Open-Source Pressure Controller Based on Compact Electro-Pneumatic Regulators for Droplet Microfluidics Applications

Microfluidics is a rapidly growing area that provides innovations in biotechnology, medical diagnostics, and life science. Along with the commercial solutions, there are opensource projects aimed to make such technologies more affordable and flexible for end users. In this article, we developed an opensource, low-cost, and easy-to-use microfluidic pressure controller with a modular design based on electropneumatic regulators to introduce liquids into microfluidic devices under constant pressures. For implementation of complex experimental protocols, the controller contains a vacuum pump, relay outputs, analog inputs, and digital inputs/outputs to connect external equipment. It can be operated using five displays and an encoder or from a personal computer in a manual or automatic regime through the custom open-source software. In this study, we applied this pressure controller for the generation of water-in-oil droplets in microfluidic flow-focusing droplet generators. Droplets' diameters linearly depended on the dispersed and continuous phases' ratio in the range 5-65 mu m. In all the cases, the generation regimes were stable for at least 4 h. Direct comparison of the droplet generation obtained with the developed pressure controller and precise syringe pumps showed that it will suit the needs of the microfluidic community for different flow-based labon-a-chip applications, as a more affordable and flexible solution for introducing liquids and controlling flow sensors, heaters, valves, light sources, and so on during experiments.