Numerical and experimental study of flow and wall mass transfer rates in capillary driven flows in microfluidic channels

Micro-channels are believed to open up the prospect of precise control of fluid flow and chemical reactions. The capillary effect can be used to pump fluids in micro-channels and the flow generated can dissolve chemicals previously deposited on the walls of the channel. In this work, numerical and experimental approaches have been developed to investigate the wall mass transfer rate generated by capillary driven flows (CD-Flow). The purpose of this work is to analyze the wall mass transfer rates generated by a CD-Flow in a micro-channel. The results have implications in the optimization and design of devices for biological assays. The correlation for Sherwood number, Reynolds number, contact angle and time is reported. This correlation can be a useful tool for design purposes of microfluidic devices that work with fast heterogeneous reaction and have capillary driven flow as passive pumping system. The numerical results have been confirmed by the experimental results.La perspectiva del uso de micro-canales para el control preciso del flujo y de las reacciones químicas está ampliamente aceptada. Considerando que el efecto de las tensiones superficiales en la micro-escala es significativo, el bombeo pasivo basado en el uso de la tensión superficial para los Lab-on-a-chip resulta ser el método más eficaz.El propósito de este trabajo es analizar la transferencia de masa en la pared en un campo dinámico de un flujo impulsado por capilaridad. Los resultados permitirán mejorar el diseño y optimizar los dispositivos para ensayos biológicos. Se presenta una correlación entre el número de Sherwood, el número de Reynolds, el ángulo de contacto y el tiempo. La correlación puede ser una herramienta útil en el diseño de dispositivos microfluídicos que trabajen con una reacción rápida y heterogénea y usen el bombeo pasivo impulsado por el flujo capilar. Los resultados numéricos han sido confirmados por los resultados experimentales

A comprehensive study on different modelling approaches to predict platelet deposition rates in a perfusion chamber

Thrombus formation is a multiscale phenomenon triggered by platelet deposition over a protrombotic surface (eg. a ruptured atherosclerotic plaque). Despite the medical urgency for computational tools that aid in the early diagnosis of thrombotic events, the integration of computational models of thrombus formation at different scales requires a comprehensive understanding of the role and limitation of each modelling approach. We propose three different modelling approaches to predict platelet deposition. Specifically, we consider measurements of platelet deposition under blood flow conditions in a perfusion chamber for different time periods (3, 5, 10, 20 and 30 minutes) at shear rates of 212 s(-1), 1390 s(-1) and 1690 s(-1). Our modelling approaches are: i) a model based on the mass-transfer boundary layer theory; ii) a machine-learning approach; and iii) a phenomenological model. The results indicate that the three approaches on average have median errors of 21%, 20.7% and 14.2%, respectively. Our study demonstrates the feasibility of using an empirical data set as a proxy for a real-patient scenario in which practitioners have accumulated data on a given number of patients and want to obtain a diagnosis for a new patient about whom they only have the current observation of a certain number of variables.Peer reviewe

Virtual Intracranial Stenting Challenge 2011: Input data

<p>Input data provided to the participants of the Virtual Intracranial Stenting Challenge 2011 (VISC'11).</p> <p> </p> <p>Fileset content:</p> <p>* surface.stl: STL surface mesh (in mm) of vascular geometry</p> <p>* ccs*.stl, ocs*.stl: STL surface meshes (in mm) of deployed stent geometries </p> <p>* geometry.pdf: Image of vascular and stent geometries with labels for inlets/outlets and regions-of-interest</p> <p>* challenge_instructions.txt: Instructions to challenge participants, including flow rate boundary conditions and blood properties</p> <p> </p> <p>More details on VISC'11:</p> <p>Cito S, Geers AJ, Arroyo MP, Palero VR, Pallarés J, Vernet A, Blasco J, San Román L, Fu W, Qiao A, Janiga G, Miura Y, Ohta M, Mendina M, Usera G, Frangi AF. Accuracy and Reproducibility of Patient-Specific Hemodynamics Models of Stented Intracranial Aneurysms: Report on the Virtual Intracranial Stenting Challenge 2011. Annals of Biomedical Engineering, 43(1):154-167, 2015.</p> <p> </p> <p>Contact:</p> <p>Arjan Geers ([email protected])</p> <p> </p> <p>Links:</p> <p>* http://dx.doi.org/10.6084/m9.figshare.1060453 : FigShare fileset "VISC'11: Particle imaging velocimetry data"</p> <p>* http://dx.doi.org/10.6084/m9.figshare.1060464 : FigShare fileset "VISC'11: CFD solutions group E"</p> <p>* https://github.com/ajgeers/visc11 : GitHub repository with code to reproduce the plots of the journal paper</p

