EP3592890A1

EP3592890A1 - Composite membrane and method for manufacturing such a membrane

Info

Publication number: EP3592890A1
Application number: EP18712985.3A
Authority: EP
Inventors: Arnaud ANTKOWIAK; Paul GRANDGEORGE; Natacha KRINS; Christel Laberty-Robert
Original assignee: Centre National de la Recherche Scientifique CNRS; Sorbonne Universite
Current assignee: Centre National de la Recherche Scientifique CNRS; Sorbonne Universite
Priority date: 2017-03-10
Filing date: 2018-03-09
Publication date: 2020-01-15
Also published as: CN110603355A; JP2020514567A; WO2018162866A1; FR3063743A1; CA3055481A1; US20200010989A1

Abstract

The present invention relates to a composite membrane (10) comprising a fibrous fabric (1) of nanofibres (11), wherein the thickness of the fabric (1) is between 10 nm and 50 μm and said fabric is impregnated with a wetting liquid (A). According to the invention, the composite membrane is immersed in a second fluid (B) which is immiscible with the wetting liquid (A), forming an A/B interface between the wetting liquid (A) and the immiscible fluid (B), and the composite membrane is capable of remaining tensioned when it is compressed from its resting state until reaching dimensions corresponding to 5% of its dimensions in the resting state, and when it is stretched from its compressed state until reaching dimensions corresponding to 2000% of the length in the compressed state. The present invention also relates to a process for manufacturing such a membrane.

Description

COMPOSITE MEMBRANE AND METHOD FOR MANUFACTURING SUCH

MEMBRANE

The present invention generally relates to a composite membrane comprising a fibrous tissue impregnated with a wetting liquid. The present invention also relates to the production of such a membrane.

It is known to those skilled in the art that composite materials can cover a wide range of mechanical, thermal and optical properties that can not be achieved with a single type of material. In the context of composite materials combining several solid state materials, there may be mentioned reinforced concrete, which has the high compressive strength of concrete, but also a tensile strength thanks to the metal rods structuring the reinforced concrete ( thus constituting its frame).

Other composite materials can combine a liquid phase and a solid phase to take advantage of their respective properties. A hollow tube filled with a little liquid (oil for example) will provide excellent thermal conductivity without electrical conductivity, the tube ensuring the structural integrity of this composite material. No single solid material can achieve this type of performance.

In addition to the combination of these two phases of different types, solid-liquid interactions can also significantly affect the mechanical properties of a composite material. For example, spider silk is made of filamentous protein fibers composed of hydrophilic and hydrophobic block copolymers and water; which moisten even more when the hygrometry is high (typically greater than 70%) or when the silk is suddenly wet. Thanks to the elasto-capillary winding of the fibers, the spider's capture silk shows a liquid behavior Unexpected in compression (it remains tense throughout the shortening of its end-to-end length), but remains solid in extension (thus showing an elastic behavior).

Inspired by the behavior of this unidimensional solid-liquid object constituted by spider capillary silk, the Applicant has developed a two-dimensional solid-liquid composite membrane having the same property as spider capillary silk.

More particularly, the applicant has developed a composite membrane comprising a fibrous nanofiber fabric, the thickness of the fabric being between 10 nm and 50 μιη, the fabric being impregnated with a wetting liquid A.

According to the invention, the composite membrane is immersed in a second fluid B immiscible with the wetting liquid A, forming an A / B interface between the wetting liquid A and said immiscible fluid B, and the composite membrane is able to remain tight. :

• when it is compressed from its rest state, until it reaches dimensions corresponding to

5% of its dimensions at rest, and

When it is stretched from its compressed state until it reaches dimensions corresponding to 2000% of the length in the compressed state.

For the purposes of the present invention, the term "composite membrane" means a membrane comprising a solid reinforcement (or a fabric) and a liquid impregnating the reinforcement by wetting it.

For the purposes of the present invention, stretched membrane means a membrane in a state of mechanical tension.

For the purposes of the present invention, miscible fluids are understood to mean fluids A and B forming only one phase and there is no surface tension at the A / B interface. Conversely, when fluids A and B are immiscible, they form two distinct phases, with non-zero surface tension at the A / B interface.

