Figure 2.

Blocking a channel with expanding polyurethane foam. (A) Schematic of the microchip prior to testing. The two reagents are separated, with architecture to mix them before sample is diverted. (B) Prior to channel blockage, dye solution freely flows through the open channel architecture. (C) Upon foam expansion and curing, the primary channel (2 mm diameter) is blocked. When new sample is added and the microdevice spun, fluid is diverted into the previously unfavorable flow path.