WO2009153380A1

WO2009153380A1 - Hybrid polymer electrolyte membrane and use thereof

Info

Publication number: WO2009153380A1
Application number: PCT/ES2009/070237
Authority: WO
Inventors: Juan Pablo Esquivel Bojorquez; María de les Neus SABATÉ VIZCARRA; Joaquín SANTANDER VALLEJO; Nuria Torres Herrero; Isabel GRÀCIA TORTADÈS; Carles Cané Ballart; Albert TARANCÓN RUBIO; Mª Cruz ACERO LEAL
Original assignee: Consejo Superior De Investigaciones Científicas
Priority date: 2008-06-19
Filing date: 2009-06-18
Publication date: 2009-12-23
Also published as: ES2336750B1; ES2336750A1

Abstract

The invention relates to a hybrid polymer electrolyte membrane comprising two different polymers arranged such that both form a structure in which one of the polymers (a siloxane polymer) serves as a perforated base so that the other polymer (a polymer electrolyte) can be distributed therein through the channel-like perforations. This membrane can be used for the production of polymer electrolyte devices, such as fuel cells, electrolysers and microbial cells, enabling greater integration of the membrane with the other components, a reduction in the size of the devices and compatibility with stiff materials.

Description

HYBRID POLYMER ELECTROLYTE MEMBRANE AND ITS APPLICATIONS

SECTOR OF THE TECHNIQUE The present invention is part of the scientific-technical area of Ia

Electrochemistry and Microelectronics, within the sector of microsystems manufacturing and energy production.

STATE OF THE TECHNIQUE The growing presence of electromechanical microsystems (MEMS) in a wide variety of applications has caused a progressive demand for power supplies that are efficient and light. These devices integrate mechanical elements, sensors, actuators and electronics in the same substrate through microfabrication processes that start from integrated circuit technology (IC). The fields of application of these devices are very diverse (automotive, food industry, safety, medicine ...), where some of the most commercialized applications are for example the accelerometers used in systems of expulsion of air bags in cars (and lately also in electronic consumer devices), inkjet systems in printers, blood pressure sensors, video projectors, among others. As an ideal solution both from the point of view of functionality and cost, greater compaction of energy sources is required, which implies the compatibility of various manufacturing technologies in order to achieve a fully integrated system, of smaller size and with the highest possible power density.

Micro fuel cells currently deserve special interest due to their potential advantages over other approaches. These advantages include a high energy density, the possibility of working at room temperature, non-polluting emissions and Ia possibility of eliminating the moving parts associated with other types of devices (such as micromotors, microturbines, resonators, etc.), simplifying the manufacturing process and reducing the chances of failure. Given these advantages, fuel cells, studied and developed for several decades for large-scale power generation, are currently being considered and evaluated by the scientific community having obtained excellent results in the field of portable systems power. In this sense, the use of manufacturing processes associated with microelectronic technology is promising given its reproducibility and mass production capacity (batch mode, where all components are completed in a workstation before moving on to the next) . Likewise, the use of microelectronic technology can increase the performance of the fuel cell since the reduction of the components of the microscale battery improves the efficiency of the transport mechanisms.

A fuel cell is basically formed by the following components: an electrolytic membrane, two electrodes (anode and cathode), two current collectors (one associated with the anode and another associated with the cathode) and the fluidic distribution structures of the different reagents and products (hydrogen, methanol, air, water, etc.). Fuel cells can be classified according to the type of electrolyte (electrolytic membrane). Up to five different types are distinguished: polymer electrolyte fuel cells, alkaline fuel cells, phosphoric acid fuel cells, solid oxide fuel cells and molten carbonate fuel cells. Although all of them base their operation on the same electrochemical principle, they differ in the materials of their components, working temperatures, fuel tolerance and operating characteristics [1]. Among all of them, batteries based on polymer electrolyte (PEM) are the ones that have the most advantageous physical-chemical characteristics for their miniaturization PEM batteries use a thin membrane of a single polymeric type as an electrolyte and use hydrogen at the anode and oxygen at the cathode as reagents. In the membrane, the protons derived from the decomposition of the hydrogen molecule are the carriers of the ionic charge, which after crossing it recombines with the oxygen molecules to generate water. This type of batteries is very attractive due to its ability to operate at room temperature and the high density of energy generated. In addition, they allow the possibility of using liquid fuel such as methanol (MeOH) that can increase the available energy density by several orders of magnitude. This type of PEM battery is known as the direct methanol fuel cell (DMFC). The most commonly used material as a proton exchange membrane is the Nafion ^® of the DuPont firm. However, there are other different materials available in the market (Aciplex ^® , Flemion ^® , Dowex ^® , Fumasep ^® , etc.) and various research groups are developing alternatives that improve their efficiency and reduce cost.

