Permeability measurement device and method

Abstract

A device for measuring the permeability of a permeable substance to a fluid, comprising an air cavity (4) of a specific volume, a support (2) configured to contain a quantity of fluid, and a substance module comprising a permeable substance (3), the air cavity (4) and the support (2) being arranged such that a specific thickness H of the permeable substance (3) is between the quantity of fluid and the air cavity, the walls of the air cavity (4) being formed from the permeable substance, and a pressure P in the cavity (4) over time. C and applying a pressure P to a volume of fluid to induce flow through the permeable material in the cavity. B and a digital means for controlling the fluid pressure, configured to apply a pressure gradient ▽P=(P B -P C ) / H, and the flow rate of the fluid through the permeable material, dP, based on the time-dependent derivative of the air pressure in the cavity. C and digital means configured to determine the flow rate, ΔV, / dt, and determine the permeability of the permeant based on the flow rate and the pressure gradient, ▽P.

Description

[Technical field]

[0001] The present invention relates to a device for measuring the permeability of a material that is permeable to a fluid. The present invention also relates to a method of using such a device.

[0002] The field of the invention is, without limitation, that of characterizing media and substances. [Background technology]

[0003] In biology, the permeability of a material, such as a tissue, is an important quantity for exchange mechanisms. This is because the tissue matrix is ​​permeable to fluids and hydrostatic pressure is maintained by blood pressure towards the lymphatic system. Permeability is controlled by interfacial tissues (called endothelium or epithelium) that form a barrier to flow. A higher resistance to flow is represented by a lower permeability coefficient.

[0004] To know the permeability of a medium or material to a fluid, it is necessary to determine the ability of this medium or material to pass a fluid under the influence of a pressure difference on both sides of the medium or material. Permeability measuring instruments are called "permeometers". In the context of biological materials, such as body tissues, permeability is linked to the mechanical properties of the material, and poromechanics will then be described.

[0005] Determining the permeability of a medium or material requires measuring the flow rate of a fluid through the material and the pressure gradient along the direction of this flow.

[0006] These two quantities are rarely known simultaneously in tools for characterizing interstitial flow in cytosols.

[0007] For example, the articles "Transport of Molecules in the Tumour Interstitium: A review", Cancer Res 47: 3039 and "Measurement of interstitial fluid pressure: Comparison of Methods", Annals Biomed Engineering 14: 139 summarize methods for measuring tissue permeability.

[0008] Also known are methods for measuring the flux of liquids through cell media or cell walls, in particular by following the transport kinetics of fluorescent tracers which provide evidence of the rate of flux.

[0009] Finally, electrical methods, such as those measuring transepithelial electrical resistance (TEER), can be used to characterize the walls, making it possible to measure ion currents at zero pressure.

[0010] These two techniques thus measure the permeability to macromolecules or ions. For characterizing the permeability to fluids, there are methods that measure the local pressure in the tissue, such as, in particular, the "wick-in needle" method, in which a needle is inserted in a target area of ​​the body and is equipped with a corresponding and offset pressure sensor. In other cases, the measurement of the fluid flow is performed by a flow meter. However, the mentioned methods and tools do not allow to directly measure both the flow rate and the pressure gradient through a medium or substance using a single measurement means.

[0011] Other tools are known in the materials field, and in particular in architecture, to measure permeability. For example, the permeability of concrete to fluids can be determined by the Blaine permeability meter, as described for example in JP Ollivier, M. Massat, "Permeability and microstructure of concrete: a review of modelling", Cement and Concrete Research, Volume 22, 1992, pp. 503-514. The Blaine permeability meter allows such measurements by means of a pressure sensor coupled to a low-speed sensor. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] “Transport of Molecules in the Tumour Interstitium: A review”, Cancer Res 47: 3039 [Non-Patent Document 2] “Measurement of interstitial fluid pressure: Comparison of Methods”, Annals Biomed Engineering 14: 139 [Non-Patent Document 3] JP Ollivier, M. Massat, "Permeability and microstructure of concrete: a review of modeling", Cement and Concrete Research, Volume 22, 1992, pp. 503-514. [Non-Patent Document 4] Rosti et al., "The Breakdown of Darcy's Law in a Soft Porous Material," Soft Matter 16. pp. 939-944 (2020) (solid line) Summary of the Invention [Problem to be solved by the invention]

[0013] The aim of the present invention is to propose a device and a method for measuring the permeability of a permeant substance, which are able to overcome these drawbacks.

