are also presented. These studies pave the way for the deeper mechanism understandings and broader implementations of the acoustic based microfluidic devices for microparticles manipulation.