Microfluidic design rules for capillary slot-based electrospray sources

摘要

We formulate microfluidic design principles for electrospray ionization sources based on a rectangular capillary slot formed by two triangular cantilevers. Spontaneous imbibition of the test liquids into the slot by capillary action provides a robust mechanism for liquid transport from a reservoir to the cantilever tip where an electrospray is generated upon application of a voltage. The correct functioning of the source requires the liquid bridging the slot to have a negative Laplace pressure. Imbibition is controlled by the ratio of slot width to height w/h and the intrinsic contact angles theta(w), theta(s) of the liquid with the slot walls and the cantilever faces, respectively. Based on these parameters we derive a simple criterion for the complete filling of the slot. (C) 2004 American Institute of Physics.