Modelling of enzyme reactions in microreactors

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Dr. Ender Ferenc
Department of Electron Devices

High through put screening (HTS) is one of the most promising branch of biomedical R\&D. Such devices are capable of testing several or even a few hundred samples parallelly (for example screening for the presence of a certain pathogen, difference in blood test or genetic mutation) or of testing a single human sample for several different agents (e.g. seeking for several different pathogens in a single sample).

The aforementioned devices usually use optical biosensors that may detect fluorescent label molecules attached to the target molecules. Many research teams are dealing with alternative detection methods, where the target molecules do not need to be labeled. These label-free methods open new possibilities to detect biomolecules that were impossible or hard to detect with optical methods \cite{cooper2006non}. Amongst label-free methods which are based on impedance measurement, spectroscopy and electrochemical measurements, calorimetric detectors are particularly significant. These detectors measure the heat produced due to chemical reactions catalyzed by enzymes.

By using the emerging technologies of microfluidics and downscaling sample volumes and sensors, the traditionally poor throughput of calorimetric devices can be increased, though by several orders of magnitude.

This MSc. thesis deals with the basic design principles of such a high throughput calorimetric system, in the following regards:

- The modeling of enzyme reactions in droplet microfluidic environment, concerning enzymes immobilized on the channel walls

- The expected throughput, sensitivity and accuracy of such a system taking into account the expected sample sizes.

To design such a device the amount of heat generated in the microchannel by the chemical reaction needs to be determined. A simplified compact model is proposed for this purpose. Our theoretical model of the enzyme kinetics is compared to experiments.

The compact model is verified using ANSYS Fluent CFD (Computational Fluid Mechanics) software. First a volumetric enzyme reaction is modelled and the results are compared to the results of our compact model. A two phase droplet flow is simulated as well. Finally, the combination of the two models resulting a multiphysical simulation to model both the chemical reaction and two phase flow in accordance to the actual processes in the Lab-On-a-Chip device.

We expect the results of this simulation to show a good agreement with our analytic compact model, and our measurement results.

Throughout the whole investigation of the Lab-On-a-Chip device the multidisciplinary approach used for MEMS (Micro Electro Mechanical) device design is applied. The thesis made from TDK paper of Pálovics Péter and Németh Márton in $2013/14/I$ semester.


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