Control Engineering in two-phase Microfluidics for Bio-Chemical applications

Current microfluidic technologies allow the reproduction of many functionalities of macro-scale bio-chemical laboratory into a single chip. Generally, the micro-channel dimensions are on the order of ten to a hundred micrometers. In this range, the physical processes are linear but flows slow down, that represents an important bottleneck for any industrial applications. To speed-up the flow, larger micro-channels with dimensions up to one millimeter can be considered, in which the processes evolve in a transition zone between the linear and nonlinear behavior. In our studies we have investigated two-phase (biphasic) microfluidics, generated both by fluid-fluid interaction or micro-particles mixed in a fluid, in irregular micro-channels of those dimensions.
In this complex scenario in which the properties the fluids, the input flow conditions, the channel geometries and the material surface properties can strongly affect the flow dynamics, a data-driven approach for the processes identification and control based on optical technology has been studied to overcome the flow nonlinearity.
The potential of these data-driven methodologies for microfluidic processes investigation and for the design of smart micro-opto-fluidics embedded systems will be discussed by the case studies presented based on slug flows and micro-hemodynamic processes. Managing optical images and signals offers the advantages of being easily embedded in portable devices for real-time applications, but requires an accurate data interpretation and control parameters definition. In the case studies considered, the procedures developed have allowed to obtain the nonlinear characterization and classification of water-air slug flows and red blood cells collective behaviors.
The study of advanced modeling and control schemes for the real-time control of two-phase microfluidics processes has been a fundamental step in the design and realization of control embedded micro-opto-fluidic PDMS devices both by soft-lithography and 3D-printing technology. Micro-optical interfaces to track the microfluidics process in micro-channels and in micro-vascular networks realized by soft-lithography will be presented as well as micro-optical light steering components and micro-opto-fluidics embedded devices realized by 3D printing for slug flow applications.
The combination between the technological advancement of 3D printing and the potential for a control methodological framework will bring a drastic reduction of the cost and the complexity in the micro-opto-fluidics devices fabrication and experimental set-up, extending their use as a new generation of disposable and portable devices for bio-chemical analyses, easy-to use and widely accessible.