Aggregation Kinetics of Colloidal Nanoparticles in a Circulating Microfluidic Cavity
M.R. Barmi1 B.D. Piorek1 M. Moskovits2 C.D. Meinhart1
1Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, CA, USA
2Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA, USA
Pressure-driven air flow is directed over the microfluidic cavity induces circulating fluid motion in the cavity. Analyte contained in the air stream is absorbed into the cavity, mixes with the nanoparticles as a result of the circulating cavity flow. Therefore, the nanoparticles sequentially aggregate into clusters of higher orders. The model captures: fluid dynamics of the air flow and microfluidic cavity, second order aggregation kinetics and at the interface, we account for momentum transport, heat transfer, mass transport through evaporation-driven phase change, and mass transport through analyte adsorption. In the case of efficient mixing inside of the cavity, there is an optimum point at t _opt = k c_NP t ≈ 0.7 where the number of formed dimers is maxima.