WO2020221833A1 - Device for measuring the viscosity of a fluid, in particular for active fluids - Google Patents

Device for measuring the viscosity of a fluid, in particular for active fluids Download PDF

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Publication number
WO2020221833A1
WO2020221833A1 PCT/EP2020/061961 EP2020061961W WO2020221833A1 WO 2020221833 A1 WO2020221833 A1 WO 2020221833A1 EP 2020061961 W EP2020061961 W EP 2020061961W WO 2020221833 A1 WO2020221833 A1 WO 2020221833A1
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WIPO (PCT)
Prior art keywords
fluid
viscosity
rheometer
rotation
parts
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PCT/EP2020/061961
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French (fr)
Inventor
Harold AURADOU
Carine Jeanne DOUARCHE
Eric CLEMENT
Adama Kpatagnon CREPPY
Xavier BENOIT-GONIN
Lionel AUFFRAY
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Centre National De La Recherche Scientifique
Ecole Superieure De Physique Et De Chimie Industrielles De La Ville De Paris
Sorbonne Universite
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Application filed by Centre National De La Recherche Scientifique, Ecole Superieure De Physique Et De Chimie Industrielles De La Ville De Paris, Sorbonne Universite filed Critical Centre National De La Recherche Scientifique
Priority to EP20723822.1A priority Critical patent/EP3963307A1/en
Publication of WO2020221833A1 publication Critical patent/WO2020221833A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
    • G01N11/14—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by using rotary bodies, e.g. vane
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
    • G01N11/14—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by using rotary bodies, e.g. vane
    • G01N11/142—Sample held between two members substantially perpendicular to axis of rotation, e.g. parallel plate viscometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0089—Biorheological properties

Definitions

  • the present invention relates to a device for measuring the viscosity of a fluid and in particular of a biological fluid containing, for example, microorganisms such as suspensions of motile bacteria, microalgae, microtubules, etc.
  • the rheology of the fluids and the activity of the bacteria are parameters that simultaneously affect performance. Rheology controls the properties of mass and heat transfer while the activity of bacteria influences the amounts produced. It is therefore important to be able to measure both the rheology and the activity of living microorganisms such as bacteria in order to determine whether they are "dead" or active.
  • the measurement of the dynamics of bacteria namely the power of the biological "engine", the swimming speed, the diffusion, the characteristic sizes of the bacteria, the concentrations, the nature of the strains, is mainly based on observations under an optical microscope and video acquisition of their trajectories in a fluid at rest. It is then necessary to record a large volume of data and then analyze them in order to establish a statistic on the whole of a population. Such a process is long and in particular requires expertise in data analysis.
  • a device for measuring the viscosity such as a rheometer makes it possible to produce a rheogram, a curve giving the viscosity of a fluid, that is to say its resistance to flow as a function of the shear rate applied to it. and which corresponds to a speed gradient imposed between the layers of a fluid.
  • Such a measurement is classic for so-called "passive" fluids and makes it possible to understand the hydrodynamic behavior at the macroscopic scale of fluids.
  • rheometers Numerous devices for measuring viscosity are known, such as rheometers.
  • a rheometer makes it possible to know the fundamental quantities such as the rate of shear, shear stress T (t) and viscosity.
  • Rotary rheometers are the most widely used.
  • the solution studied fills the space between two coaxial parts (the rotor and the stator).
  • the angle of rotation f ( ⁇ ) can also be measured at any time t.
  • a rheometer therefore makes it possible to study the effect of the properties of the particles of a suspension on the rheological properties.
  • rheometers such as those with coaxial cylinders of the Searle or Couette type.
  • a very common Searle type rheometer is suitable for fluid samples: the inner cylinder constituting the rotor offers a large contact surface, to increase the resistive torque and therefore the sensitivity.
  • the air gap which can be modified from 0.2 to 3 mm, makes it possible to study “particle” or charged samples (example: molten polymer product).
  • the shear rate is variable in the measurement volume: zero at the center and maximum at the periphery.
  • a rheogram is established, that is to say a curve giving the viscosity of a fluid as a function of the shear rate applied to it.
  • active fluids rheograms of suspensions of motile bacteria, called active fluids.
  • a device for measuring the viscosity such as a Couette rheometer comprising two concentric metallic cylinders.
  • the internal cylinder is immersed in the external cylinder, also called the cup, the surface between the air and the fluid is reduced and the suspension which is between the metal cylinders is then quickly found under anaerobic conditions. This insufficient diffusion of a quantity of oxygen leads to the suffocation of the bacteria after a few minutes.
  • Current rheometers cannot maintain the swimming activity of bacteria for several hours.
  • ORC Oxygen Release Compound
  • rheometers there are also rheometers, one of the supports of which is made of a porous material.
  • document AU3107577 discloses a device for measuring the rheological properties of biological fluids such as blood, saliva, cervical mucus which are heterogeneous fluids, composed of several liquid fractions of chemical compositions, of molecular weights and of different rheological properties.
  • One of the rheometer support surfaces is made porous so that the low viscosity components are absorbed into the porous component, leaving only the high viscosity components in the test area.
  • Such a device thus makes it possible to carry out measurements of rheological properties of reproducible values, on the components of high viscosity, in particular avoiding variations in the measurements linked to the random structural variations of this type of heterogeneous composition.
  • a device for determining the coagulation point at which the blood forms a clot.
  • This device consists of a rheometer in which one of the measuring supports is provided porous and in which endothelial cells and fibroblasts are introduced so as to constitute a biomimetic surface of the blood.
  • These porous structures are microporous polymer films therefore incorporating living cells.
  • a rotor is made of a porous material, in this case hardened mortar, to study suspensions with a high concentration of mortar or cement.
  • the porosity of the material makes it possible to absorb an excess of water contained in the solution, which makes it possible to avoid a "slip" layer on the rotor which would adversely affect the analyzes.
  • the porosity of the material used in these devices makes it possible either to absorb part of the suspension, that is to say a porosity allowing the absorption of water or other fluids, or to incorporate elements making it possible to create an environment favorable to the suspension.
  • an oscillating rheometer intended to measure the rheological properties of blood samples or the blood coagulation capacity.
  • This rheometer has two surfaces (plates) between which a blood sample is introduced.
  • one of the plates is porous and covered with a gas permeable membrane. Below the porous plate, a gas flow circulates which allows, passing through the porous plate and the gas permeable membrane, to maintain the pressure equilibrium inside the sample being analyzed.
  • This device dedicated to the analysis of blood samples makes it possible to control the environment of the blood sample, in particular the gas composition of the blood, in relation to the coagulation conditions studied, by making it possible in particular to control the level of oxygen, d nitrogen and CO2.
  • the porous support is covered with a gas permeable membrane and cannot be used without this membrane which forms a barrier for the fluid studied.
  • the cited geometries do not subject the samples to homogeneous and identical shear for the entire volume of the sample. The methods considered therefore make it possible to obtain a pseudo viscosity.
  • the present invention aims to provide a rheometer in which it is possible to maintain a level of oxygen or any other suitable gas, sufficient and constant in the suspension studied to maintain a metabolic activity of the living microorganisms studied contained. in said solution.
  • the invention relates to a device for measuring the viscosity of a fluid such as a rheometer comprising two coaxial parts, one of which is rotated with respect to the other which remains fixed, a space or compartment reception being arranged between the two parts to receive the fluid to be studied, characterized in that at least one of said parts is made of a porous material.
  • the invention thus relates to a device for measuring the viscosity of an active fluid such as a suspension comprising living microorganisms, such as a rheometer comprising two coaxial parts, one of which is rotated relative to the other. , a receiving compartment being provided between the two parts to accommodate a fluid to be studied, characterized in that at least one of said parts is made of a porous material, permeable to gases, while being impermeable to the suspension and to microorganisms it contains.
  • the measuring device according to the invention due to the porosity of the material, which is an unclosed porosity, constituting one of the parts defining the space in which the suspension to be studied is located allows, by keeping this space in the air, to carry out continuous, repeatable and precision measurements on fluids, in particular biological fluids, the chemical composition of which needs to be controlled, in particular at the level of the pH, the oxygen concentration, or still controlled using injections of antibiotics, active ingredients or any other element of interest, for example elements that can influence or modify the environment in which the microorganisms are found.
  • the injections can in particular be carried out by diffusion linked to the porosity of the part, by point injection using an orifice made in one of the parts of the device according to the invention.
  • the porosity of the material is in a range of 5 to 40%.
  • the size of the pores is advantageously chosen to be non-wetting in the suspension and less than the size of the microorganisms in suspension, preferably of size less than 20 microns.
  • the porous material is chosen not to wetting the fluid placed in the rheometer, or at least with pores small enough so that the fluid does not flow through, and therefore impermeable to the fluid of the suspension.
  • the porous material has a pore size such that it has a permeability to gases, while being impermeable to the suspension and to the microorganisms it contains.
  • the porous material according to the invention has pores with a size of less than 20 microns, in particular when it is made of PTFE. Even more preferably, the pores are 1 micron in size.
  • the material used is permeable to gases and allows the diffusion of gases (such as oxygen) with a diffusion coefficient close to that in air, preferably between 2.5 and 3.5. 10 -9 m 2 / s.
  • gases such as oxygen
  • a porous material exhibiting such permeability is advantageously impermeable to a suspension and to the microorganisms contained therein.
  • the material being permeable to gaseous fluids such as air oxygen can thus diffuse through the material constituting at least one of the parts.
  • a suspension which contains bacteria needing oxygen and which is housed in the reception space between the coaxial parts is no longer in an anaerobic environment, oxygen being able to diffuse towards the suspension in sufficient quantity. to maintain the metabolic activity of bacteria of the suspension.
  • the gas is different from oxygen and may in particular be nitrogen or carbon dioxide, for example.
  • the porous material permeable to gaseous fluids can be used to supply another gas to the solution studied, depending on the type of living microorganisms in suspension, which again makes it possible to control the chemical composition of the active fluid.
  • a material whose porosity and permeability to gaseous fluids are suitable is chosen from porous plastic materials such as ABS (acrylonitrile butadiene styrene), sintered materials such as PTFE (polytetrafluoroethylene), a silico-aluminous ceramic such as C530 mullite, or a polymer material through which gases can diffuse such as PDMS (polydimethylsiloxane).
