Pressure-driven flow in open fluidic channels.

At the boundary between a hydrophilic and hydrophobic surface coating a large contact angle hysteresis exists which can be used to retain fluid on a flat surface, a similar effect exists at the edge of a solid surface. In this work, pressure-driven flow is used to create fluid flow through a fluid volume confined along a 1 mm wide strip of glass. Very high flow rates are shown to be achievable, reaching a value of 500 μL/min over a 30 mm length; at such values the maximum flow velocity is found through modeling to be 0.13 m/s. By consideration of the minimum energy state the shape a certain fluid volume will adopt on a strip of material are well known for static fluids, we demonstrate flow through the two key types, the case resembling a section of a cylinder and the case of a pronounced bulge. This combination of fluid constrained though locations of high contact angle hysteresis combined with induced flow allows applications in detection of air-borne contaminants, the detection of changing fluid composition, and easy interfacing between microfluidic system and external tools.