Geometry and surface assisted flow discretization

This paper presents a micro flow discretizer that autonomously digitizes continuous liquid flow into nanoliter segments without consuming any electricity or requiring any external control. In the prototype demonstration, the discretizer is made of PDMS microfluidic channels with desired geometry and surface properties. Employing a new self-aligned masking process followed by oxygen plasma to pattern the 3-dimensional PDMS surfaces, areas exposed to plasma are converted from naturally hydrophobic into hydrophilic while areas covered by the mask remain hydrophobic. With the assistance of channel geometry and properties of hydrophobic/hydrophilic surface patterns, a continuous water flow has been split into segments with controllable and predetermined volumes from 10 to 40 nanoliters. As such, this autonomous flow discretizer opens up a new class of metering and manipulation scheme in microfluidic applications including lab-on-a-chip.