  • porous plastic materials such as ABS (acrylonitrile butadiene styrene), sintered materials such as PTFE (polytetrafluoroethylene), a silico-aluminous ceramic such as C530 mullite, or a polymer material through which gases can diffuse such as PDMS (polydimethylsiloxane).
  • parts of the viscosity measuring device made of ABS the porosity of which is adjustable during manufacture, in PMDS through which a gas such as oxygen diffuses with a diffusion coefficient of 2.5 and 3.5 10 9 m 2 / s very similar to that in air as well as in sintered C530 mullite, the porosity of which is 24%, combine the desired properties of porosity and permeability to gases.
  • the part made of ABS can be easily produced with additive manufacturing techniques such as 3D printing.
  • the manufacture of a PTFE molded part is carried out by compression and sintering of PTFE granules or by any other additive manufacturing method.
  • the manufacture of a mullite part is carried out by precision machining.
  • a part in PDMS is advantageously produced by molding, and also has the advantage of being transparent, which can allow the observation of microorganisms and thus enrichment of the measurements made.
  • the device for measuring the viscosity is a Couette rheometer, for example such as that known under the reference “low shear Contraves LS-30”.
  • the fluid to be analyzed is thus placed between the two concentric cylindrical surfaces formed by an external cylinder in the form of an environmental cup and an internal cylinder fixed on a torsion wire and which hangs in the center of the solution.
  • the bucket constitutes the rotor and is rotated at an adjustable constant speed.
  • the cup is made of a porous material permeable to gaseous fluids and in particular to air.
  • the cup is thus made of ABS, for example made using three-dimensional printing.
  • the internal cylinder can also be made of a porous material or else for the internal and external cylinders to both be made of porous material.
  • the cup made of porous material becomes the fixed part but still offers the possibility of controlling the environment of the fluid studied in the receiving compartment consisting of the air gap between the two parts of the rheometer.
  • the rheometer is of the type with parallel plates (plane-plane, PP).
  • the plates can be made of a porous material, permeable to gaseous fluids, thus also making it possible to control the environment of the fluid under study.
  • the rheometer is of the plane cone type, and in this case, one or both of the parts of the cone and of the plane are made of a porous material.
  • a measuring device comprising a part made of porous material permeable to gaseous fluids thus makes it possible to control the environment of the fluid studied, in particular at the level of the pH and of the oxygen concentration.
  • the porosity can also make it possible to control the chemical composition of the biological fluid studied, by allowing the diffusion of antibiotics, active ingredients, acting on the living microorganisms in the fluid. Provision can also be made for an orifice to be made in the bottom of the cup, for example to allow injection of active ingredients into the suspension.
  • the invention also relates to a method for measuring the viscosity of an "active" fluid comprising active particles such as living motile microorganisms, using a measuring device according to the invention, comprising the following steps
  • the invention also relates to a method for analyzing an active fluid from the curve obtained during the measurement method.
  • the values are obtained by linear adjustment of the data over predefined ranges, by calibration carried out on fluids of known viscosity (such as water) making it possible to translate the signal into viscosity.
  • the temporal variations of the signals during the starting or stopping phases also give useful information such as the concentration of microorganisms, for example bacteria, or the existence of collective movement.
  • FIG. 1 a schematic view of a viscosity measuring device according to a first embodiment of the invention
  • FIG. 2a a perspective view of a bucket for a device of Figure 1;
  • FIG. 2b a view in longitudinal section of the bucket of FIG. 2a;
  • FIG. 2c a top view of the bucket of Figure 2a
  • FIG. 3 a curve obtained with a viscosity measuring device according to the invention provided with a PTFE cup;
  • FIG. 4 a curve similar to that of FIG. 3 with a PDMS bucket
  • FIG. 5 a curve similar to that of Figure 3 with an ABS bucket
  • FIG. 6 a curve representing the measurement of the viscosity as a function of the shear rate
  • FIG. 7 a schematic view of a measuring device according to a second embodiment of the invention.
  • FIG. 8 a schematic view of a viscosity measuring device according to a third embodiment of the invention.
  • FIG. 9 a schematic view of a viscosity measuring device according to a fourth embodiment of the invention.
  • a Couette rheometer 1 has two concentric cylindrical parts 11 and 12.
  • One of these parts has the shape of a cup 12 and is mounted to be driven in rotation around it. 'an axis of rotation R thus constituting a rotor.
  • This air gap thus forms a receiving space or compartment 13 for an active fluid whose viscosity is to be studied.
  • the internal part 1 1 is fixed to a twist wire 14.
  • the cup 12 preferably has a substantially frustoconical shape, and is made for example by 3D printing in ABS.
  • This material allows the cup 12 to have a porosity of the order of 10% and the pore size of which is less than 15 ⁇ m is suitable for not allowing the suspension and the bacteria studied to diffuse and nevertheless giving it permeability to gaseous fluids. , and in particular to oxygen for which the diffusion coefficient through the porous ABS is of the order of approximately ⁇ 10 9 m 2 / s; value very close to that in the air.
  • the bottom 12a of the bucket 12 has in particular a conical shape with an angle a of 20 °, for example, the stator part 1 1 is of a shape complementary to the internal shape of the bucket 12 as shown in Figure 2b and of suitable dimensions for create the air gap in which the suspended solution is introduced.
  • the reception space 13 accommodates a volume of 1 ml. In this volume of 1 ml, there is preferably an amount ranging from 10 6 to 10 1 ° bacteria per ml.
  • the bacteria used are Escherichia coli (E.Coli).
  • the bucket 12 is rotated at an adjustable constant speed thus allowing the flow of the fluid which then exerts a torque of forces on the torsion wire 14.
  • the variation of the torque with the speed of rotation allows after processing of the recorded signal to deduce the viscosity of the fluid and its dependence on the shear rate which is controlled by the speed of rotation of the bucket 12.
  • the concentric parts 1 1 and 12 are metallic and the area between the air and the fluid contained in the space 13 is reduced to approximately 15 mm 2. Therefore, when the fluid is a suspension containing living microorganisms such as bacteria, there cannot be diffusion of a sufficient quantity of oxygen to maintain the metabolic activity of the bacteria.
  • the cup 12 is made of PTFE. The cup 12 thus produced has a pore size of 10 ⁇ m and an air permeability allowing the diffusion of oxygen towards the suspension in the space 13.
  • a measurement was first carried out using a reference fluid such as a buffered aqueous solution or a solution without bacteria.
  • the bucket 12 was thus rotated, at a shear rate of 0.04 s -1 , 30 seconds between the instants 1.5 min and 2 min.
  • the amplitude of the signal increases rapidly before becoming constant as can be seen in curve 10 of figure 3.
  • the signal decreases sharply and stabilizes. The difference between these two values makes it possible to determine the viscosity of the fluid.
  • curve 10 makes it possible to measure a viscosity of 0.9 mPa.s.
  • FIG. 3 shows that the curve 20 of the signal obtained is markedly different from the curve 10 of the signal of the reference fluid. Indeed, once the rotation of the bucket 12 has been initiated, the signal increases and then slowly relaxes before reaching a plateau. Once the rotation is stopped, the signal drops sharply before increasing again and regaining its value before measurement. The difference between the two plates gives the viscosity of the suspension with the bacteria.
  • viscosity values 5 to 100% lower than that of the carrier fluid alone are systematically found.
  • the difference between these two viscosity values makes it possible to measure the activity of bacteria.
  • temporal variation is also an indicator of the activity of living microorganisms.
  • FIGS. 4 and 5 represent the same measurements carried out respectively with a cup 12 in PDMS and a cup 12 in ABS having respectively an air permeability of about 3.10 -9 m 2 / s and a pore size of 10 ⁇ m.
  • FIG. 6 represents the measurement of the viscosity of a fluid loaded with bacteria for different shear rates (that is to say by changing the speed of rotation of cup 2) using a Couette rheometer ( of the type known under the trade name Contraves LS-30) provided with a cup 12 made of porous material according to the invention and preferably as in FIGS. 2a, 2b and 2c and with a rheometer of the state of the art .
  • a Couette rheometer of the type known under the trade name Contraves LS-30
  • Such a rheometer makes it possible to explore the range from 0.01 to 60 s -1 .
  • the viscosity measuring device it is possible to establish curves making it possible to identify important characteristics of bacterial activity, such as the average speed, the frequency of change of orientation, the diffusion coefficient or the concentration.
  • the measurement requires recording the rheometer signal with a frequency of at least two measurements per second.
  • the rheometer must allow controlled changes over time in its rotational speed.
  • FIG 7 there is shown a Searle rheometer 2 according to the invention which has two concentric cylindrical parts 21 and 22.
  • One of these parts has the shape of a cup 22 and is fixed while the other is mounted. rotatable about an axis of rotation R thus constituting a rotor.
  • Inside this bucket 22 is thus engaged the part 21 of cylindrical shape complementary to the bucket 22 but whose outer radius R1 is less than the inner radius R2 of the bucket 22 so as to leave an air gap between the two parts 21, 22.
  • This air gap thus forms a reception space 23 for a fluid whose viscosity is to be studied.
  • the cup 22 is preferably made of a porous material permeable to gaseous fluids.
  • the rheometer 3 is of the type with parallel plates (plane-plane, PP).
  • one of the plates 31 is driven in rotation with respect to to the plate 32 and one or both can be made of a porous material, permeable to gaseous fluids, thus also making it possible to control the environment of the fluid studied housed in the space 33 between the plates.
  • the rheometer 4 is of the plane cone type, and in this case, one or both of the parts of the cone 41 and of the plane 42 are made of a porous material thus allowing the study of the fluid housed in the space 43 formed between the cone 41 and the plane 42.
  • a measuring device comprising a part made of a porous material permeable to gases thus makes it possible to control the environment of the suspension under study, in particular with regard to the pH and the oxygen concentration.

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  • Life Sciences & Earth Sciences (AREA)
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Abstract

The invention relates to a device for measuring the viscosity of a fluid, such as a rheometer (1), the device comprising two coaxial parts (11, 12), one of which is rotated relative to the other, which remains stationary, a receiving compartment (13) being provided between the two parts in order to accommodate a fluid to be examined. The invention is characterised in that at least one of the parts is made of a porous material.

