Kristóf Iván

Design, realisation and validation of microfluidic stochastic mixers integrable in bioanalytical systems using CFD modeling

In this work we present the design aspects of special microfluidic structures applicable to dilute and transport analyte solutions (such as whole blood) to the sensing area of biosensors. Our goal is to design and realise a reliable microfluidic system which is applicable for effective sample transport and can accomplish simple sample preparation functions such as mixing to ensure homogeneous concentration distribution of the species along the fluidic channel. The behaviour of different chaotic mixers were analysed by numerical modeling and experimentally to determine their efficiency. At first we used the concentration distribution method, however because of numerical diffusion this required higher mesh resolutions. Using the particle tracing method is more efficient according to the experimental results and requires lower computational effort. The microstructures were realised by micro-fabrication in polydimethylsiloxane (PDMS) and integrated into a real microfluidic transport system. The functional performance was verified by biological analyte.

An integrated and mixed technology LOC hydrodynamic focuser for cell counting application

In our project a standard microfluidic analyzer background system and its construction steps were developed to analyze biologic fluids. The obtained micro-Total-Analysis-System (μTAS) is based on the integration of different microflu-idic systems. Each part follows well-defined rules to make the integration of the large-scale production microchip technology with the cheap polymer support system possible. The compiled system is based on the SensoNor glass/silicon/glass multilayer technology [1] and ThinXXS plastic slide technology, which are made from low cost materials, easily producible in large-scale and in the same time biocompatible. In this project hydrodynamic focusers were designed to sort and analyze particles and cells in one continuous focused line, in a 50 μm wide channel. The advantage of this Lab-On-a-Chip (LOC) structure is the easy interfaceability with electrodes and optical systems. The designed microchannels contain electrodes for electrical characterization and because of the anodic bonding process it is possible to observe the channel with an upright microscope [2]. With these two fundamental methods our system is able to analyze and measure any biological liquid, which contain less than 10 μm size particles or cells, and count the number of morphologically well-separated different elements in the focused liquid flow with image processing algorithms.

Modelling and Characterisation of Droplet Generation and Trapping in Cell Analytical Two-Phase Microfluidic System

Present study analyses the influence of flow characteristics of special water-oil two-phase microfluidic systems regarding the droplet generation, cell encapsulation and trapping processes. Water droplets were dispersed in oil continuous phase with the requirement of precise size distribution to enable effective cell entrapment. The evolving droplet size and the number of encapsulated cells were examined considering the applied flow rate ratios of the two phases. The hydrodynamic behaviour of the microfluidic system was modelled by Finite Element Method (FEM) coupled with particle trajectory calculation applying COMSOL Multiphysics code. The experimental results were compared to the simulation and the applicability of our droplet based cell encapsulating and trapping microfluidic system was characterised.

Microvesicle fractionation using deterministic lateral displacement effect

We demonstrate a novel integrated microfluidic device to separate circulating extracellular vesicles from blood stream using the deterministic lateral displacement principle. The device continuously fractionates extracellular vesicles and cells according to size and membrane flexibility by displacing them perpendicularly to the fluid flow direction in a micro-fabricated array of post. Direct separation of different size micro- and nanospheres were demonstrated using a multi-stage separation strategy thus offering a potential route for novel cancer diagnostic approaches where microvesicles can be targeted and intercepted during cell to cell communication.