Spatially controlled chaotic mixing in microfluidic devices using local geometrical features to enhance reactivity conditions

Abstract

Lab-on-a-chip technology has enabled chemical reactions to take place under precisely controlled flow conditions, improving reproducibility and efficiency. However, microscale mixing remains a challenge due to the predominantly laminar flow regime, which lacks turbulent eddies that are typically used to enhance mass transport at larger scales In some specific cases, enhanced micromixing is desired to increase mass-transport in certain areas of the chip. Such an effect could be achieved by using pumps, but more advanced configurations have been explored to indirectly induce mixing in well-defined areas of the microchannel. For example, chaotic mixing has been implemented to enhance mixing in low Reynolds number flows. This method leverages base-relief structures on the microchannel surface, inducing flow perturbation while improving mixing efficiency. Unlike active methods such as pumps, chaotic mixing allows for localized and controlled mixing in the microfluidic device through geometrically optimized channel designs. This final degree project focuses on the rational design and implementation of chaotic advection in microchannels, integrating computational simulations and experimental validation. To evaluate the impact of the different geometries on the mass-transport undergoing events, two different case studies are performed in lab-on-a-chip devices fabricated applying microfabrication techniques where printed mold is used. The first study will rely on the use of micrometric (i) passive particles and (ii) colored dyes to track such flows, while the second one will be based on the electrochemical detection of Prussian blue in a lab-on-a-chip system with integrated miniaturized sensors where performance in real sensing applications of our optimized device will be evaluated. Different areas of expertise will be covered, from fluid dynamics to microfabrication technologies, performing a systematic study to find out how materials and design are key to developing advanced microfluidic systems, optimizing their design for enhanced performance in chemical and biosensing applications.