[0014] One object of the present invention is to propose a device and a method for determining the permeability of a permeable substance, making it possible to directly measure the pressure gradient and the flow rate of a fluid through said substance.

[0015] Another object of the invention is to propose a device and method for determining the permeability of permeable substances, the use of which allows to easily measure different types of substances and to be adapted to the scanning of experimental conditions with only one measurement.

[0016] Yet another object of the invention is to propose a device and a method for determining the permeability of a permeant substance, the implementation of which can be automated. [Means for solving the problem]

[0017] At least one of these objects is achieved by means of a device for measuring the permeability of a substance permeable to a fluid, the device comprising: - an air cavity of a certain volume; - a material module, A support configured to contain / transport a quantity of fluid, and · Penetrating substances A material module, Including, wherein the air cavity and the support are arranged such that a particular thickness H of the permeable material is disposed between the quantity of fluid and the air cavity, and a wall of the air cavity is formed in part by the permeable material; - pressure P in the air cavity as a function of time Cand a means for measuring - A flow pressure P is applied to induce fluid flow through the permeable material into the air cavity. B a means for controlling said pressure of the volume of fluid configured to apply - Digital means, The pressure gradient between a volume of fluid and an air cavity, ▽P = (P B -P C ) / H, The flow rate of fluid through a permeable material, dP, from the drift of the air pressure in the cavity over time C Determine / dt, and · Determine the permeability of a permeable substance from the flow rate and pressure gradient ▽P Digital means and Further comprising: device.

[0018] The measuring device according to the invention is considered to be a penetrometer, i.e. an instrument for measuring permeability. The response of the device is considered to be that of a capacitor. This means that the application of pressure to a volume of fluid is not performed in a permanent regime. Thus, with a one-time application of pressure to said volume of fluid, it is possible to obtain a response curve of permeability as a function of the pressure gradient.

[0019] Advantageously, the device according to the invention makes it possible to directly measure the flow rate of a fluid through a permeable material and the pressure gradient applied to this material. The permeability of the material being measured is readily inferred from these two quantities.

[0020] The device according to the invention further allows for a very simple and easy to implement integration of a pressure sensor: standard sensors available commercially can be used in the device.

[0021] In practice, the pressure sensor may be offset at a distance from the air cavity. According to one example, the pressure sensor may be connected to the air cavity by means of a tube of known volume.

[0022] Thus, the same pressure control means, such as a single pressure controller, may be used for multiple substance module / air cavity assemblies.

[0023] The device according to the invention is compatible with cell incubation conditions and it is possible to carry out measurements with the device according to the invention, for example in tissue engineering contexts, in particular for producing organs-on-chips, inside an incubator. Measurements and pressure control are performed remotely.

[0024] The device according to the invention is easily adapted for organ-on-a-chip designs.

[0025] Furthermore, the device according to the invention can be used with several different types of permeable substances, for example, all types of cellular tissues, with or without a barrier layer, or other permeable substances such as polymer membranes or polymer concretes, can be measured using the device according to the invention.

[0026] The fluid may be a liquid or a gas, for example water or air.

[0027] According to one embodiment, the digital means may be further configured to determine the elastic modulus of the permeable material from the pressure gradient between the volume of fluid and the air cavity as a function of time.

[0028] In engineering, a material may be characterized by its Young's modulus, or elastic modulus, and its Poisson's ratio.

[0029] From the measurement of the pressure in the cavity as a function of time, it is possible to access both the mechanical and hydrodynamic properties of the material, using differentiated kinetics of the pressure response. When a material is subjected to hydrostatic pressure, it undergoes a deformation which, due to the permeability of the material, is responsible for the increase in pressure in the air cavity. These two mechanisms have very different time scales, allowing pressure gradients to be analyzed.

[0030] The magnitude of the deformation increases with a corresponding decrease in Young's modulus as the material becomes more elastic. Poisson's ratio allows one to characterize the contraction of the material perpendicular to the direction of application of hydrostatic pressure, which contraction is due to the structural reorganization of the material. For a given Young's modulus, Poisson's ratio influences the onset of the deformation response kinetics.

