Interfacing centrifugal microfluidics with linear-oriented 8-tube strips and multichannel pipettes for increased throughput of digital assays

We present a centrifugal microfluidic cartridge for the eight-fold parallel generation of monodisperse water-in-oil droplets using standard laboratory equipment. The key element is interfacing centrifugal microfluidics with its design based on polar coordinates to the linear structures of standard high-throughput laboratory automation. Centrifugal step emulsification is used to simultaneously generate droplets from eight samples directly into standard 200 mu l PCR 8-tube strips. To ensure minimal manual liquid handling, the design of the inlets allows the user to load the samples and the oil via a standard multichannel pipette. Simulation-based design of the cartridge ensures that the performance is consistent in each droplet generation unit despite the varying radial positions that originate from the interface to the linear oriented PCR 8-tube strip and from the integration of linear oriented inlet holes for the multichannel pipettes. Within 10 minutes, sample volumes of 50 mu l per droplet generation unit are emulsified at a fixed rotation speed of 960 rpm into 1.47 x 10(5) monodisperse droplets with a mean diameter of 86 mu m. The overall coefficient of variation (CV) of the droplet diameter was below 4%. Feasibility is demonstrated by an exemplary digital droplet polymerase chain reaction (ddPCR) assay which showed high linearity (R-2 >= 0.999) across all of the eight tubes of the strip.

Automated summary

This article presents a centrifugal microfluidic cartridge that can generate eight-fold parallel monodisperse water-in-oil droplets using standard laboratory equipment. The cartridge design interfaces centrifugal microfluidics with linear structures of standard high-throughput laboratory automation, enabling simultaneous droplet generation from eight samples into standard PCR 8-tube strips. The inlets of the cartridge allow for minimal manual liquid handling, and droplets with a mean diameter of 86 μm and a coefficient of variation below 4% can be generated within 10 minutes. Additionally, a digital droplet polymerase chain reaction (ddPCR) assay demonstrated the feasibility of the method.