Micro-Flows Measurement from a LED Micro-PIV System

In this study, light emitted from LED is adopted as the light source of a micro Particle Image Velocimetry system for micro-flows measurement. The strobe frequency of LED can easily reach 20,000Hz, which is high enough to provide the time resolution required for most micro-flows measurement. The problem of relative low power of LED is resolved by adopting a cardioid annular condenser in the microscope, so LED light is focused on the micro-flows and image quality is significantly improved; in addition, image resolution is improved from half of wavelength to one-fifth of wavelength. Clear, dark background particle images of micro-flows are recorded from the proposed LED micro-PIV system. The LED micro-PIV system developed is then applied to measure flow past circular cylinder and hydrodynamic focusing flow in micro channels. Satisfactory results are obtained for all the flows measured.