Composite material

Abstract

A fibrous composite material comprising a first electrospun polymer fibre population; and a second electrospun polymer fibre population dispersed within at least part of the first electrospun polymer

Description

Field of the invention The invention relates to a fibrous composite material comprising two populations of electrospun polymer fibre and use thereof in medicine, filters, and apparel. In particular, the invention relates to a fibrous composite material comprising a hydrophilic electrospun polymer fibre population and a second electrospun polymer fibre population and its use in stents, wound dressings, fluid filters, and apparel. Background to the invention Fibrous materials made using electrospun polymer fibres have been explored for use in several different applications, from medical uses to filtration techniques. For example, porous electrospun scaffolds have been considered for use as a replacement to amniotic membranes for ophthalmological purposes (see e.g. WO2022023745A1). As a further example, porous electrospun materials have been used in air filtration systems (see e.g. WO2016094906A1). Materials made of non-woven fibre networks created by the electrospinning process have several advantages over other material manufacture methods. Electrospinning is highly-scalable, there is a wide selection of readily available polymers, and the material is highly amenable to regulatory requirements in terms of preparation in a controlled environment and sterilization of the final material. Compared to the use of natural fibres for such devices, the benefits of electrospun polymers are well known in terms of material properties, scalability of manufacture, and supply of raw materials. Previous attempts have been made to further functionalize electrospun materials to make them more suited to particular use cases by providing mixed fiber populations. The focus in the art has been on improving the physical characteristics of the material structure, offering co-spun polymers with mixed degradation rates or otherwise varying the size of fibres to offer unique surface topography in the material. US20170326270A1 demonstrates an approach where two different polymers were used to electrospin two fiber populations for use as a synthetic dura mater replacement. The first fiber population is made of poly(lactic-co-glycolic acid) and the second polydioxanone. Such combinations are said to provide optimal strength, handling, and suturability. US20200149198A1 demonstrates the use of a mixed fiber population wherein the degradation rate of the first and second electrospun fibres differs. US11246959B2 describes using a polymer mixture to spin a single population of fibres, and further describes post-processing said fibres to add functionality. Gu et al., (2011) demonstrates mixing PVA and polyurethane fibers in a blended material. The paper focuses on the optimal conditions for co-spinning these materials but mentions that the blend has optimal physical characteristics compared to mats made of a single polymer. Hussein et al., (2022) similarly discloses a blend of PVA and Pll in combination with therapeutic compounds for managing diabetic wounds. Wlodarczyk et al. (2022) discloses electrospun materials comprising a mixture of fibre populations containing varying hydrophobic and hydrophilic polycarbonate urethanes) with biodegradable poly(D,L-lactide-co-glycolide) in order to assess degradation and mechanical properties thereof. WO2015116917A1 discloses absorbable materials combining two fiber populations to produce fibers having improved thermal stability. US10208331B2 discloses fibrous filters for bioparticle and aerosol collection. US7592277B2 discloses electrospun fibrous mats having two small diameter fibre populations. US11739452B2 discloses a thermally stable electrospun barrier comprisingtwo independent fiber populations - a major fiber population comprising at least one thermally unstable fiber species, and a minor fiber population comprising at least one thermally stable fiber species. US10632228B2 discloses a resorbable non-woven graft material consisting of a single layer comprising a first electrospun non-woven fiber composition consisting of poly (glycolic acid) and a second electrospun non-woven fiber composition comprising poly(lactide-co-caprolactone), in which the compositions are commingled. US2014 / 0205647A1 discloses an artificial dura mater which includes electrospun layers, at least one of which is a hydrophobic electrospun layer. Above the hydrophobic electropsun layer, there may be at least one ehydrophilic electrospun layer. A transition layer can be included between the hydrophobic and hydrophilic electrospun layers. However, the hydrophobic layer is not dispersed within at least part of the hydrophilic layer. What is missing in the field so far are materials which are structured in such a way as to preserve the beneficial mechanical properties whilst maintaining chemical characteristics of the electrospun polymer for optimal function of the material in any given use case. In addition, whilst the blending of hydrophilic or hydrophobic polymers into a single electrospun fibre population has been explored, what is needed are materials which expand the toolbox of what is possible to provide advanced materials with new functionality as a result of novel structure. Applicants have surprisingly found that combinations of water insoluble hydrophilic electrospun polymer fibres with other water insoluble but hydrophobic electrospun polymer fibres having similar fibre diameters confer several advantages to the properties of the cospun material. Surpisingly we have found that the combination of co-spun materials is not just the sum of its constituent parts but shows unexpected properties. Summary of the invention In accordance with a first aspect of the invention, there is provided a fibrous composite material comprising: a first electrospun polymer fibre population; and a second electrospun polymer fibre population dispersed within at least part of the first electrospun polymer fibre population, wherein the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 1:5 to 9:5; wherein the first electrospun polymer fibre population comprises a hydrophilic polyurethane; wherein the second electrospun polymer fibre population comprises a synthetic, non-degradable, hydrophobic polymer; and wherein the first electrospun polymer fibre population and the second electrospun polymer fibre population are water insoluble. In accordance with a second aspect of the invention there is provided the fibrous composite material of the first aspect of the invention for use in therapy. In accordance with a third aspect of the invention there is provided a method for producing a fibrous composite material as defined in the first aspect of the invention, comprising electrospinning a first precursor polymer solution from a first source; and electrospinning a second precursor polymer solution from a second source, onto a collector to form the fibrous composite material which comprises a second electrospun polymer fibre population dispersed within at least part of a first electrospun polymer fibre population. Further aspects of the invention provide objects, such as stents, comprising or coated with the fibrous composite material according to the first aspect of the invention. A final aspect of the invention provides a method for producing a fibrous composite material, comprising the steps of: providing an electrospinning device comprising a collector, a first needle, and a second needle, wherein the collector has a rotating mandrel, the first needle is in fluid communication with a first reservoir containing a first precursor polymer solution, and the second needle is in fluid communication with a second reservoir containing a second precursor polymer solution, wherein the rotating mandrel is oppositely charged as compared to the first needle and the second needle, wherein the first needle is disposed on an opposite side of the rotating mandrel to the second needle in the rotational axis direction, wherein the first and second needle are each 5 to 50 cm away from the rotating mandrel; wherein the mandrel is provided with a voltage of -60 to +60 kV; providing a gas shield around the first needle prior to delivering, at a constant feed rate between 0.1 and 100 ml / hr, the first precursor polymer solution at an accelerating voltage of -60 to +60 kV; delivering, at