On importance of surface forces in a microfluidic fluidized bed

Fluidized beds potentially offer a means of significantly enhancing mixing, heat and mass transfer under the low Reynolds number flow conditions that prevail in microfluidic devices. However, as surface forces at the microscale can be significant relative to hydrodynamics forces, fluidization within a microfluidic channel can be potentially hindered or even prevented through particle adhesion to the channel walls. We have used the acid–base theory of van Oss, Chaudhury and Good to predict the propensity for adhesion of particles on microfluidic fluidized bed walls for various practically important wall material/particle/fluid combinations. Comparison of the results from this approach with experimental observations indicates that it provides a robust means of predicting the adhesion propensity. It is also demonstrated how results from the model can be used to estimate for a system of interest the particle size range in which the particle–wall surface forces transition from being dominant to being insignificant.