Microfluidic inductors designed via topology optimization

Abstract

The equivalent circuit design method has evolved into a relatively mature technique for designing microfluidic devices. This approach simplifies microfluidic device design by approximating fluid behavior within the devices as analogous to electron behavior in electrical circuits, thereby leveraging the analogy between microfluidic hydraulics and electrical circuits. Based on this technique, scientists have developed microfluidic devices with various functionalities, such as multi-concentration mixing, cell capture, flow distribution, concentration gradient generation, and droplet generation. However, due to the disparity in physical properties between microfluidic systems and electrical circuits, the impedance effect experienced by fluids during the analogical design process is not pronounced—specifically, when mapping fluidic characteristics like high and low Reynolds numbers to circuit properties such as high and low current frequencies. This gap has resulted in a lack of microchannel design methods analogous to inductive components in electrical circuits when applying the equivalent circuit approach to microfluidic chip design. Here, we propose a design strategy for microfluidic valves with inductive properties and their topological optimization. The valve structures designed by this method exhibit high flow resistance under high Reynolds number conditions and low resistance under low Reynolds number conditions. Consequently, this work enriches the equivalent circuit design methodology by introducing the equivalent inductive microfluidic module—Microfluidic inductor as a new available module, along with its corresponding design method.