Numerical Simulation of Second-Order Microfluidic Filter

In this paper, we present a microfluidic filter to improve mixing index and eliminate the pulsatile component within microfluidic devices, which is similar to a second-order RC low-pass filter in electronics. COMSOL Multiphysics, a kind of simulation software, is used to evaluate the analytical method and the efficiency of the device. Compared with the results obtained from the equivalent circuit theory, the simulation method has been verified. In addition, the equivalent circuit theory, in other words the fluid dynamical equivalent of Ohm’s law, is adopted to make the theoretical analysis. This microfluidic filter is equipped with multiple simple channels and microcavities having elastic membrane at the top layer, just like the series–parallel connection of resistors and capacitors. Based on the results, one microcavity is equivalent to first-order filter and two microcavities in series equal second-order filter which shows the better filtering effect. Actually, when the driving frequency exceeds 60 Hz, this device can export almost steady fluid. The mixing effect is improved compared with the simple microfluidic junctions. The combined application of microfluidics and equivalent circuit theory will gain insightful ideas and practical design methods for developing unique microfluidic devices to address a broad range of biological and chemical challenges.