[0031] According to an advantageous embodiment, the amount of fluid may be partially contained within a microchannel passing through the permeable material.

[0032] The support may also include a system of channels and reservoirs in which a volume of fluid is contained and transported, the system being in fluid communication with the microchannel.

[0033] According to one example of implementation, the support may be made of silicone, in particular of the polydimethylsiloxane (PDMS) type.

[0034] PDMS has advantageous properties: in particular it is chemically harmless, non-toxic and transparent.

[0035] To be able to perform selective flow measurements through the permeable material layer, the absence of gaps at the material / support interface is required to ensure impermeability at the interface. For this purpose, a sealed joint between the two materials is provided to implement the material module.

[0036] According to a first embodiment, the permeable material may be permanently adhered to the support.

[0037] Permanent adhesion is particularly suitable when the permeable material is collagen, which is in fact very soft and fragile, and adhesion to the support represents a non-damaging means of fixation.

[0038] According to another embodiment, the permeable material may be held by clamping to the support with an insulating joint at the material / support interface.

[0039] According to another aspect of the invention, there is provided a method for measuring the permeability of a material permeable to a fluid, comprising: a predetermined thickness H of the permeable material being disposed between an air cavity of a predetermined volume and a quantity of fluid, the walls of the air cavity being partially formed by the permeable material, the method comprising the steps of: - pressure P is applied to a volume of fluid to induce flow through the permeable material into the air cavity B and applying - pressure P in the air cavity as a function of time C and measuring - Pressure gradient between a volume of fluid and an air cavity, ▽P = (P B -P C ) / H; - The flow rate of fluid through a permeable material, dP, from the drift of the air pressure in the cavity over time C determining / dt; and - determining the permeability of a permeable material from said flow rate and said pressure gradient ▽P; A method has been proposed, which includes:

[0040] The method according to the invention makes it possible to determine the permeability of a permeable substance, ie its ability to allow itself to be passed by a fluid under the effect of a pressure gradient.

[0041] The method according to the invention makes it possible to directly measure the flow rate of a fluid through a permeable material and the pressure difference on either side of this material. The permeability of the material being measured can be readily inferred from these two quantities.

[0042] According to one embodiment, the method may further comprise the step of determining the elastic modulus of the permeable material from the pressure gradient, ▽P, between the volume of fluid and the air cavity (4) as a function of time.

[0043] Advantageously, the step of measuring the pressure in the cavity may be performed by a remote pressure sensor connected to the air cavity.

[0044] Alternatively, the step of measuring the pressure within the air cavity may be performed by a pressure sensor in the immediate vicinity of the cavity.

[0045] According to one embodiment, the step of measuring the pressure in the cavity comprises measuring the pressure on a volume of fluid (P B ) may be performed at regular intervals from the start of application of

[0046] The frequency of pressure measurements within the cavity can be adapted according to the barrier of the permeable material.

[0047] According to one embodiment, the method according to the invention may further comprise a preparatory step, which is as follows: - providing a material support, an air cavity, and a permeable material, the support being configured to contain / transport a quantity of fluid; - applying a permeable material to a support; - providing an air cavity on the material; - providing means for measuring the pressure in the air cavity; - providing means for controlling the pressure of the quantity of fluid; may include.

[0048] This preparation step makes it possible to use the measuring device according to the invention with a substance whose permeability it is desired to measure. A new substance module comprising the support and the permeable substance must be prepared for each new measurement. This is because it is necessary to be able to guarantee the permeability at the interface so that a selective flow measurement through the permeable substance layer can be performed. For this purpose, a sealing joint between the two substances is provided to prepare the substance module.

[0049] For this purpose, the support of a previous measurement can be reused by arranging thereon a new permeable substance to be measured, this being shown in particular with respect to a robust substance which can be removably fixed to the support, for example by clamping.

[0050] Alternatively, if the substance must be permanently fixed to the support, for example by adhesion, a new support must be used for each new permeant substance to be measured.

[0051] The connection part with the air cavity can be reused in several different substance modules, said part being fixed to the substance modules in an interchangeable manner.

