The influence of polydimethylsiloxane curing ratio on capillary pressure in microfluidic devices

► PDMS surface properties as effect of different degree of cross-linking. ► Tailoring PDMS wettability and surface properties to modulate the dynamics of PDMS microdevices. ► Negative capillary pressure induced by a modulation of surface properties. ► Confinement of liquids inside PDMS microchannels. Investigations on surface properties of poly(dimethylsiloxane) (PDMS) are justified by its large application ranges especially as coating polymer in fluidic devices. At a micrometer scale, the liquid dynamics is strongly modified by interactions with a solid surface. A crucial parameter for this process is microchannel wettability that can be tuned by acting on surface chemistry and topography. In literature, a number of multi-step, time and cost consuming chemical and physical procedures are reported. Here we selectively modify both wetting and mechanical properties by a single step treatment. Changes of PDMS surface were investigated by X-ray photoelectron spectroscopy and atomic force microscopy and the effects of interface properties on the liquid displacement inside a microfluidic system were evaluated. The negative capillary pressure obtained tailoring the PDMS wettability is believed to be promising to accurately control sample leakage inside integrated lab-on-chip by acting on the liquid confinement and thus to reduce the sample volume, liquid drying as well as cross-contamination during the operation.