Scanning defocusing particle tracking for the experimental characterization of flows in demanding microfluidic systems.

A novel scanning particle image velocimetry technique, to the best of our knowledge, is proposed to characterize flows in microfluidic applications. Three-dimensional information is acquired by oscillating the target sample over a fixed focal plane, allowing the reconstruction of particle trajectories with micrometer accuracy over an extended depth. This technology is suited for investigating acoustic flows with unprecedented precision in microfluidic applications. In this contribution, we describe the experimental setup and the data processing pipeline in detail; we study the technique's performance by reconstructing pressure-driven flow; and we report the three-dimensional trajectory of a 2 µm particle in an acoustic flow in a 525µ m ×375µ m microchannel with micrometric accuracy.