Opto-fluidic velocimetry using liquid crystal microfluidics

The coupling between flow and orientation of nematic liquid crystal molecules has been utilized to devise a non-intrusive opto-fluidic velocimetry technique on a microfluidic platform. The flow-induced reorientation of the liquid crystal molecules in a diverging channel possessing homeotropic surface anchoring produced distinct birefringent domains, directly observable through their interference colors, which are characteristic to the local flow velocity. The flow-induced effective birefringence was characterized using polarizing optical microscopy, confocal fluorescence polarizing microscopy, and particle tracking methods.