In the fibrous tissue of the membrane according to the invention, the nanofibers are arranged in the form of a mat comprising between 1 and 20 layers of nanofibers.

For the purposes of the present invention, nanofibers are fibers having a diameter of between 10 nm and 5 μm, and typically of the order of 200 nm.

In the sense of the present invention, a liquid wetting the fabric is understood to mean a liquid having a contact angle of less than 90 ° with a flat surface of the material composing the nanofibers of the fabric.

Advantageously, the interface A / B formed by the wetting liquid A and the immiscible fluid B may be an oil / air interface, an oil / water interface, or a glycerol / air interface, or a water interface with surfactant. air. The A / B interface is stable over time (that is to say in the time of use of the composite membrane) because the liquid A which impregnates the fibrous mat does not diffuse into the fluid B. The A / B interface is present on both sides of the composite membrane

By surfactant (or detergent) is meant, in the sense of the present invention, a body, which even used in small quantities, significantly modifies the surface tension of the fluid containing it, for example water when the detergent used is dissolved soap. In this case, if the composite membrane of the invention impregnated with soapy water is brought into contact with the air, the A / B interface is a soapy water / air type interface.

The composite membrane according to the invention can adapt its surface and its shape to remain always under tension whatever the nature of the mechanical stress to which it is subjected, in the same way as a simple liquid film soapy, without ever breaking thanks to its solid character. For this, the fibrous mattress folds spontaneously within the liquid layer which soaks when the edges of the composite membrane are close together. The surface tension developed by the A / B interface allows the membrane to remain taut even when compressed, as opposed to a dry membrane that would plaster beneath its weight. In other words, the membrane according to the invention has the property of remaining in a state of tension irrespective of the nature of the mechanical stressing of the membrane:

on the one hand, when it is compressed, from its rest state, to a compression ratio that can range from its dimensions to the rest state

(That is, the membrane is in a non-pre-stretched or mechanically prestressed state), the membrane functions as a liquid film;

on the other hand, when it is stretched from its compressed state to a stretching rate of up to 2000% in length in the compressed state, the membrane functions as a liquid film at first, then as a solid film.

For the purposes of the present invention, compression ratio means the ratio between the distance between the ends of a characteristic dimension of the fabric, under the effect of a mechanical deformation by compression, and this distance in the state. rest.

The thickness of the fabric may advantageously be between 500 nm and 30 μm, and preferably between 1 μm. The nanofibers of the fabric may advantageously have a diameter of between 100 nm and 500 nm, and preferably of the order of 200 nm. .

Thus, it can be used in multiple applications, and especially as an artificial muscle, or for constitute a stretchable electronic circuit, or as a smart circuit, or also as SLIPS membrane (acronym for "Slippery Liquid-Infused Porous Surfaces").

By artificial muscle is meant, in the sense of the present invention, an organ capable of developing a mechanical force in response to an external stimulus.

For the purposes of the present invention, an intelligent circuit is understood to mean a circuit whose electrical behavior depends on the mechanical deformation imposed on the membrane.

For the purposes of the present invention, the SLIPS membrane is understood to mean a membrane impregnated with a wetting liquid A. When placed in contact with an immiscible liquid B, the surface of the membrane impregnated with the liquid A is slippery for the liquid B. .

Another subject of the present invention is a method for producing by electro-assisted extrusion a composite membrane according to the invention, comprising the following steps:

A. dissolving, in a solvent medium, a material capable of being dissolved by said solvent medium;

B. injecting said solution at a flow rate Q in a capillary of diameter d _c subjected to an electrical voltage U between 1 kV and 100 kV, preferably between 10 kV and 30 kV, the diameter d _c being 0, 5 mm and 2 mm, and preferably of the order of 1 mm;

C. forming, at the outlet of the capillary, a drop of said solution, said drop being electrically charged so as to cause its destabilization in the form of a so-called TaylortU _' cone; D. ejecting from said cone a liquid cylinder to an electrically conductive target which is electrically grounded;

E. evaporation of said solvent upon ejection of the liquid cylinder, leading to a swirling instability generating solid nanofibers of the material;

F. collection, on a face of said target directed towards said cylinder, solid nanofibers to form a mat of nanofibers forming a fibrous tissue, said target being, prior to step B, coated with an anti adhesive coating ^¬;

said method being characterized in that it further comprises, at the end of step F, an additional step G of wetting the fibrous tissue with a wetting liquid A, so as to form a wet membrane; and

in that it comprises a step of immersing the wet membrane thus obtained in a fluid B immiscible with the wetting liquid A, so as to create an A / B interface between the wetting liquid A and the immiscible fluid B and thus forming the composite membrane according to the invention.

