Water Purification in Micromagnetofluidic Devices: Mixing in MHD Micromixers

AbstractThis contribution addresses a possible solution for water purification from heavy metals by magnetic nanoparticles in microfluidic water flow systems. In this technique, the most important component is the micromixer while efficient mixing and particle driving is achieved by external magnetic fields. For the simulation of water flow and nanoparticles, Computational Fluid Dynamics methods are used. The 2D and 3D Navier-Stokes equations are solved for the flow field while trajectories of the magnetic nanoparticles are simulated by the use of a Lagrangian method. Compared to traditional techniques, this method is expected to succeed chemical speed and increased water purification times

Computational Study of the Optimum Gradient Magnetic Field for the Navigation of the Spherical Particles in the Process of Cleaning the Water from Heavy Metals

AbstractThe usage of magnetic spherical nanoparticles, coated with substances and driven to targeted areas in tanks, is proposed for cleaning the water from heavy metals. In the present paper, a computational study for the estimation of the optimum gradient magnetic field is presented in order to ensure the optimum driving of the particles into the targeted area. The optimization of the gradient magnetic field rates’ is verified with the particles’ deviation from a desired trajectory. Using the above mentioned method, it was depicted that with the increase of the optimization parameters number, the particles’ deviation from the desired trajectory is decreased

Mixing of Particles in Micromixers under Different Angles and Velocities of the Incoming Water

A possible solution for water purification from heavy metals is to capture them by using nanoparticles in microfluidic ducts. In this technique, heavy metal capture is achieved by effectively mixing two streams, a nanoparticle solution and the contaminated water. In the present work, particles and water mixing is numerically studied for various inlet velocity ratios and inflow angles of the two streams. The Navier-Stokes equations are solved for the water flow while the discrete motion of particles is evaluated by a Lagrangian method. Results showed that as the velocity ratio between the inlet streams increases, by increasing the particles solution flow, the mixing of particles with the contaminated water is increased. Thus, nanoparticles are more uniformly distributed in the duct. On the other hand, angle increase between the inflow streams ducts is found to be less significant

