General Defocus Particle Tracking

Sammanfattning: Three-dimensional particle tracking is a valuable tool in microfluidics for obtaining information about a system. General Defocus Particle Tracking (GDPT) is a straightforward method of 3D particle tracking that only requires a single-camera plane, making it applicable to existing equipment in a laboratory.  This project's aim was to evaluate the open-source module DefocusTracker which uses GDPT. DefocusTracker was used to track particles that were levitated in a microchip using ultrasonic standing waves.  The effects of different calibration methods used and the evaluation of the acoustic energy density over an active part of a piezo on an microchip device were investigated. Different procedures to generate a depth model from the calibration images showed that the choice of step length affects the accuracy of the depth model. A depth model created from the middle part of the field of view provides more accurate results compared to one made from the edge. Levitation experiments demonstrate that higher applied voltages result in a stronger acoustic energy density field over the field of view. The acoustic energy density field and pressure amplitude field show variations across the active piezo on the device, potentially due to a non-uniform thickness of the fluid layer and variations in energy delivery from the piezo. Overall, GDPT proves to be a useful method for evaluating unknown aspects of a microfluidic system under the influence of ultrasonic standing waves.