A highly integrated vertical SU8 valve for stepwise in-series reactions

Stepwise performance of reactions demands highly integrated microfluidic control. The vertical valve presented in this work allows performing reactions in cascade with reduced control requirements, by controlling the rupture of an SU8 wall that separates a chamber from an adjacent evacuation channel. Owing to its vertical construction, the valve can be readily integrated into any geometry with a low increase in footprint. Two valve approaches are presented, which differ in the location of the rupture region, the breaking pressures and the size of the fluidic path open. Breaking the wall about its upper end has proven to be more limited in terms of geometry and resulting gap size, whereas breaking the wall about its root opens a wider fluidic path that allows smooth filling of downstream chambers. Following these conclusions, a sequence of two reactions has been demonstrated, using a wall-valve-regulated double-chamber device. The chosen protocol, DNA concentration, elution and transport, has been successfully accomplished, as evidenced by positive on-chip polymerase chain reaction in a second double-chamber device.