a constant feed rate between 0.1 and 100 ml / hr, the second precursor polymer solution at an accelerating voltage in the range -60 to +60 kV; de-activating the gas shield around the first needle during delivery of the first precursor polymer solution to the rotating mandrel. Brief description of the drawings Figure 1 shows exemplary electrospun materials; Figure 2 shows how the water contact angle measurement is taken; Figure 3 is an SEM image of co-spun Hydromed™ and Chronoflex® (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 4 shows the average Young’s modulus, ultimate tensile strength, and break strain (left to right) of electrospun Hydromed™, Chronoflex® and co-spun material when dry (top) and wet (bottom); Figure 5 is an image of a straight stent covered with co-spun PET and Hydromed™ in the process of being wetted; Figure 6 is an SEM image of co-spun Hydromed™ and PET from the stent covering (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 7 shows an image of combination hydrophilic TPU and hydrophobic PET sheet (Hydrothane™ / PET), indicating that the fibre populations are within 50% of each other; Figure 8 shows the mechanical properties of the PET / Hydrothane™ combination from figure 7; Figure 9 is an SEM image of co-spun Hydromed™ and polycarbonate-based silicone elastomer (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 10 shows the mechanical testing data of the sample from figure 9 - average Young’s modulus, ultimate tensile strength, break strain, and ultimate force (left to right) of electrospun Hydromed™, polycarbonate-based silicone polyurethane (PC S Pll) and cospun material with an average fibre diameter of 2-3 pm when dry (top) and wet (bottom); Figure 11 is an SEM image of co-spun Hydromed™ and polycarbonate-based silicone elastomer (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 12 shows the mechanical testing data of the sample from figure 11 - average Young’s modulus, ultimate tensile strength, and break strain (left to right) of electrospun Hydromed™, polycarbonate-based silicone polyurethane (PC S Pll) and co-spun material with an average fibre diameter of 4-5 urn when dry (top) and wet (bottom); Figure 13 is an SEM image of co-spun Hydrothane™ and polycarbonate-based silicone elastomer (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 14 shows the mechanical testing data of the sample from figure 13 - average Young’s modulus, ultimate tensile strength, and break strain (left to right) of electrospun Hydrothane™, polycarbonate-based silicone polyurethane (PC S Pll) and co-spun material with an average fibre diameter of 2-3 urn when dry (top) and wet (bottom); Figure 15 is an SEM image of co-spun Hydrothane™ and polycarbonate-based silicone elastomer (left) and a histogram showing the distribution of fibre diameters in the material (right); Figure 16 shows the transparency of the combination of hydrophobic TPU / hydrophilic TPU (Hydrothane™ / Carbosil® 2-3 pm); Figure 17 shows the transparency of the combination of hydrophobic TPU / hydrophilic TPU (Hydrothane™ / Carbosil® 2-3 pm); and Figure 18 shows water drop experiments: 10 pl of brilliant blue dyed water was pipetted onto polycarbonate-based silicone elastomer (left), co-spun TPU containing Hydrothane™ as the hydrophilic component (middle), and co-spun TPU containing Hydromed™ as the hydrophilic component (right). Detailed description of the invention Referring now to the present invention, the fibrous composite material comprises a first electrospun fibre population and a second electrospun fibre population. The fibrous composite material is a sheet-like material which is produced by electrospinning. The electrospinning technique produces a network of fibres which is more uniform compared to other methods known in the art. The second electrospun fibre population is dispersed within at least part of the first electrospun polymer fibre population. The electrospun nature of the fibres means that the first electrospun fibre population and the second electrospun fibre populations produce a non-woven network of fibres. In other words, the first and second electrospun polymer fibre populations comprise fibres which are randomly or semi-randomly orientated or at least have low alignment. As such, by having the second disposed within at least part of the first, the fibres of each fibre population are held together without any kind of bonding such as stitching, knitting, weaving or melting. The second electrospun fibre population is dispersed within at least part of the first electrospun fibre population but does not have to be dispersed throughout the entirety of it. Exemplary electrospun materials are shown in Figure 1, with black representing the first electrospun polymer fibre population, white representing the second electrospun polymer fibre population, and grey representing a mix of the two. The length (L) and thickness (T) are labeled for reference and apply to each figure, and the boundaries of the material are indicated with a dashed line. Figure 1A shows an exemplary embodiment where a top face 102 is made of the first electrospun polymer fibre population and the bottom face 103 is made of the second electrospun polymer fibre population, with a mixture therebetween. In some embodiments, the second electrospun fibre population is dispersed within half of the thickness of the fibrous composite material. An example is shown in Figure 1B, where the upper half of the material is made of the first electrospun polymer fibre population and then the lower half contains a blend of the first and second electrospun polymer fibre populations terminating at the lower face which is made of the second electrospun polymer fibre population. This means that in one half there is a mixture of the first electrospun polymer fibre population and the second electrospun polymer fibre population which are intertwined, and in the other half there is only fibres from the first electrospun polymer fibre population. In some embodiments, the second electrospun polymer fibre population is dispersed within about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% of the total volume as circumscribed by the first electrospun polymer fibre population. “Dispersed within” does not mean the internal volume of each fibre, but refers to the total three dimensional volume as defined by the whole first population of fibres. In other words the second population of fibres will be dispersed within the porous structure defined by the first population of electrospun fibres. In some embodiments, the second electrospun polymer fibre population is dispersed throughout the first electrospun polymer fibre population. In other words, the fibrous composite material consists of a mixture of the first electrospun polymer fibre population and the second electrospun polymer fibre population. This is shown in Figure 1C, wherein the material comprises a mixture of the first electrospun polymer fibre population and the second electrospun polymer fibre population throughout. Finally, in some embodiments, the upper and lower face may be made of the second electrospun polymer fibre population with the internal structure being a mixture of the first and second electrospun polymer fibre populations, optionally comprising a portion solely made of the first electrospun polymer fibre population. Such an arrangement is shown in Figure 1D, where the upper and lower faces are made of the second electrospun polymer fibre populations, with a blend of the first and second electrospun polymer fibre populations from each end towards a center portion of the material which comprises only the first electrospun polymer fibre population. In the alternative, the position of the first and second electrospun polymer fibre populations may be swapped. Each electrospun fibre population will have an average fibre diameter through its length. Average fibre diameter can be measured using analysis of multiple images obtained using scanning electron microscopy (SEM), which enable a mean average fibre diameter to be obtained. A suitable method for doing this is explained in the Examples. Briefly, fibre diameter and scaffold morphology characterisation can be performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. In the present invention, the first electrospun polymer fibre population has an average fibre diameter within 80% of the average fibre diameter of the second electrospun polymer fibre population. By this, we mean