Capillary filling of micro-reservoirs with various cross sections

Any microfluidic device depends on a proper and complete filling with liquid. In many cases entrapped air bubbles will drastically alter device performance and thus have to be avoided. Especially the dosing of liquids with micropumps or free jet dispensers is heavily influenced by the existence of gas bubbles. Also optical detection in microfluidic systems may fail due to light reflection at entrapped gas bubbles. In consequence a reliable liquid filling is a key design issue in microfluidics. Although the importance of this attribute is commonly accepted there is no established set of design rules for the geometry of "filling-friendly" microfluidic structures. We have therefore examined the filling of fluidic reservoirs and channels with arbitrary cross-sections to provide design rules for self-priming.