Integrated high-speed flow sensor based on pressure difference measuring

During the past decade, high-through put volume transfers of liquids in the submicroliter range have become an important feature of liquid-handling robotic instruments in protein crystallization, drug discovery and medical diagnostics. Applications requiring quickly measurement of submicroliter to nanoliter quantities flow rate to provide closed-loop control for accurately dispensing liquids with a large range of viscosities and detecting air bubbles or nozzle clogs in real time. In this paper, an integrated high-speed liquid flow sensor based on the measurement of the pressure difference across a flow restriction is presented. The micro-fluidic channel was etched on the backside of two Silicon piezo-resistive pressure sensors. Equations are derived to describe the sensor behavior both statically as well as dynamically, which is helpful for sensor dimension designing. From the dynamics analyses, a working range bandwidth of about 1 KHz is expected. The sensors' low dead volume, high speed and accuracy allow it to control submicroliter to nanoliter liquid quantities.