A quick thermal response digital acoustofluidic system for rapid on-chip PCR

Polymerase chain reaction (PCR) has been widely used in gene identification, pathogen detection, tumor research since invented in the last century. Microfluidic chips, which have low sample consumption, contactless operation, and rapid response, have been proven to be an ideal carrier for PCR technology. However, due to the precise temperature control required in the PCR process, additional temperature modules need to be integrated, which will present challenges to the application of microfluidic PCR devices. In this study, we proposed a rapid PCR system based on digital acoustofluidics with low detection limit (as low as 0.5 ng/mL) and rapid thermal response rate (up to 9.4 °C/s). Specifically, the movement of droplets is prevented by a polydimethylsiloxane (PDMS) ring, and the coupling effect of acoustic thermal with acoustic stream is used for heating micro droplets from inside out. We enhanced the temperature rise capability of the droplets by increasing their viscosity through the addition of glycerol, and equilibrium temperature for fluids with different viscosities was fitted. Based on the adjustment of input power, we determined the temperature control scheme for PCR thermal cycling. Compared to the standard PCR process, this digital acoustofluidic system shows a consistent trend and has a higher amplification efficiency (97.23 %), which can achieve 40 cycles in 57 min. We expect this device to provide support for point-of-care testing (POCT) and rapidly nucleic acid testing in the future.