Low-cost open-source flow velocity sensor for droplet generators

Droplet microfluidics enables the manipulation of small sample and reagent volumes in physically discrete droplets, each acting as a separate microreactor. This opens up new analytical routes in cell analysis and chemical synthesis. Flow regulation, and in particular, flow sensing, is vital to enable controlled and automated droplet generation. However, precision flow sensing technology is typically complex and expensive, or lacking in certain performance metrics. This work targets development and demonstration of an optical flow velocity/flow rate sensor, which is compact and low-cost, communicates and functions wirelessly, and has performance metrics comparable to currently available flow sensors. The demonstrated experimental flow sensor prototype was evaluated using commercially available pressure sensors in conjunction with an in-house developed dual-channel pressure pump at various flow rates. Based on the evaluation, the sensor had a measurement resolution of 0.6 µl/min, measurement accuracy of 0.76–13.03 % at a total cost of ~ € 100.