Transient Electro-Osmotic And Pressure Driven Flows Through A Microannulus

At present, with the rapid development of MEMS sensors, Micro-pumps and other micro-devices, Microfluid transmission phenomena in these devices has become a new research field. Among them, the electroosmotic flow (EOF) micro-pump with characteristics of a continuous flow mode, simple structure and other characteristics, not only has applications in micro-electro-mechanical systems, but also has a very broad application prospects in mechanical physics, biotechnology, medical technology and aerospace technology. In addition, as a new clean energy, the direct methanol fuel battery has become a hot research topic, some of its internal mechanism are closely related to EOF phenomenon. Thus, in-depth study the fluid characteristics of EOF in microscale channel not only has advantages in the development of these modern high-techs, but also has an important theoretical significance for enhancing the characteristic of the fuel battery.This paper studies transient electro-osmotic flows of Newtonian fluid driven by pressure and DC/AC electric field in a microannulus. Using the Laplace transform method solving the linear Poisson-Boltzmann equation and the transient Cauchy momentum equation, the semi-analytical expressions equation of Newtonian fluid EOF velocity can be obtained. By numerical computations of inverse Laplace transform, the effects of inner to outer wall zeta potential ratio β、 the normalized pressure gradient Ω、the oscillation Reynolds number Re and the inner to outer radius ratio a on transient EOF velocity are presented.