Capillary flow control using hydrophobic patterns

This note presents a simple method to control the speed of the autonomous capillary flow using an array of hydrophobic patterns. The microfluidic system in this note was composed of two planar parallel plates that were separated by spacers. The bottom plate had a hydrophilic microchannel which was surrounded by hydrophobic tracks. The top surface was relatively hydrophobic compared to the bottom plate. These hydrophobic tracks and the hydrophobic patterns in the middle of the microchannels were patterned using PDMS stamps by contact printing. By controlling the ratio of hydrophobic area to the whole channel width and the distance between two plates, it was possible to control the capillary flow speed at specific positions. Using this method, it is expected to achieve a sufficient incubation time for biological reactions in microfluidic devices using the capillary flow.