Iris segmentation

The quality of eye image data become degraded particularly when the image is taken in the non-cooperative acquisition environment such as under visible wavelength illumination. Consequently, this environmental condition may lead to noisy eye images, incorrect localization of limbic and pupillary boundaries and eventually degrade the performance of iris recognition system. Hence, this study has compared several segmentation methods to address the abovementioned issues. The results show that Circular Hough transform method is the best segmentation method with the best overall accuracy, error rate and decidability index that more tolerant to ‘noise’ such as reflection

Effect of micro-channel geometry on fluid flow and mixing

Understanding the flow fields at the micro-scale is key to developing methods of successfully mixing fluids for micro-scale applications. This paper investigates flow characteristics and mixing efficiency of three different geometries in micro-channels. The geometries of these channels were rectangular with a dimension of; 300 lm wide, 100 lm deep and 50 mm long. In first channel there was no obstacle and in the second channel there were rectangular blocks of dimension 300 lm long and 150 lmwide are placed in the flow fields with every 300 lm distance attaching along the channel wall. In the third geometry, there were 100 lm wide fins with 150_ angle which were placed at a distance of 500 lm apart from each other attached with the wall along the 50 mm channel. Fluent software of Computational Fluid Dynamics (CFD) was used to investigate the flow characteristics within these microfluidic model for three different geometries. A species 2D model was created for three geometries and simulations were run in order to investigate the mixing behavior of two different fluid with viscosity of water (1 mPa s). Models were only built to investigate the effect of geometry, therefore only one fluid with similar viscosity was used in these models. Velocity vector plots were used in the CFD analysis to visualise the fluid flow path. Mass fractions of fluid were used to analyse the mixing efficiency. Two different colours for water were used to simulate the effect of two different fluids. The results showed that the mixing behaviour strongly depended on the channel geometry when other parameters such as fluid inlet velocity, viscosity and pressure of fluids were kept constant. In two geometries lateral pressure and swirling vortexes were developed which provided better mixing results. Creation of swirling vortexes increased diffusion gradients which enhanced diffusive mixing

Virtual prototyping of pressure driven microfluidic systems with SystemC-AMS extensions

The design of "Lab on a Chip" microfluidic devices is, typically, preceded by a long and costly period of prototyping stages in which the system is gradually refined by an iterative process, involving the manufacturing of a physical prototype and the making of a lot of laboratory experiments. In this scenario, a virtual prototyping framework which allows the emulation of the behavior of the complete system is greatly welcome. This paper presents such a framework and details a virtual prototyping methodology able to soundly handle microfluidic behavior based on SystemC-AMS extensions. The use of these extensions will permit the communication of the developed microfluidic models with external digital or mixed signal devices. This allows the emulation of the whole Lab on a Chip system as it usually includes a digital control and a mixed-signal reading environment. Moreover, as SystemC-AMS is also being extended to cover other physical domains within the CATRENE CA701 project, interactions with these domains will be possible, for example, with electromechanical or optical parts, should they be part of the system. The presented extensions that can manage the modeling of a micro-fluidic system are detailed. Two approaches have been selected: to model the fluid analytically based on the Poiseuille flow theory and to model the fluid numerically following the SPH (Smoothed Particle Hydrodynamics) approach. Both modeling techniques are, by now, encapsulated under the TDF (Timed Data Flow) MoC (Model of Computation) of SystemC-AMS.This work has been supported by CATRENE CA701H-INCEPTION Projec

Organ-on-a-Chip systems for new drugs development

Research on alternatives to the use of animal models and cell cultures has led to the creation of organ-on-a-chip systems, in which organs and their physiological reactions to the presence of external stimuli are simulated. These systems could even replace the use of human beings as subjects for the study of drugs in clinical phases and have an impact on personalized therapies. Organ-on-a-chip technology present higher potential than traditional cell cultures for an appropriate prediction of functional impairments, appearance of adverse effects, the pharmacokinetic and toxicological profile and the efficacy of a drug. This potential is given by the possibility of placing different cell lines in a three-dimensional-arranged polymer piece and simulating and controlling specific conditions. Thus, the normal functioning of an organ, tissue, barrier, or physiological phenomenon can be simulated, as well as the interrelation between different systems. Furthermore, this alternative allows the study of physiological and pathophysiological processes. Its design combines different disciplines such as materials engineering, cell cultures, microfluidics and physiology, among others. This work presents the main considerations of OoC systems, the materials, methods and cell lines used for their design, and the conditions required for their proper functioning. Examples of applications and main challenges for the development of more robust systems are shown. This non-systematic review is intended to be a reference framework that facilitates research focused on the development of new OoC systems, as well as their use as alternatives in pharmacological, pharmacokinetic and toxicological studies

Membrane integration in biomedical microdevices

The present work has been performed under the Erasmus Mundus Doctorate in Membrane Engineering (EUDIME) program. The home institute was the Chemical and Environmental Engineering Department at the University of Zaragoza, within the Nanostructured Films and Particles (NFP) group. The NFP is a member of the Nanoscience Institute of Aragon (INA). Two host universities were: Faculdade de Ciências e Tecnologia at the University Nova de Lisboa (Portugal) and Mesoscale Chemical Systems group at the University of Twente (The Netherlands). This research has been carried out for approximately 4 years (2013-2017) and it was part of the EUDIME (FPA 2011-0014, SGA 2012-1719), which was funded by the European Union. The target of the research presented in this thesis is a design, development and fabrication of a microfluidic device with integrated membrane in the form of a membrane contactor for various biological applications. The microfluidic devices are fabricated and tested for oxygenation of blood and separation of anaesthetic gas. In the first part of the work, the microfluidic system for blood oxygenation, so called lungon- a-chip, is introduced. In such system, one chamber is devoted to pure oxygen, and the other chamber is designed for blood and they are separated by a dense permeable membrane. Computer modelling is performed in order to design the liquid chamber with homogenous liquid flow, low pressure drop of the system and low shear stress without compensation of high oxygenation. Two different microdevice geometries are proposed: alveolar and meander type design with vertical membrane arrangement. Fabricated devices as well as integrated membranes are made of PDMS by soft-lithography and their surface is modified in order to make them more hydrophilic. The experiments of blood oxygenation are performed and the oxygen concentration is measured by an oximeter electrode and compared to the mathematically modelled values. The sensitivity analysis of the key parameters and the possible improvements of the proposed architectures based on the mathematical simulations are presented as well. The second part of the thesis, introduces the concept of an alveolar microfluidic device as gas-ionic liquid micro-contactor for removal of CO2 from anaesthesia gas, containing Xe. The working principle involves the transport of CO2 through a flat PDMS membrane followed by the capture and enzymatic bioconversion in the ionic liquid solvent. As proof of concept demonstration, simple gas permeability experiments are performed followed by the experiments with ionic liquid and ionic liquid with the enzyme. Finally, an alternative concept of a silicon/glass microfluidic device with an integrated membrane in the form of a fractal geometry with nanonozzles as pores at the vertices of the third-level octahedra for the controlled addition of gaseous species is introduced. Fractal geometry, that is a three-dimensional repetitive unit, is fabricated by a combination of anisotropic etching of silicon and corner lithography. As a proof of concept, simple gas permeation experiments are performed, and the achieved results reveal the potentialities of the chip for high temperature gas-liquid contactors