Magnetic navigation of particles in newtonian and non - newtonian fluids

Cancer, also known as malignant tumor, is a disease that is related to unnatural cell evolution. Chemotherapy fights against cancer cells, where drug is injected into the human body and attacks into both healthy and cancer cells. This results to several side effects, eg. kidney or liver toxicity.In order to reduce the above mentioned side-effects, researchers in the late '70s proposed navigation of drug loaded magnetic particles towards the tumors. Nanoparticles enter the human body through a catheter and external magnetic fields produced by a Magnetic Resonance Imaging (MRI) device are used. As a result, increased quantity of drug, that reaches the area of interested in the human body, is achieved. The purpose of the present study is magnetic driving of micro- and nanoparticles into the targeted areas under a gradient magnetic field. Since an analytical study for the evaluation of the effect of the magnetic field on particles is impossible, a numerical model for magnetically guided drug delivery is attended.The computational platform uses Computational Fluid Dynamics techniques. The fluid flow was determined using the incompressible Navier-Stokes equations, where the magnetic field is estimated with Lorentz force. The motion of particles in fluid flow was evaluated by Lagrange method. The equations were solved with the OpenFOAM platform. To verify the optimal magnetic field a Covariance Matrix Adaptation Evolution Strategy (CMAES) was used to navigate the particles into the desired area.Series of simulations with newtonian and non-newtonian fluid under the influence of permanent and gradient magnetic fields were performed. The non-newtonian fluid (blood) was modeled by using the Carreau method. The validation of the model was performed through the comparison between existing experimental and numerical results.Due to the small particles' size, their magnetic response was small. Using paramagnetic nanoparticles their response was maximized and under the influence of steady magnetic field they formed into chains.The particles' interaction and the aggregates that form were verified through a series of simulations under the influence of permanent and gradient magnetic field. Parameters, such as the size of the particles and their material were taken into consideration. Also, simulations with particles of different diameter were performed in order to verify their aggregation behavior, under the influence of constant and gradient magnetic field. The influence of newtonian and non-newtonian fluid in particles' motion and interaction was verified by comparing the computational results. The purpose of particles' navigation is to maximize the number of particles that can be driven into the targeted areas. To achieve this, a method that estimates the time evolution of the gradient magnetic field in order to navigate them into the desired area was developed. To verify the potential of the model and the parameters that affect the driving process, simulations in geometries with different diameters which had branches were performed. Moreover, the effect of magnitude of the magnetic field gradient in particles' driving process, as well as, the number of particles, which are simulated, were examined. In addition, the effect of the amount of the optimization parameters that were used in order to navigate the particles into the desired areas was also analyzed. The fluid velocity effect and the role of the branches diameter were estimated.Σκοπός της παρούσας έρευνας είναι η οδήγηση μίκρο και νάνο σωματιδίων σε συγκεκριμένες περιοχές με την χρήση του μαγνητικού πεδίου. Η μοντελοποίηση πραγματοποιήθηκε με τη χρήση μεθόδων της υπολογιστικής ρευστοδυναμικής (Computational Fluid Dynamics) με βασικά χαρακτηριστικά τις μη-μόνιμες και τρισδιάστατες προσομοιώσεις νευτωνικών και μη-νευτωνικών ροών σε αρτηρίες με διακλαδώσεις. Το πεδίο ροής προσδιορίστηκε από τη λύση της εξίσωσης Navier-Stokes όπου το μαγνητικό πεδίο μοντελοποιείται μέσω της δύναμης Lorentz. Για τη κίνηση των νανοσωματιδίων μέσα στη ροή χρησιμοποιήθηκαν διακριτές αριθμητικές μέθοδοι τύπου Lagrange. Για την επίλυση των εξισώσεων χρησιμοποιήθηκε το λογισμικό ανοικτού κώδικα OpenFOAM. Η οδήγηση των νανοσωματιδίων γίνεται με την επιλογή της κατάλληλης βαθμίδας του μαγνητικού πεδίου που είναι σε κάθε χρονική στιγμή η καταλληλότερη για να τα οδηγήσει προς την επιθυμητή πλευρά. Για τον σκοπό αυτό, χρησιμοποιείται η μέθοδος βελτιστοποίησης Covariance Matrix Adaptation Evolution Strategy (CMAES).Για την μοντελοποίηση του μη-νευτωνικού ρευστού χρησιμοποιήθηκε το μοντέλο Carreau του οποίου η σωστή λειτουργία εξακριβώθηκε με την σύγκριση των υπολογιστικών με πειραματικά αποτελέσματα. Αναπτύχθηκε και εξακριβώθηκε η σωστή λειτουργία του μοντέλου κίνησης και αλληλεπίδρασης των σωματιδίων με το μαγνητικό πεδίο μέσω σύγκρισης των υπολογιστικών αποτελεσμάτων με δημοσιευμένες πειραματικές μετρήσεις. Η αλληλεπίδραση των σωματιδίων και ο τρόπος συσσωμάτωσης τους εξακριβώθηκε μέσα από σειρές προσομοιώσεων υπό διαφορετικά μόνιμα και χωρικά μεταβαλλόμενα μαγνητικά πεδία σε σωματίδια διαφορετικού μεγέθους αλλά και υλικού κατασκευής. Αναλύθηκε η επίδραση της διαμέτρου των σωματιδίων στον σχηματισμό συσσωματωμάτων. Επίσης έγινε προσομοίωση διαφορετικών κατανομών διαμέτρου των σωματιδίων με σκοπό την εξακρίβωση της επίδρασης του μαγνητικού πεδίου στην οδήγηση των σωματιδίων. Διαφορετικές βαθμίδες του μαγνητικού πεδίου σε συνδυασμό με διαφορετικές εντάσεις του μόνιμου μαγνητικού πεδίου προσομοιώθηκαν σε μία προσπάθεια εύρεσης της επίδρασης της βαθμίδας του μαγνητικού πεδίου στην κίνηση των (μίκρο και νάνο) σωματιδίων. Η επίδραση του νευτωνικού και μη-νευτωνικού ρευστού στην κίνηση και στην αλληλεπίδραση των σωματιδίων εξακριβώθηκε μέσο της σύγκρισης των υπολογιστικών αποτελεσμάτων. Σκοπός της οδήγησης των σωματιδίων είναι η μεγιστοποίηση του ποσοστού των σωματιδίων που μπορούν να οδηγηθούν σε περιοχές-στόχους με τον έλεγχο και την κατάλληλη χρονική μεταβολή της μαγνητικής βαθμίδας για την οδήγηση μίκρο και νάνο σωματιδίων τα οποία κινούνται μέσα σε διάλυμα σε γεωμετρίες με διακλαδώσεις. Για την πιστοποίηση των δυνατοτήτων του μοντέλου αλλά και για την εξακρίβωση των παραμέτρων που επηρεάζουν την οδήγηση των σωματιδίων σε περιοχές έγιναν προσομοιώσεις σε γεωμετρίες με διαφορετικές διαμέτρους οι οποίες είχαν διακλαδώσεις. Εξετάστηκε η επίδραση της έντασης του μαγνητικού πεδίου στην οδήγηση των σωματιδίων καθώς επίσης και του αριθμού των σωματιδίων τα οποία κάθε φορά προσομοιώνονται. Επιπλέον αναλύθηκε η επίδραση του αριθμού των αλλαγών και του εύρους έντασης της βαθμίδας του μαγνητικού πεδίου κατά την διαδικασία της οδήγησης. Τέλος, προσδιορίστηκε η επίδραση της ταχύτητας του ρευστού καθώς επίσης και ο ρόλος της διαμέτρου των αγωγών στην οδήγηση των σωματιδίων

