Combined effects of pump and capillary pressures for the filling of microchannel networks: the difficulty of synchronization

J. Berthier, M.L. Diakite
CEA-Leti (University Grenoble Alpes),
France

Keywords: network, synchronization, pump pressure, pressure drop, capillary pressure, Laplace pressure

Summary:

In this work, we first propose a model for the filling of a capillary tube driven by a pressure pump. It is shown that the filling time depends not only on the pump pressure but also on the wetting properties of the tube walls. The capillary filling may even be stopped if the walls are sufficiently lyophobic, and the pressure low. A non dimensional number Pin/Plaplace characterizes the relative effect of capillarity. In a second step, the filling of a network is investigated. It is shown that a high injection pressure considerably reduce the de-synchronization. In case of low injection pressure, de-synchronization occurs; it is shown that the capillary effect is important and modifies the filling of the device. The results are applied to the filling of microchambers for simultaneous PCR reaction. Parallelization requires the precise filling and loading of these chambers, and the best synchronization is searched for. De-synchronization triggers the formation of air bubbles and leads to anomalous functioning of the device.