Programming of capillary effects for liquid confinement and automatic flow control in microfluidic probes

Abstract

We present a microfluidic probe (MFP) [1,2] that exploits capillary effects for confining and flowing a liquid in a micrometer-sized gap formed between the probe head and a surface. The probe head is formed of a mesa that is wettable on the top, and non-wettable on the side walls, and that includes apertures for injecting and aspirating the liquid. The aligned superposition of surface chemical pattern with topography imparts efficient confinement of the liquid between mesa and surface, both with non-wettable and wettable surfaces. The MFP further augmented with a capillary system (CS), which offers flow control: the flow automatically starts when the MFP is brought in proximity of the substrate and the flow automatically stops when the MFP is retracted. Using such an MFP, lines have been drawn on surfaces by scanning across them, and disconnected spots have been patterned at arbitrary location on a surface in parallel by approaching and retracting an array of MFPs. Copyright © 2005 by the Transducer Research Foundation, Inc.