Virtual Sensor Development for Continuous Microfluidic Processes

In continuous microfluidic processes, such as factory-on-chips, most valuable variables to be sensed for implementing an optimal control are usually not accessible. This is, for instance, the case of the shape and position tracking of the flow interfaces in a flow-focusing microdevice. In this context, virtual sensors are promising tools to improve the current control systems aiming at a zero-defect strategy. This article presents a methodology for building an accurate virtual sensor, based on computer-aided engineering simulations, both analytical and numerical, and model order reduction techniques. The methodology is applied to a given flow-focusing microchip. The outcome is a real-time model (virtual sensor) able to predict the shape and location of the multiphase fluid interfaces from the volumetric flow rate measured in the system. Results are successfully validated against the experimental data. The main challenge of this approach is to minimize uncertainties associated with the microfluidics setup.