Mauricio Hoyos

École Supérieure de Physique et de Chimie Industrielles | ESPCI · PMMH

In this work we study the parameters which are often modified to optimize the separation in asymmetrical field flow fractionation, and we observe their impact on the retention behavior of the analyte. The aim of the work is to improve our knowledge of the phenomena which govern the behavior of the analytes in the channel and to have a better unders...

In the separation sciences, sample species are separated according to their physicochemical properties, the nature of the selective field, and, if present, the properties of the medium in which they are dissolved or suspended. Separations may be carried out on a continuous basis in microfluidic devices or split-flow thin channel (SPLITT) devices by...

We propose an experimental methodology to determine the secondary Bjerknes force between rigid particles. Measurements done for different particles sizes showed acoustical inter particles interactions. We use and extend the methodology presented in a previous work. The determination of this force will lead us a better understanding of the aggregati...

Bimetallic nanorods are propelled without chemical fuels in MHz acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two me...

Pulse acoustics allow us to control or manipulate particles smaller than 2µm in acoustic resonators

In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing wav...

A method for the experimental measurement of inter-particle forces (secondary Bjerknes force) generated by the action of an acoustic field in a resonator micro-channel is presented. The acoustic radiation force created by an ultrasonic standing wave moves suspended particles towards the pressure nodes and the acoustic pressure induces particle volu...

The recent discovery of fuel-free propulsion of nanomotors using acoustic energy has provided a new avenue for using nanomotors in biocompatible media. Crucial to the application of nanomotors in biosensing and biomedical applications is the ability to remotely control and steer them toward targets of interest, such as specific cells and tissues. W...

The acoustic radiation force concentrates particulate materials at the nodes or antinodes of an ultrasonic standing wave (USW), in function of different physicochemical parameters: size, shape, density or elastic properties. Thus, frequencies from 0.5 to 10 MHz are adapted for manipulating micron-sized particles, cells, bacteria, vesicles, drops, b...

Autonomously moving micro-objects, or micromotors, have attracted the attention of the scientific community over the past decade, but the incompatibility of phoretic motors with solutions of high ionic strength and the use of toxic fuels have limited their applications in biologically relevant media. In this letter we demonstrate that ultrasonic st...

We propose a technique based on pulsed ultrasounds for controlling, reducing to a minimum observable value the acoustic streaming in closed ultrasonic standing wave fluidic resonators. By modifying the number of pulses and the repetition time it is possible to reduce the velocity of the acoustic streaming with respect to the velocity generated by t...

Cell aggregation in ultrasonic resonators can be obtained in a few seconds. Hundreds even thousands of cells can be levitated in suspension and generate 2D or 3D aggregates. Nevertheless, the aggregation rate and the 2D or 3D configurations of the resultant aggregates are very difficult to control. This work reports on a novel way of generating and...

Levitation, aggregation and separation of micron-sized particulate materials can be generated in a fluidic resonator by an ultrasonic standing wave field force. A piezoelectric transducer generates standing waves between the two walls of a parallel plate channel composing the resonator. The number of pressure nodes n is given by the relationship: w...

Elution time measurements of colloidal particles injected in a symmetrical flow field-flow fractionation (flow FFF) system when the inlet and outlet cross-flow connections are closed have been performed. This no-field method has been proposed earlier for void time (and void volume) determination in flow FFF Giddings et al. (1977). The elution times...

The Quadrupole Magnetic Sorter (QMS), employing an annular flow channel concentric with the aperture of a quadrupole magnet, is well established for cell and particle separations. Here we propose a magnetic particle separator comprising a linear array of cylindrical magnets, analogous to the array proposed by Klaus Halbach, mated to a substantially...

We consider two systems of active swimmers moving close to a solid surface, one being a living population of wild-type E. coli and the other being an assembly of self-propelled Au-Pt rods. In both situations, we have identified two different types of motion at the surface and evaluated the fraction of the population that displayed ballistic traject...

We propose a new separation scheme for micrometer-sized particles combining acoustic forces and gravitational field in split-flow lateral-transport thin (SPLITT)-like fractionation channels. Acoustic forces are generated by ultrasonic standing waves set up in the channel thickness. We report on the separation of latex particles of two different siz...

