Concentration gradient generator using a convective-diffusive balance.

Since biomolecular concentration gradients are an important factor in various biological phenomena, many concentration gradient generators utilizing microfluidic techniques have been devised in order to establish stable in vitro biomolecular concentration gradients, each with their own strengths. However, all the fundamental issues, simplicity in apparatus, dynamic controllability, and convection-free conditions, have not been addressed simultaneously. In this paper, we describe a novel way of establishing concentration gradients using a convective-diffusive balance in a counterflow configuration. With the help of this method, stable, reproducible concentration gradient profiles can be formed in under a minute and the shape of the profiles are easily predicted with a simple mathematical formula.