Versatile microfluidic generation of chemical concentration gradients in a flow-free setting

This paper presents a novel class of microfluidic concentration gradient generation (CGG) devices capable of producing virtually arbitrary user-specified gradient profiles in a flow-free setting. Intended for use in cell biology studies where fluid flow disturbances are to be avoided, our devices allow cells to be studied in a stationary fluid medium while constantly replenishing chemical solution and buffer to establish temporally stable gradients in an efficient manner. By exploiting a gradient forming channel network, gradient profiles of arbitrary shapes can be attained. We describe the concept, design and experimental demonstration of flow-free generation of stable gradients with different prescribed shapes.