The MicroPIVOT : an Integrated Particle Image Velocimeter and Optical Tweezers Instrument for Microscale Investigations

Abstract

This dissertation describes the development of a device capable of suspending a microscale object in a controlled flow. The μPIVOT is a system integrating two laserbased techniques: micron particle image velocimetry (μPIV) and optical tweezers (OT).The OT allows the suspension and manipulation of micron-sized objects such as microspheres or biological cells. μPIV provides imaging of the suspended object and velocity measurements from which fluid induced stresses can be determined. Using this device, we measured fluid velocities around an optically suspended polystyrene microsphere (an experimental first) and studied the interaction between two particles suspended in a uniform flow. The results were consistent with theoretical low Reynolds number, Newtonian flow predictions. Additionally, we analyzed a single cell's mechanical response to a controlled and measurable multiaxial external force (fluid flow) without the cell being physically attached to a surface. The cell's mechanical response was monitored by observing its morphology and measuring its deformation.The results show significant deformations of optically suspended cells at substantially smaller stresses than previously reported and demonstrate the opportunity to optically distinguish a cell by its trapping efficiency. These initial applications of the PIVOT demonstrate the potential of this unique device as a research tool for novel studies in the fields of fluid/particle(s) interactions, non-Newtonian fluid mechanics, and single cell biomechanics.ii ACKNOWLEDGMENTS