US Patent 8182765 Fluid transfer mechanism

A microfluidic device for transferring liquid from a first chamber to a second chamber is provided. The device has a first chamber; a second chamber; and a barrier between the first chamber and the second chamber, the barrier having least one opening fluidly connecting the first chamber to the second chamber, the at least one opening being sized such that a retention force, such as surface tension, keeps the liquid in the first chamber. The fluid is transferred from the first chamber to the second chamber when an initiation input such as fluid pressure is introduced to the liquid that is sufficient to overcome the retention force. The device may be a sensor strip.