In this study, we propose a new technique to bring most of the particles in a horizontal plane at mid-height of a micro-channel in order to improve the quality of the micro-PIV measurements. The basic principle is to create a stationary acoustic wave along the channel height so that the resulting acoustic force moves the particles toward the pressu...

After a primary infection protocol of macrophages with Leishmania amazonensis, the percentage of infection drops as infection progresses and the uninfected population of macrophages mask the effects of infection for electrophysiological studies. In order to increase or maintain the infection percentage, we introduce an enrichment process after prim...

In this study, we propose a new technique to bring most of the particles in a horizontal plane at mid-height of a micro-channel in order to improve the quality of the micro-PIV (Particle Image Velocimetry) measurements. The basic principle is to create a stationary acoustic wave along the channel height so that the resulting acoustic force moves pa...

Split-flow thin channel (SPLITT) fractionation is a technique for continuous separation of particles or macromolecules in a fluid stream into fractions according to the lateral migration induced by application of a field perpendicular to the direction of flow. Typical applications have involved isolation of different fractions from a polydisperse s...

A mini splitterless-split-flow thin fractionation (SPLITT) device has been developed to achieve fast separations of micrometer-sized species. In this device, inlet and outlet steps have replaced the splitters, which are common to conventional SPLITT channels. By elimination of the splitters, it becomes straightforward to reduce channel dimensions w...

Field-flow fractionation (FFF) encompasses a broad family of methods of separation and characterization of supramolecular species. They are all based on the application of a field force perpendicularly to the direction of the flow of a carrier liquid in a thin parallel plate channel. The principle of the method is described and the general relation...

By means of an acoustic technique, we follow the time and space dependence of the concentration of a settling suspension composed of spherical glass beads in water. The concentration profile consists of two shock fronts, one at the top, one at the bottom of the sedimentation column. The velocity determination of these two fronts allows a precise an...

The gravitational split-flow lateral transport thin fractionation is known to be a fast, simple, theoretically tractable and tunable tool for the binary separation of molecular or particulate samples into different dimensional fractions. This fractionation is performed in a so-called SPLITT cell and is due to the combined effect of the gravitationa...

One of the most appealing features of FFF (Field-Flow Fractionation) techniques is their capability of easily finding out direct mathematical relationships between the retention parameter and physico-chemical parameters of the analytes. In the case of thermal FFF applied to macromolecules in solution, these parameters are the Soret coefficient and...

We investigate the use of a digital holographic microscope working in partially coherent illumination to study in three dimensions a micrometer-size particle flow. The phenomenon under investigation rapidly varies in such a way that it is necessary to record, for every camera frame, the complete holographic information for further processing. For t...

We have investigated the retention behavior of chromatographic particles in thermal field-flow fractionation (FFF). Retention time is found to increase with increasing temperature drop across the channel thickness, as expected for species exhibiting a thermophoretic mobility. Experiments have been performed with a vertically oriented channel rather...

The first experimental evidence that noncolloidal particles exhibit a thermophoretic migration when placed in a temperature gradient is provided by observing the retention of micron-sized porous spherical particles, used as packing in liquid chromatography, in a thermal field-flow fractionation instrument. To eliminate the perturbing gravitational...

Antibody binding capacity (ABC) is a term representing a cell's ability to bind antibodies, correlating with the number of specific cellular antigens expressed on that cell. ABC allows magnetically conjugated antibodies to bind to the targeted cells, imparting a magnetophoretic mobility on each targeted cell. This enables sorting based on differenc...

Because of the temperature dependence of the carrier liquid density, the mass of carrier which is contained in a thermal field-flow fractionation channel depends on the cold wall temperature and on the temperature difference across the channel thickness. It is observed that the void time of the solvent peak decreases when increasing the average tem...

A continuous flow, magnetic separation method has been proposed to isolate large numbers of cells for clinical and biotechnological applications. The separation system, based on the quadrupole magnet flow sorter, has been tested on magnetically labeled, human blood progenitor cells using monoclonal antibody against the cluster of differentiation 34...

The continuous sorting of hematopoietic stem cells, lymphocytes or other blood cells can be performed using a membraneless hydrodynamic technique called split-flow thin channel fractionation, SPLITT. Two streams are introduced to the separator: carrier at one inlet and a suspension containing a mixture of immunomagnetically-labeled cells and unlabe...