that the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 0.2:1 to 1.8:1. This ratio can alternatively be expressed as 1:5 to 9:5. Alternatively, the first electrospun polymer fibre population has an average fibre diameter within 70% or 60% of the average fibre diameter of the second electrospun polymer fibre population. By this, we mean that ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the ranges 0.3:1 to 1.7:1 (this ratio can alternatively be expressed as 3:10 to 17:10); 0.4:1 to 1.6:1 (this ratio can alternatively be expressed as 2:5 to 8:5). In the present invention, it is preferred that the first electrospun polymer fibre population has an average fibre diameter within 50% of the average fibre diameter of the second electrospun polymer fibre population. By this, we mean that ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 0.5:1 to 1.5:1. This ratio can alternatively be expressed as 1:2 to 3:2. In some embodiments, the average fibre diameter of the first electrospun polymer fibre population is within 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% or 1% of the average fibre diameter of the second electrospun polymer fibre population. Accordingly the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population may be in the range 0.45:1 to 1.45:1, 0.40:1 to 1.40:1, 0.35:1 to 1.35:1, 0.30:1 to 1.30:1, 0.25:1 to 1.25:1, 0.20:1 to 1.20:1, 0.15:1 to 1.15:1, 0.10:1 to 1.10:1, 0.05:1 to 1.05:1 or 0.01:1 to 1.01:1. In some embodiments, the average fibre diameter is the same in both electrospun polymer fibre populations. The two populations of fibres having a similar average fibre diameter means that the structure of the material is maintained in terms of porosity and average pore diameter for any given fibre diameter. The relationship between these properties is explained in, for example, Greiner and Weddorff, Angew. Chern. Int. Ed. 2007, 46, 5670-5703. This is advantageous for the typical use of electrospun materials in biological applications which range from open scaffolds that allow for cell ingrowth and integration to barrier layers that either guide surface migration of cells or act as an anti-adhesion material. The first electrospun polymer fibre population comprises or is made of a hydrophilic polymer. In particular, in the invention it is made from a hydrophilic polyurethane polymer and preferably, a thermoplastic hydrophilic polyurethane polymer. This means that a hydrophilic polyurethane polymer is provided as a solution and then once the polymer is electrospun into a fibre population, said fibre population will itself have the hydrophilic property of the polymer. However in another disclosure the first electrospun polymer fibre population is not made from polyurethane. There is accordingly provided a fibrous composite material comprising: a first electrospun polymer fibre population; and a second electrospun polymer fibre population dispersed within at least part of the first electrospun polymer fibre population, wherein the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 1:5 to 9:5; wherein the second electrospun polymer fibre population comprises a synthetic, non-degradable, hydrophobic polymer; and wherein the first electrospun polymer fibre population and the second electrospun polymer fibre population are water insoluble. The second electrospun polymer fibre population comprises a synthetic, non-degradable, hydrophobic polymer. Preferably, the second electrospun polymer fibre population is made of or comprises a hydrophobic polymer selected from polyurethane, Polyethylene terephthalate, Polyvinylidene fluoride, Polyacrylonitrile, Polycarbonate, Poly(methyl methacrylate), Polyvinyl chloride, Acrylonitrile butadiene styrene, Polystyrene, Polysulfone, Polyimide, Polyamide, Polyvinyl butyral, or Poly(Glycerol Sebacate). The first electrospun polymer fibre population and the second electrospun polymer fibre population are water insoluble. This means that when used for any purpose where contact with water or an aqueous solution is likely, the fibrous composite material will not dissolve over time due to the presence of water molecules. This is essential for maintaining the structure of the material for several use cases such as when used in surgical procedures or as part of filtration systems where contact with aqueous solutions is likely. If either fibre population was water soluble, the structure would dissolve and the macrostructure of the material would degrade. The term “water insoluble” is well understood in the art and is outlined for instance in textbook Physical Pharmacy (3d ed. 1983) by Martin et al. The invention according to the first aspect allows for a material which retains the strength and durability of one polymer, with the wettability and hydrophilic interactions of a hydrophobic polymer. Applicants have surprisingly found, as demonstrated in the examples, that the combination of features of the claimed invention produce a fibrous composite material with mechanical properties which exceed what would be expected. For instance, we have found that the composite material can be stiffer than both of its constituent parts when dry. This is especially beneficial for the processing of the composite, as it is less likely than the pure polymers to be accidentally permanently deformed during processing. Advantageously, the material may have low stiffness when wet, in line with human tissue, which makes it suitable for use in soft tissue repair. The material may also have benefits in ophthalmological applications due to its transparency (a benefit when it is important to be able to see underneath the implant). There may also be aesthetic benefits - the material will not be immediately visible on a patient compared to a hydrophobic material. There are several use cases of such a material as will be described below. In some embodiments, the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population is between 90:10 to 10:90 by weight. In some embodiments, the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population is 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60, 35:65, 30:70, 25:75, 20:80, 15:85 by weight. A ratio of about 50:50 is particularly advantageous because this ratio provides for optimal characteristics from both the hydrophobic and hydrophilic polymers. For example, it may soak up water due to the hydrophilic fibre population whilst maintaining the structural strength, workability, and integrity provided by the hydrophobic fibre population. The mixture of the first electrospun polymer fibre population does not have to be 50:50 for it to impart its beneficial hydrophilic profile onto the material. Indeed, varying the amount of hydrophilic polymer to other polymer will alter the degree to which the material overall is hydrophilic, and allows the material to be tailored to a particular use case. For example, if we have a material where we have a purely hydrophobic portion and a mixed portion containing hydrophobic and hydrophilic fibre populations, the ratio may be about 75:25 of hydrophobic polymer fibres as compared to hydrophobic polymer fibres by weight overall. In this example, half of the device would be purely hydrophobic polymer fibres, and then the other half would be a 50:50 mixture of the two fibre populations. In such a device the hydrophobic portion will only have the properties provided by the hydrophobic polymer, and then the mixed portion will have the mixed properties from both the hydrophobic and hydrophilic polymers. In an example device, the mixed layer is more lubricious due to its hydrophilic properties and so is ideal for deployment through closed spaces such as the lumen of a catheter. However, without the structural integrity provided by the hydrophobic fibre population it would not survive the deployment process. In some embodiments, the average fibre diameter of the first electrospun polymer fibre population and / or the second electrospun polymer fibre population is greater than 1 pm. For each of the electrospun polymer fibre populations, the average fibre diameter may be around 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, or 10000 nm. Each electrospun polymer fibre population is made up of one or more electrospun polymer fibres having an average fibre diameter. The average fibre diameter can be measured using Scanning Electron Microscopy (SEM). In some embodiments, the first electrospun polymer fibre population and / or second electrospun polymer fibre