A review of acoustofluidic separation of bioparticles

Acoustofluidics is an emerging interdisciplinary research field that involves the integration of acoustics and microfluidics to address challenges in various scientific areas. This technology has proven to be a powerful tool for separating biological targets from complex fluids due to its label-free, biocompatible, and contact-free nature. Considering a careful designing process and tuning the acoustic field particles can be separated with high yield. Recently the advancement of acoustofluidics led to the development of point-of-care devices for separations of micro particles which address many of the limitations of conventional separation tools. This review article discusses the working principles and different approaches of acoustofluidic separation and provides a synopsis of its traditional and emerging applications, including the theory and mechanism of acoustofluidic separation, blood component separation, cell washing, fluorescence-activated cell sorting, circulating tumor cell isolation, and exosome isolation. The technology offers great potential for solving clinical problems and advancing scientific research

Pinching Dynamics and Multiple Droplet Generation in Partial Coalescence

When a drop merges with its homophase, a liquid cylinder appears in certain conditions, which is pinched off leading to partial coalescence. We investigate the process experimentally and numerically, and find that the Rayleigth-Plateau instability is able to pinch off the cylinder when its height-to-neck ratio exceeds one. Surfactants are found to attenuate the cylinder and produce multiple droplets at moderate concentrations. For both the pinch-off of the mother drop and the subsequent breakup of the liquid threads in partial coalescence, the neck thinning is initially in the inertial (I) regime and then shifts to the inertial-viscous (IV) regime. An intermediate regime is seen at larger surfactant concentrations, which accelerates the thinning and favours the generation of multiple droplets

A mechanistic model for the prediction of flow pattern transitions during separation of liquid-liquid pipe flows

A one-dimensional mechanistic model that predicts the flow pattern transitions during the separation of dispersed liquid-liquid flows in horizontal pipes was developed. The model is able to capture the evolution along the pipe of the four characteristic layers that develop from initially dispersed flows of either oil-in-water or water-in-oil at a range of mixture velocities: a pure water layer at the bottom, a settling (flotation/sedimentation) layer, a dense-packed zone, and a pure oil layer on the top. Coalescence correlations from literature were included in the model to predict the drop growth due to binary drop coalescence and the coalescence rate of drops with their corresponding interface. The model predictions on the evolution of the heights of the different layers were partly compared against available experimental data obtained in a pilot scale two-phase flow facility using tap water and oil (828 kg m−3, 5.5 mPa s) as test fluids. It was shown that the evolution of the four characteristic layers depends on the rates of drop settling and drop-interface coalescence. Oil-in-water dispersions separated faster than water-in-oil ones, while dispersions with smaller drop-sizes were more likely to exhibit depletion of the dense-packed zone

Mechanistic modelling of separating dispersions in pipes using model-based design of experiments techniques

This work presents a parametric study on a mechanistic model for separating liquid–liquid dispersions in pipes. The model considers drop-settling, drop-interface coalescence and drop-drop coalescence, predicting the evolution of four characteristic layers during separation. Parameter estimation, parametric sensitivity analysis (PSA), and model-based design of experiments (MBDoE) techniques are employed to acquire precise parameter estimates and propose optimal experimental conditions, thereby enhancing the accuracy of existing models. Experimental data from literature using oil-in-water dispersions are used for parameter estimation. PSA reveals regions of high sensitivity of the model outputs to uncertain parameters, which are corresponding to favourable sampling locations. Manipulating the mixture velocity, the dispersed phase fraction, and the layer heights at the inlet influences these sensitive regions. Clustered measurements around highly sensitive regions in the pipe enhance the information content they provide. MBDoE demonstrates that either of the A-, D-, or E-optimal experimental design criteria improves the expected parameter precision

Intensified liquid-liquid extraction of biomolecules using ionic liquids in small channels

The continuous extraction of an amino acid from an aqueous solution into an ionic liquid phase was studied experimentally in small channels, demonstrating a double intensification of the solvent used and the overall process. Channels with 0.5, 1 and 2 mm internal diameter were used for the extraction of the amino acid, L-tryptophan from an aqueous solution (0.005 mol L−1), into a hydrophobic ionic liquid, 1-Butyl-3-methylimidazolium Bis (trifluoromethanesulfonyl)imide, [C4mim][Tf2N] in the presence of a crown ether extractant, Dicyclohexano-18-crown-6, (DC18C6). A mechanism was proposed for the extraction which involved the ammonium centre of the amino acid forming hydrogen bonds with the 18-crown-6 part of the extractant at a 1:1 ratio. Partition coefficients up to 25 were obtained. The continuous extraction experiments were carried out during plug flow where the interfacial areas reported reached up to 5500 m2m−3 at 50% volume fractions. Extraction efficiencies up to 90% were obtained for residence times less than 30 s. Overall mass transfer coefficients (KLα) found reached up to 0.14 s−1

Viscoelastic effects of immiscible liquid-liquid displacement in microchannels with bends

The displacement flow of an organic Newtonian fluid by a pure viscoelastic aqueous solution is experimentally investigated inside a circular microchannel of 200 µm. Displacement is commonly encountered in many industrial applications, from cleaning to enhanced oil recovery. In this study, a pure viscoelastic fluid (known as Boger fluid) made up of polyethylene oxide (PEO), polyethylene glycol (PEG) and zinc chloride (ZnCl2) is used to displace an immiscible organic liquid (silicone oil). The results were compared with the Newtonian fluid displacement of similar density and viscosity as the viscoelastic one. High speed imaging is used to track both the residual film thickness of the organic phase and the interface deformations during displacement. It is found that the Boger fluid displacing phase produces a thinner displaced phase film compared to the Newtonian fluid, particularly at high capillary numbers. A correlation is proposed for the film thickness which includes the Weissenberg number for the viscoelastic case. After the displacement front, the interface becomes unstable with two modes of instability identified. In the case of the Boger fluid, the two modes of instability are core shifting, which is also present in the Newtonian case, and a periodic instability from the elastic stresses during displacement. Additionally, the shape of the interfacial instabilities switches freely from asymmetric to axisymmetric ones throughout the flow. The frequency of the periodic instabilities increases with the displacing phase flowrate. It was also found that microchannel bends downstream of the observation point affect the shape and frequency of the instabilities

