Bubble-free rapid microfluidic PCR

Microfluidic polymerase chain reaction (PCR) has been of great interest owing to its ability to perform rapid and specific nucleic acid amplification and analysis on small volumes of samples. One of the major drawbacks of microfluidic PCR is bubble generation and reagent evaporation, which can cause malfunctions. Here, through theoretical modeling and characterization of bubble behavior, we propose a bubble-free microfluidic PCR device via controlled fluid transfer. Our approach exploits a thin impermeable polyethylene (PE) top layer that minimizes the generation of bubbles by inhibiting mass transport along a vertical direction. Simulation results demonstrate that a calculated mass flow difference of approximately 370% can be obtained by utilizing an impermeable membrane as the vertical barrier layer. To demonstrate proof-of-concept, two nanoporous polymeric materials, poly(dimethylsiloxane) (PDMS) and PE, were used for stand-alone self-powered sample loading (approximately 70s) and for use as a vertical barrier layer, respectively. Consequently, we demonstrate successful amplification of the cMET gene, a nucleic acid (NA) biomarker for lung cancer, and complete an ultrafast PCR test in less than 3 min using a high powered Peltier-based thermal cycler under bubble-free conditions. This approach will result in a new paradigm for ultrafast molecular diagnosis and can facilitate NA-based nearly instantaneous diagnostics for point-of-care testing and for personalized and preventive medicine.