Research and development in the field of micro fuel cells has focused its efforts on the improvement of the different elements that make up the device resulting in an optimization of efficiency and power produced. The main advances have been made in obtaining materials that improve ionic conduction and catalysis of the reactions, as well as in the design of fluidic structures that allow optimizing the distribution of reagents along the battery. Although several works have proposed new architectures to miniaturize the components, the integration of all the parts continues to represent a technological challenge due to the incompatibility of materials, being normally necessary the incorporation of additional plates, screws or adhesives to keep all the parts together device (anode, cathode, current collectors and polymeric membrane). This incompatibility lies in the fact that polymeric membranes do not allow direct adhesion with the materials with which the current collectors are manufactured. In addition, the problem is aggravated by the volumetric expansion that the membranes suffer when they become wet during operation. This expansion can create fractures in the rigid structure of the collectors, such as silicon in the case of integrated microdevices, causing the system to fail.

It is for this reason that in all the works existing in the literature, an encapsulation is required that allows the different parts of the stack to be pressed by means of screws, rivets or adhesives. These external auxiliary elements make the device more bulky, hindering its miniaturization, as well as its assembly using simple and automatable processes.

There are multiple examples of developments in micro fuel cells in the literature where this need to introduce the aforementioned auxiliary elements is evident. Most of the micro batteries described use a sandwich system where they place a membrane-electrode assembly, also called MEA for its acronym in English Membrane Electrode Assembly, between two current collectors, which can be of various materials. See Figures 1a and 1b for the development proposed by Shimizu et al. [2], which describes a micropile based on a Nafion ^® membrane assembled between two current collectors of micromachined stainless steel. The final device also consists of two methacrylate covers, used to give consistency to the structure and distribute the fuel and is held together by 4 screws located in the corners. In the literature you can find works with an approach similar to that described [3-5]. Figures 1c and 1d show a microfabricated micropile where the current collectors have been made in a rigid polymer [6]. The device consists of a Nafion ^® membrane as a proton exchange membrane assembled between two current collectors of Polydimethylmethacrylate polymer (PMMA), to which a gold coating or a silver metallic mesh is added to confer conductive properties. Again, the final assembly requires the placement of 4 screws at the ends of the structure. Figures 1e and 1f show the scheme and the photograph of a micropile where the current collectors have been manufactured in silicon [7]. The device consists of a Nafion membrane assembled between two metallic silicon current collectors and attached to a piece of Pyrex ^® that gives them robustness. It can be seen again that the different parts of the micropile have been adjusted through the use of small screws at the ends of the chip. In the literature, various silicon-based devices that use this encapsulation method [8-11] can be found. Finally, Figures 1g and 1 h show a micropile in which the current collectors are made of thin metal layers fixed on a polyamide, whereby the device has the quality of being flexible [13]. In this device it is necessary to incorporate adhesive materials to hold together the different elements of the micropile.

Thus, the present invention has been carried out to solve the problem existing in the development of micro fuel cells relating to the compatibility of materials, therefore the objective of the present invention is to obtain a hybrid polymer electrolyte membrane that can be integrated with components manufactured using microsystems technology, and their use in micro fuel cells and / or electrolysers as a source of energy for microsystems such as sensors or actuators, as well as for portable electronic devices such as personal communication devices or laptops DESCRIPTION OF THE INVENTION Brief Description

An aspect of the invention constitutes a hybrid polymer electrolyte membrane, hereinafter membrane of the invention, which comprises two different polymers spatially arranged such that both constitute a structure where one of the polymers, which is a siloxane polymer, makes perforated base so that the other polymer, which is a polymeric electrolyte, can be distributed in the perforations in the form of channels. A particular aspect of the invention constitutes the membrane of

The invention where the polymer electrolyte is an ion exchange polymer belonging, by way of illustration and without limiting the scope of the invention, to the group of perfluorinated polymers with terminal chains of sulfonic acid and perfluorosulfonic acid. Another particular aspect of the invention constitutes the membrane of

The invention where the siloxane polymer is a polymer that has siloxane groups.