Advantages of the continuous magnetic flow sorting for biomedical applications over current, batch-wise magnetic separations include high throughput and a potential for scale-up operations. A continuous magnetic sorting process has been developed based on the quadrupole magnetic field centered on an annular flow channel. The performance of the sort...

A quadrupole magnetic field coupled with a flow in an axisymmetric annular thin channel is used for the continuous sorting of magnetic particles and of magnetically-labeled lymphocytes differing in magnetophoretic mobilities. The channel is composed of two concentric cylinders; in the thin annulus two flow splitters are placed at each extremity. Th...

Instabilities can develop at the "interface" between two miscibles fluids which exihibit patterns very similar to those observed between immiscible fluids. For example, a layer of colored glycerine hanged-up below a glass plate and placed into a water tank, gives rise to organized patterns. Also, a thin layer of glycerine falling into water is unst...

Instabilities can develop at the 'interface' between two miscibles fluids which exhibit patterns very similar to those observed between immiscible fluids. For example, a layer of colored glycerine hanged-up below a glass plate and placed into a water tank, gives rise to organized patterns. Also, a thin layer of glycerine falling into water is unsta...

In some field-flow fractionation (FFF) techniques, the basic analyte-field interaction parameter, λ, is not constant but varies within the channel cross section as a result of the nonuniformity of the force exerted by the field on the analyte. This is the case, for instance, in thermal FFF, because of the temperature dependence of the relevant phys...

Model methylmethacrylate-styrene, linear di-block, copolymers were used to investigate the respective influnnces of temperature, of molar mass and of chemical composition on their Soret coefficient, sT, by means of thermal field-flow fractionation (thermal FFF) in toluene and in THF. A recently developed thermal FFF retention model, which takes int...

In field-flow fractionation with secondary chemical equilibria (SCE-FFF), small solutes can be separated according to their distribution coefficient between a carrier additive species affected by the applied field and the bulk carrier. Due to its interaction with the applied field, the average additive concentration within the FFF channel is genera...

This paper uses an acoustic technique to determine the concentration profile developing during the sedimentation of noncolloidal bidisperse suspensions of glass beads in a Newtonian fluid. Various bead diameter ratios have been used and a wide range of relative concentrations is covered. From the shock front velocities and the concentrations in dif...

Equilibrium concentration profiles of non-dilute colloidal suspensions are calculated by means of the Carnahan-Starling expression for the osmotic compressibility of hard sphere liquids. The profiles depend on the average volume fraction of the suspension, , and on the field interaction parameter, ?0 (reciprocal of the Péclet number at infinite dil...

Exact velocity profiles in thermal field-flow fractionation (FFF) were numerically computed for twelve solvents and forty different combinations of the temperature drop ΔT across the channel and of the cold wall temperature, Tc. An expression with six coefficients relating the ν parameter of a third-degree polynomial velocity profile which approxim...

In field-flow fractionation (FFF) of concentrated suspensions, particle interactions result in deviations of the equilibrium concentration profile and velocity profile from their respective exponential and parabolic infinite dilution limits. Following the Einstein diffusion formalism, the sedimentation equilibrium concentration profile of a concent...

The shape of the velocity profile established in a carrier liquid flowing in a duct of rectangular cross-section under conditions of isoviscous flow is well known and can be calculated by using an approximate or the exact solution of Navier-Stokes equation. The series evaluated when applying the exact solution were found to converge very rapidly. C...

An apparatus has been constructed to characterize transient fluid displacements in porous media, and probe sedimenting suspensions. The technique used is to propagate an ultrasonic wave in the sample. Both ultrasonic attenuation and velocity are related to the static and hydrodynamic properties of the medium. The system was built so as to perform a...

By means of an ultrasonic technique, the nucleation rate J in depletion experiments has been measured. An array of 8 ultrasonic transducers, fixed along a rock sample, continuously scans the sound velocity and the attenuation in the sample. Due to the great difference in sound velocity between the gas and the liquid, bubbles are easily detected and...

We have studied the thermophoretic migration of a pharmaceutical oil-in-water emulsion flowing in a Hele-Shaw cell, under the effect of a thermal gradient applied perpendicularly to the flow. Under this strong thermal gradient (several thousands =B0c/cm), a small volume (20 microlitters) of emulsion, migrates toward one wall; simultaneously, a diff...