[0052] Other advantages and features will emerge from a consideration of the detailed description of examples, which are in no way limiting, and from the accompanying drawings, in which: [Brief description of the drawings]

[0053] [Figure 1] 1 is an exploded schematic view of a non-limiting exemplary embodiment of a measuring device that may be used in the context of the present invention; [Diagram 2] 2 is a partial schematic cross-sectional view of the measuring device of FIG. 1; [Diagram 3] FIG. 2 is a partial cross-sectional schematic diagram of a permeable material layer having microchannels extending therethrough, as implemented in a device according to one embodiment of the present invention. [Figure 4] FIG. 2 is a schematic exploded view of another non-limiting exemplary embodiment of a measuring device that can be used in the context of the present invention; [Diagram 5] FIG. 2 is a schematic diagram of a non-limiting exemplary embodiment of a measurement method according to the present invention. [Figure 6] FIG. 13 is an example of a flow measurement obtained using the present invention. [Figure 7] FIG. 13 is an example of a pressure measurement obtained using the present invention. [Figure 8] FIG. 11 is another example of a pressure measurement obtained using the present invention. [Figure 9] FIG. 11 is yet another example of pressure measurements obtained using the present invention. [Figure 10] FIG. 11 is yet another example of pressure measurements obtained using the present invention for various permeable materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] Of course, the embodiments described below are in no way limiting. In particular, it will be possible to imagine a variant of the invention that includes only a selection of the features described below, isolated from the other features described, if this selection of features is sufficient to provide a technical advantage or to differentiate the invention over the prior art. This selection includes at least one preferably functional feature without structural details or with only a portion of structural details (if this portion alone is sufficient to provide a technical advantage or to differentiate the invention over the prior art).

[0055] In particular, all of the variants and all of the described embodiments can be combined with each other, unless there is something against this combination at a certain technical level.

[0056] In the figures, elements that are common to several figures may retain the same reference numbers.

[0057] Embodiments of a measuring device that can be used in the context of the present invention are described below with reference to Figures 1, 2 and 4. Figure 1 is a semi-exploded schematic view of an example of a measuring device. Figure 2 is a partial cross-sectional view of the measuring device of Figure 1. Figure 4 is a schematic view of another example of a measuring device.

[0058] The device 1 shown in the embodiment of Figures 1 and 2 comprises a support 2 in which a permeable material layer 3 and an air cavity 4 are arranged. The assembly comprising the support 2 and the permeable material layer 3 is considered to be a material module. The permeable material layer 3 is adhered in its position within the support 2 over the entire length of its bottom surface.

[0059] The support 2 is preferably made of polydimethylsiloxane (PDMS). Of course, other materials, in particular polymers, can be used for the support 2.

[0060] The device 1 further comprises a cavity 4 containing air. In this example shown in Figures 1 and 2, the air cavity 4 is created in a connection part 5. The connection part 5 can be a 3D printed part or a machined part. The air cavity 4 has a predetermined volume. One of the walls of the air cavity 4 is formed by a permeable material layer 3.

[0061] In the exemplary implementation of the device 1 shown in Figures 1 and 2, the support 2 comprises a channel system for containing and transporting a volume of liquid to the permeable material layer 3. The channel system comprises two lateral channels 7a, 7b in fluid communication with the microchannel 8 and the air cavity 4.

[0062] The microchannels 8 are created by passing needles through the permeable material. In the case of collagen, the needles are inserted while the collagen is in a gel form. The gel is then cross-linked and once the collagen gel is solid, the needles are removed, allowing the creation of passageways for the fluids.

[0063] After the needle is removed, a channel 8 remains through the permeable material layer 3 adjacent to the face opposite that adjacent the air cavity 4. Thus, a significant thickness of the permeable material layer 3 is disposed between the defined air cavity 4 and the fluid within the microchannel 8. It is the thickness H of the layer 3 between the microchannel 8 and the air cavity that is considered for determining the permeability of the permeable material.

[0064] The liquid is, for example, water.

[0065] The connecting part 5 is connected to the pressure P B 1 and 2, this cavity 9, called the control cavity, has an annular shape and is disposed around the air cavity 4.

[0066] To control the pressure in the control cavity 9 , the device 1 includes pressure control means, such as a pressure controller 11 .

[0067] The device 1 according to the invention also comprises pressure measuring means. They are, in particular, the pressure P C The pressure measuring means includes a remote pressure sensor 10. The pressure sensor 10 may be connected to the air cavity 4 by means of a tube (not shown) having a calibrated volume. The volume of the tube is then added to the volume of the air cavity 4.

