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UBC Theses and Dissertations

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UBC Theses and Dissertations

Acoustic forces and microparticles manipulation using CMUT arrays Ye, Ruolan


Microparticle manipulation means actively controlling the position and dynamics of micro-/nano-particles in a microfluidic environment, which is of great interest to many fields, especially in biomedical science, for example, bioanalysis, disease diagnosis, and drug delivery. Many mechanisms such as acoustophoresis, electrical forces, thermophoresis, magnetophoresis, and optical forces have been used to solve this task. The acoustophoresis method is an effective non-contact solution, which makes use of the acoustic streaming force and the acoustic radiation force to gather and migrate microparticles. Normally, acoustophoresis is achieved through the generation of standing acoustic waves. This requires a piezoelectric substrate and a pair of IDTs (interdigitated transducers) at the ends of the microfluidic channels for one-dimensional manipulation, or two pairs of IDTs for two-dimensional (in-plane) manipulation. This thesis proposes a novel technique of creating a patterned pressure field, by using a CMUT (Capacitive Micromachined Ultrasonic Transducer) array to manipulate microparticles in two-dimensional space. CMUTs are MEMS-based ultrasound transducers, that can generate and receive ultrasound signals. By digitally controlling the amplitude and phase of the acoustic beam generated by each element in the CMUT array, the acoustic field can be adjusted to form a desired pressure pattern on a target plane. Microparticles will be moved to the target locations due to acoustophoresis effects in the field. CMUT arrays are chosen to accomplish this task because CMUTs can be easily fabricated into large arrays at a low cost. In addition, the CMUT array is reconfigurable and can be controlled in real-time. This provides the feasibility of real-time closed-loop control of microparticles. In this thesis, we derive the equations of the acoustophoresis effects. Then create the numerical model using COMSOL Multiphysics® software to verify the feasibility of manipulating microparticles using a CMUT array. Finally, we discuss the potential physical experiment setup and the closed-loop system to manipulate microparticles in real-time.

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