A Vacuum-Driven Microfluidic Array for Multi-Step Sample Digitalization

We present herein a facile vacuum-driven microfluidic device that is capable of multi-step sample digitalization based on the gas permeability of PDMS. The device features 1) a suction layer that is connected to an external vacuum to generate a continuous negative pressure within the device, and 2) an outlet-free microarray layer with treelike multi-level bifurcated microchannels connecting to 4096 dead-end microwells to realize multiple loading steps until all the microwells being filled. To efficiently prevent sample evaporation at high temperatures, we use a glass slide that is pre-poured with thermosetting oil to seal the gas-permeable PDMS. Moreover, we demonstrated successful detection of single-cell methicillin-resistant Staphylococcus aureus (MRSA) with three loading steps targeting the resistance marker gene MecA via digital PCR amplification on the device.