[0068] The pressure controller 11 and the pressure sensor 10 may be connected by adapted software of the Labview (registered trademark of National Instruments) type to carry out the pressure control and the acquisition of the pressure measurements.

[0069] The device also comprises digital means for determining the permeability of the permeable substance 3. These digital means include at least one computer, central unit or processor, microprocessor and / or adapted software means.

[0070] Thus, when the device 1 is used to measure the permeability of a permeable substance 3, the pressure P B is applied to a volume of fluid, and the pressure P B 3 shows a partial cross-section of a permeable layer of material 3 through which a microchannel 8 passes, the bottom surface of the layer of material 3 being fixed to its support (not shown). The pressure P B When is increased, the fluid flow located in the channel system and the microchannels 8 passes through the permeable material 3 and crosses into the air cavity 4. The fluid flow can be characterized by its flow velocity (q). The air volume in the air cavity 4 then decreases, and the air pressure P C By measuring the change in pressure in the air cavity 4 and the flow rate of the fluid, the permeability of the permeable material 3 can be determined.

[0071] Another embodiment of the device according to the invention is shown in Fig. 4. The device 1 also comprises a support 2 on which a permeable substance layer 3 and an air cavity 4 are arranged. The permeable substance layer 3 is neither glued nor arranged on the support 2. The substance 3 is suspended by their lateral edges in the perforations 6 of the support part 2a. The substance 3 is preferably in the form of a membrane that is clamped on its edges in the perforations 6. The bottom and top surfaces of the substance 3 are therefore free to move. The support part 2a is arranged in the support 2 in such a way that liquid can flow through the substance 3 into the air cavity 4. A pressure sensor 10 closes the air cavity 4. The support part 2a is removable, making it easier to arrange other substances in the device 1.

[0072] To avoid temperature changes that may cause changes in the air pressure in the cavity, the device can be provided with a protective housing, for example a plastic housing, which makes it possible to guarantee temperature stability and uniformity within the device.

[0073] The device 1 according to the embodiment shown in Figures 1, 2 and 4 may be used to carry out the steps of the determination method described below.

[0074] FIG. 5 is a schematic diagram of a non-limiting exemplary embodiment of a method for determining the permeability of a permeable substance according to the present invention.

[0075] The method 100 shown in Fig. 5 comprises a preparation step 105 in which a permeable substance layer whose permeability is to be determined is placed between an air cavity and a quantity of fluid. The substance layer has a known thickness H. For this purpose, the permeable substance layer is placed in a support such that the air cavity is located directly on one side of said layer and the fluid on the other side. This positioning can be performed by a substance module and a connection piece 5, as described above with reference to Figs. 1 and 2. Means for measuring the pressure in the air cavity and for controlling the pressure applied to the fluid can then be provided, as described above.

[0076] This preparation step 105 makes it possible to arrange the measuring device with the required substance. The device 1 can be as described with reference to figures 1 and 2. The connection part 5 with the air cavity can be reused with other substance modules. It is fixed to the substance modules interchangeably. A seal such as a conventional rubber lug can be used to carry out this assembly. If the permeable substance is collagen or another fragile substance of this kind, the collagen must be glued to the support, so that the substance module must be prepared anew for each new measurement of the permeable substance. The other permeable substance can be removed from the support, which can then be reused.

[0077] The method 100 comprises applying a pressure P B The pressure in the control cavity 9 can be controlled, in particular, so that it rises to a predetermined value. Thus, the pressure P B rises and the fluid passes through the permeable material and accumulates in the air cavity 4.

[0078] When the fluid is a liquid, the amount of air in the air cavity 4 decreases, and as a result the pressure of the air in the cavity 4 increases as a function of the flow through the permeable material layer.

[0079] If the fluid is a gas, the number of air and gas component molecules (which may also be air) already present in the cavity will increase within the cavity, thus increasing the pressure therein.

[0080] In the step 120 of measuring, the pressure P C is measured as a function of time.

[0081] Pressure in the air cavity P C From the measurement of , the pressure gradient between the volume of fluid and the air cavity can be determined in step 130. This pressure gradient can be expressed as:

[0082]

number

[0083] At the same time, the flow rate of the fluid through the permeable material is controlled by the air pressure P in the cavity in step 140 of the method. C drift over time, dP C / d can be determined.

