Conventional flow control systems, such as syringe and peristaltic pumps, are not well adapted to the control of flow in microchannels. They often result in long equilibration times, hysteresis and low stability. Herein, we present a new method to control the flows in microchannels based on a pressure actuation, by pressurization of reservoirs filled with fluids to be injected in the microsystem. The regulated pressure within the reservoirs generates pulse-free and very stable flows through the microchannels, with short settling time. To control the flow-rate with pressure actuation, highly precise flow sensors are implemented in the fluidic system and an algorithm has been developed to adjust automatically the pressure orders to reach the targeted flow-rates. Unlike a conventional PID regulation which is very sensitive to any transient behavior, our algorithm deals with any coupling effect between the different channels, and is designed to deliver the fastest and the most stable flow response. It calculates a matrix image of the microsystem with the relations between each actuated pressure channels and the measured flow-rates. Furthermore, the system can cope with any external disturbances of the system (presence of air bubble, partial clogging, variation of viscosity or temperature, etc…), and continuously re-adjust the applied pressures. The technology is perfectly suited for droplet manipulation experiments (among other applications) where we can generate 2pL water-in-oil droplets with very high monodispersity (1.63% CV) at an up to 12 kHz/s frequency. Only few seconds are needed to stop the droplets flow, reducing costs by a huge factor.
Thibaut Thupnot, Benjamin Rouffet, Anne Le Nel, and Nicolas Petit, "Innovative flow control solutions for a wide variety of applications
(Conference Presentation)," Proc. SPIE 9705, Microfluidics, BioMEMS, and Medical Microsystems XIV, 970506 (Presented at SPIE BiOS: February 13, 2016; Published: 26 April 2016); https://doi.org/10.1117/12.2213013.4848702704001.
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