Description

Description Description
Titre de l'invention : Dispositif de mesure de la viscosité d’un fluide, en particulier pour des fluides actifs Title of the invention: Device for measuring the viscosity of a fluid, in particular for active fluids
La présente invention concerne un dispositif de mesure de la viscosité d’un fluide et en particulier d’un fluide biologique contenant, par exemple, des micro-organismes tel que des suspensions de bactéries motiles, de micro-algues, de microtubules... The present invention relates to a device for measuring the viscosity of a fluid and in particular of a biological fluid containing, for example, microorganisms such as suspensions of motile bacteria, microalgae, microtubules, etc.
Au cours des dernières années, et du fait de leur pertinence en médecine et en écologie ainsi que de leur importance dans de nombreux domaines technologiques, l’hydrodynamique des suspensions actives, c’est-à-dire comprenant des microorganismes vivants, est au centre de nombreuses études. En effet, de nombreux microorganismes se déplacent de manière autonome dans des fluides et on a pu mettre en évidence que les fluides dits « actifs » tels que des suspensions de bactéries motiles montrent une relation entre l’activité des bactéries en suspension et la viscosité de la suspension. In recent years, and because of their relevance in medicine and ecology as well as their importance in many technological fields, the hydrodynamics of active suspensions, that is to say comprising living microorganisms, is at the center many studies. Indeed, many microorganisms move autonomously in fluids and it has been possible to demonstrate that so-called “active” fluids such as suspensions of motile bacteria show a relationship between the activity of bacteria in suspension and the viscosity of the bacteria. suspension.
Le développement croissant de l’utilisation de ce type de micro-organismes vivants dans des procédés industriels nécessite de pouvoir les caractériser, et en particulier pour pouvoir les sélectionner. Dans une application comme les bioréacteurs ou les fermenteurs, la rhéologie des fluides et l’activité des bactéries sont des paramètres qui jouent simultanément sur les performances. La rhéologie contrôle les propriétés de transfert de masse et de chaleur tandis que l’activité des bactéries influe sur les quantités produites. Il est donc important de pouvoir mesurer à la fois la rhéologie et l’activité des microorganismes vivants comme les bactéries de manière à déterminer si elles sont « mortes » ou actives The growing development of the use of this type of living microorganism in industrial processes requires us to be able to characterize them, and in particular to be able to select them. In an application such as bioreactors or fermenters, the rheology of the fluids and the activity of the bacteria are parameters that simultaneously affect performance. Rheology controls the properties of mass and heat transfer while the activity of bacteria influences the amounts produced. It is therefore important to be able to measure both the rheology and the activity of living microorganisms such as bacteria in order to determine whether they are "dead" or active.
A l’heure actuelle, la mesure de la dynamique des bactéries, à savoir la puissance du « moteur » biologique, la vitesse de nage, la diffusion, les tailles caractéristiques des bactéries, les concentrations, la nature des souches, se base principalement sur des observations sous microscope optique et sur l’acquisition vidéo de leurs trajectoires dans un fluide au repos. Il est alors nécessaire d’enregistrer un grand volume de données pour ensuite les analyser afin d’établir une statistique sur l’ensemble d’une population. Un tel procédé est long et demande en particulier une expertise dans l’analyse des données. At the present time, the measurement of the dynamics of bacteria, namely the power of the biological "engine", the swimming speed, the diffusion, the characteristic sizes of the bacteria, the concentrations, the nature of the strains, is mainly based on observations under an optical microscope and video acquisition of their trajectories in a fluid at rest. It is then necessary to record a large volume of data and then analyze them in order to establish a statistic on the whole of a population. Such a process is long and in particular requires expertise in data analysis.
Un dispositif de mesure de la viscosité tel qu’un rhéomètre permet de réaliser un rhéogramme, courbe donnant la viscosité d’un fluide, c’est-à-dire sa résistance à l’écoulement en fonction du taux de cisaillement qui lui est appliqué et qui correspond à un gradient de vitesse imposé entre les couches d’un fluide. Une telle mesure est classique pour les fluides dits « passifs » et permet de comprendre le comportement hydrodynamique à l’échelle macroscopique des fluides. A device for measuring the viscosity such as a rheometer makes it possible to produce a rheogram, a curve giving the viscosity of a fluid, that is to say its resistance to flow as a function of the shear rate applied to it. and which corresponds to a speed gradient imposed between the layers of a fluid. Such a measurement is classic for so-called "passive" fluids and makes it possible to understand the hydrodynamic behavior at the macroscopic scale of fluids.
Des études récentes ont permis d’obtenir de manière fiable et reproductibles des rhéogrammes de fluides « actifs » tels que des suspensions de bactéries motiles. Ces rhéogrammes ont permis de caractériser leur activité mécanique sur le fluide porteur. Recent studies have provided reliable and reproducible rheograms of "active" fluids such as suspensions of motile bacteria. These rheograms made it possible to characterize their mechanical activity on the carrier fluid.
Ainsi, dans l’article « Rafaï Salima, Jibuti Levan, Peyla Philippe », 2010. Physical Review Letters 104, 098102, on a montré que la viscosité effective des suspensions cisaillées de microalgues vivantes unicellulaires (Chlamydomonas reinhardtii) est beaucoup plus importante que pour les suspensions contenant la même fraction volumique de ces cellules mortes. Thus, in the article “Rafaï Salima, Jibuti Levan, Peyla Philippe”, 2010. Physical Review Letters 104, 098102, it was shown that the effective viscosity of the sheared suspensions of living unicellular microalgae (Chlamydomonas reinhardtii) is much greater than for suspensions containing the same volume fraction of these dead cells.
De même, dans l’article « Lopez Hector, Gachelin Jérémie, Douarche Carine, Auradou Harold et Clément Eric », PRL 1 15, 028301 (2015) de Physical Review Letters of American Physical Society, on a pu mettre en évidence que des bactéries s’organisent d’un point de vue spatial et sous l’effet de cisaillement, l’activité de nage rendant possible la diminution de la viscosité macroscopique à des valeurs inférieures à la viscosité du fluide de la suspension. Likewise, in the article "Lopez Hector, Gachelin Jérémie, Douarche Carine, Auradou Harold and Clément Eric", PRL 1 15, 028301 (2015) of Physical Review Letters of American Physical Society, it was possible to demonstrate that bacteria are organized from a spatial point of view and under the effect of shearing, the swimming activity making possible the reduction of the macroscopic viscosity to values lower than the viscosity of the fluid of the suspension.
On a également pu se rendre compte que des bactéries en suspension peuvent réduire la viscosité de fluides ordinaires comme l’eau et leur permettre notamment de s’écouler plus facilement parfois même jusqu’à un point où la viscosité est quasi nulle voir, « Aurore Loisy, Jens Eggers, Tanniemola B. Liverpool », Physical Review Letters 121.018001 , (2018). We have also been able to realize that bacteria in suspension can reduce the viscosity of ordinary fluids like water and in particular allow them to flow more easily sometimes even to a point where the viscosity is almost zero see, "Aurora Loisy, Jens Eggers, Tanniemola B. Liverpool ”, Physical Review Letters 121.018001, (2018).
Il est donc important de pouvoir étudier la viscosité de fluides biologiques dits actifs à l’aide de dispositifs de mesure de la viscosité appropriés. It is therefore important to be able to study the viscosity of so-called active biological fluids using appropriate viscosity measuring devices.
On connaît de nombreux dispositifs de mesure de la viscosité tel que les rhéomètres. Un rhéomètre permet de connaître les grandeurs fondamentales telles que le taux de cisaillement, la contrainte de cisaillement T(t) et la viscosité. Les rhéomètres rotatifs sont les plus utilisés. Numerous devices for measuring viscosity are known, such as rheometers. A rheometer makes it possible to know the fundamental quantities such as the rate of shear, shear stress T (t) and viscosity. Rotary rheometers are the most widely used.
Pour ce type de rhéomètre, la solution étudiée remplit l'espace entre deux pièces coaxiales (le rotor et le stator). Le rapport entre le couple de rotation M(t) transmis d'une pièce à l'autre par la substance cisaillée, et la vitesse de rotation Q(t) du rotor, donne la viscosité, à une constante géométrique près. L'angle de rotation f(ί) peut aussi être mesuré à chaque instant t. On distingue les appareils à vitesse de rotation imposée (les plus fréquents) et ceux à couple imposé. For this type of rheometer, the solution studied fills the space between two coaxial parts (the rotor and the stator). The ratio between the torque M (t) transmitted from one part to another by the sheared substance, and the rotational speed Q (t) of the rotor, gives the viscosity, up to a geometric constant. The angle of rotation f (ί) can also be measured at any time t. A distinction is made between devices with imposed rotation speed (the most frequent) and those with imposed torque.
Un rhéomètre permet donc d'étudier l'effet des propriétés des particules d'une suspension sur les propriétés rhéologiques. Il existe plusieurs types de rhéomètres tels que ceux à cylindres coaxiaux de type Searle ou Couette. Un rhéomètre de type Searle, très courant, est adapté aux échantillons fluides : le cylindre intérieur constituant le rotor offre une grande surface de contact, pour augmenter le couple résistant et donc la sensibilité. A rheometer therefore makes it possible to study the effect of the properties of the particles of a suspension on the rheological properties. There are several types of rheometers such as those with coaxial cylinders of the Searle or Couette type. A very common Searle type rheometer is suitable for fluid samples: the inner cylinder constituting the rotor offers a large contact surface, to increase the resistive torque and therefore the sensitivity.
Il existe également des rhéomètres à plateaux parallèles (plan-plan, PP). L'entrefer, modifiable de 0,2 à 3 mm, permet d'étudier des échantillons à « particules » ou chargés (exemple : produit polymère fondu). Le taux de cisaillement est variable dans le volume de mesure : nul au centre et maximum à la périphérie. There are also rheometers with parallel plates (plane-plane, PP). The air gap, which can be modified from 0.2 to 3 mm, makes it possible to study “particle” or charged samples (example: molten polymer product). The shear rate is variable in the measurement volume: zero at the center and maximum at the periphery.
