Optimization of the microfluidic cartridge for a COVID-19 diagnostic device
Point-of-care (POC) diagnostic devices were vital in the response to the COVID-19 pandemic, enabling more timely evaluations of infected areas to better control the spread of disease. In response to COVID-19, a microfluidic cartridge-based sample prep-PCR system, previously developed for DNA genotyping was quickly adapted to a POC device for SARS-CoV2 detection from self-collected saliva samples. One of the critical components of the microfluidic cartridge is the saliva metering, requiring to meter 20mL of saliva sample which is subsequently mixed with primer solution. Initial cartridge prototyping has not been successful due to the viscous and bubbling nature of saliva, which disrupts consistent fluid movement. In this study, the initial cartridge design was modified to achieve proper metering and mixing. New prototypes were designed using AutoCad, fabricated by CNC machining, and assembled manually. Each prototype underwent functional testing using dye-colored saliva samples to accentuate fluid flow. Through 11 cartridge redesigns, we optimized channel layout to accommodate for bubble formation from saliva while accurately metering saliva sample and enabling the metered saliva to mix with the PCR primers at a correct ratio. Future work involves incorporating the new cartridge design into the whole system and evaluating it with real saliva samples for SARS- CoV2 detection.