populations are non-degradable. The phrase ‘non-degradable’ means that the average molecular weight of the polymer does not substantially reduce. In other words, there is no reduction in the chain length of the polymer(s) due to chain scission, though the fibre structures may physically degrade. This is an advantageous feature as it means that the structure of the material does not degrade once it is in situ in surgical and medical uses. In some embodiments, the first electrospun polymer fibre population is degradable. This is an advantageous feature which means that the fibre population may degrade over time. This may be preferable in cases where the function performed by the fibre population is only required temporarily. This is preferable where the user wishes to have either the first population of fibres remain whilst the other degrades over time. This may be beneficial where the fibre populations has a specific functional window after which it is undesirable for it to remain, meaning only the other fibre population endures and continues to perform its function. For example, it may be preferable to have the hydrophilic first electrospun polymer fibre population degrade once it is in place. The hydrophilic fibre population may be important for its interaction with placement instrumentation or for passing through bodily passages smoothly, and once the material is in place, this property may no longer be required. The fibrous composite material may have a total thickness between 20 and 5000 micrometers. For example, the total thickness may be 20, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 1500, 1750, 2000, 2250, 2500, 2750, 3000, 3250, 3500, 3750, 4000, 4250, 4500, 4750, or 5000 micrometers. The electrospun nature of the populations of fibres is that thickness can be controlled on demand using the electrospinning process without altering the micro-structure of the fibres or the way in which the first and second electrospun polymer fibre populations are mixed. For example, by a simple alteration of spin time and parameters, you could still produce a composite fibrous material having a hydrophobic face and a hydrophilic face regardless of whether the thickness is 20 micrometers or 5000 micrometers. The fibrous composite material may have a variable ratio between the first electrospun polymer fibre population and the second electrospun polymer fibre population by weight which varies through the length, width, and / or thickness of the material. Examples of such profiles are shown in Figure 1A, 1B, and 1D. For example, the material may have a length, width, and thickness, the thickness being defined as the distance between a first face and a second face. The ratio of the hydrophilic first electrospun polymer fibre population to the second electrospun polymer fibre population at the first face may be 100:0, meaning the material only has the first electrospun polymer fibre population at its first face. Through the thickness of the material, the second electrospun polymer fibre population is introduced such that in between the first and second face, the ratio reaches 50:50. The first electrospun polymer fibre population is slowly withdrawn, meaning that at the second face, the ratio of the first to the second is 0:100. Such a material is shown in Figure 1A. The ratio can be varied like this in numerous ways, meaning that materials with a specific profile of hydrophilic polymer fibre to other fibre can be created based on the intended use. This is advantageous as it allows fine control of the ingress of water and aqueous solutions which is beneficial for certain use cases. In the alternative, the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population may be homogenous throughout. In other words, regardless of which direction the ratio is measured in (thickness, length, width), it remains constant throughout. Such a material is shown in Figure 1C. In some embodiments, the material further comprises one or more additional electrospun polymer fibre populations. For example, the material may further comprise one, two, three, four, five or more additional electrospun polymer fibre populations. Such additional populations of fibres can impart further functionality on the material. For example, alongside water insoluble hydrophilic first electrospun polymer fibre population and a water insoluble hydrophobic second electrospun polymer fibre population, you may have a third population of fibres which is water soluble. This would mean that the hydrophilic first and hydrophobic second populations will continue to function in situ, but the third population would be dissolved in situ having served its function. One possible function of said third fibre population would be to increase the average pore size in the material after deployment. Electrospinning has a limit for how large a pore size can be for a given fibre diameter size. Using this third, sacrificial fibre population allows manufacture of a material which will have said larger pore size after it is manufactured when the third population is dissolved but has a sufficiently small pore size for manufacture via electrospinning methods. This dissolution could occur in situ, or as a post-processing method where it is dissolved in an aqueous solvent before use. In one embodiment, the one or more additional electrospun polymer fibre population(s) can be water soluble or resorbable and comprise bioactive additives. Such bioactive additives may include growth factors such as VEGF. An additive may alternatively be an oxygen-releasing material such as CaO2 or haemoglobin. Suitable additives may be selected from the following: Haemoglobin, Peroxides (for instance, H2O2, CaO2, MgO2, U2O2, Na2O2), Sodium Percarbonate (Na2CO3), Perfluorocarbons, Hydroxyapatite, Tricalcium phosphate (bone growth promoting materials), Growth factors, Catalase and other enzymes. Other bioactive additives may include, in some embodiments, antimicrobials, antivirals, anti-fungals, and / or silver nanoparticles. Examples of Growth factors may include any one or more of the following: Colony Stimulating Factors (m-CSF, G-CSF, GM-CSF), Epidermal growth factor (EGF), Erythropoietin (EPO), Fibroblast growth factor (FGF), Hepatocyte growth factor (HGF), Hepatoma-derived growth factor (HDGF), interleukins, Keratinocyte growth factor (KGF), Migration-stimulating factor (MSF), Macrophage-stimulating protein (MSP), also known as hepatocyte growth factor-like protein (HGFLP), Myostatin (GDF-8), Neuregulins (e.g. Neuregulin 1,2, 3 or 4), Neurotrophins (e.g. Brain-derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrophin-3 or 4), Placental growth factor (PGF), Platelet-derived growth factor (PDGF), Renalase (RNLS), T-cell growth factor (TCGF), Thrombopoietin (TPO), Transforming growth factors such as Transforming growth factor alpha (TGF-a) or beta (TGF-P), Tumour necrosis factor-alpha (TNF-a), Vascular endothelial growth factor (VEGF) or factors involved in the Wnt Signalling Pathway. In particular, the growth factor may be insulin and / or an insulin-like growth factor. Also preferred are Cytokines including the interleukins mentioned above. The hydrophilic fibres of the first electrospun polymer fibre population will have a set hydrophilicity. Where the first electrospun polymer fibre population is mixed with another fibre type, this will alter the overall hydrophilic profile of the material, and this is dependent on the ratio of hydrophilic fibres and to non-hydrophilic fibres by weight, the pore size, the structure of the surface, and the size of the fibres. One way to measure the overall hydrophobic profile of a face of the material is to use the ‘water contact angle’ (see e.g. Huhtamaki et al., 2017). In essence, by measuring the angle between a water droplet and the planar surface of the material, a quantifiable estimate of the overall hydrophilicity of the face of the material can be attained. Figure 2 shows how the water contact angle measurement is taken. A water droplet 210 is shown at rest on an upper face 202 of the material 201 of the invention. An angle (x) is measured from the surface upon which the water droplet rests (e.g. a face of the material of the invention) to the angle of the water surface adjacent to said surface. Hydrophilic surfaces have a water contact angle between 0 and 90 degrees, and hydrophobic surfaces have a water contact angle over 90 degrees. In Figure 2A and Figure 2B, the water contact angle is less than 