A particular embodiment of the invention constitutes a membrane of the invention where the siloxane polymer is polydimethylsiloxane (PDMS) and the ion exchange polymer is Naphion.

Another particular aspect of the invention constitutes the membrane of the invention in which the perforations must have dimensions between 5 μm and 1000 μm in width and must be distanced in a range between 5 μm and 1000 μm, as well as have a height between 50 and 500 μm.

Another aspect of the invention constitutes the method of manufacturing the hybrid polymer electrolyte membrane, hereinafter the method of the invention, which comprises: i) a first stage to provide a siloxane polymer membrane with a microperforation matrix (Figure 3), ii) the filling of the microperforations of i) with a polymeric electrolyte in the form of a liquid solution (see Figure 4a), and iii) plasma oxidation of the exposed surfaces of siloxane polymer on both sides, (see Figure 5a).

Another particular aspect of the invention constitutes the process of the invention in which the perforation of the siloxane polymer membrane is carried out by means of a process belonging, by way of illustration and without limiting the scope of the invention, to the following group: lithography soft, mechanical drilling, chemical attack or ablation; and especially by soft lithography.

A particular embodiment of the invention constitutes the process of the invention where stage a) is carried out by means of a soft lithography process comprising the following steps: a) Manufacture of a micromachined mold made of silicon, b) Pouring and curing of the siloxane polymer on the mold and c) Extraction of the polymer from the mold.

Another particular aspect of the invention constitutes the process of the invention in which the columns of the mold must be defined in a range between 5 μm and 1000 μm in width, must be distanced in a range between 5 μm and 1000 μm, as well as having a height in a range of 50 μm and 500 μm.

Thus, another aspect is the use of the membrane of the invention comprising an ion exchange polymer in the manufacture of polymer electrolyte devices, such as, for example, fuel cells, electrolysers and microbial batteries.

Another aspect of the invention constitutes the method of manufacturing the hybrid polymer electrolyte membrane where the electrolyte is a proton exchanger for use in fuel micropiles and in which between the stage ii) of filling and iii) of oxidation a stage of incorporating catalysts, if necessary, in the current collectors, in the membrane on both sides to function as a membrane-electrode assembly or in a diffuser layer that can be added between the membrane and the current collectors.

Detailed description

The present invention describes a new hybrid polymer electrolyte membrane, a method of manufacturing said membrane compatible with microelectronic technology and its use in devices based on polymer electrolytes, such as fuel micropiles.

In accordance with the first object of this invention, the inventors have made a hybrid polymer electrolyte membrane consisting of two spatially distinct polymers so that both constitute a structure where one of the polymers is the basis for the other polymer to be distribute in it through perforated channels, which can be joined directly with materials such as silicon, glass or other polymers with the property of absorbing the volumetric expansion of the electrolyte upon hydration, thereby increasing the degree of miniaturization of the devices in Those who join. The inventors have observed that one of the polymers should constitute a polymeric electrolyte and the other should be a siloxane polymer such as polydimethylsiloxane (PDMS) or another of similar physicochemical characteristics. This PDMS polymer is a silicone elastomer, viscoelastic and biocompatible that can be prepared from the mixture of a prepolymer and a curing agent. Despite having hydrophobic properties, its surface can be functionalized by oxygen plasma, becoming hydrophilic, which allows it to form covalent bonds by contacting it with materials such as silicon, glass or other polymers. The functionalization confers on the membrane the property of being able to join said materials. When the membrane of Ia This invention is incorporated in devices based on polymer electrolytes, this ability to establish covalent bonds has the advantage, compared to the systems described in the state of the art, which results in a higher level of integration of the membrane with the rest of the components , and therefore, allows a reduction in the size of the devices by removing auxiliary elements such as external plates and screws.

Specifically, the present invention involves multiple advantages with respect to the state of the art, among which are: - higher level of integration of the membrane with the rest of the components, which represents a reduction in the size of the devices when eliminating auxiliary elements such as external plates and screws;

- compatibility with rigid materials such as silicon since the membrane supports the volumetric expansion of the proton exchange polymer when hydrated; simple manufacturing process that can be developed on a large scale, with a reduced cost since the membrane material is low cost and easy to machine and the amount of ionic conductive polymer needed is smaller;

- Possibility of incorporating alternative catalysts, such as enzymes or biocatalysts, to obtain a complete low-cost micro stack; and the possibility of obtaining a micropile with flexible characteristics if the current collectors are made of flexible material.

