A Valve-free 2D Concentration Gradient Generator

Abstract

Microfluidic chip is a promising platform for multiple discipline, like biology, medicine, chemistry and material synthesis. It could offer some unique advantages that large scale platforms don’t share. In this thesis, a specific aspect of microfluidic chip, the gradient generator is mainly studied, also an annoying phenomenon is observed and investigated semi-quantitatively. What I’ve designed is a valve-free 2D concentration generator is. This 2D concentration generator features in valve-free and simultaneous 2D concentration gradient generating. While other designs may involve pneumatic activated valves (PAVs) or require successive infusion of analytes. By using multilayer 3D chip fabrication, this chip has discarded the usage of valves at the nodes where two perpendicular channels encounters, thus avoided some cumbersome external instrument for air infusion and make the chip closer to a portable device. Also my design can achieve simultaneous infusion of chemicals. However an annoying problem was observed in this design. The delay in infusion from branch chamber to chamber along the main channel will cause non-uniformity in generated gradient. We have raised a hypothesis and try to testify it by an experiment, then give a semi-quantitative explanation based on our hypothesis and had a conclusion that the smaller the branch channel is, the weaker the delay problem is.