Importance of surface forces in a micro-fluidized bed

Fluidized beds (FBs) potentially offer a means of significantly enhancing heat and mass transfer under the low Reynolds number flows that prevail in microfluidic devices. However, as surface forces start to dominate over gravity at the microscale, adhesion of particles to the walls of the micro-FB can prevent fluidization. We used the acid-base theory of van Oss, Chaudhury and Good to understand adhesion forces at the particlewall interface in a micro-FB. This approach, novel to the fluidization field, successfully predicts the adhesion problem in a micro-FB system as verified by our experimental results for liquid fluidization in a typical PDMS microfluidics channel. This demonstrates the importance of considering surface forces in the design of micro-FB, unlike for traditional large FBs where surface forces are often less of an issue.