Self-propelled continuous-flow PCR in capillary-driven microfluidic device: Microfluidic behavior and DNA amplification

• The PCR solution is autonomously transported by capillary forces.
• The capillary flow during temperature switching is mathematically formulated.
• We examine the viscosities and capillary pressures in PCR microchannel.
• The simulated and experimental data of the capillary flow are excellently matched.
• We verify the specific DNA amplification in capillary-driven microfluidic device.

Continuous-flow polymerase chain reaction (CF-PCR) in microfluidic devices has a great potential for on-site detection of various pathogens and food species because of their high speed deoxyribo nucleic acid (DNA) amplification. However, flow-controlled pumps such as syringe pumps are absolutely necessary, which cause complex and difficult operations. Here, we present a self-propelled CF-PCR (SP-CF-PCR) in a microfluidic device which requires no external pumps to control the flow. The PCR solution is simply dropped onto the inlet and is autonomously transported by capillary forces. One of the difficulties in addressing the capillary flow in PCR microfluidic device is that the temperature of the PCR solution is periodically switched. Differing from previous theoretical approaches which deal with single steady-state temperature zone, for the first time, the displacement of capillary flow during temperature switching was mathematically formulated and was simulated by using experimental values of viscosities and capillary pressures at each temperature as parameters for simulation. Basing on the excellent matching between simulated and experimental data of the capillary flow, we were able to reveal the optimized design of 150-μm-wide and 150-μm-deep microchannel that successfully transported over 1600 mm for carrying out PCR within less than 14 min solely by capillary forces. We also demonstrated the SP-CF-PCR for verifying our concept. The specific amplifications of 295 bp of β-actin from human genome, 232 bp of AH1pdm influenza virus and 95 bp of 16S rDNA of Escherichia coli genomic DNA were successfully achieved, proving the application potentials of our device.