Enfin, on peut également utiliser un rhéomètre de type cône plan, l’angle de cône Q étant très faible (en général 0,5 < Q < 4) pour obtenir un quasi constant dans le volume de mesure. Pour une même vitesse de rotation, plus Q est faible, plus le taux de cisaillement est élevé. Finally, it is also possible to use a flat cone type rheometer, the cone angle Q being very small (generally 0.5 <Q <4) to obtain a quasi constant in the measurement volume. For the same speed of rotation, the lower Q, the higher the shear rate.
A partir de ces dispositifs de mesure de viscosité, on établit un rhéogramme c’est-à- dire une courbe donnant la viscosité d’un fluide en fonction du taux de cisaillement qui lui est appliqué. Lors d’études menées, on peut obtenir de manière fiable et reproductible les rhéogrammes de suspensions de bactéries motiles qu’on appelle fluides actifs. Ces rhéogrammes permettent de caractériser l’activité mécanique des bactéries sur le fluide porteur. From these viscosity measuring devices, a rheogram is established, that is to say a curve giving the viscosity of a fluid as a function of the shear rate applied to it. In studies carried out, rheograms of suspensions of motile bacteria, called active fluids, can be obtained reliably and reproducibly. These rheograms are used to characterize the mechanical activity of bacteria on the carrier fluid.
Comme déjà évoqué, pour effectuer de telles mesures, on peut utiliser un dispositif de mesure de la viscosité tel qu’un rhéomètre de Couette comportant deux cylindres concentriques métalliques. Or, une fois le cylindre interne plongé dans le cylindre externe également appelé godet, la surface entre l’air et le fluide est réduite et la suspension qui se trouve entre les cylindres métalliques se trouve alors rapidement dans des conditions anaérobies. Cette insuffisance de diffusion d’une quantité d’oxygène conduit à l’asphyxie des bactéries après quelques minutes. Les rhéomètres actuels ne permettent pas de maintenir l’activité de nage des bactéries pendant plusieurs heures. As already mentioned, to perform such measurements, it is possible to use a device for measuring the viscosity such as a Couette rheometer comprising two concentric metallic cylinders. However, once the internal cylinder is immersed in the external cylinder, also called the cup, the surface between the air and the fluid is reduced and the suspension which is between the metal cylinders is then quickly found under anaerobic conditions. This insufficient diffusion of a quantity of oxygen leads to the suffocation of the bacteria after a few minutes. Current rheometers cannot maintain the swimming activity of bacteria for several hours.
Des solutions ont été proposées pour fournir de l’oxygène dans des solutions aqueuses sous forme d’un ajout d’éléments chimiques dans la solution que l’on nomme généralement « Oxygen Release Compound (ORC) », composés libérant de l’oxygène. On compte parmi ces ORC les peroxydes d’hydrogène, de calcium et de magnésium. Cependant, il est difficile de contrôler alors le niveau d’oxygène qui se trouve dissous dans la solution et si celui-ci devient trop important on risque l’hyperoxie des bactéries ce qui arrête toute activité métabolique. Solutions have been proposed to deliver oxygen in aqueous solutions as an addition of chemicals to the solution commonly referred to as "Oxygen Release Compound (ORC)", compounds that release oxygen. These ORCs include hydrogen, calcium and magnesium peroxides. However, it is then difficult to control the level of oxygen which is dissolved in the solution and if this becomes too high there is a risk of hyperoxia of the bacteria which stops all metabolic activity.
Il existe également des rhéomètres dont l’un des supports est constitué d’un matériau poreux. Ainsi, on connaît par le document AU3107577, un dispositif de mesure des propriétés rhéologiques de fluides biologiques tels que le sang, la salive, la glaire cervicale qui sont des fluides hétérogènes, composés de plusieurs fractions liquides de compositions chimiques, de poids moléculaires et de propriétés rhéologiques différents. L'une des surfaces de support du rhéomètre est réalisée poreuse de sorte que les composants de faible viscosité sont absorbés dans le composant poreux, ne laissant que les composants de haute viscosité dans la zone de test. Un tel dispositif permet ainsi de réaliser des mesures de propriétés rhéologiques de valeurs reproductibles, sur les composants de viscosité élevée évitant notamment de variations dans les mesures liées aux variations structurelles aléatoires de ce type de compositions hétérogènes. There are also rheometers, one of the supports of which is made of a porous material. Thus, document AU3107577 discloses a device for measuring the rheological properties of biological fluids such as blood, saliva, cervical mucus which are heterogeneous fluids, composed of several liquid fractions of chemical compositions, of molecular weights and of different rheological properties. One of the rheometer support surfaces is made porous so that the low viscosity components are absorbed into the porous component, leaving only the high viscosity components in the test area. Such a device thus makes it possible to carry out measurements of rheological properties of reproducible values, on the components of high viscosity, in particular avoiding variations in the measurements linked to the random structural variations of this type of heterogeneous composition.
Dans le document US2009/176261 est proposé un dispositif pour déterminer le point de coagulation auquel le sang forme un caillot. Ce dispositif est constitué d’un rhéomètre dans lequel l'un des supports de mesure est prévu poreux et dans lequel on introduit des cellules endothéliales et des fibroblastes de manière à constituer une surface biomimétique du sang. Ces structures poreuses sont des films polymères microporeux incorporant donc des cellules vivantes. In document US2009 / 176261, a device is proposed for determining the coagulation point at which the blood forms a clot. This device consists of a rheometer in which one of the measuring supports is provided porous and in which endothelial cells and fibroblasts are introduced so as to constitute a biomimetic surface of the blood. These porous structures are microporous polymer films therefore incorporating living cells.
Dans le document JP2008/261724, un rotor est réalisé en matériau poreux, en l'occurrence du mortier durci, pour étudier des suspensions à concentration élevée de mortier ou ciment. La porosité du matériau permet d’absorber un excès d'eau contenu dans la solution ce qui permet d’éviter une couche de "glissage" glissement sur le rotor qui nuirait aux analyses. In document JP2008 / 261724, a rotor is made of a porous material, in this case hardened mortar, to study suspensions with a high concentration of mortar or cement. The porosity of the material makes it possible to absorb an excess of water contained in the solution, which makes it possible to avoid a "slip" layer on the rotor which would adversely affect the analyzes.
La porosité du matériau utilisé dans ces dispositifs permet soit d’absorber une partie de la suspension, c’est-à-dire une porosité permettant l’absorption d’eau ou autres fluides, soit d’incorporer des éléments permettant de créer un environnement favorable à la suspension. The porosity of the material used in these devices makes it possible either to absorb part of the suspension, that is to say a porosity allowing the absorption of water or other fluids, or to incorporate elements making it possible to create an environment favorable to the suspension.
De tels dispositifs ne peuvent être utilisés avec des suspensions comportant des micro-organismes, la porosité du matériau provoquant un risque de modifications des suspensions étudiées par migration du fluide ou des microorganismes vers le matériau poreux. Such devices cannot be used with suspensions comprising microorganisms, the porosity of the material causing a risk of modifications of the suspensions studied by migration of the fluid or of the microorganisms towards the porous material.
On connaît également par le document US2010/139375 un rhéomètre oscillant destiné à mesurer les propriétés rhéologiques d'échantillons sanguins ou la capacité de coagulation du sang. Ce rhéomètre présente deux surfaces (plaques) entre lesquelles un échantillon de sang est introduit. De manière à contrôler l’environnement de l’échantillon sanguin et en particulier, la composition gazeuse du sang, l’une des plaques est poreuse et recouverte d'une membrane perméable aux gaz. Au-dessous de la plaque poreuse, circule un flux de gaz qui permet en traversant la plaque poreuse et la membrane perméable aux gaz de maintenir l'équilibre de pression à l’intérieur de l’échantillon analysé. Ce dispositif dédié à l’analyse d’échantillons sanguins permet de contrôler l’environnement de l’échantillon sanguin en particulier la composition gazeuse du sang, par rapport aux conditions de coagulation étudiée, en permettant notamment de contrôler le niveau d’oxygène, d’azote et de CO2. Toutefois, le support poreux est recouvert d’une membrane perméable aux gaz et ne peut être utilisé sans cette membrane qui forme une barrière pour le fluide étudié. D’autre part, les géométries citées ne soumettent pas les échantillons à un cisaillement homogène et identique pour tout le volume de l’échantillon. Les méthodes considérées permettent donc d’obtenir une pseudo viscosité. Also known from document US2010 / 139375 is an oscillating rheometer intended to measure the rheological properties of blood samples or the blood coagulation capacity. This rheometer has two surfaces (plates) between which a blood sample is introduced. In order to control the environment of the blood sample and in particular the gas composition of the blood, one of the plates is porous and covered with a gas permeable membrane. Below the porous plate, a gas flow circulates which allows, passing through the porous plate and the gas permeable membrane, to maintain the pressure equilibrium inside the sample being analyzed. This device dedicated to the analysis of blood samples makes it possible to control the environment of the blood sample, in particular the gas composition of the blood, in relation to the coagulation conditions studied, by making it possible in particular to control the level of oxygen, d nitrogen and CO2. However, the porous support is covered with a gas permeable membrane and cannot be used without this membrane which forms a barrier for the fluid studied. On the other hand, the cited geometries do not subject the samples to homogeneous and identical shear for the entire volume of the sample. The methods considered therefore make it possible to obtain a pseudo viscosity.
Afin de pallier ces inconvénients, la présente invention a pour but de proposer un rhéomètre dans lequel on puisse maintenir un niveau d’oxygène ou de tout autre gaz approprié, suffisant et constant dans la suspension étudiée pour maintenir une activité métabolique des microorganismes vivants étudiés contenus dans ladite solution. A cet effet, l’invention concerne un dispositif de mesure de la viscosité d’un fluide tel qu’un rhéomètre comprenant deux pièces coaxiales dont l’une est entraînée en rotation par rapport à l’autre qui reste fixe, un espace ou compartiment de réception étant ménagé entre les deux pièces pour accueillir le fluide à étudier, caractérisé en ce qu’au moins l’une desdites pièces est réalisée en un matériau poreux. In order to overcome these drawbacks, the present invention aims to provide a rheometer in which it is possible to maintain a level of oxygen or any other suitable gas, sufficient and constant in the suspension studied to maintain a metabolic activity of the living microorganisms studied contained. in said solution. To this end, the invention relates to a device for measuring the viscosity of a fluid such as a rheometer comprising two coaxial parts, one of which is rotated with respect to the other which remains fixed, a space or compartment reception being arranged between the two parts to receive the fluid to be studied, characterized in that at least one of said parts is made of a porous material.