Flow patterns of ionic liquid based aqueous biphasic systems in small channels

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by the addition in water of a hydrophilic ionic liquid (1-Butyl-3-methylimidazolium Chloride, C4mimCl) and a kosmotropic salt (tripotassium phosphate, K3PO4). The flow patterns of IL-ABS were studied in capillary channels with 0.2, 0.5 and 0.8 mm internal diameter; this is the first time such two-phase flows have been investigated. Three weight concentrations of the ionic liquid and the salt (18, 20 and 22 wt %) were chosen within the biphasic region. The main flow patterns included plug, dispersed and parallel flow. It was found that both channel diameter and weight concentrations would affect the flow patterns observed. Finally, a generalized flow pattern map was plotted using a combination of capillary and Reynolds numbers, where the transition boundaries of plug flow collapsed for all ionic liquid and salt concentrations studied

Effect of polydispersity and bubble clustering on the steady shear viscosity of semidilute bubble suspensions in Newtonian media

In this work, we examine the steady shear rheology of semidilute polydisperse bubble suspensions to elucidate the role of polydispersity on the viscosity of these systems. We prove theoretically that the effect of polydispersity on suspension viscosity becomes apparent only if the bubble size distribution is bimodal, with very small and very large bubbles having similar volume fractions. In any other case, we can consider the polydisperse suspension as monodisperse, with the average bubble diameter equal to the De Brouckere mean diameter (d43). To confirm the theoretical results, we carried out steady shear rheological tests. Our measurements revealed an unexpected double power-law decay of the suspension relative viscosity at average capillary numbers between 0.01 and 1. To investigate this behavior further, we visualized the produced bubble suspensions under shear. The visualization experiments revealed that bubbles started forming clusters and threads at an average capillary number around 0.01, where we observed the first decay of viscosity. Clustering and alignment have been associated with shear-thinning behavior in particle suspensions. We believe that the same holds for bubble suspensions, where bubble clusters and threads align with the imposed shear flow, reducing the streamline distortions and, in turn, resulting in a decrease in the suspension viscosity. Consequently, we can attribute the first decay of the relative viscosity to the formation of bubble clusters and threads, proving that the novel shear-thinning behavior we observed is due to a combination of bubble clustering and deformation

Οι Πειρασμοί του Ιησού στην ερμηνευτική προσέγγιση του Ιωάννου του Χρυσοστόμου

Ο πειρασμός περιγράφεται στην Παλαιά και στην Καινή Διαθήκη. Κάνει την εμφάνισή του στον Παλαιό Αδάμ και συνεχίζει στον Νέο Αδάμ, τον Χριστό. Η Βάπτιση του Χριστού αποτελεί την έναρξη του σωτηριώδους έργου του, κατά την στιγμή της οποίας φανερώνεται για πρώτη φορά σύσσωμη η Αγία Τριάδα. Οι Συνοπτικοί Ευαγγελιστές, Μάρκος (1,12-13), Ματθαίος (4,1-11) και Λουκάς (4,1-13), παρεμβάλλουν τη διήγηση των πειρασμών του Ιησού στην έρημο, όπου οδηγήθηκε από το Άγιο Πνεύμα, μετά της Βάπτισης και προ της έναρξης της δημόσιας δράσης του, προκειμένου να πειρασθεί από τον διάβολο. Υπό το πρίσμα της ιστορικοκριτικής μεθόδου ερμηνείας γίνεται η αναλυτική ερμηνευτική προσέγγιση των Πειρασμών των αφηγήσεων καθενός εκάστου των Συνοπτικών Ευαγγελιστών. Παρουσιάζεται η ερμηνευτική μέθοδος του αγίου Ιωάννου του Χρυσοστόμου και ακολούθως αναλυτική περιγραφή-παρουσίαση της ερμηνείας του ιερού Χρυσοστόμου στο κείμενο των πειρασμών του Ιησού βάσει του υπομνήματος αυτού στο κατά Ματθαίον Ευαγγέλιο, η τριπλή διάσταση της διήγησης των πειρασμών αλλά και η προσπάθεια των πιστών να αντικρούσουν και τους δικούς τους πειρασμούς με πίστη και εμπιστοσύνη στον Θεό Πατέρα.The temptation is described in the Old and the New Testament. It appears through the Old Adam and continues through the New Adam, Jesus. The Holy Baptism of Jesus Christ inaugurates His action for our salvation, it also sustains the first time that the Holy Trinity appears all together. The Synoptical Evangelists, Mark (1, 12 – 13), Matthew (4, 1 – 11) and Lucas (4, 1 – 13), insert the description of the Temptation of Jesus Christ on the desert, where He was led by the Holy Spirit, after the Holy Baptism and before the inauguration of His public action, in order to be tempted by devil. In the light of the historical-critical method of interpretation is analyzed the interpretive approach of the Temptations of the narratives of each of the Synoptic Evangelists. It is presented the interpretative methodology of Saint John Chrysostom and also his detailed description and approach on the text of the Jesus’ temptations based on his memorandum on the Gospel of Matthew, highlighted the triple dimension of Chrysostom’s narration of the temptations and also the effort of the flock to confront and refute their own temptations through faith and trust to our Holy Father, God