90 degrees indicating that the shown face is hydrophilic, with the surface shown in Figure 2A being more hydrophilic than the surface in Figure 2B. In Figure 2C, the water contact angle is over 90 degrees indicating that the shown face is hydrophobic. Herein, it can be seen that the water contact angle x is less than 90 degrees, indicating that the face of the material upon which the water droplet sits is hydrophilic. In some embodiments of the invention, the water contact angle on at least one face of said material is in the range of 0 to 90 degrees. In some embodiments of the invention, the water contact angle on at least one face of said material is over 90 degrees. In some embodiments, the water contact angle on an opposing face of said material to the at least one face is in the range of 0 to 90 degrees. In other embodiments, the water contact angle on an opposing face of said material to the at least one face is over 90. This demonstrates the varied profiles each face of the material may have, and though it may not be hydrophobic or hydrophilic at a molecular level, the surface of the material can have an overall profile which alters how said material interacts with its environment. Each of the first and second electrospun polymer fibre populations is a random distribution of fibres which forms a non-woven but connected net of fibres with spaces therebetween. These spaces form pores or channels allowing fluid to pass through. In some embodiments, the average pore size of the material is between 50 nm to 200 pm. For example, the average pore size of the material is about 50 nm, 100nm, 200nm, 300nm, 400nm, 500nm 600nm, 700nm, 800nm, 900nm, 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, 10 pm, 20 pm, 30 pm, 40 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, 100 pm, 125 pm, 150 pm, 175 pm or 200 pm. The pore size may be varied by altering the parameters of the electrospinning apparatus during manufacture. Pore size is not simple to measure accurately. This is because pore size depends on how far through the scaffold you measure. No two pores are the same shape due to the random orientation of the fibres deposited during the electrospinning process. However, by taking an SEM and fitting the biggest inscribed circle inside the irregular polygon of the pore, the pore size can be measured. Having measured a number of exemplary pores of a sample of the material, the average pore size can then be measured. Pore size can be calculated using the following equation: 2 ¢ = d In this equation, average pore area (A) is converted into average pore diameter (d). A simple definition of a pore size for the purposes of this invention is the diameter of the largest inscribed circle that can be fit into an irregular polygon formed by the crossing of three or more fibres. Such a procedure is described in Martinez (2012). It should be understood that the pore size, porosity and / or average fibre diameter may vary through any dimension of the material such that the material has a gradient of these properties. In some embodiments, the first electrospun polymer fibre population comprises a hydrophilic, thermoplastic polyurethane. In a further embodiment, the second electrospun polymer fibre population comprises polyethylene terephthalate (PET) and / or a hydrophobic, thermoplastic polyurethane. Combinations of different Plls and Plls with PETS are useful for medical (e.g. cardiovascular), wearable, textile, and filtration technologies as the combination is easily processed, flexible, and resistant to breakage. The fibrous composite material of the invention may further comprise bioactive additives, preferably mixed with the first electrospun polymer fibre population and / or second electrospun polymer fibre population. Such bioactive additives may include growth factors such as VEGF. An additive may alternatively be an oxygen-releasing material such as CaO2 or haemoglobin. Suitable additives may be selected from the following: Haemoglobin, Peroxides (for instance, H2O2, CaO2, MgO2, Li2O2, Na2O2), Sodium Percarbonate (Na2CO3), Perfluorocarbons, Hydroxyapatite, Tricalcium phosphate (bone growth promoting materials), Growth factors, Catalase and other enzymes. Other bioactive additives my include, in some embodiments, antimicrobials, antivirals, anti-fungals, and / or silver nanoparticles. Examples of Growth factors may include any one or more of the following: Colony Stimulating Factors (m-CSF, G-CSF, GM-CSF), Epidermal growth factor (EGF), Erythropoietin (EPO), Fibroblast growth factor (FGF), Hepatocyte growth factor (HGF), Hepatoma-derived growth factor (HDGF), interleukins, Keratinocyte growth factor (KGF), Migration-stimulating factor (MSF), Macrophage-stimulating protein (MSP), also known as hepatocyte growth factor-like protein (HGFLP), Myostatin (GDF-8), Neuregulins (e.g. Neuregulin 1,2, 3 or 4), Neurotrophins (e.g. Brain-derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrophin-3 or 4), Placental growth factor (PGF), Platelet-derived growth factor (PDGF), Renalase (RNLS), T-cell growth factor (TCGF), Thrombopoietin (TPO), Transforming growth factors such as Transforming growth factor alpha (TGF-a) or beta (TGF-P), Tumour necrosis factor-alpha (TNF-a), Vascular endothelial growth factor (VEGF) or factors involved in the Wnt Signalling Pathway. In particular, the growth factor may be insulin and / or an insulin-like growth factor. Also preferred are Cytokines including the interleukins mentioned above. In a further aspect, the invention provides a method for producing a fibrous composite material as defined in the first aspect of the invention (or any of its embodiments), comprising electrospinning a first precursor polymer solution from a first source, and electrospinning a second precursor polymer solution from a second source onto a collector to form the fibrous composite material which comprises a second electrospun polymer fibre population dispersed within at least part of a first electrospun polymer fibre population. The first electrospun polymer fibre population and / or second electrospun polymer fibre population may be manufactured by known electrospinning methods, such as those outlined in US20120115386A1. An adjustment required for the fibrous composite material of the present invention is to, for at least a short period of time, co-spin the polymers of the first electrospun polymer fibre population and the second electrospun polymer fibre population such that the second electrospun polymer fibre population is dispersed within at least part of the first electrospun polymer fibre population. As stated previously, the electrospinning process produces flat sheets of fibrous, non-woven, porous membranes made of the polymer(s) which were electrospun. These can be collected in a roll-to-rolI fashion, on flat collectors, or on a rotating drum. The material can then be cut and / or shaped into an appropriate form for the intended use. For example, it could be folded and thermally welded to itself to form a device having a void in the middle, or it could be attached to other devices or materials to serve a function. In the method of the invention, a gas shield (for instance, as described in Larsen et al) is typically provided around the first source, preferably wherein the gas shield is activated during the electrospinning of the first precursor polymer solution and then deactivated before the electrospinning of the first precursor polymer solution is complete. Typically, the gas shield is deactivated after around 5-10% of the total spinning time has taken place. It has been found that use of a gas shield is particularly advantageous when the first electrospun polymer fibre population has an average fibre diameter of greater than 1pm. In a further aspect, the invention provides a method for producing a fibrous composite material, comprising the steps of: providing an electrospinning device comprising a collector, a first needle, and a second needle, wherein the collector has a rotating mandrel, the first needle is in fluid communication with a first reservoir containing a first precursor polymer solution, and the second needle is in fluid communication with a second reservoir containing a second precursor polymer solution, wherein the rotating mandrel is oppositely charged as compared to the first needle and the second needle, wherein the first needle is disposed on an opposite side of the rotating mandrel to the second needle in the rotational axis