L’invention concerne ainsi un dispositif de mesure de la viscosité d’un fluide actif tel qu’une suspension comportant des microorganismes vivants, tel qu’un rhéomètre comprenant deux pièces coaxiales dont l’une est entraînée en rotation par rapport à l’autre, un compartiment de réception étant ménagé entre les deux pièces pour accueillir un fluide à étudier, caractérisé en ce qu’au moins l’une desdites pièces est réalisée en un matériau poreux, perméable aux gaz, tout en étant imperméable à la suspension et aux microorganismes qu’elle contient. The invention thus relates to a device for measuring the viscosity of an active fluid such as a suspension comprising living microorganisms, such as a rheometer comprising two coaxial parts, one of which is rotated relative to the other. , a receiving compartment being provided between the two parts to accommodate a fluid to be studied, characterized in that at least one of said parts is made of a porous material, permeable to gases, while being impermeable to the suspension and to microorganisms it contains.
Ainsi, de manière très avantageuse, le dispositif de mesure selon l’invention du fait de la porosité du matériau, qui est une porosité non fermée, constituant l’une des pièces définissant l’espace dans lequel se trouve la suspension à étudier permet, en maintenant cet espace à l’air, de réaliser des mesures continues, répétables et de précision sur des fluides, en particulier biologiques, dont la composition chimique nécessite d’être contrôlée, au niveau notamment du pH, de la concentration en oxygène, ou encore contrôlée à l’aide d’injections d'antibiotiques, de principes actifs ou de tout autre élément d’intérêt, par exemple des éléments pouvant influer, modifier le milieu dans lequel se trouve les microorganismes. Thus, very advantageously, the measuring device according to the invention due to the porosity of the material, which is an unclosed porosity, constituting one of the parts defining the space in which the suspension to be studied is located allows, by keeping this space in the air, to carry out continuous, repeatable and precision measurements on fluids, in particular biological fluids, the chemical composition of which needs to be controlled, in particular at the level of the pH, the oxygen concentration, or still controlled using injections of antibiotics, active ingredients or any other element of interest, for example elements that can influence or modify the environment in which the microorganisms are found.
Les injections peuvent notamment être réalisées par diffusion liée à la porosité de la pièce, par injection ponctuelle à l’aide d'un orifice ménagé dans l’une des pièces du dispositif selon l’invention. The injections can in particular be carried out by diffusion linked to the porosity of the part, by point injection using an orifice made in one of the parts of the device according to the invention.
De préférence, la porosité du matériau se trouve dans une plage de 5 à 40 %. De plus, la dimension des pores est avantageusement choisie non mouillante à la suspension et inférieure à la dimension des microorganismes en suspension, de préférence de dimension inférieure à 20 microns. Preferably, the porosity of the material is in a range of 5 to 40%. In addition, the size of the pores is advantageously chosen to be non-wetting in the suspension and less than the size of the microorganisms in suspension, preferably of size less than 20 microns.
En effet, la matière poreuse est choisie non mouillante au fluide placé dans le rhéomètre, ou du moins avec des pores suffisamment petits pour que le fluide ne s’écoule pas à travers, donc imperméable au fluide de la suspension. Par contre, le matériau poreux présente une dimension de pores tel qu’il présente une perméabilité aux gaz, tout en étant imperméable à la suspension et aux microorganismes qu’elle contient. De préférence le matériau poreux selon l’invention présente des pores de dimension inférieure à 20 microns, en particulier lorsqu’il est constitué de PTFE. De manière encore plus préférée, les pores ont une dimension de 1 micron. Indeed, the porous material is chosen not to wetting the fluid placed in the rheometer, or at least with pores small enough so that the fluid does not flow through, and therefore impermeable to the fluid of the suspension. On the other hand, the porous material has a pore size such that it has a permeability to gases, while being impermeable to the suspension and to the microorganisms it contains. Preferably, the porous material according to the invention has pores with a size of less than 20 microns, in particular when it is made of PTFE. Even more preferably, the pores are 1 micron in size.
Ainsi, le matériau utilisé est perméable aux gaz et permet la diffusion des gaz (comme l’oxygène) avec un coefficient de diffusion proche de celui dans l’air, de préférence entre 2,5 et 3,5. 10-9 m2/s. Un matériau poreux présentant une telle perméabilité est avantageusement imperméable à une suspension et aux micro-organismes contenus dedans. Thus, the material used is permeable to gases and allows the diffusion of gases (such as oxygen) with a diffusion coefficient close to that in air, preferably between 2.5 and 3.5. 10 -9 m 2 / s. A porous material exhibiting such permeability is advantageously impermeable to a suspension and to the microorganisms contained therein.
Ainsi de manière avantageuse, le matériau étant perméable aux fluides gazeux tel que l’air, de l’oxygène peut ainsi diffuser au travers du matériau constituant au moins l’une des pièces. De ce fait, une suspension qui contient des bactéries ayant besoin d’oxygène et qui est logée dans l’espace de réception entre les pièces coaxiales, ne se trouve plus en milieu anaérobie, de l’oxygène pouvant diffuser vers la suspension en quantité suffisante pour maintenir l’activité métabolique de bactéries de la suspension. Thus, advantageously, the material being permeable to gaseous fluids such as air, oxygen can thus diffuse through the material constituting at least one of the parts. As a result, a suspension which contains bacteria needing oxygen and which is housed in the reception space between the coaxial parts is no longer in an anaerobic environment, oxygen being able to diffuse towards the suspension in sufficient quantity. to maintain the metabolic activity of bacteria of the suspension.
On peut également envisager qu’en fonction des micro-organismes présents dans la suspension, le gaz soit différent de l’oxygène et peut être notamment de l’azote ou du dioxyde de carbone par exemple. It is also conceivable that depending on the microorganisms present in the suspension, the gas is different from oxygen and may in particular be nitrogen or carbon dioxide, for example.
Comme l’activité métabolique des micro-organismes vivants présents dans la suspension est maintenue, il est possible d’établir une seule mesure macroscopique de la viscosité de ce fluide biologique et on peut alors en déduire les caractéristiques de dynamique des micro-organismes vivants en solution à l’aide d’un modèle déjà établi caractérisant la puissance du « moteur » biologique, la vitesse de nage, la diffusion, les tailles caractéristiques des cellules, la concentration, la nature des souches, etc. As the metabolic activity of the living microorganisms present in the suspension is maintained, it is possible to establish a single macroscopic measurement of the viscosity of this biological fluid and one can then deduce the dynamic characteristics of the living microorganisms by solution using an already established model characterizing the power of the biological "motor", swimming speed, diffusion, characteristic cell sizes, concentration, nature of strains, etc.
En variante, le matériau poreux perméable aux fluides gazeux peut être utilisé pour apporter un autre gaz à la solution étudiée, en fonction du type de microorganismes vivants en suspension ce qui permet là encore de contrôler la composition chimique du fluide actif. As a variant, the porous material permeable to gaseous fluids can be used to supply another gas to the solution studied, depending on the type of living microorganisms in suspension, which again makes it possible to control the chemical composition of the active fluid.
Un matériau dont la porosité et la perméabilité aux fluides gazeux sont appropriées, est choisi parmi des matériaux plastiques poreux tels que l’ABS (acrylonitrile butadiène styrène), les matériaux frittés comme le PTFE (polytétrafluoroéthylène), une céramique à base de silico-alumineux telle que la mullite C530, ou encore un matériau polymère par lequel les gaz peuvent diffuser comme le PDMS (polydiméthylsiloxane). A material whose porosity and permeability to gaseous fluids are suitable is chosen from porous plastic materials such as ABS (acrylonitrile butadiene styrene), sintered materials such as PTFE (polytetrafluoroethylene), a silico-aluminous ceramic such as C530 mullite, or a polymer material through which gases can diffuse such as PDMS (polydimethylsiloxane).
Ainsi, des pièces du dispositif de mesure de la viscosité réalisées en ABS dont la porosité est ajustable lors de la fabrication, en PMDS au travers duquel un gaz comme l’oxygène diffuse avec un coefficient de diffusion de 2.5 et 3.5 10 9 m2/s très proche de celui dans l’air ainsi qu’en fritté de mullite C530 dont la porosité est de 24%, réunissent les propriétés de porosité et de perméabilité aux gaz souhaitées. Thus, parts of the viscosity measuring device made of ABS, the porosity of which is adjustable during manufacture, in PMDS through which a gas such as oxygen diffuses with a diffusion coefficient of 2.5 and 3.5 10 9 m 2 / s very similar to that in air as well as in sintered C530 mullite, the porosity of which is 24%, combine the desired properties of porosity and permeability to gases.
De manière avantageuse, la pièce réalisée en ABS peut être facilement réalisée avec des techniques de fabrication additive comme l’impression 3D. Advantageously, the part made of ABS can be easily produced with additive manufacturing techniques such as 3D printing.
La fabrication d’une pièce moulée en PTFE est réalisée par compression et frittage de granulés de PTFE ou par tout autre méthode de fabrication additive. The manufacture of a PTFE molded part is carried out by compression and sintering of PTFE granules or by any other additive manufacturing method.
La fabrication d’une pièce en mullite est réalisée par usinage de précision. The manufacture of a mullite part is carried out by precision machining.
Une pièce en PDMS est avantageusement réalisée par moulage, et présente en outre l’intérêt d’être transparente ce qui peut permettre l’observation des microorganismes et ainsi l’enrichissement des mesures effectuées. A part in PDMS is advantageously produced by molding, and also has the advantage of being transparent, which can allow the observation of microorganisms and thus enrichment of the measurements made.
Selon un premier mode de réalisation, le dispositif de mesure de la viscosité est un rhéomètre de Couette, par exemple tel que celui connu sous la référence « low shear Contraves LS-30 ». Le fluide à analyser est ainsi placé entre les deux surfaces cylindriques concentriques formées par un cylindre externe se présentant sous forme d’un godet environnemental et un cylindre interne fixé sur un fil de torsion et qui pend au centre de la solution. Le godet constitue le rotor et est mis en rotation à une vitesse constante réglable. Dans cette forme de réalisation, le godet est réalisé en un matériau poreux perméable aux fluides gazeux et en particulier à l’air. According to a first embodiment, the device for measuring the viscosity is a Couette rheometer, for example such as that known under the reference “low shear Contraves LS-30”. The fluid to be analyzed is thus placed between the two concentric cylindrical surfaces formed by an external cylinder in the form of an environmental cup and an internal cylinder fixed on a torsion wire and which hangs in the center of the solution. The bucket constitutes the rotor and is rotated at an adjustable constant speed. In this embodiment, the cup is made of a porous material permeable to gaseous fluids and in particular to air.