The composite membrane, the fibrous tissue and the nanofibers, which constitute it, the wetting liquid A and the fluid B immiscible with the liquid A (and consequently the A / B interface) are as defined above.

Thus, the A / B interface obtained after immersion of the wet membrane in the fluid B may advantageously be an oil / air interface, an oil / water interface, or a glycerol / air interface, or a water interface with surfactant or detergent / air, for example of the soapy water type. For the purposes of the present invention, the term "material" means the material constituting the nanofibers of the fibrous tissue.

Advantageously, used as release coating a parchment paper, for example parchment paper marketed by Monoprix® under the trade name PAPER COOKING 8 METERS.

Advantageously, the surface of the target which is oriented towards the cylinder is a flat face located at a distance L from the outlet (3a) of the capillary (3) between 5 cm and 15 cm, the capillary being subjected to a tension electrical U between 10 kV and 15 kV.

Preferably, this flat surface of the target is located at a distance L from the outlet (3a) of the capillary (3) which is of the order of 10 cm, the capillary being subjected to an electrical voltage U of the order of 12 kV.

Advantageously, the material constituting the fabric may be a polymeric material selected from the group consisting of the following polymers:

polyacrylonitrile (PAN),

polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP),

Polyvinylpyrrolidone (PVP),

polyvinyl alcohol (PVA),

- polyethylene oxide (PEO), and

polyvinylidene fluoride (PVDF).

In addition to the abovementioned polymeric materials, it may also be advantageously a hybrid polymer-inorganic network material, where the inorganic network may be, for example, SiO ₂ (silica), TiO ₂ (titanium dioxide), Fe ₂ O ₃ (oxide of iron), in the form of amorphous lattice or crystallized nanoparticles.

Other advantages and features of the present invention will result from the description which follows, given by way of nonlimiting example and with reference to the examples and the appended figures:

FIG. 1 represents a schematic side perspective view of an electro-assisted extrusion device for carrying out the method according to the invention;

FIG. 2 schematically represents the formation of the so-called Taylor cone at the outlet of the capillary of the device of FIG. 1 (see part 2a of FIG. 2) and the behavior in compression and extension of the composite membrane according to the invention obtained after the implementation of the method according to the invention using the device of Figure 1 (see part 2b of Figure 2); FIG. 3 shows the use of the composite membrane according to the invention as a smart circuit;

FIG. 4 shows the use of the composite membrane according to the invention as SLIPS membrane.

The technical characteristics common to these figures are each designated by the same reference numeral in the figures concerned.

In Figures 1 and 2, is shown schematically in side view an extrusion apparatus for electro ^¬ assisted implementation of the method according to the invention. The operation of this device is as follows:

a material capable of being dissolved by this solvent medium is introduced into a solvent medium; in the case of a polymer material, a solution 2 of polymer is formed;

this solution 2 is then injected at a flow rate Q into a capillary 3 subjected to an electrical voltage U of between lkV and 100 kV (see FIG. 1 and photograph A of FIG. 2); the formation, at the outlet 3a of the capillary 3, of a drop 4 of solution 2 is observed (see photographs A and B of FIG. 2);

this drop 4 is electrically charged, which causes its destabilization in the form of a cone 5 (see photo B of Figure 2);

then, a liquid cylinder 6 (see photograph B of Figure 2) is ejected continuously from the cone 5, to a conductive target 7 of electricity (visible in Figures 1 and Figures A and B of the figure 2a), which is electrically grounded,

during the ejection of the liquid cylinder 6, the solvent evaporates, which leads to a swirling instability generating solid nanofibers of the material (see photograph A of Figure 2a) at a flow rate consisting of thousands of nanofibers per second ), leading to the formation of a nanofiber mat forming the fibrous fabric 1 (see photo C of Figure 2a);

then, on a face 7a of the target 7 facing the cylinder 6, collecting the fibrous tissue 1, the face 7a of the target 7 being previously covered with a non-stick coating 7b such as parchment paper;

then, the fibrous tissue 1 thus obtained (see photograph D of FIG. 2) is wetted with a wetting liquid A (in this case water) so as to form a wet membrane.