[0084] The amount of fluid passing through the material during a time interval dt is equal to qSdt, where S is the surface area of ​​the microchannels in the permeable material and q is the fluid flow rate. The compressibility coefficient of air, at constant temperature t, can be defined as:

[0085]

number

[0086] For unidirectional flow with low Reynolds numbers, the permeability coefficient κ is defined by Darcy's law:

[0087]

number

[0088] μ is the viscosity coefficient of the fluid, dP / dx = (P B -P C ) / H is the pressure gradient. The coefficient μ characterizes the viscosity of the fluid (for example, 0.001 Pa.s for water). From this, it can be deduced that

[0089]

number

[0090] Pressure in the cavity P C The drift of over time is then expressed as:

[0091]

number

[0092] The factor β is the compressibility of air at ambient temperature, and V C is the volume of the air cavity. This volume V C can be adjusted depending on the fluid flow rate that is expected to be measured. In this embodiment, and the input pressure P M By applying the equation, it is possible to integrate the mechanical deformation of the material with the change in pressure inside the cavity using a simplified one-dimensional model.

[0093]

number

[0094] where τ = μH 2 / κ and λ n is the equation αλ n tan(λ n ) = 1, α = βV C M / SH, where M is defined as the elastic modulus of the one-dimensional model.

[0095] In step 150 of method 100, the permeability κ of the permeant is determined from equation (5).

[0096] For hydrogels, the permeability is approximately 10 -12 m 2 From 10 -20 m 2 That is until now.

[0097] In the representation of "Equation 4", the parameters H and S are the geometric factors of the material. These factors can be modified by numerical flow simulation when the geometry of the measurement device with the permeable material is complex.

[0098] In the following, examples of methods and devices according to the invention are described.

[0099] According to a first example, collagen permeability was determined for collagen of types IP and IA offered by Nitta Gelatin, which correspond to gelatin from porcine tendons, extracted enzymatically (pepsin) or chemically, respectively, in an acidic medium.

[0100] The air cavity is connected to a tube of 45 cm length and 3 mm diameter, i.e. a total volume of 3.6 mL. To control the pressure in the cavity, a triangular signal of amplitude 1000 Pa and duration 500 s repeated 10 times is applied in the tube. The sampling rate is 500 ms.

[0101] Figure 6 shows the measurement of the collagen flow rate q as a function of the pressure difference applied to the collagen matrix for collagen of type IP (measurement point referenced 12) and type IA (measurement point referenced 13). The hysteresis of the response due to the increase or decrease of the pressure in the air cavity can be observed for the two graphs. The data are averaged over 5 seconds for each point shown in the diagram.

[0102] The change in pressure per unit time in the air cavity is multiplied by the volume of the cavity and the compressibility of air at atmospheric pressure to obtain the flow rate, which is shown as a function of the pressure difference applied between the tube and the air cavity, as seen by direct measurement in real time.

[0103] In the diagram of Figure 6, the reaction q (ΔP) is fitted to a fourth-order polynomial as described in Rosti et al., "The Breakdown of Darcy's Law in a Soft Porous Material," Soft Matter 16. 939-944 (2020) (solid line). The permeate flow Q is a fourth-order polynomial function of the pressure difference ΔP.

[0104]

number

[0105] D is the diameter of the pores in the material.

[0106]

number

[0107] is its porosity,

[0108]

number

[0109] Here, G is the stiffness modulus of collagen.

[0110] The measured stiffness moduli are 2982 Pa and 4433 Pa for collagen IA and IP, respectively.

[0111] A second example illustrates the properties of the cell wall of endothelial tissue.

[0112] In this example, the collagen microchannel described above is coated with a solution of human umbilical vein endothelial cells (HUVEC) at a concentration of 10 million cells per mL for 2 times for 5 minutes. The cells are then incubated in an incubator at 37° C. and 5% CO2 for 1 to 3 days.

[0113] FIG. 7 shows the pressure response P in the air cavity after application of a pressure of 100 Pa in a microchannel with (measurement point referenced 15) or without (measurement point referenced 14) HUVEC cells. C The measurement of the hydrodynamic resistance of the cell wall is shown as the time response of the pressure in the air cavity P C This is done by fitting (t) to the following equation:

[0114]

number

[0115] τ is a time constant that depends on the permeability of the permeating material and the viscosity of the fluid. The fit is shown by the solid line in the diagram of Figure 7. The fit to curves 14 and 15 can be improved by integrating the elasticity of the material in the model, based on equation (6).

