Novel strategies for controlled lateral force fields in planar resonators for biomedical applications

The levitation and manipulation of small particles has attracted much interest, especially for lab-on-a-chip devices and the possibilities of controlling the position of human cells, bacteria, and microbeads. Latterly, the use of acoustic radiation as a way to levitate particles in small channels has encountered plentiful success for many applications including sorting, aggregating and multiple other biomedical operations. Most devices used for these applications used static acoustic radiation force patterns inducing non-configurable trapping positions. Recent years have seen the emergence of dynamic trapping in micro channel which is necessary to widen the range or possible application for such techniques including transport and rotation of single particles and aggregates. This thesis investigates novel ways of structuring static force fields in planar resonators, and also creating dynamic levitation techniques especially design for biomedical related projects. Several possible approaches are explored all using planar resonators as a basis. Initially the lateral forces in a standard planar resonator are explored, assessing the impact of design parameters on the ‘naturally occurring’ lateral force components. Secondly, novel devices which add an extra control layer to direct the acoustic excitation of the fluid layer are explored. The third approach consists of having this intermediate control layer be formed of a channel with a two phase flow. The droplet movement in this control layer changes the structure of the acoustic radiation field, which dynamically following the droplet. The thesis concludes with the design of a planar resonator with strong lateral force components for the culture of discoid-shaped liver cancer cell aggregates. The resulting aggregates are cultured and studied, demonstrating that they present characteristics and functional protein expression that more closely matches in-vivo cells and hence could provide a better model for drug screening applications.