Comparative iss accelerometric analyses

Two accelerometric records coming from the SAMSes es08 sensor in the Columbus module, the so-called Runs 14 and 33 in terms of the IVIDIL experiment, has been studied here using standard digital signal analysis techniques. The principal difference between both records is the vibrational state of IVIDIL, that is to say, during Run 14 the shacking motor of the experiment is active while that in Run 33 this motor is stopped. Identical procedures have been applied to a third record coming from the SAMSII 121f03 sensor located in the Destiny module during an IVIDIL quiescent period. All records have been downloaded from the corresponding public binary accelerometric files from the NASA Principal Investigator Microgravity Services, PIMS website and, in order to be properly compared, have the same number of data. Results detect clear differences in the accelerometric behavior, with or without shaking, despite the care of the designers to ensure the achievement of the ISS pg-vibrational requirements all along the experiments. Copyright © (2012) by the International Astronautical Federation.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Fluido-Dynamic and Electromagnetic Characterization of 3D Carbon Dielectrophoresis with Finite Element Analysis

The following work presents the fluido-dynamic and electromagnetic characterization of an array of 3D electrodes to be used in high throughput and high efficiency Carbon Dielectrophoresis (CarbonDEP) applications such as filters, continuous particle enrichment and positioning of particle populations for analysis. CarbonDEP refers to the induction of Dielectrophoresis (DEP) by carbon surfaces. The final goal is, through an initial stage of modeling and analysis, to reduce idea-to-prototype time and cost of CarbonDEP devices to be applied in the health care field. Finite Element Analysis (FEA) is successfully conducted to model flow velocity and electric fields established by polarized high aspect ratio carbon cylinders, and its planar carbon connecting leads, immersed in a water-based medium. Results demonstrate correlation between a decreasing flow velocity gradient and an increasing electric field gradient toward electrodes’ surfaces which is optimal for selected CarbonDEP applications. Simulation results are experimentally validated in the proposed applications

Visualization and measurement of capillary-driven blood flow using spectral domain optical coherence tomography.

Capillary-driven flow (CD-flow) in microchannels plays an important role in many microfluidic devices. These devices, the most popular being those based in lateral flow, are becoming increasingly used in health care and diagnostic applications. CD-flow can passively pump biological fluids as blood, serum or plasma, in microchannels and it can enhance the wall mass transfer by exploiting the convective effects of the flow behind the meniscus. The flow behind the meniscus has not been experimentally identified up to now because of the lack of high-resolution, non-invasive, cross-sectional imaging means. In this study, spectral-domain Doppler optical coherence tomography is used to visualize and measure the flow behind the meniscus in CD-flows of water and blood. Microchannels of polydimethylsiloxane and glass with different cross-sections are considered. The predictions of the flow behind the meniscus of numerical simulations using the power-law model for non-Newtonian fluids are in reasonable agreement with the measurements using blood as working fluid. The extension of the Lucas-Washburn equation to non-Newtonian power-law fluids predicts well the velocity of the meniscus of the experiments using blood

Influence of different computational approaches for stent deployment on cerebral aneurysm haemodynamics

Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost 50 per cent after stent deployment for both initial positions. Results highlighted that, although some differences in calculated parameters existed across the cases based on the modelling simplifications, all the approaches described the most important effects on intra-aneurysmal haemodynamics. Hence, simpler and faster modelling approaches could be included in clinical workflow and, despite the adopted simplifications, support clinicians in the treatment planning

Virtual Intracranial Stenting Challenge 2011: Particle imaging velocimetry data

<p>Particle imaging velocimetry data belonging to the Virtual Intracranial Stenting Challenge 2011 (VISC'11). The dataset was used to validate CFD solutions provided by challenge participants. Specifically, the dataset was used to validate the in-plane velocity field on the xy-plane at z = 0 mm for the untreated case.</p> <p> </p> <p>Fileset content:</p> <p>* piv.vti: PIV dataset (in mm) stored in a vtkImageData object</p> <p> </p> <p>Notes:</p> <p>* The image region for x < -6 mm was excluded from data analysis for the journal paper. The normal of the glass surface was nearly perpendicular to the optical axis in this region and the PIV technique could not reliably estimate the velocity field. As mentioned in the paper, even after excluding part of the PIV image, relatively large differences between CFD and PIV were found near the lower bound of the x-axis.</p> <p>* The PIV image and vascular geometry were placed in the same coordinate system. They were positioned such that the xy-plane at z = 0 mm (corresponding to the PIV plane) approximately sliced the main flow jet into the aneurysm along its axis.</p> <p> </p> <p>More details on VISC'11:</p> <p>Cito S, Geers AJ, Arroyo MP, Palero VR, Pallarés J, Vernet A, Blasco J, San Román L, Fu W, Qiao A, Janiga G, Miura Y, Ohta M, Mendina M, Usera G, Frangi AF. Accuracy and Reproducibility of Patient-Specific Hemodynamics Models of Stented Intracranial Aneurysms: Report on the Virtual Intracranial Stenting Challenge 2011. Annals of Biomedical Engineering, 43(1):154-167, 2015.</p> <p> </p> <p>Contact:</p> <p>Arjan Geers ([email protected])</p> <p> </p> <p>Links:</p> <p>* http://dx.doi.org/10.6084/m9.figshare.1060443 : FigShare fileset "VISC'11: Input data"</p> <p>* http://dx.doi.org/10.6084/m9.figshare.1060464 : FigShare fileset "VISC'11: CFD solutions group E"</p> <p>* https://github.com/ajgeers/visc11 : GitHub repository with code to reproduce the plots of the journal paper</p