Effect of Micropolar Fluid Properties on the Blood Flow in a Human Carotid Model

Blood is a non-homogeneous fluid that flows inside the human artery system and provides the cells with nutrients. In this study the auto rotation effect of blood’s microstructure on its flow inside a human carotid model is studied by using a micropolar fluid model. The study aims to investigate the flow differences that occur due to its microstructure as compared to a Newtonian fluid. We focus on the vortex viscosity effect, i.e., the ratio of microrotation viscosity to the total one, because this is the only parameter that affects directly the fluid flow. Simulations in a range of vortex viscosities, are carried out in a 3D human carotid model that is computationally reconstructed. All of the simulations are conducted at the diastolic Reynolds number that occurs in the human carotid. Results indicate that micropolarity affects blood velocity in the range of parameters studied by 4%. As micropolarity is increased, higher velocities in the center of vessels and lower near the boundaries are found as compared to a Newtonian fluid consideration. This is an indication that the increase of the fluid’s micropolarity leads to an increase of the boundary layer thickness. More importantly, an increase in vortex viscosity and the resulting increase in microrotation result in decreased shear stress in the carotid’s walls; this finding can be significant in regards to the onset and the development of atherosclerosis. Finally, the flow distribution at the carotid seems to heavily be affected by the geometry and the micropolarity of the fluid

Mixing of Particles in Micromixers under Different Angles and Velocities of the Incoming Water

A possible solution for water purification from heavy metals is to capture them by using nanoparticles in microfluidic ducts. In this technique, heavy metal capture is achieved by effectively mixing two streams, a nanoparticle solution and the contaminated water. In the present work, particles and water mixing is numerically studied for various inlet velocity ratios and inflow angles of the two streams. The Navier-Stokes equations are solved for the water flow while the discrete motion of particles is evaluated by a Lagrangian method. Results showed that as the velocity ratio between the inlet streams increases, by increasing the particles solution flow, the mixing of particles with the contaminated water is increased. Thus, nanoparticles are more uniformly distributed in the duct. On the other hand, angle increase between the inflow streams ducts is found to be less significant