direction, wherein the first and second needle are each 5 to 50 cm away from the rotating mandrel; wherein the mandrel is provided with a voltage of -60 to +60 kV; providing a gas shield around the first needle prior to delivering, at a constant feed rate between 0.1 and 100 ml / hr, the first precursor polymer solution at an accelerating voltage of -60 to +60 kV; delivering, at a constant feed rate between 0.1 and 100 ml / hr, the second precursor polymer solution at an accelerating voltage in the range -60 to +60 kV; de-activating the gas shield around the first needle during delivery of the first precursor polymer solution to the rotating mandrel. On an industrial scale, multiple needles may be provided. Gas shields have previously been used in electrospinning processes. Historically, a gas shield if turned on during initialisation, is required for the duration of the run (Larsen et al). However, we have surprisingly found that in the process described above, once stability is achieved, the gas shield can be turned off without affecting the stability of the jets. As a result, in a preferred embodiment of the invention, the gas shield is turned off prior to the start of the run to improve on the cost effectiveness and safety of the process by advantageously removing the need to rely on filling the electrospinning chamber with toxic gas for the duration of the run. In a further aspect, the invention provides for the use of the fibrous composite material of the prior aspect in medicine or therapy. Having a fibrous composite material comprising a first electrospun polymer fibre population which is hydrophilic mixed with a second electrospun polymer fibre population confers unique advantages to medical applications. The increased wettability of the fibrous composite material due to the hydrophilic component improves handling, lubricity and adsorbent properties of the material. The second component can be tailored to improve the overall strength and structure of the material. The invention thus offers the functionality of the hydrophilic component without compromising its structural properties. The fibrous composite material may be used in soft tissue regeneration, soft tissue reconstruction, coverings for metal stents and frames, orthopedic applications (e.g. at the bone / muscle or bone / tendon interface) and / or ophthalmic applications (e.g. as a shunt in glaucoma). In one exemplary use, the fibrous composite material of the first aspect is used to cover a stent. Covered stents are known in the art (see e.g. WO2005032400A3), where the use of electrospun fibers covering the stent is beneficial because it prevents hyperplasia local to the stent. One problem with current fibrous electrospun stent covers is delamination of the covering from the stent frame during deployment. In deployment, stents are compressed and passed down tubing until they are deployed at their intended site in the cardiovascular system. Friction from the tubing against the stent cover can degrade the structure of the fibrous material it is made from and in some cases can cause the fibrous stent cover to detach from the stent, comprising its function and causing potential safety issues for the patient. The present invention improves upon known stent coverings using the fibrous composite material of the first aspect or any of its embodiments. In an aspect, the invention provides a stent comprising a stent frame and a stent cover, wherein the stent cover comprises the fibrous composite material of the first aspect of the invention or any of its embodiments. By providing the fibrous composite material of the first aspect in the stent cover, the hydrophilic nature of the material improves its lubricity and wettability. In use, this reduces the friction the stent cover and the internal walls of the stent tubing it is deployed through for placement in situ. This greatly reduces the risk of the fibrous electrospun stent cover being degraded or detached from the stent frame. Further embodiments of the fibrous composite material according to the first aspect may be used to further improve the covered stent. As an example, the stent frame may be pre-coated with a polymer. The same polymer may then be used initially during the electrospinning process to create the second electrospun polymer fibre population which will cause the electrospun stent cover to be better adhered to the stent frame. Given the compression and expansion processes during deployment, having the stent cover bonded to the stent frame in this way can reduce the risk of detachment during deployment. Thereafter, the hydrophilic first electrospun polymer fibre population can be introduced in order to improve the functionality of the stent as described above. As such, in one aspect, the invention provides a stent comprising a stent frame and a stent cover, wherein the stent cover comprises the fibrous composite material of the first aspect or any of its embodiments, wherein the fibrous composite material has a first face and a second face, the first face being in intimate contact with the stent frame, and the second face distal to the stent frame and opposite the first face. In an embodiment, the second face has a water contact angle between 0 and 90 degrees. This is achieved by ensuring the appropriate ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population by weight, for example. In a further embodiment, the stent frame comprises a coating comprising a coating polymer and the second electrospun fibre population comprises the coating polymer, wherein the first face comprises the second electrospun polymer fibre population. This means that the first face will adhere better to the stent frame by virtue of the coating polymer shared between the stent frame and the first face of the fibrous composite material. Alternatively, different polymers may improve the adhesion between the first face and the stent frame. Exemplary coating polymers are PET, polyurethane, stabilized collagen, stabilized gelatin, and / or combinations thereof. The stent as described herein is only one example of the potential of the fibrous composite material of the present invention. Other potential uses for the fibrous composite material include valve covers for artificial heart valves, wound dressings, or other medical uses. In the case of wound dressings, the fibrous composite material of the present invention is particularly advantageous. In an aspect, the invention provides a wound dressing comprising the fibrous composite material of the first aspect and any of its embodiments. This wound dressing has improved adsorption characteristics by virtue of the first electrospun polymer fibre population of the fibrous composite material, which confers improved wettability, whilst the second electrospun polymer fibre population ensures that the structure does not degrade. The fibrous composite material may be combined with any other known wound dressing to confer these improved characteristics. In an embodiment of this aspect, the wound dressing comprises the fibrous composite material having the hydrophilic first electrospun polymer fibre population and the second electrospun polymer fibre population, wherein the second electrospun polymer fibre population comprises a hydrophobic polymer, and wherein the ratio of the first electrospun polymer fibre population and the second electrospun polymer fibre population by weight varies through the thickness of the fibrous composite material, such that the ratio is between 60:40 to 100:0 towards a first face and is between 40:60 and 0:100 towards a second face, the second face opposing the first face. This establishes an adsorbent side where the majority of fibres are from the first electrospun polymer fibre population at the first face, and a hydrophobic side where the majority of fibres are from the second electrospun polymer fibre population at the second face. In the alternative, the ratio may vary such that a hydrophobic plane of material, where the majority of fibres are from the hydrophobic second electrospun polymer fibre population, is disposed in between the first face and the second face of the material, such that it prevents further ingress of liquid from either side. An additional benefit of the fibrous composite material according to the first aspect or any of its embodiments is that the hydrophilic nature of the first electrospun polymer fibre population will allow for fast release of any active pharmaceutical