[0116] A more rapid pressure response in the case of collagen without cell walls is observed in Figure 7. This is because the cell walls reduce the fluid flow, which causes a slower rise in pressure in the air cavity.

[0117] According to a third example, the response of a collagen matrix, which may or may not be loaded with fibroblasts, is measured.

[0118] The concentrations of collagen used are 2.4 mg / mL, 1.9 mg / mL, and 1.4 mg / mL. For measurements with fibroblasts, the concentration of fibroblasts is 40 cells per μl of collagen diluted to a concentration of 2.4 mg / mL for a total volume of 30 μl of collagen. After 5 days of maturation, the collagen and cells are fixed with a volume of 4% paraformaldehyde (PFA) for 30 minutes and then rinsed 5 times with deionized water.

[0119] A measurement of the pressure in the air cavity is made after pressurization of the air cavity at 100 Pa. The pressure is then released in the collagen microchannel. Flow is then observed proceeding from the cavity into the tube, and as a result, a drop in pressure in the cavity is observed.

[0120] Figure 8 shows measurements of air cavity pressure relief for collagen concentrations of 2.4 mg / mL with fibroblasts (Graph 16), 2.4 mg / mL without fibroblasts (Graph 17), 1.9 mg / mL (Graph 18), and 1.4 mg / mL (Graph 19). The kinetics of air cavity pressure relief appears to depend on the collagen concentration and the presence of fibroblasts in the matrix.

[0121] A fourth example illustrates the characterization of the mechanical response of a collagen layer or membrane under hydrostatic pressure.

[0122] This characterization is carried out using a measurement device in which the collagen can undergo deformation, for example in the device shown in Figure 4, in which the layer of material is suspended by its lateral edges, in which the permeable material is free to deform in the direction of the applied flow.

[0123] Figure 9 shows the normalized pressure response in the air cavity using the collagen layer after application of a pressure operation of 100 Pa. The collagen gel is prepared according to the same method as in the third example.

[0124] At t = 0, it can be seen that the normalized pressure is greater than 0, unlike the curve shown in figure 7. This sudden rise is due to the collagen layer quickly deforming by buckling when it is exposed to hydrostatic pressure. This mechanical deformation reduces the volume in the air cavity 4. As the buckling instability is determined by the elastic modulus of the material, the sudden rise allows to access this elastic modulus. The pressure field then propagates into the material, which leads to a modification of the shape of the top interface of the material in the cavity (determined by the Poisson's ratio) and the movement of liquid through said material, both due to osmotic flow. This leads to a slower decrease in the volume of the cavity 4. The pressure in the cavity therefore rises due to both the deformation and the permeability of the material. These two mechanisms have very different time scales.

[0125] Figure 10 shows the short rise in pressure response in a cavity for a model material simulated with the COMSOL software by COMSOL Inc., varying the properties of the material, specifically Poisson's ratio and Young's modulus. For the three different Young's moduli shown, it is known that the smaller the elastic modulus, in other words the larger the buckling deformation, the larger the amplitude of the first pressure operation. Furthermore, it is possible to measure the Poisson's ratio, which produces different curves for all of the elastic moduli, depending on whether its value is equal to 0.1, 0.25 or 0.4. This difference is explained by the change in the contour of the top layer of collagen under the effect of hydrostatic pressure.

[0126] In particular, for a Poisson's ratio of 0.4, an abrupt transition is observed between the initial deformation and the subsequent kinetics. As the Poisson's ratio decreases, more and more "softening" kinetics are observed. The structural reorganization of the material, characterized by the smaller Poisson's ratio, then causes an increase in the time required to achieve the same deformation as with a higher Poisson's ratio.