De préférence, le godet est ainsi réalisé en ABS, par exemple fabriqué à l’aide d’une impression en trois dimensions. Preferably, the cup is thus made of ABS, for example made using three-dimensional printing.
On peut également prévoir en variante, que le cylindre interne est réalisé en matériau poreux ou bien que les cylindres interne et externe soient tous deux en matériau poreux. En variante dans un rhéomètre Searle, le godet en matériau poreux devient la pièce fixe mais offre toujours la possibilité de contrôler l’environnement du fluide étudié dans le compartiment de réception constitué de l’entrefer entre les deux pièces du rhéomètre. As a variant, provision can also be made for the internal cylinder to be made of a porous material or else for the internal and external cylinders to both be made of porous material. As a variant in a Searle rheometer, the cup made of porous material becomes the fixed part but still offers the possibility of controlling the environment of the fluid studied in the receiving compartment consisting of the air gap between the two parts of the rheometer.
Selon un autre mode de réalisation, le rhéomètre est du type à plateaux parallèles (plan-plan, PP). Dans ce type de rhéomètre, l’un des plateaux ou les deux peuvent être constitués d’un matériau poreux, perméable aux fluides gazeux permettant ainsi également de contrôler l’environnement du fluide étudié. According to another embodiment, the rheometer is of the type with parallel plates (plane-plane, PP). In this type of rheometer, one or both of the plates can be made of a porous material, permeable to gaseous fluids, thus also making it possible to control the environment of the fluid under study.
Selon encore un autre mode de réalisation, le rhéomètre est de type cône plan, et dans ce cas, l’une des pièces ou les deux du cône et du plan sont en matériau poreux. According to yet another embodiment, the rheometer is of the plane cone type, and in this case, one or both of the parts of the cone and of the plane are made of a porous material.
Un dispositif de mesure selon l’invention comportant une pièce en matériau poreux perméable aux fluides gazeux permet ainsi de réaliser un contrôle de l’environnement du fluide étudié, en particulier au niveau du pH, de la concentration en oxygène. A measuring device according to the invention comprising a part made of porous material permeable to gaseous fluids thus makes it possible to control the environment of the fluid studied, in particular at the level of the pH and of the oxygen concentration.
La porosité peut permettre également de contrôler la composition chimique du fluide biologique étudié, en permettant la diffusion d’antibiotiques, de principes actifs, agissant sur les microorganismes vivants dans le fluide. On peut également prévoir qu'un orifice est ménagé dans le bas du godet par exemple pour permettre une injection de principes actifs dans la suspension. The porosity can also make it possible to control the chemical composition of the biological fluid studied, by allowing the diffusion of antibiotics, active ingredients, acting on the living microorganisms in the fluid. Provision can also be made for an orifice to be made in the bottom of the cup, for example to allow injection of active ingredients into the suspension.
L’invention concerne également un procédé de mesure de la viscosité d’un fluide « actif » comportant des particules actives tel que des microorganismes vivants motiles, à l’aide d’un dispositif de mesure selon l’invention, comportant les étapes suivantes The invention also relates to a method for measuring the viscosity of an "active" fluid comprising active particles such as living motile microorganisms, using a measuring device according to the invention, comprising the following steps
(a) mise en place du fluide à l’intérieur de l’espace de réception ménagé entre les deux pièces coaxiales dont au moins l’une est en un matériau poreux, (a) placing the fluid inside the receiving space between the two coaxial parts, at least one of which is made of a porous material,
(b) entraînement en rotation à vitesse constante réglable ou variable temporellement selon une courbe prescrite de l’une des pièces par à l’autre, ce qui met en écoulement le fluide qui exerce un couple de forces sur la pièce fixe, (b) rotating drive at constant speed adjustable or variable over time according to a prescribed curve from one of the parts to the other, which puts the fluid into the flow which exerts a couple of forces on the fixed part,
(c) mesure de la variation du couple avec la vitesse de rotation, (c) measurement of the variation of the torque with the speed of rotation,
(d) calcul à partir de la variation de du couple, de la viscosité du fluide et de sa dépendance avec le taux de cisaillement contrôlé par la vitesse de rotation de la pièce entraînable en rotation. L’invention a trait également à un procédé d’analyse d’un fluide actif à partir de la courbe obtenue lors du procédé de mesure. Les valeurs sont obtenues par ajustement linéaire des données sur des plages prédéfinies, par étalonnage réalisé sur des fluides de viscosité connue (comme l’eau) permettant de traduire le signal en viscosité. Les variations temporelles des signaux lors des phases de mise en route ou d’arrêt donnent aussi des informations utiles comme la concentration en micro-organismes, par exemple en bactéries, ou l'existence de mouvement collectif. (d) calculation from the variation of the torque, the viscosity of the fluid and its dependence on the shear rate controlled by the speed of rotation of the part which can be driven in rotation. The invention also relates to a method for analyzing an active fluid from the curve obtained during the measurement method. The values are obtained by linear adjustment of the data over predefined ranges, by calibration carried out on fluids of known viscosity (such as water) making it possible to translate the signal into viscosity. The temporal variations of the signals during the starting or stopping phases also give useful information such as the concentration of microorganisms, for example bacteria, or the existence of collective movement.
On décrira maintenant l’invention plus en détails en référence au dessin qui représente : The invention will now be described in more detail with reference to the drawing which represents:
[Fig. 1 ] une vue schématique d’un dispositif de mesure de la viscosité selon un premier mode de réalisation de l’invention ; [Fig. 1] a schematic view of a viscosity measuring device according to a first embodiment of the invention;
[Fig. 2a] une vue en perspective d’un godet pour un dispositif de la figure 1 ; [Fig. 2a] a perspective view of a bucket for a device of Figure 1;
[Fig. 2b] une vue en coupe longitudinale du godet de la figure 2a ; [Fig. 2b] a view in longitudinal section of the bucket of FIG. 2a;
[Fig. 2c] une vue du dessus du godet de la figure 2a ; [Fig. 2c] a top view of the bucket of Figure 2a;
[Fig. 3] une courbe obtenue avec un dispositif de mesure de la viscosité selon l’invention pourvu d’un godet en PTFE ; [Fig. 3] a curve obtained with a viscosity measuring device according to the invention provided with a PTFE cup;
[Fig. 4] une courbe similaire à celle de la figure 3 avec un godet en PDMS ; [Fig. 4] a curve similar to that of FIG. 3 with a PDMS bucket;
[Fig. 5] une courbe similaire à celle de la figure 3 avec un godet en ABS ; [Fig. 5] a curve similar to that of Figure 3 with an ABS bucket;
[Fig. 6] une courbe représentant la mesure de la viscosité en fonction du taux de cisaillement ; [Fig. 6] a curve representing the measurement of the viscosity as a function of the shear rate;
[Fig. 7] une vue schématique d’un dispositif de mesure selon un deuxième mode de réalisation de l’invention ; [Fig. 7] a schematic view of a measuring device according to a second embodiment of the invention;
[Fig. 8] une vue schématique d’un dispositif de mesure de la viscosité selon un troisième mode de réalisation de l’invention ; [Fig. 8] a schematic view of a viscosity measuring device according to a third embodiment of the invention;
[Fig. 9] une vue schématique d’un dispositif de mesure de la viscosité selon un quatrième mode de réalisation de l’invention. [Fig. 9] a schematic view of a viscosity measuring device according to a fourth embodiment of the invention.
Comme on peut le voir à la figure 1 , un rhéomètre de Couette 1 selon l’invention présente deux pièces cylindriques concentriques 11 et 12. L’une de ces pièces présente la forme d’un godet 12 et est montée entraînable en rotation autour d’un axe de rotation R constituant ainsi un rotor. A l’intérieur de ce godet 12 est engagée la pièce 1 1 de forme cylindrique complémentaire au godet 12 mais dont le rayon extérieur R1 est inférieur au rayon intérieur R2 du godet 12 de manière à ménager entre les deux pièces 1 1 , 12 un entrefer. Cet entrefer forme ainsi un espace ou compartiment de réception 13 pour un fluide actif dont on souhaite étudier la viscosité. La pièce interne 1 1 est fixée à un fil de torsion 14. As can be seen in FIG. 1, a Couette rheometer 1 according to the invention has two concentric cylindrical parts 11 and 12. One of these parts has the shape of a cup 12 and is mounted to be driven in rotation around it. 'an axis of rotation R thus constituting a rotor. Inside this bucket 12 is engaged the part 1 1 of cylindrical shape complementary to the bucket 12 but whose outer radius R1 is less than the inner radius R2 of the bucket 12 so as to provide between the two parts 1 1, 12 an air gap. This air gap thus forms a receiving space or compartment 13 for an active fluid whose viscosity is to be studied. The internal part 1 1 is fixed to a twist wire 14.
Comme on peut le voir aux figures 2a, 2b et 2c, le godet 12 présente de préférence une forme sensiblement tronconique, et est réalisé par exemple par impression 3D en ABS. Ce matériau permet que le godet 12 présente une porosité de l’ordre de 10% et dont la dimension de pores est inférieure à 15 pm est appropriée pour ne pas laisser diffuser la suspension et les bactéries étudiées et lui conférant cependant une perméabilité aux fluides gazeux, et en particulier à l’oxygène pour lequel le coefficient de diffusion au travers l’ABS poreux est de l’ordre d’environ ~10 9 m2/s; valeur très proche de celui dans l’air. Le fond 12a du godet 12 présente notamment une forme conique avec un angle a de 20°, par exemple, la partie stator 1 1 est de forme complémentaire à la forme intérieure du godet 12 tel que visible à la figure 2b et de dimensions appropriées pour réaliser l’entrefer dans lequel la solution en suspension est introduite. As can be seen in Figures 2a, 2b and 2c, the cup 12 preferably has a substantially frustoconical shape, and is made for example by 3D printing in ABS. This material allows the cup 12 to have a porosity of the order of 10% and the pore size of which is less than 15 μm is suitable for not allowing the suspension and the bacteria studied to diffuse and nevertheless giving it permeability to gaseous fluids. , and in particular to oxygen for which the diffusion coefficient through the porous ABS is of the order of approximately ~ 10 9 m 2 / s; value very close to that in the air. The bottom 12a of the bucket 12 has in particular a conical shape with an angle a of 20 °, for example, the stator part 1 1 is of a shape complementary to the internal shape of the bucket 12 as shown in Figure 2b and of suitable dimensions for create the air gap in which the suspended solution is introduced.