Therefore, one aspect of the invention constitutes a hybrid polymer electrolyte membrane, hereinafter membrane of the invention, which comprises two different polymers spatially arranged such that both constitute a structure where one of the polymers, which is a polymer of siloxane, it makes a perforated base so that the other polymer, which is a polymeric electrolyte, can be distributed in the perforations in the form of channels.

A particular aspect of the invention constitutes the membrane of

The invention where the polymer electrolyte is an ion exchange polymer belonging, by way of illustration and without limiting the scope of the invention, to the group of perfluorinated polymers with terminal chains of sulfonic acid and perfluorosulfonic acid.

Another particular aspect of the invention constitutes the membrane of the invention where the siloxane polymer is a polymer having siloxane groups.

A particular embodiment of the invention constitutes a membrane of the invention where the siloxane polymer is polydimethylsiloxane (PDMS) and the ion exchange polymer is Naphion. Another particular aspect of the invention constitutes the membrane of

The invention in which the perforations must have dimensions between 5 μm and 1000 μm in width and must be spaced in a range between 5 μm and 1000 μm, as well as have a height between 50 and 500 μm.

To achieve the microperforation matrix, procedures such as soft lithography, mechanical perforation, chemical attack or ablation can be used. By way of illustration, the soft lithography process It consists in the transfer of motifs to a polymer from a mold. For this application it is based on a mold that can be microfabricated in silicon. Sets of square or round base columns are defined in this mold, although other shapes can also be selected. The inventors have observed that the dimensions of the columns must be defined in a range between 5 μm and 1000 μm in width with distances between the columns within the same micrometric range and height of up to 500 μm, in order to optimize the area ratio of the polymers and maintain the ionic conductivity of the electrolyte polymer at acceptable levels, since exceeding this height the membrane acquires thickness dimensions such that its ionic conduction capacity is seriously affected. Likewise, the wider the columns, the greater the amount of electrolyte polymer can be introduced, which will favor a greater ionic conduction capacity per unit area. Specifically, to obtain the perforated polymer membrane from side to side, siloxane polymer is poured over the micromachining mold, which flows between the columns by capillarity. The amount of siloxane polymer poured into the mold is controlled so that it does not exceed the height of the columns. Polymer cure time is performed based on the manufacturer's specifications, typically varying in a range of 24 hours for room temperature and 15 minutes for a temperature of 15O ⁰ C for PDMS. Once the polymer has cured, it is extracted from the mold, so that the membrane is obtained with perforations of the desired size of the columns of the mold. Another particular aspect of the invention constitutes the process of the invention in which the perforation of the siloxane polymer membrane is carried out by means of a process belonging, by way of illustration and without limiting the scope of the invention, to the following group: lithography soft, mechanical drilling, chemical attack or ablation; and especially by soft lithography. A particular embodiment of the invention constitutes the process of the invention where stage a) is carried out by means of a soft lithography process comprising the following steps: a) Manufacture of a micromachined mold made of silicon, b) Pouring and curing of the siloxane polymer on the mold and c) Extraction of the polymer from the mold.

With respect to the second stage of the manufacturing method of the present invention, the inventors have observed that any polymer electrolyte can be used, the DuPont Nafion ^® polymer being one of the most used due to its wide commercial availability, which is commercialized both in membrane form as in solution at different concentrations.

The third stage of the manufacturing method of the present invention after filling, consists in the plasma oxidation of the exposed surfaces of siloxane polymer on both sides, so that said surfaces can adhere by means of chemical bonds to other elements such as example, electrodes and / or current collectors.

According to another aspect of the present invention, the above described hybrid membrane can be incorporated or manufactured devices based on polymer electrolytes, such as, for example, the manufacture of fuel micropiles, electrolysers, microbial batteries, etc.