Finally, the wet membrane thus obtained is immersed in a fluid B (in this case air), which is immiscible with the wetting liquid A, so as to create an A / B interface between the wetting liquid (A) and said immiscible fluid (B). We obtain a membrane composite 10 according to the invention (see photograph E of FIG.

Figures 1 and 2 show that the face 7a of the target 7 on which the nanofibers / fibrous tissue is collected is a flat face. But, it is possible to use a target that is not flat, for example in the form of a sphere.

The photograph D of FIG. 2 is a photograph showing the compression behavior of the non-wet fibrous tissue: a sagging / buckling of the tissue in compression is observed.

The photograph E of FIG. 2 shows the compression behavior of the composite membrane 10 according to the invention: it is observed that once wet, the membrane is self-tensing under the action of a capillary tension. This self-tension recalls that of a classic soap film on a frame.

In the photographs D and E of FIG. 2, Xo corresponds to the distance between the two ends of the membrane (Xo = 6 cm for the two images).

The photograph F is a detailed view of a portion of the composite membrane according to the invention, showing an excess of wrinkles inside the liquid film.

Figure 3 shows the use of the composite membrane according to the invention as a smart circuit, and also as a stretchable electronic circuit. In particular, this figure shows that the electrical response of a smart tissue depends on its extension state, while a stretchy electronic circuit refers to an extensible fabric that can carry electronic information in any state of being. extension. For such uses, the composite membrane according to the invention does not undergo fatigue and therefore, information Electronics can be realized through many compression cycles.

Figure 4 shows the use of the composite membrane according to the invention as SLIPS membrane. This figure shows in particular that these membranes are interchangeable, replaceable and adaptable to several surfaces. Thus, a SLIPS membrane according to the invention

PVDF-HFP (tissue) with a silicone oil / air type A / B interface or silicone / water oil can be fixed on any type of surface, it will adapt to its shape to cover it closely. It gives excellent results for self-cleaning surfaces:

- In Figure A, the membrane SLIPS according to the invention is disposed on a self-cleaning surface: a droplet of water falling on the glass does not attach. Thanks to the SLIPS coating, it starts to slip from a low contact angle, of the order of 4 ° (scale bar: 0.5 cm).

- In Figure B, the SLIPS membrane according to the invention is disposed on a hydrophobic surface. Thanks to this treatment

SLIPS, the drop falls on the surface without leaving any traces (scale bar 1 cm)

in FIG. C, the SLIPS membrane according to the invention is disposed on a hemisphere of glass treated with this SLIPS membrane according to the invention; the water droplets slip on the SLIPS coating while they remain trapped on an untreated normal glass.

- It is the same for paper cocktail umbrellas shown in Figure D: the water droplets slip if a SLIPS membrane according to the invention has been placed on the umbrella. List of references

[1] G. Taylor. "Oisintegration of water drops in an electric field." Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, 280 (1382): 383-397, 1964.

[2] M. S. Wilm and M. Mann. "Electrospray and Taylor-Cone Theory, Dole's beam of macromolecules at last." International Journal of Mass Spectrometry and Ion Processes 136.2-3 (1994): 167-180.

Claims

1. Composite membrane (10) comprising a fiber fabric (1) fibrous nanofibers (11), the thickness of the fabric (1) being between 10 nm and 50 μιη, said fabric being impregnated with a wetting liquid (A), said composite membrane (10) being characterized:

in that it (10) is immersed in a second fluid (B) immiscible with the wetting liquid (A), forming an A / B interface between the wetting liquid (A) and said immiscible fluid (B), and

in that it (10) is able to remain tense:

When it is compressed from its rest state, until it reaches dimensions corresponding to 5% of its dimensions at rest, and

2. composite membrane according to claim 1, wherein the thickness of said fibrous tissue (1) is between 500 nm and 30 μιη, and preferably between 1 end and 5 μη.

