Microfluidics is an emerging field that has applications in many areas of research, including the study of biological systems and the development of biomedical sensors and drug delivery devices. In many of these systems, it is crucial that large particles or cells are assessed individually. This is typically accomplished by transporting them single-file in a channel nearly the same size as the particle. One key step toward being able to model these types of systems is to be able to predict the fluid velocity required to initiate movement of a particle adhered to the surface of the microchannel. When fluid flow is introduced in a microchannel, it is important that the velocity is sufficient to entrain particles into the moving stream and to prevent redeposition along the length of the channel. In addition, particle adhesion to channel walls has been identified as a major problem in two-phase microchannel flow, so being able to predict the force required to dislodge a particle is critical when designing microfluidic devices. These adhesion forces are a function of many particle properties, including the ratio of particle diameter, dp, to channel diameter, D.

The proposed research will experimentally investigate the effect of particle size on the fluid velocity required to initiate movement of a particle adhered to a microchannel surface. This will be accomplished by inserting a single spherical particle into a microchannel that is nearly the same size as the particle and allowing it to settle. Fluid flow will be introduced, and the velocity will be gradually increased and stabilized in a stepwise manner until particle movement is observed. A range of particle sizes will be used to determine the effect of dp/D on the velocity required for incipient motion. This work will be very important to the microfluidics community and will be the foundation for many future investigations identifying the factors that influence large particle detachment in a microchannel.