In the case of using the membrane of the invention to manufacture fuel micropiles, it is necessary that the polymer electrolyte of the hybrid polymer electrolyte membrane be an ion exchange polymer. Thus, another aspect is the use of the membrane of the invention comprising an ion exchange polymer in the manufacture of polymer electrolyte devices, such as, for example, fuel cells, electrolysers and microbial batteries. For the manufacture of a fuel micropile, the electrodes and current collectors must be coupled to the hybrid electrolyte membrane. The structures of the electrodes that carry the reagents in the fuel cell and collect the produced electrons can be manufactured in a variety of materials compatible with microsystem technologies such as silicon, glass, rigid or flexible polymers. Therefore, another particular aspect of the invention constitutes the use of an electrode made of flexible polymers to obtain a fuel micropile with flexible characteristics.

The membrane of the invention can be used to manufacture any type of polymeric electrolyte micro fuel cell. Most batteries need catalysts to be able to break fuel molecules. Depending on the principle of operation of the battery and the fuel used, said catalysts can be metals such as Pt, Ru, Pd, Sn or combinations thereof, as well as alternative materials such as ceramic oxides, enzymes or biocatalysts. However, there are also some batteries that do not need catalysts, such as microbial fuel cells.

In the case of fuel cells in which the use of catalysts is necessary, these can be incorporated into: 1. the current collectors

2. membrane surfaces

3. a diffuser layer

If the catalysts are incorporated in the current collectors the assembly of the device would be illustrated according to Figure 5 If the catalysts are incorporated in the surfaces of the perforated membrane of siloxane polymer and with holes filled with Polymeric electrolyte described in this invention, it can be used independently of the current collectors to form a membrane-electrode assembly, also called MEA by its acronym in English Membrane Electrode Assembly, for application in micro fuel cells (see Figure 4b). The MEA is a structure composed of a layer of polymer electrolyte between two electrodes. The typical method for the manufacture of MEAs is to make a catalytic ink from a mixture of catalyst, ionomer in solution and carbon particles. Then the electrolyte is coated on both sides by a layer of this catalytic ink to obtain the MEA.

A diffuser layer, usually carbon cloth or paper, can also be added between the membrane and the current collectors to incorporate the catalysts in addition to improving the distribution of the reagents along the surface of the membrane. For the integration of the components, an oxygen plasma is applied on both sides of the siloxane polymer membrane (see Figure 5), so that the chemical bonds of their surfaces are broken, causing the material to acquire hydrophilic properties and allow Ia formation of covalent bonds with the surface of other materials such as silicon, glass or other polymer. In this way the current collectors can be adhered on both sides of the membrane to form a compact micro fuel cell.

Thus, another aspect of the invention constitutes the method of manufacturing the hybrid polymer electrolyte membrane where the electrolyte is a proton exchanger for use in fuel micropiles and in which between the stage ii) of filling and iii) of oxidation is includes a stage of incorporation of catalysts, if necessary, in the current collectors, in the membrane on both sides to function as a membrane-electrode assembly or in a diffuser layer that can be added between the membrane and the current collectors . In this way, the plasma oxidation of the polymer membrane surfaces (step iii)) allows the adhesion by means of chemical bonds to the current collectors and that the membrane is integrated with the necessary components to form the fuel micropile by means of the compression of the membrane between the current collectors.

DESCRIPTION OF THE FIGURES

Figure 1.- Examples of micropiles with different architectures. Figure 2.- Diagram of polymeric membrane with perforation matrix. Figure 3.- Polymer membrane manufacturing process with the soft lithography method, (a) micromachining mold with columns, (b) pouring and curing of polymer onto mold, (c) - (e) polymer extraction. Figure 4.- (a) Polymeric membrane with perforations filled with ion exchange polymer, (b) membrane-electrode assembly.

Figure 5.- Example of assembling a hybrid membrane to current collectors for the manufacture of a micro fuel cell, (a) An oxygen plasma is applied on both sides of the hybrid membrane, (b) the membrane is pressed between Current collectors, (c) the micropile is formed.

EXAMPLES OF EMBODIMENT OF THE INVENTION

Example 1.- Manufacture of the hybrid polymer electrolyte membrane and silicon current collectors A PDMS membrane with a microperforation matrix, of

250 μm wide with 300 μm high, separated from each other with a distance of 250 μm, was manufactured by the soft lithography method using as a mold a micromachined silicon wafer, as shown in Figure 3. The PDMS solution is prepared by mixing the prepolymer and the curing agent in the proportion marked in the manufacturer's specifications. For a membrane of dimensions of 10 x 10 mm between 20 and 30 microliters of PDMS were added to the mold until a membrane height of 300 μm was achieved. The mold with PDMS was placed in an oven to cure the polymer at a temperature of 15O ⁰ C for a time of 15 minutes. After this time the mold was removed with PDMS from the oven and the PDMS membrane was removed from the mold. Next, the perforations of the PDMS membrane were filled with 10 microliters of Nafion ^® in solution form (Figure 4a), which solidified at room temperature in 24 hours.