L’espace de réception 13 accueille un volume de 1 ml. Dans ce volume de 1 ml, on a de préférence une quantité allant de 106 à 101° bactéries par ml. Les bactéries utilisées sont des Escherichia coli (E.Coli). The reception space 13 accommodates a volume of 1 ml. In this volume of 1 ml, there is preferably an amount ranging from 10 6 to 10 1 ° bacteria per ml. The bacteria used are Escherichia coli (E.Coli).
Le godet 12 est entraîné en rotation à une vitesse constante réglable permettant ainsi la mise en écoulement du fluide qui exerce alors un couple de forces sur le fil de torsion 14. La variation du couple avec la vitesse de rotation permet après un traitement du signal enregistré de déduire la viscosité du fluide et sa dépendance avec le taux de cisaillement qui est contrôlé par la vitesse de rotation du godet 12. The bucket 12 is rotated at an adjustable constant speed thus allowing the flow of the fluid which then exerts a torque of forces on the torsion wire 14. The variation of the torque with the speed of rotation allows after processing of the recorded signal to deduce the viscosity of the fluid and its dependence on the shear rate which is controlled by the speed of rotation of the bucket 12.
Dans un rhéomètre classique, les pièces concentriques 1 1 et 12 sont métalliques et la surface entre l’air et le fluide contenu dans l’espace 13 est réduite à environ 15 mm2. De ce fait, lorsque le fluide est une suspension contenant des microorganismes vivants tels que des bactéries, il ne peut y avoir diffusion d’une quantité d’oxygène suffisante pour maintenir l’activité métabolique des bactéries. Selon un autre exemple de réalisation, le godet 12 est réalisé en PTFE. Le godet 12 ainsi réalisé présente une taille de pores de 10 pm et une perméabilité à l’air permettant la diffusion d’oxygène vers la suspension dans l’espace 13. In a conventional rheometer, the concentric parts 1 1 and 12 are metallic and the area between the air and the fluid contained in the space 13 is reduced to approximately 15 mm 2. Therefore, when the fluid is a suspension containing living microorganisms such as bacteria, there cannot be diffusion of a sufficient quantity of oxygen to maintain the metabolic activity of the bacteria. According to another exemplary embodiment, the cup 12 is made of PTFE. The cup 12 thus produced has a pore size of 10 μm and an air permeability allowing the diffusion of oxygen towards the suspension in the space 13.
On a réalisé d’abord une mesure à l’aide d’un fluide de référence tel qu’une solution aqueuse tamponnée ou une solution sans bactéries. On a ainsi mis en rotation le godet 12, à un taux de cisaillement de 0.04 s-1, 30 secondes entre les instants 1 ,5 min et 2 min. Pendant cet intervalle de temps, l’amplitude du signal (correspondant à la variation du couple) augmente rapidement avant de devenir constant comme on peut le voir sur la courbe 10 de la figure 3. Lorsque la rotation est arrêtée, le signal diminue brusquement et se stabilise. L’écart entre ces deux valeurs permet de déterminer la viscosité du fluide. Ainsi pour une solution aqueuse tamponnée servant de fluide de référence, la courbe 10, permet de mesurer une viscosité de 0.9 mPa.s. A measurement was first carried out using a reference fluid such as a buffered aqueous solution or a solution without bacteria. The bucket 12 was thus rotated, at a shear rate of 0.04 s -1 , 30 seconds between the instants 1.5 min and 2 min. During this time interval, the amplitude of the signal (corresponding to the variation of the torque) increases rapidly before becoming constant as can be seen in curve 10 of figure 3. When the rotation is stopped, the signal decreases sharply and stabilizes. The difference between these two values makes it possible to determine the viscosity of the fluid. Thus, for a buffered aqueous solution serving as reference fluid, curve 10 makes it possible to measure a viscosity of 0.9 mPa.s.
Si on réalise cette mesure avec un fluide chargé de bactéries, la figure 3 montre que la courbe 20 du signal obtenue est nettement différente de la courbe 10 du signal du fluide de référence. En effet, une fois la rotation du godet 12 initiée, le signal augmente puis relaxe lentement avant d’atteindre un plateau. Une fois la rotation stoppée, le signal diminue brusquement avant d’augmenter de nouveau et de retrouver sa valeur d’avant la mesure. La différence entre les deux plateaux donne la viscosité de la suspension avec les bactéries. If this measurement is carried out with a fluid loaded with bacteria, FIG. 3 shows that the curve 20 of the signal obtained is markedly different from the curve 10 of the signal of the reference fluid. Indeed, once the rotation of the bucket 12 has been initiated, the signal increases and then slowly relaxes before reaching a plateau. Once the rotation is stopped, the signal drops sharply before increasing again and regaining its value before measurement. The difference between the two plates gives the viscosity of the suspension with the bacteria.
En présence de bactéries de type pousseuse (pusher) comme les E-coli utilisées dans l’étude, on trouve systématiquement des valeurs de viscosité inférieures de 5 à 100 % à celle du fluide porteur seul. La différence entre ces deux valeurs de viscosité permet de mesurer l’activité des bactéries. Par ailleurs, la variation temporelle est également un indicateur de l’activité des micro-organismes vivants. In the presence of pusher-type bacteria such as E-coli used in the study, viscosity values 5 to 100% lower than that of the carrier fluid alone are systematically found. The difference between these two viscosity values makes it possible to measure the activity of bacteria. Furthermore, temporal variation is also an indicator of the activity of living microorganisms.
Les figures 4 et 5 représentent les mêmes mesurées réalisées respectivement avec un godet 12 en PDMS et un godet 12 en ABS présentant respectivement une perméabilité à l’air d’environ 3.10-9 m2/s et une taille de pore de 10 pm. FIGS. 4 and 5 represent the same measurements carried out respectively with a cup 12 in PDMS and a cup 12 in ABS having respectively an air permeability of about 3.10 -9 m 2 / s and a pore size of 10 μm.
Ces mesures ont été réalisées dans des godets 12 réalisés en matériau poreux, ABS, PDMS ou PTFE, 60 minutes après que la solution avec bactéries ait été introduite dans le dispositif ainsi équipé. De tels résultats montrent que les bactéries sont toujours vivantes alors que, si on avait utilisé un godet de l’état de la technique, métallique non poreux, on aurait constaté qu’au bout d’une minute, l’oxygène aurait été entièrement consommé et les bactéries seraient mortes. These measurements were carried out in cups 12 made of porous material, ABS, PDMS or PTFE, 60 minutes after the solution with bacteria had been introduced into the device thus equipped. Such results show that the bacteria are still alive whereas, if a cup of the state of the art had been used, non-porous metal, it would have been observed that after one minute, the oxygen would have been completely consumed and the bacteria would have died.
La figure 6 représente la mesure de la viscosité d’un fluide chargé en bactéries pour différents taux de cisaillement (c’est-à-dire en changeant la vitesse de rotation du godet 2) à l’aide d’un rhéomètre de Couette (du type connu sous la dénomination commerciale Contraves LS-30) muni d’un godet 12 en matériau poreux selon l’invention et de préférence tel que dans les figures 2a, 2b et 2c et d’un rhéomètre de l’état de la technique. Un tel rhéomètre permet d’explorer la gamme de 0,01 à 60 s-1. FIG. 6 represents the measurement of the viscosity of a fluid loaded with bacteria for different shear rates (that is to say by changing the speed of rotation of cup 2) using a Couette rheometer ( of the type known under the trade name Contraves LS-30) provided with a cup 12 made of porous material according to the invention and preferably as in FIGS. 2a, 2b and 2c and with a rheometer of the state of the art . Such a rheometer makes it possible to explore the range from 0.01 to 60 s -1 .
Ainsi, on peut voir sur la courbe de la figure 6 que, pour les faibles taux de cisaillement, on retrouve la perte de viscosité de la figure 3, tandis que, lorsque le taux de cisaillement augmente, la viscosité croît pour atteindre la viscosité du fluide sans bactérie. Thus, we can see from the curve of Figure 6 that, for low shear rates, we find the viscosity loss of Figure 3, while, when the shear rate increases, the viscosity increases to reach the viscosity of bacteria-free fluid.
A partir de cette courbe et du taux de cisaillement pour lequel on passe d’un régime à l’autre, on obtient des informations sur la population de bactéries. From this curve and the shear rate for which we switch from one regime to another, we obtain information on the population of bacteria.
Ainsi, grâce au dispositif de mesure de la viscosité selon l’invention, il est possible d’établir des courbes permettant d’identifier des caractéristiques importantes de l’activité bactérienne, telles que la vitesse moyenne, la fréquence de changement d’orientation, le coefficient de diffusion ou la concentration. La mesure demande à enregistrer avec une fréquence d’au moins deux mesures par seconde le signal du rhéomètre. Le rhéomètre doit permettre des changements contrôlés dans le temps de sa vitesse de rotation. Thus, thanks to the viscosity measuring device according to the invention, it is possible to establish curves making it possible to identify important characteristics of bacterial activity, such as the average speed, the frequency of change of orientation, the diffusion coefficient or the concentration. The measurement requires recording the rheometer signal with a frequency of at least two measurements per second. The rheometer must allow controlled changes over time in its rotational speed.
