Optical Measurement of the Relative Motion of a Spherical Particle in a Micro-Capillary

The motion of a neutrally buoyant spherical micro particle suspended in a liquid inside a ‘U’ shaped micro channel is detected using particle tracking velocimetry. The ratio of the particle diameter to the hydraulic diameter of the channel is found to be 0.1. Poiseuille velocity profile is observed inside the micro channel and the spherical particle is convected with the Poiseuille velocity field. The magnitude of the lag factor is determined experimentally and is compared with the values reported in existing literature. The effect of other forces and interactions on the particle is quantitatively studied. It was found that effects of Brownian, Van der Waals and electrostatic forces do not significantly contribute to the velocity of the particle.