Subsequently, the surfaces of the hybrid membrane were oxidized by means of plasma for 30 seconds using a Hand-Held Laboratory Corona Treater model BD-20AC model of the Electro-Technic Products brand, to then be assembled between two current collectors based on chips Micromachining of silicon with micro channels to obtain the fuel micropile, as seen in Figure 5. The chips have the double function of distributing the reagents in the battery and collecting the released electrons.

Example 2.- Fuel micropila with hybrid polymer electrolyte membrane and glass current collectors A micro fuel cell is manufactured using the same method described in Example 1, except that the current collecting chips are micromachined on a glass substrate .

Example 3.- Fuel micropila with hybrid polymer electrolyte membrane and rigid polymer current collectors

A micro fuel cell is manufactured using the same method described in Example 1, except that the current collecting chips are made on a polymeric polymethylmethacrylate (PMMA) substrate.

Example 4.- Fuel micropila with hybrid polymer electrolyte membrane and flexible polymer current collectors A micro fuel cell is manufactured with the same method described in Example 1, except that the chips are formed in PDMS which has been provided with a metallic layer by sputtering to allow current conduction. The micro fuel cell obtained by this method has flexible characteristics.

Example 5.- Direct methanol fuel micropile with hybrid polymer electrolyte membrane and silicon current collectors

A PDMS membrane with a microperforation matrix is manufactured by the soft lithography method using as a mold a micromachined silicon wafer, as shown in Figure 3. The PDMS solution is prepared by mixing the prepolymer and the curing agent in the proportion marked in the manufacturer's specifications. For a membrane measuring 10 x 10 mm, between 20 and 30 microliters of PDMS are added to the mold until a membrane thickness of 300 μm is achieved. The PDMS mold is introduced into an oven for curing of the polymer at a temperature of 150 ⁰ C for 15 min. After this time, the mold with PDMS is removed from the oven and the PDMS membrane is removed from the mold. Next, the perforations of the PDMS membrane are filled with 10 microliters of Nafion ^® in solution form (Figure 4a), which solidifies at room temperature in 24 hours. Catalytic inks are produced from a mixture of catalyst, ionomer in solution (Nafion diluted in 10% water) and carbon particles. The mixture is stirred for 24 hours with a magnetic stirrer. One side of the electrolyte of the membrane is covered with catalytic ink composed of Pt / C (at 20% by weight, of the E-TEK brand) as a catalyst for the cathodic reaction, the other side of the electrolyte of the membrane is covered with a Pt-Ru / C composite ink (at 20% by weight, of the brand E-TEK) for the reaction at the anode (Figure 4b). In this way an electrode-membrane assembly capable of being used in a direct micro methanol fuel cell is obtained.

Subsequently, the exposed surfaces of the membrane PDMS were oxidized by means of plasma for 30 seconds using a Hand-Held Laboratory Corona Treater model BD- system.

20AC of the Electro-Technic Products brand, to then be assembled between two current collectors based on micromachined silicon chips with micro channels to obtain the direct micro methanol fuel cell, as seen in Figure 5. The chips have the double function of distributing the reagents in the battery and collecting the released electrons.

Example 6.- Direct methanol fuel micropile of alternative catalysts with hybrid polymer electrolyte membrane and silicon current collectors

A micro fuel cell is manufactured using the same method described in Example 5, except that the catalysts used consist of enzymatic compounds. The micro fuel cell obtained by this method considerably reduces the cost of the device by dispensing with expensive metal catalysts such as Pt.

Example 7.- Direct methanol fuel micropile of alternative catalysts with hybrid polymer electrolyte membrane manufactured by mechanical drilling and silicon current collectors

A micro fuel cell is manufactured with the same method described in Example 6, except that the manufacturing process of the perforated PDMS membrane is based on an automatic mechanical drilling process. This method consists in the perforation of homogeneous membranes of PDMS cured by means of pressure indentation.

The micro fuel cell obtained by this method allows to reduce the manufacturing costs of the device because this production process of the hybrid membranes can be easily adapted to mass production.