3. Composite membrane according to claim 2, wherein said nanofibers (11) of the fibrous tissue (1) have a diameter of between 100 nm and 500 nm, and preferably of the order of 200 nm.

The hybrid membrane of any one of claims 1 to 3, wherein said A / B interface is an oil / air interface, an oil / water interface, or a glycerol / air interface, or a water interface with surfactant / air.

5. Use of the membrane as defined in any one of claims 1 to 4 as a member adapted to develop a mechanical force in response to an external stimulus, typically an artificial muscle.

6. Use of the membrane as defined in any one of claims 1 to 4 to form a stretchable electronic circuit (20).

7. Use of the membrane as defined in any one of claims 1 to 5 as a smart circuit.

8. Use of the membrane as defined in any one of claims 1 to 5 as SLIPS membrane.

9. Process for manufacturing a composite membrane as defined in any one of claims 1 to 4, comprising the following steps:

A. dissolving (2), in a solvent medium, a material capable of being dissolved by said solvent medium;

B. injecting said solution (2) at a flow rate Q in a capillary (3) of diameter d _c subjected to an electrical voltage U between IKV and 100 kV, the diameter d _c being between 0.5 mm and 2 mm , and preferably of the order of 1 mm;

C. forming, at the outlet (3a) of said capillary (3), a drop (4) of said solution, said drop (4) being electrically charged so as to destabilize in the form of a cone (5);

D. ejecting, from said cone (5), a liquid cylinder (6) to a conductive target (7) of electricity, which is electrically grounded, said;

E. evaporation of said solvent upon ejection of said liquid cylinder (6), leading to a swirling instability generating solid nanofibers (11) of the material;

F. collects, on a face (7a) of said target (7) facing said cylinder (6), said solid nanofibers (11) to form a nanofiber mat forming a fibrous tissue (1), said target (7) being before step B, coated with a non-stick coating (7b); said method being characterized in that it further comprises, at the end of step F, an additional step G of wetting said fibrous tissue (1) with a wetting liquid

(A) to form a wet membrane, and

in that it comprises a step H of immersion of the wet membrane thus obtained in a fluid (B) immiscible with the wetting liquid (A), so as to create an A / B interface between the wetting liquid (A) and said immiscible fluid (B) and thereby forming the composite membrane

(10) according to the invention.

The method of claim 9, wherein said release coating (7b) is parchment paper.

11. Method according to one of claims 9 and 10, wherein: Said surface face (7a) of the target (7) is a flat face located at a distance L from the outlet (3a) of said capillary (3) which is between 5 cm and 15 cm, and

Said capillary is subjected to an electrical voltage U of between 10 kV and 15 kV.

The method of claim 11, wherein:

Said flat surface (7a) of the target (7) is located at a distance L from the outlet (3a) of said capillary (3) which is of the order of 10 cm, and

Said capillary is subjected to an electrical voltage U of the order of 12 kV.

The method of any one of claims 9 to 12, wherein said material constituting the fabric (1) is a polymeric material selected from the group consisting of the following polymers:

polyacrylonitrile (PAN),

polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)

Polyvinylpyrrolidone (PVP),

polyvinyl alcohol (PVA),

- polyethylene oxide (PEO),

polyvinylidene fluoride (PVDF).

The method according to any one of claims 9 to 12, wherein said material constituting the fabric (1) is a hybrid polymer-inorganic network material, where the inorganic network maybe, for example, SiO ₂ (silica), TiO ₂ (titanium dioxide), Fe ₂ O ₃ (iron oxide), in the form of amorphous lattice or crystallized nanoparticles.

The method of any one of claims 9 to 14, wherein said A / B interface is an interface oil / air, an oil / water interface, or a glycerol / air interface, or a water interface with surfactant / air [DESCRIPTION: soapy water / air].