A droplet-based multivolume microfluidic device for digital polymerase chain reaction

Digital PCR plays an essential role in detecting and quantifying nucleic acid targets. At the same time, there are still challenges in its applications, including reduction of cost, simplification of operations, and system miniaturization. This work proposes a droplet-based multivolume microfluidic device for easy-to-operate and integrated droplet digital PCR (ddPCR). With an “asymmetrical droplet-splitting” microstructure, we have successfully prepared both small and big droplets within the same main channel of the microfluidic chip. With the size of (59.1 ± 2.2) μm and (106.3 ± 3.9) μm in diameter, about 30,000 droplets are produced for multivolume ddPCR, and thus to perform a dynamic range of over 104 for DNA molecule quantification. The chip integrates droplet generation, droplet array self-assembly, droplet dPCR, and fluorescence detection on a single device. The quantitative capability of the ddPCR chip was evaluated by measuring template DNA at concentrations from 20 to 12,500 copies·μL-1. Benefiting from the characteristics of the wide dynamic range (10 ~ 104 copies·μL-1), easy operation, and miniaturization, the proposed ddPCR device is expected to be used in applications involving DNA molecule quantification, including diagnosis of genetic disease, single-cell gene expression, and other biomedical fields.