Three-dimensional Flow Measurements around Micro-pillars Made by UV-NIL in Water via Micro-digital Holographic Particle Tracking Velocimetry (Micro-DHPTV)

A refractive index matching method in water to measure the velocity field around micro pillars was investigated. The micro-pillars were fabricated from an optical material whose refractive index was 1.333, which is the same as that of water. The fabrication method used was UV imprint lithography (UV-NIL) with photolithography with a replica mold. The moving tracer particles on the pillars were measured by micro-digital holographic particle tracking velocimetry (micro-DHPTV). Because the refractive indices of the pillars and water were the same, the hologram images could be obtained clearly without diffraction around the micro-pillars. As a result, tracking of particles and measurement of velocity fields using reconstructed particles could be achieved without optical distortion. The moving particles could be captured around the micro-pillars.