Simulations of Tesla Valve Micromixer for Water Purification with Fe3O4 Nanoparticles

Heavy metals can contaminate water through both natural processes and anthropogenic activities. Unlike organic contaminants, heavy metals are toxic, not biodegradable, and possess the ability to accumulate in organisms. Effective mixing between contaminated water and nanoparticles is of great importance in various purification applications of microfluidics, especially when heavy metals are involved. In these terms, a series of simulations were performed to succeed in an effective mixing of iron oxide nanoparticles in the duct. The selected geometry for the simulations was the Tesla valve which was used as a micromixer. In the present work, a stream loaded with nanoparticles and a stream with contaminated water are numerically studied for various inlet velocity ratios of the two streams. Better mixing is achieved, compared with relative works, under Vp/Vc = 10, for an inlet rate of the Fe3O4 nanoparticles per second equal to 1000

Micromixing Efficiency of Particles in Heavy Metal Removal Processes under Various Inlet Conditions

Water quality problems are a persistent global issue since population growth has continually stressed hydrological resources. Heavy metals released into the environment from plating plants, mining, and alloy manufacturing pose a significant threat to the public health. A possible solution for water purification from heavy metals is to capture them by using nanoparticles in micromixers. In this method, conventionally heavy metal capture is achieved by effectively mixing two streams, a particle solution and the contaminated water, under the action of external magnetic fields. In the present study, we investigated the effective mixing of iron oxide nanoparticles and water without the use of external magnetic fields. For this reason, the mixing of particles and the contaminated water was studied for various inlet velocity ratios and inflow angles of the two streams using computational fluid dynamics techniques. The Navier-Stokes equations were solved for the water flow, the discrete motion of particles was evaluated by a Lagrangian method, while the flow of substances of the contaminated water was studied by a scalar transport equation. Results showed that as the velocity ratio between the inlet streams increased, the mixing of particles with the contaminated water was increased. Therefore, nanoparticles were more uniformly distributed in the duct and efficiently absorbed the substances of the contaminated water. On the other hand, the angle between two streams was found to play an insignificant role in the mixing process. Consequently, the results from this study could be used in the design of more compact and cost efficient micromixer devices

Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review

Research on contamination of groundwater and drinking water is of major importance. Due to the rapid and significant progress in the last decade in nanotechnology and its potential applications to water purification, such as adsorption of heavy metal ion from contaminated water, a wide number of articles have been published. An evaluating frame of the main findings of recent research on heavy metal removal using magnetic nanoparticles, with emphasis on water quality and method applicability, is presented. A large number of articles have been studied with a focus on the synthesis and characterization procedures for bare and modified magnetic nanoparticles as well as on their adsorption capacity and the corresponding desorption process of the methods are presented. The present review analysis shows that the experimental procedures demonstrate high adsorption capacity for pollutants from aquatic solutions. Moreover, reuse of the employed nanoparticles up to five times leads to an efficiency up to 90%. We must mention also that in some rare occasions, nanoparticles have been reused up to 22 times

Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review

Research on contamination of groundwater and drinking water is of major importance. Due to the rapid and significant progress in the last decade in nanotechnology and its potential applications to water purification, such as adsorption of heavy metal ion from contaminated water, a wide number of articles have been published. An evaluating frame of the main findings of recent research on heavy metal removal using magnetic nanoparticles, with emphasis on water quality and method applicability, is presented. A large number of articles have been studied with a focus on the synthesis and characterization procedures for bare and modified magnetic nanoparticles as well as on their adsorption capacity and the corresponding desorption process of the methods are presented. The present review analysis shows that the experimental procedures demonstrate high adsorption capacity for pollutants from aquatic solutions. Moreover, reuse of the employed nanoparticles up to five times leads to an efficiency up to 90%. We must mention also that in some rare occasions, nanoparticles have been reused up to 22 times