Handling and control setups for microfluidic devices

The fine control of physical and chemical parameters plays a critical role in determining the success of a microfluidic application. All control systems must possess the fundamental property of stability, which means that the system is able to return to the same equilibrium point after being perturbated from its initial position. Embedded controllers fit better with microfluidic applications, allowing miniaturization and easy integration with other components of the control system, making possible a rapid prototyping of the microfluidic device. Feedforward controllers lack robustness of the control performance; thus a closed-loop control system is suitable for microfluidic setups. In specific, in the case of a microfluidic device, there might be the need to control and monitor the pressure and flow rate of the liquids driven in microchambers or microchannels, the temperature and moisture of the surrounding environment, and liquid chemical parameters (like pH, dissolved oxygen, optical density, etc.). Moreover, if biological samples are used in the microfluidic platforms, biological information should be managed by specific sensors. This chapter will face these concepts and a case of an Arduino-based PID controller for a cell incubator will be illustrated. It should also be considered that the control setups should be connected to a microfluidic device by an interface system. Iinterfacing microfluidic systems still represents a nonstandardized challenge. Due to the multiplicity of microfluidic applications, finding the interfacing techniques which best suit is fundamental. Fluidic, electrical, and optical interfaces will be discussed in detail in this chapter as well. Finally, since microfluidic cellular applications often need to be monitored, an overview about microscopy and spectroscopy techniques will be presented. In the last section the reader will find a discussion about the main pumping methods that can be used in microfluidic applications, with a particular focus on the main issues related to their use.