Laser Speckle Contrast Imaging of flow in a microfluidic device

Laser speckle contrast imaging (LSCI) is a well established technique for imaging blood flow in the brain. Microfluidic devices were designed and fabricated in PDMS and TiO2 to mimic the capillary network in the brain, with different channel sizes (10microns to 150microns). The flow of intralipid through the channels was imaged with LSCI. The microfluidic devices were used as a tissue phantom to perform controlled experiments to investigate the effect of factors that influence speckle contrast like speed., concentration of intralipid, depth of channels and exposure time. A speckle imaging instrument that allows image acquisition over a wide range of exposure times is presented. Speckle contrast was found to be a function of speed and exposure time. with concentration and channel depth serving to improve signal strength. Exposure time is shown to influence the sensitivity of speckle contrast to speed. It is also shown that speckle contrast as a function of exposure time can potentially be used a method to obtain qualitative measurements of speed.