Pulsatile reverse flow actuated microfluidic injector: toward the application for single-molecule chemotropism assay

Microfluidic sample plug injection often relies on electrokinetic means which restrict the application of this technology to biological studies involving living cells. Here, we present a microfluidic injector device that is coupled with a cell culture chamber for chemotropic pollen tubes in order to study the directional cellular growth triggered by ligand–receptor interactions at single molecule resolution. In the reported device, unidirectional fluidic flow is introduced by a syringe pump, and a temporal change in the flow direction that is required for a sample plug injection is realized by operating an on-chip electro-osmotic pump that generates pulsatile reverse flow. A fraction of an injected sample plug can be transferred to the cell culture chamber in a controlled manner, which potentially allows us to study the cellular responses to an injected ligand at high spatiotemporal resolution.