ingredients therein, such as the additives recited previously. In an aspect, the fibrous composite material according to the first aspect or any of its embodiments is for use in fluid filtration. These can include, for example, biofiltration, such as laboratory filtration equipment or bioprocessing and manufacturing equipment. The fibrous composite material combines strength and durability with wettability and can be manufactured to provide filters of varying thicknesses and pore sizes depending on application. In one example embodiment, the first electrospun polymer fibre population comprises hydrophilic, thermoplastic polyurethane and the second electrospun polymer fibre population comprises hydrophobic, thermoplastic polyurethane. The combination provides sufficient strength to be processed (e.g. heat bonding and other manufacturing processes) whilst providing strength to withstand water pressure whilst in use, without resisting the passage of water molecules. Another benefit of the fibrous composite material according to the first aspect in filtration is that, when comprising hydrophobic and a hydrophilic electrospun polymer fibre populations, the amphiphilic membrane will be anti-fouling. Amphiphilic membranes have better properties when it comes to water filtration use cases. In an aspect, the fibrous composite material according to the first aspect or any of its embodiments is for use in apparel (high performance textiles). Technical fabrics combine wicking technology and fluid control properties to enable specialist garment functionality. This is illustrated for instance in figure 18.The present fibrous composite material can be used in such a way, by providing a layer having the characteristics of wettability and structural integrity, the movement of fluid in a piece of apparel can be tightly controlled. As an example, the use of a fibrous composite material having the hydrophilic first electrospun polymer fibre population and the second electrospun polymer fibre population as a liner in a piece of apparel will allow the wicking of moisture away from the skin. In a particularly advantageous embodiment, the apparel comprises the fibrous composite material having the hydrophilic first electrospun polymer fibre population and the second electrospun polymer fibre population, wherein the second electrospun polymer fibre population comprises a hydrophobic polymer, and wherein the ratio of the first electrospun polymer fibre population and the second electrospun polymer fibre population by weight varies through the thickness of the fibrous composite material, such that the ratio is between 60:40 to 100:0 towards a first face and is between 40:60 and 0:100 towards a second face, the second face opposing the first face. This establishes an adsorbent side where the majority of fibres are from the first electrospun polymer fibre population at the first face, and a hydrophobic side where the majority of fibres are from the second electrospun polymer fibre population at the second face. In use, this ensures that moisture is wicked away from the skin from the first face into the fibrous composite material, but moisture from the external environment (e.g. rainfall) does not penetrate into the material through the second face, due to its hydrophobic properties. By tailoring the ratio of each electrospun polymer fibre population by weight through the thickness of the material, different wicking levels can be achieved for different activities. In addition, pore size, fibre diameter, and thickness of the material can be varied to maximize function and comfort of the material. A further use of the fibrous composite material is implantable materials useful in surgery and may promote, for instance, soft tissue regeneration. The material may be dipped in a drug or bioactive-containing solution and then implanted into the body. In one embodiment, the material is dipped in a platelet rich plasma (PRP) solution and then implanted into the body. One example of a suitable use of the material in medicine is as a hernia mesh. In an aspect, the invention provides the fibrous composite material according to the first aspect or any of its embodiments for use in hygiene products. In an example, a mixture of hydrophilic, thermoplastic polyurethane in the first electrospun polymer fibre population and hydrophobic, thermoplastic polyurethane in the second electrospun polymer fibre population provides a combination having both wettability and strength and as such the use in hygiene products is advantageous. The invention will now be illustrated by the following Examples. EXAMPLES EXAMPLE 1 The membrane was manufactured by simultaneously electrospinning a hydrophobic thermoplastic aromatic polycarbonate-based polyurethane (C-PU) (Chronoflex®, Mitsubishi Chemical, US) and a hydrophilic thermoplastic ether-based polyurethane (HM-PU) (Hydromed™ D, Mitsubishi Chemical Group, US). A solution containing 6.0 wt% of C-PU in Hexafluoro-2-propanol (HFIP) (Sigma Aldrich, UK) and a solution containing 7.0 wt% of H-PU in HFIP were prepared. The membrane was produced in a climate-controlled electrospinning machine (LE-100, Bioinica, Spain) with temperature and humidity set to 25°C and 65% respectively. Two nozzle arrays were positioned on opposite sides of a rotating collector, 15 cm from needle tip to drum. C-PU was delivered at a constant feed rate of 2 ml / hr via a syringe pump and electrospun with an accelerating voltage of +13.5 kV. Simultaneously HM-PU was delivered at a constant feed rate of 2 ml / hr via a syringe pump and electrospun with an accelerating voltage of +11.5 kV. Fibres were collected on a release paper sheet wrapped around the rotating collector. The collector was rotated at 100 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 40 mm / s. Electrospinning was performed for 108 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at -10 mbar for over 12 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter was -600 nm with a standard deviation of ±35%, SEM image and fibre histogram shown in figure 3. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 55 pm with a standard deviation of ±10%. The tensile properties of the three TPU samples were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in triplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. Standard composite theory dictates that a material made up of equal amounts of A and B will A Ba have mechanical properties equivalent to - + -.1 Figure 4 shows that by combining C-PU and HM-PU in this fibre diameter range, a composite whose break strain is greater than that of its two parts under both wet and dry conditions was made. This presents an advantage for both post processing and in medical applications in which the membrane will be stretched. The co-spun membrane exhibits full wettability with a water contact angle of 0°, this is also an unexpected outcome of combining two materials with relative water contact angles of 0° and >90. Along with this, the wet membrane is fully transparent when wet. The co-spun membrane has a wet stiffness and tensile strength that are appropriate for medical devices for soft tissue applications. EXAMPLE 2a A solution containing 17.0% PET (ICF Mercantile, US) in Hexafluoro-2-propanol (HFIP) (Sigma Aldrich, UK) was made. A final solution of 18.0% hydrophilic thermoplastic ether-based polyurethane (HM-PU) (Hydromed™ D, Mitsubishi Chemical Group, US) in HFIP was made. A straight nitinol stent was placed onto a rotating mandrel in an electrospinning machine (LE-100, Bioinica, Spain). Two nozzle arrays were positioned on opposite sides of the mandrel. The 17.0% PET solution (comprising the hydrophobic polymer) was delivered at a constant feed rate of 3 ml / hr via a syringe pump and electrospun with an accelerating voltage of +10.6 kV, the distance from the needle tip to the mandrel was ~5 cm. Simultaneously H-PU was delivered at a constant feed rate of 3 ml / hr via a syringe pump and electrospun with an accelerating voltage of +10.0 kV, the distance from the needle tip to mandrel was ~10 cm. The drum was charged with an accelerating voltage of -2 kV. The collector was rotated at 100 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 25 mm / s. Electrospinning was performed for 12 minutes. The stent was heat treated at 90°C for 2 minutes. Figure 5 illustrates the results of Example 2.Theleft image shows wettability and transparency in the bottom part of stent. The combination of the two polymers being hydrophilic and wettable was unexpected as one would expect the water contact angle to have a value between those of the two polymers. We have surprisingly found that it has the same value as the first polymer while having combined mechanical properties. PET is an important and commonly used material for cardiovascular applications and is innately hydrophobic. It can be made hydrophilic with post-processing, which adds additional complications. This Example provides an advantageous material that is inherently hydrophilic as manufactured. