PDMS microchannels with slanted grooves embedded in three walls to realize efficient spiral flow

This paper presents functional three-dimensional microchannels whose top and side walls have slanted microgrooves. These microchannels can generate short pitch spiral flow for efficient chaotic mixing. We proposed a novel fabrication method for 3-D SU-8 molds using two-step inclined backside exposures and additional two-step top side exposures. The width and depth of the SU-8 microchannel are 100 μm. Slanted grooves of 50 μm in width and 30 μm in depth were patterned on the top and the side walls of the microchannel. Their orientation angle was 63.5° with the microchannel axis. It was demonstrated that the microchannel with slanted grooves on three walls achieved short pitch spiral flow compared to the microchannel with slanted grooves on one wall. Since liquid in the channel flows along the grooves on the walls, optimum design of the pitch and placement of the slanted grooves enables efficient spiral flows in the channel.