Electroosmotic flow and particle transport in micro/nano nozzles and diffusers

Micro/nano nozzles and diffusers have been used for ionic transport, drug and gene delivery. In this paper, a mathematical model is developed to simulate the electroosmotic flow (EOF) and particle transport in micro/nano nozzles/diffusers. The electrical potential and the flow field are investigated using the lubrication and the Debye-Huckel approximations specially for nanonozzles (overlapped electric double layers) and microdiffusers (thin EDLs) for which experimental results exist. The results show that a pressure field is induced by the presence of EDLs and the magnitude of this induced pressure is proportional to the ratio of the Debye length to the channel half-height. Embedded particles are often employed to illustrate the flow field and thus measure the local fluid velocity. The direction of particle motion is found to be dependent primarily on the particle charge and the wall charge. The calculated particle velocities compare well with experimental data.