A vortex-type micromixer utilizing pneumatically driven membranes

Micromixers are commonly employed for chemical or biological analysis in micro-total-analysis-system applications. Mixing performance is important since it allows for rapid and efficient chemical or biological reactions. This study, therefore, reports a new vortex-type micromixer which utilizes pneumatically driven membranes to generate a swirling flow in a mixing chamber. The micromixer chip is fabricated by using micro-electro-mechanical-systems technology as well as a computer-numerically controlled machine for rapid prototyping. Two different membrane layouts and driving frequencies are evaluated to determine if there is a significant improvement in the mixing performance. Experimental results indicate that the mixing efficiency increases with increasing driving frequencies and the mixing time is reduced by approximately tenfold as the driving frequency increases from 1 to 6 Hz. A mixing efficiency as high as 95% can be achieved, in time periods as short as 0.6 and 0.7 s for the two- and four-membrane layouts, respectively. Furthermore, numerical simulations are also employed to characterize the swirling flow field, the concentration distribution and the mixing mechanism as well. Combined experimental data and numerical results illustrate the fluid dynamic phenomena that allow for rapid mixing in this vortex-type micromixer.