Digital concentration gradient generators on a microfluidic chip

Microfluidic is now a common tool for developing chemical or biological applications. One of the main particularities of microfluidic is the difficulty to mix several products due to the Reynolds number which becomes very low at the microscale. For this reason, several research groups report active or passive micromixers integrated in analysis devices. In this paper we take advantage of miniaturisation to achieve a concentration gradient of a chemical specise over a 1D or 2D chambers array. The concentration varies by steps in the chambers array over 4 decades, while it is maintained successfully constant in each chamber thanks to diffusion, which becomes fast at microscale. Principles are based on chemical diffusion and the Fick's Law. We propose an active version of the device enabling a dynamic control of a 2D digital concentration gradient. Application of this work is envisioned for the high throughput screening in pharmacology.