An extrusion fluidic driving method for continuous-flow polymerase chain reaction on a microfluidic chip

A novel extrusion driving protocol was developed based on micro-fabricated polydimethylsiloxane (PDMS) pneumatic valves. High efficiency liquid transfer was performed by using entirely overlapping control channels and fluid channels. A 0.5-s time is sufficient for the transfer of 9 μL sample solution between two chambers in the microchip with a nitrogen pressure of 70 kPa. The driving method was used in a microfluidic polymerase chain reaction (PCR) system, and rapid cycling of the PCR mixture in a closed loop was achieved. The amplification of DNA was demonstrated via both three-stage and two-stage PCR thermal cycling on the microchips resulting in significant reduction of the PCR time. The amplifications of 144-bp and 200-bp DNA fragments were achieved within 24 min using a three-stage protocol with 30 thermal cycles, and 130-bp DNA fragments within 12 min by using 20 thermal cycles in the two-stage system, compared to about 2 h in benchtop PCR with the same number of thermal cycles.