A size reduction method for rapid digital PCR using thin-film chip and vacuum pouch microfluidic system

The digital polymerase chain reaction (dPCR) is a high efficacy detection method that is widely applied in lab-on-a-chip systems. Reported dPCR microfluidic devices usually require a high level of system integration, including a fluidic manipulating system, a thermal cycling system, an optical system, and a power source. To effectively reduce system size and complexity, we integrate thin-film dPCR chip and the vacuum pouch microfluidic (VPM) system to eliminate the fluidic manipulation system and to reduce energy demand on the thermal cycler. The VPM system integrates fluidic handling system on-chip by using a vacuum seal bag to enclose the thin-film dPCR chip and to store negative pressure. This design makes operation simple: load PCR mix and oil on the pouch surface then pierce the film surface to initiate loading and droplet generation. The thin-film dPCR chip is a 0.288 mm-thick cyclo-olefin-polymer film embedded with a passive droplet generator, and the distance from droplets to the chip surface is less than 50 mu m. This design makes this chip have a low thermal mass and a short thermal conducting length, and the demand on the heating and cooling power of the thermal cycler can be largely reduced. A polyimide thermofoil heater and a small cooling fan are sufficient to complete 35 amplification cycles in 4.84 min. Combining these two technologies, this VPM-dPCR system is lightweight, compact, and conserves energy, and the dPCR chip is disposable. Finally, its capability to perform dual-target detection also is demonstrated by quantifying two microRNA targets in one VPM-dPCR chip.

Automated summary

The study integrates thin-film dPCR chip and the vacuum pouch microfluidic (VPM) system to reduce system size and complexity. The VPM-dPCR system is lightweight, compact, and energy-saving, with disposable dPCR chips. In addition, it is capable of performing dual-target detection.