Characterization and modelling of micro and nanofluidic systems

by Edxon Eduardo Licon Bernal

Institution: Universitat Polit├Ęcnica de Catalunya
Year: 2015
Record ID: 1124237
Full text PDF: http://hdl.handle.net/10803/288227


Lab-on-a-chip arrangements are ever more frequently used for the miniaturization of chemical and biochemical analysis. In these arrangements, all the manipulations of analyte transport, separation, mixing with reactants and detection are integrated and implemented at the scale of a microchip of several cm in size. This makes possible a dramatic reduction in the required amounts of analytes and reactants, as well as in the time of analysis. Besides that, automation and high-throughput operations (due to parallelization) become much easier than in the conventional "macro-laboratory" environments. According to the great interest in the development of new porous materials including their subsequent integration into biomedical devices and industrial applications, the description of the characteristics of nanoporous media (for example membranes) and the development of characterization techniques are crucial for controlling the behavior of systems that include separation and purification processes with such technologies. Within this thesis various developments in the field of microfluidics, separation and purification of substances has been carried out: For the field of microfluidics, this study may be useful for the description of the first stages of the concentration polarization in microfluidic systems coupling membrane technology or micro/nano interfaces. Furthermore, it was shown that for such systems, Taylor-Aris theory is applicable locally in large open microchannels within a range of Peclet numbers. Furthermore, it was possible to derive a simple analytical approach for internal concentration gradient within long channels in terms of only a few parameters, determined numerically. This approach is useful for developing future experimental studies. In equipment used for measuring the zeta potential of porous media, the variation in the channel height is technically possible. This thesis shows that under such conditions, the fluid flow can become undeveloped turbulent, which provokes that conventional approaches to the interpretation of electrokinetic measurements should be changed accordingly. A mathematical model for arbitrary electrolytes mixtures has been defined to describe the transport phenomena occurring in several osmotic separation processes. The limited number of adjustable parameters contained in this model makes possible its unequivocal determination from a limited set of experimental data. According to the results of this work, hollow fibers membrane contactors are useful as a polishing step for removing low levels of ammonia in water. It has been determined and validated experimentally a mathematical model which helps to describe the influence of operating conditions, such as flow, ammonia concentration and pH of the system for both configurations, closed and open loop. These results are important for designing production systems of ultrapure water that can be used in the production of hydrogen by water electrolysis. The application of microfluidics technologies at industrial scale is one of the…