Optimizing Liquid Transport Velocity of Bioinspired Open-type Micro-blade Arrays

Abstract

Microfluidic devices are used in many ways, including bioanalysis and chemical synthesis. Nevertheless, these devices have some issues, such as their susceptibility to bubble entrapment and impurities, and their necessity for high pressure to transport liquid as these devices consist of various closed tubes. To solve these problems, we have focused our research on a coastal animal, the wharf roach, which has open-type flow micro-passages composed of micro-blade arrays driven by surface free energy. Inspired by the microstructures, we fabricated a series of flow passages composed of micro-scaled epoxy blades on a silicon wafer through photolithography. The purpose of the present study was to control the liquid transport velocity and understand the liquid film thickness during transport, with the goal of manipulating liquid transport without external forces using the microstructures. The relationship between the interval of the blades and the liquid transport velocity was investigated. Furthermore, the variation of the liquid film thickness ratio with elapsed time was visualized using fluorescent dyes. As a result, we found that the liquid transport velocity was maximized when the blade height was high, and the cross-sectional shape between the two blades was square. Moreover, the interval in the vertical direction was narrow. In addition, it was clear that the liquid film of the water temporarily became thick near the three-phase contact line and the thin water film preceded the uniform thick water film. These findings are important for optimizing liquid transport in open-type microfluidic devices.