References

[I] R. O'Hayre, S.W. Cha, W. CoIeIIa and F. B. Prinz, Fuel CeII Fundamentalis, Ed. John Wiley & Sons, New York, USA, 2006

[2] T. Shimizu et al., Journal of Power Sources 137 (2004) 277-283

[3] S. K. Kamarudin et al., Journal of Power Sources 163 (2007) 743-754

[4] Y.H. Pan, Journal of Power Sources 161 (2006) 282-289

[5] J. G. Liu et al., Electrochemistry Communications 7 (2005) 288-294 [6] S. H. Chan, NT. Nguyen, Z. Xia and Z. Wu, J. Micromech. Microeng 15 (2005) 231-236

[7] J.-Y. Kim et al., Journal of Power Sources 161 (2006) 432-436 [8] SJ. Lee, A. Chang-Chien, S.W. Cha, R. O'Hayre, Y.l. Park, Y. Saito, F. B. Prinz, Journal of Power Sources 112 (2002) 410-418 [9] J. Yu, P. Cheng, Z. Ma, B. Yi, Journal of Power Sources 124 (2003) 40-46

[10] K. Shah, W.C. Shin, R.S. Besser, Sens. Actuators B 97 (2004) 157-167

[I I] J. Yeom, R.S. Jayashree, C. Rastogi, M.A. Shannon, P.J.A. Kenis, Journal of Power Sources 160 (2006) 1058-1064.

[12] G.Q. Lu et al., Electrochimica Acta 49 (2004) 821-828

[13] R. Hahn, S. Wagner, A. Schmitz, H. Reichl, Journal of Power Sources

131 (2004) 73-78

Claims

1.- Hybrid polymer electrolyte membrane characterized in that it comprises two spatially different polymers arranged in such a way that both constitute a structure where one of the polymers, which is a siloxane polymer, acts as a perforated base so that the other polymer, which is a polymer electrolyte, can be distributed in the perforations in the form of channels (Figure 2).

2. Membrane according to claim 1 characterized in that the polymer electrolyte is an ion exchange polymer belonging to the group of perfluorinated polymers with terminal chains of sulfonic acid and perfluorosulfonic acid.

3. Membrane according to claim 1 characterized in that the siloxane polymer is a polymer having siloxane groups.

4. Membrane according to claim 1 characterized in that the siloxane polymer is polydimethylsiloxane (PDMS) and the ion exchange polymer is Nafion.

5. Membrane according to claim 1 characterized in that the perforations have dimensions between 5 μm and 1000 μm wide and are spaced in a range between 5 μm and 1000 μm, as well as having a height between 50 and 500 μm.

6. Method of manufacturing the membrane according to claims 1 to 5, characterized in that it comprises: i) a first stage to provide a siloxane polymer membrane with a microperforation matrix (Figure 3), ii) the filling of the microperforations of i) with a polymeric electrolyte in the form of a liquid state solution (Figure 4a), and iii) plasma oxidation of the exposed surfaces of siloxane polymer on both sides. (Figure 5a).

7. Method according to claim 6, characterized in that the perforation of the siloxane polymer membrane of i) is carried out by means of a procedure belonging to the following group: soft lithography, mechanical perforation, chemical attack or ablation, and preferably by soft lithography.

8. Method according to claim 6, characterized in that step a) is carried out by means of a soft lithography process comprising the following steps: a) Manufacture of a micromachining mold made of silicon, b) Pouring and curing of the siloxane polymer on the mold and c) Extraction of the polymer from the mold.

9. Method according to claim 6 characterized in that the columns / perforations of the mold are defined in a range between 5 μm and 1000 μm wide, are spaced in a range between 5 μm and 1000 μm, as well as have a height in a range of 50 μm and 500 μm.

10. Method according to claim 6 characterized in that the electrolyte is a proton exchanger, the membrane is to be used in a fuel micropile and in which between the stage ii) of filling and iii) of oxidation a step of including incorporation of catalysts in the membrane on both sides to function as a membrane-electrode assembly or in a diffuser layer that can be added between the membrane and the current collectors.

11. Use of the membrane according to claims 1 to 5 in the manufacture of polymer electrolyte devices, such as, for example, fuel cells, electrolysers and microbial batteries.

12. Use of the membrane according to claim 11 characterized in that it comprises an ion exchange polymer.