A la figure 7, est représenté un rhéomètre de Searle 2 selon l’invention qui présente deux pièces cylindriques concentriques 21 et 22. L’une de ces pièces présente la forme d’un godet 22 et est fixe tandis que l’autre est montée entraînable en rotation autour d’un axe de rotation R constituant ainsi un rotor. A l’intérieur de ce godet 22 est ainsi engagée la pièce 21 de forme cylindrique complémentaire au godet 22 mais dont le rayon extérieur R1 est inférieur au rayon intérieur R2 du godet 22 de manière à ménager entre les deux pièces 21 , 22 un entrefer. Cet entrefer forme ainsi un espace de réception 23 pour un fluide dont on souhaite étudier la viscosité. Le godet 22 est de préférence réalisé en un matériau poreux et perméable aux fluides gazeux. In Figure 7, there is shown a Searle rheometer 2 according to the invention which has two concentric cylindrical parts 21 and 22. One of these parts has the shape of a cup 22 and is fixed while the other is mounted. rotatable about an axis of rotation R thus constituting a rotor. Inside this bucket 22 is thus engaged the part 21 of cylindrical shape complementary to the bucket 22 but whose outer radius R1 is less than the inner radius R2 of the bucket 22 so as to leave an air gap between the two parts 21, 22. This air gap thus forms a reception space 23 for a fluid whose viscosity is to be studied. The cup 22 is preferably made of a porous material permeable to gaseous fluids.
Selon la figure 8, le rhéomètre 3 est du type à plateaux parallèles (plan-plan, PP). Dans ce type de rhéomètre 3, l’un des plateaux 31 est entraîné en rotation par rapport au plateau 32 et l’un ou les deux peuvent être constitués d’un matériau poreux, perméable aux fluides gazeux permettant ainsi également de contrôler l’environnement du fluide étudié logé dans l’espace 33 entre les plateaux. According to FIG. 8, the rheometer 3 is of the type with parallel plates (plane-plane, PP). In this type of rheometer 3, one of the plates 31 is driven in rotation with respect to to the plate 32 and one or both can be made of a porous material, permeable to gaseous fluids, thus also making it possible to control the environment of the fluid studied housed in the space 33 between the plates.
Selon encore un autre mode de réalisation comme visible à la figure 9, le rhéomètre 4 est de type cône plan, et dans ce cas, l’une des pièces ou les deux du cône 41 et du plan 42 sont en matériau poreux permettant ainsi l’étude du fluide logé dans l’espace 43 ménagé entre le cône 41 et le plan 42. According to yet another embodiment as visible in FIG. 9, the rheometer 4 is of the plane cone type, and in this case, one or both of the parts of the cone 41 and of the plane 42 are made of a porous material thus allowing the study of the fluid housed in the space 43 formed between the cone 41 and the plane 42.
Un dispositif de mesure selon l’invention comportant une pièce en matériau poreux perméable aux gaz permet ainsi de réaliser un contrôle de l’environnement de la suspension étudiée, en particulier au niveau du pH, de la concentration en oxygène. A measuring device according to the invention comprising a part made of a porous material permeable to gases thus makes it possible to control the environment of the suspension under study, in particular with regard to the pH and the oxygen concentration.

Claims

Revendications Claims
1 . Dispositif de mesure de la viscosité d’un fluide actif tel qu’une suspension comportant des microorganismes vivants, tel qu’un rhéomètre (1 , 2, 3, 4) comprenant deux pièces coaxiales (1 1 , 12 ; 21 , 22 ; 31 ,32 ; 41 ,42) dont l’une est entraînée en rotation par rapport à l’autre, un compartiment de réception (13, 23, 33, 43) étant ménagé entre les deux pièces pour accueillir un fluide à étudier, caractérisé en ce qu’au moins l’une desdites pièces est réalisée en un matériau poreux, perméable aux gaz, tout en étant imperméable à la suspension et aux microorganismes qu’elle contient. 1. Device for measuring the viscosity of an active fluid such as a suspension comprising living microorganisms, such as a rheometer (1, 2, 3, 4) comprising two coaxial parts (1 1, 12; 21, 22; 31 , 32; 41, 42) one of which is rotated relative to the other, a receiving compartment (13, 23, 33, 43) being provided between the two parts to accommodate a fluid to be studied, characterized in that at least one of said parts is made of a porous material, permeable to gases, while being impermeable to the suspension and to the microorganisms it contains.
2. Dispositif selon la revendication 1 , caractérisé en ce que le matériau présente une porosité de 5 à 40%. 2. Device according to claim 1, characterized in that the material has a porosity of 5 to 40%.
3. Dispositif selon l’une des revendications 1 et 2, caractérisé en ce que le matériau présente une perméabilité aux fluides gazeux comprise dans la plage de 2,5 à 3,5 10-9 m2/s. 3. Device according to one of claims 1 and 2, characterized in that the material has a permeability to gaseous fluids in the range of 2.5 to 3.5 10 -9 m 2 / s.
4. Dispositif selon l’une des revendications 2 et 3, caractérisé en ce que le matériau est de l’acrylonitrile butadiène styrène (ABS). 4. Device according to one of claims 2 and 3, characterized in that the material is acrylonitrile butadiene styrene (ABS).
5. Dispositif selon l’une des revendications 2 et 3, caractérisé en ce que le matériau est un matériau fritté à partir de granules de polytétrafluoroéthylène (PTFE). 5. Device according to one of claims 2 and 3, characterized in that the material is a sintered material from polytetrafluoroethylene (PTFE) granules.
6. Dispositif selon l’une des revendications 2 et 3, caractérisé en ce que le matériau est du polydiméthylsiloxane (PDMS). 6. Device according to one of claims 2 and 3, characterized in that the material is polydimethylsiloxane (PDMS).
7. Dispositif selon l’une des revendications 2 et 3, caractérisé en ce que le matériau est une céramique poreuse à base telle que la mullite C530. 7. Device according to one of claims 2 and 3, characterized in that the material is a porous ceramic base such as C530 mullite.
8. Dispositif selon l’une des revendications 1 à 7, tel qu’un rhéomètre de Couette (1 ), dans lequel la solution à analyser est placée dans le compartiment de réception (13) ménagé entre deux surfaces cylindriques concentriques formées par un cylindre externe se présentant sous forme d’un godet (12) entraînable en rotation et un cylindre interne (1 1 ) fixé sur un fil de torsion et qui pend fixe au centre de la solution, caractérisé en ce que le godet (12) et/ou le cylindre interne (1 1 ) sont réalisés en matériau poreux. 8. Device according to one of claims 1 to 7, such as a Couette rheometer (1), in which the solution to be analyzed is placed in the receiving compartment (13) formed between two concentric cylindrical surfaces formed by a cylinder. external in the form of a cup (12) which can be driven in rotation and an internal cylinder (1 1) fixed on a torsion wire and which hangs fixed in the center of the solution, characterized in that the cup (12) and / or the internal cylinder (1 1) are made of porous material.
9. Dispositif selon l’une des revendications 1 à 7, tel qu’un rhéomètre Searle (2), dans lequel la solution à analyser est placée dans le compartiment de réception (23) ménagé entre deux surfaces cylindriques concentriques formées par un cylindre externe (22) se présentant sous forme d’un godet fixe et un cylindre interne (21 ) entraînable en rotation, caractérisé en ce que le godet et/ou le cylindre interne sont réalisés en matériau poreux. 9. Device according to one of claims 1 to 7, such as a Searle rheometer (2), in which the solution to be analyzed is placed in the receiving compartment (23) formed between two concentric cylindrical surfaces formed by an external cylinder. (22) in the form of a fixed cup and an internal cylinder (21) which can be driven in rotation, characterized in that the cup and / or the internal cylinder are made of porous material.
10. Dispositif selon l’une des revendications 1 à 7, tel qu’un rhéomètre à plateaux parallèles (plan-plan, PP) (3), caractérisé en ce qu’au moins l’un des plateaux est constitué d’un matériau poreux. 10. Device according to one of claims 1 to 7, such as a rheometer with parallel plates (plane-plane, PP) (3), characterized in that at least one of the plates consists of a material. porous.
11. Dispositif selon l’une des revendications 1 à 7, tel qu’un rhéomètre de type cône plan (4), caractérisé en ce que le cône et/ou le plan sont en matériau poreux. 11. Device according to one of claims 1 to 7, such as a flat cone type rheometer (4), characterized in that the cone and / or the plane are made of a porous material.
12. Procédé de mesure de la viscosité d’un fluide « actif » comportant des particules actives tel que des microorganismes vivants motiles, mis en oeuvre dans un dispositif de mesure selon l’une des revendications 1 à 11 comportant les étapes suivantes : (a) mise en place du fluide à l’intérieur de l’espace de réception ménagé entre les deux pièces coaxiales dont au moins l’une est en un matériau poreux, (b) entraînement en rotation à vitesse constante réglable de l’une des pièces par à l’autre, ce qui met en écoulement le fluide qui exerce un couple de forces sur la pièce fixe 12. A method of measuring the viscosity of an “active” fluid comprising active particles such as living motile microorganisms, implemented in a measuring device according to one of claims 1 to 11 comprising the following steps: (a ) placing the fluid inside the reception space formed between the two coaxial parts, at least one of which is made of a porous material, (b) drive in rotation at an adjustable constant speed of one of the parts by to the other, which puts the fluid in flow which exerts a couple of forces on the fixed part
(c) mesure de la variation du couple avec la vitesse de rotation(c) measurement of the variation of the torque with the speed of rotation
(d) calcul à partir de la variation de du couple, de la viscosité du fluide et de sa dépendance avec le taux de cisaillement contrôlé par la vitesse de rotation de la pièce entraînable en rotation. (d) calculation from the variation of the torque, the viscosity of the fluid and its dependence on the shear rate controlled by the speed of rotation of the part which can be driven in rotation.
PCT/EP2020/061961 2019-04-30 2020-04-29 Device for measuring the viscosity of a fluid, in particular for active fluids WO2020221833A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP20723822.1A EP3963307A1 (en) 2019-04-30 2020-04-29 Device for measuring the viscosity of a fluid, in particular for active fluids

Applications Claiming Priority (2)

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FR1904555A FR3095697B1 (en) 2019-04-30 2019-04-30 Device for measuring the viscosity of a fluid, in particular for active fluids
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US20090176261A1 (en) 2005-04-20 2009-07-09 Uws Ventures Limited Method of determining the point at which coagulating blood forms a clot
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AU3107577A (en) 1977-11-30 1979-06-07 Ovutime Inc Viscometer
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EP3963307A1 (en) 2022-03-09
FR3095697B1 (en) 2024-02-16

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