A liquid-triggered liquid microvalve for on-chip flow control

This work introduces a novel surface tension and geometry based liquid-triggered liquid microvalve for on-chip liquid flow control. The simultaneous presence of two liquid plugs at the uncomplicated valve junction triggers the further movement of the liquids and overcomes the stop valve function of the device, thereby providing a precise means of timing liquid movement on-chip. The generic structure was shown to successfully function and forms the basis for several novel and useful functions, including fluidic AND gates, contactless on-chip liquid sample control, timing of independent processes on the same microchip, bubble-free joining of liquids, all of which pose great challenges in the area of microfluidics. The device may be applied to chemical analysis, drug discovery, medical diagnostics and biochemistry. (C) 2004 Elsevier B.V. All rights reserved.