[0127] Naturally, the invention is not limited to the embodiments just described, to which numerous variations can be made without departing from the scope of the invention. [Explanation of symbols]

[0128] 1 Device 2 Support 2a Support parts 3 Permeable material layer, permeable material 4. Air Cavity 5 Connection parts 6 Perforated part (of supporting part) 7a, 7b Horizontal Channel 8 Microchannel 9 Second Cavity, Control Cavity 10 Remote pressure sensor, means for measuring pressure 11 Pressure controller, means for controlling pressure 14, 15 curve Graphs 16, 17, 18, and 19 100 ways 110 (Pressure P B of) application

Claims

1. A device (1) for measuring the permeability of a permeable substance to a fluid, comprising: - an air cavity of a certain volume (4); - a material module, a support (2) configured to contain a quantity of fluid, and the permeable substance (3) A material module, Including, wherein said air cavity (4) and said support (2) are arranged such that a certain thickness H of said permeable material (3) is arranged between said quantity of fluid and said air cavity, and the walls of said air cavity (4) are partially formed by said permeable material, - pressure P in said air cavity (4) as a function of time C A means (10) for measuring - applying a fluid pressure P to the quantity of fluid to induce fluid flow through the permeable material and into the air cavity; B a means (11) for controlling the pressure of said quantity of fluid, the means (11) being adapted to apply - Digital means, The pressure gradient between the volume of fluid and the air cavity, ▽P = (P B -P C ) / H, From the drift over time of the air pressure in the cavity, the flow rate of fluid through the permeable material, dP C Determine / dt, and determining the permeability of the permeable material from the flow rate and the pressure gradient, ▽P; Digital means and The device (1), further comprising:

2. 2. The device (1) according to claim 1, characterized in that the digital means are further configured to determine the elastic modulus of the permeable material from the pressure gradient, ▽P, between the quantity of fluid and the air cavity (4) as a function of time.

3. 3. The device (1) according to claim 1 or 2, characterized in that the means (10) for measuring the pressure comprise a remote pressure sensor (10) connected to the air cavity (4).

4. 4. A device (1) according to any one of claims 1 to 3, characterized in that the amount of fluid is partially contained within a microchannel (8) passing through the permeable material.

5. Device (1) according to any one of claims 1 to 4, characterized in that the support (2) is made from polydimethylsiloxane, PDMS.

6. 6. The device (1) according to any one of claims 1 to 5, characterized in that the air cavity (4) is manufactured by 3D printing.

7. 7. The device (1) according to any one of claims 1 to 6, characterized in that the permeable substance (3) is adhered to the support (2).

8. 7. The device (1) according to any one of claims 1 to 6, characterized in that the permeable substance (3) is removably arranged on the support (2).

9. A method (100) for measuring the permeability of a material (3) permeable to a fluid, comprising: a predetermined thickness H of said permeable material (3) being arranged between an air cavity (4) of a predetermined volume and a quantity of fluid, the walls of said air cavity (4) being partially formed by said permeable material (3), said method (100) comprising: - applying a pressure P to the quantity of fluid to induce a flow through the permeable material (3) into the air cavity (4); B A step (110) of multiplying - pressure P in said air cavity (4) as a function of time C measuring (120); - the pressure gradient between the quantity of fluid and the air cavity (4), ▽P = (P B -P C ) / H (130); - the flow rate of fluid through the permeable material (3), dP, from the drift over time of the air pressure in the cavity (4); C A step (140) of determining / dt; and - determining (150) the permeability of the permeable substance (3) from the flow rate and the pressure gradient ▽P; A method comprising:

10. 10. The method (100) of claim 9, further comprising the step of determining an elastic modulus of the permeable material from the pressure gradient, ▽P, between the quantity of fluid and the air cavity (4) as a function of time.

11. 11. The method (100) according to claim 9 or 10, characterized in that the step (120) of measuring the pressure in the air cavity (4) is performed by a remote pressure sensor (10) connected to the air cavity (4).

12. The step (120) of measuring the pressure in the air cavity (4) includes measuring the pressure, P B , at regular intervals, and B 12. The method (100) according to any one of claims 9 to 11, characterized in that it makes it possible to follow the changes in the fluid flow rate over the entire range of pressure gradient values ​​▽P between / H and 0.

13. The method comprises the steps of: providing a material support (2), the air cavity (4) and the permeable material (3), the support (2) being configured to contain a quantity of fluid; - applying said permeable substance (3) to said support (2); - disposing said air cavity (4) on said material; - providing means (10) for measuring the pressure in the air cavity (4); - providing means (11) for controlling said pressure of said quantity of fluid; 13. The method (100) according to any one of claims 9 to 12, further comprising a preceding preparatory step (105) comprising:

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