A one-step hot-embossing process for fabricating a channel with superhydrophobic inner walls

To produce microfluidic chips cheaply, efficiently, and by mass production, a "one-step" method is proposed herein for fabricating a chip channel and its superhydrophobic inner walls. The flake bulge and micro-pit structure were prepared by chemically etching an S45C steel mold. The influences of etching-solution concentration and etching time on the formation of the hydrophobic structure were studied. A superhydrophobic mold was obtained with a surface contact angle of 156.29 degrees and a sliding angle of 4 degrees. The channel and its inner walls were then duplicated by hot embossing with a poly (methyl methacrylate) substrate. The influences of temperature, pressure, and pressure-holding time on the reproduction accuracy of the superhydrophobic structure were investigated. Stable chip replication was obtained with the following optimal combination of process parameters: a temperature of 145 degrees C, a pressure of 0.8 MPa, and a pressure-holding time of 120 s. The average duplication accuracy achieved was 99.29%, the average surface contact angle was 151.37 degrees, and the average surface sliding angle was 9.3 degrees. The bottom and inner walls of the channel were both observed to be hydrophobic.