Method and system for generating spatially and temporally controllable concentration gradients

A method of creating a concentration gradient in a microfluidic device, the device comprising a microfluidic channel formed in a substrate material connecting an inlet port and an outlet port, the method comprising:

• filling the microfluidic channel with a non-viscous solution;
• injecting a gradient material solution into the inlet port according to at least one alternating flow cycle, the flow cycle comprising:
• pumping a predefined amount of gradient material solution into the inlet port at a first predefined flow rate and causing a forward flow of the gradient material solution in the microfluidic channel;
• waiting a predefined delay;
• withdrawing a predefined amount of the gradient material solution from the inlet port at a first predefined withdrawal flow rate and causing a backward flow of the gradient material solution in the microfluidic channel;
• and
• sealing the inlet port.

A method of creating a cross-concentration gradient in a microfluidic device, the device comprising a microfluidic channel formed in a substrate material connecting an inlet port and an outlet port, the method comprising:

• providing a microfluidic device having a concentration gradient of a first gradient material in the microfluidic channel;
• applying a predefined amount of a second gradient material solution to the outlet port, whereby a large drop of the second gradient material solution forms over the outlet port;
• withdrawing a predefined amount of solution from the inlet port at a predefined withdrawal flow rate and causing the second gradient material solution to enter the outlet port and causing a backward flow of the second gradient material solution from the outlet port to the inlet port in the microfluidic channel;
• and
• pumping a predefined amount of solution into the inlet port at a predefined flow rate and causing a forward flow of the second gradient material solution from the inlet port to the outlet port in the microfluidic channel.