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter was -3.90 pm with a standard deviation of ±28% as shown in figure 6. Example 2b A solution containing 17.0% PET (ICF Mercantile, US) in Hexafluoro-2-propanol (HFIP) (Sigma Aldrich, UK) was delivered at a constant feed rate of 12.5 ml / hr via a syringe pump and electrospun with an accelerating voltage of+15 kV. Simultaneously, a second solution of 14.0% hydrophilic thermoplastic aromatic polyurethane (HT-PU) (Hydrothane AR, Mitsubishi Chemical Group, US) in HFIP was delivered at a constant feed rate of 15 ml / hr via a syringe pump and electrospun with an accelerating voltage of +28.9 kV. During jet initialisation the HT-PU jets showed poor stability and were prone to blocking up immediately in the absence of a gas shield. Thus, a HFIP gas shield was run through the HT-PU nozzle during jet initialisation at a set flow rate between 300-500 ml / min to stabilise the jets. Fibres were collected on a release paper sheet wrapped around the rotating collector. The collector was rotated at 50 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 20 mm / s. Electrospinning was performed for 30 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at -10 mbar for -24 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter, shown in figure 7, was -4.20 pm with a standard deviation of ±17%. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 109 pm with a standard deviation of ±5%. The tensile properties of electrospun hydrothane with an average fibre diameter between 4-5 pm and membrane described above were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in quadruplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. The results of this are shown in figure 8. Example 3 The membranes were manufactured by simultaneously electrospinning a hydrophobic polycarbonate-based silicone polyurethane with a shore hardness of 55D (S-PU) (examples of this include Chronosil® 55D, Mitsubishi Chemical Group, US; and Carbosil® 55D, DSM, US) and a hydrophilic thermoplastic ether-based polyurethane (HM-PU) (Hydromed™ D, Mitsubishi Chemical Group, US). Solutions containing 18.0% and 23.0% respectively of S-PU in a solvent system containing an 80 / 20 ratio of N, N-Dimethylformamide (DMF) (Sigma-Aldrich, UK) / Tetrahydrofuran (THF) (Sigma-Aldrich, UK) were made. Solutions containing 14.0 wt% and 18.0% of HM-PU in Hexafluoro-2-propanol (HFIP) (Sigma Aldrich, UK) were prepared. In a climate-controlled electrospinning machine (LE-100, Bioinica, Spain) with temperature and humidity set to 25°C and 30% respectively, two nozzle arrays were positioned on opposite sides of a rotating collector. The distance between the S-PU needle to the collector was -20 cm and the distance between the HM-PU needle to the collector was -25 cm. Example 3.1 The 18% S-PU solution was delivered at a constant feed rate of 5.5 ml / hr via a syringe pump and electrospun with an accelerating voltage of+17 kV. Simultaneously. The 14% HM-PU was delivered at a constant feed rate of 7.1 ml / hr via a syringe pump and electrospun with an accelerating voltage of +29 kV. The collector was charged at -4 kV. During jet initialisation the jets showed poor stability, often spitting, and jumping, which would remain an issue throughout the run duration. A HFIP gas shield was run through the HM-PU nozzle during jet initialisation at a set flow rate between 100-300 ml / min to stabilise the jets at this stage. Fibres were collected on a release paper sheet wrapped around the rotating collector. The collector was rotated at 50 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 20 mm / s. Electrospinning was performed for 72 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at -10 mbar for ~24 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter, as shown in figure 9, was -2.20 pm with a standard deviation of ±15%. The figure demonstrates that both fibre populations have average diameters that are within 50% of each other. Furthermore, larger fibre diameters are demonstrated than seen in the prior art. Use of the gas shield which is turned off after startup advantageously leads to some beneficial results. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 151 pm with a standard deviation of ±5%. The tensile properties of electrospun Hydromed™, polycarbonate-based silicone polyurethane and a 2-3 pm average fibre diameter membrane containing an -1:1 ratio of both polymers were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in quadruplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. The results of this tensile testing are shown in figure 10. As detailed in Tham etal, standard composite theory dictates that a material made up of equal amounts of two materials A and B will have mechanical properties equivalent to + ^-.2 This is not the case for this membrane, and this unexpected behaviour is best exemplified by the composite material being stiffer than both of its constituent parts when dry. This is especially beneficial for the processing of the composite, as it is less likely than the pure polymers to be accidentally permanently deformed during processing. The other tensile properties are more in line with what is expected from traditional composite theory and are good enough for soft tissue repair with a notably low stiffness when wet, in the range of human tissue (Akhtar et al). The hydrophilicity of the membrane produced using this method is exemplified in figure 17, which shows the co-spun membrane when wet (left) vs dry (right). It is clear from this image that the appearance of the membrane is affected by its wetting, leading to a transparent membrane. This is unexpected behaviour from a material made from an ~1:1 ratio of 0° water contact angle polymer and >90° water contact angle polymer. This material may have benefits for ophthalmological applications where it is important to be able to see underneath the implant. There may also be aesthetic benefits - the material will not be immediately visible on a patient compared to a hydrophobic material. Advantageously, all of these benefits are conferred to a membrane while still maintaining the beneficial mechanical properties. Example 3.2 The 23% S-PU solution was delivered at a constant feed rate of 6.8 ml / hr via a syringe pump and electrospun with an accelerating voltage of+14 kV. Simultaneously. The 18% HM-PLI was delivered at a constant feed rate of 9.0 ml / hr via a syringe pump and electrospun with an accelerating voltage of +28 kV. The collector was charged at -4 kV. A HFIP gas shield was run through the HM-PLI nozzle during jet initialisation at a set flow rate between 100-300 ml / min to stabilise the jets at this stage. Once stability was achieved, the gas shield could be turned off without affecting the stability of the jets. However, in the absence of the gas shield the jets tended to favour electrowriting over electrospinning. Electrowriting often results in thicker, less defined fibres which are less favourable than those produced by electrospinning. Thus, whilst the process could be run stably without the gas shield once stable initialisation was achieved, it was run at a constant rate of 100 ml / min to deposit fibres in the desired diameter range. Fibres were collected on a release paper sheet wrapped around the rotating collector. The collector was rotated at 50 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 20 mm / s. Electrospinning was performed for 50 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at -10 mbar for ~24 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter, as seen in figure 11, was -4.09 pm with a standard deviation of ±29%. The figure demonstrates that both fibre populations have average fibre diameters that are within 50% of each other. Furthermore, larger fibre diameters are produced compared to the prior art which can be beneficial for certain applications such as in-vitro cell production. Large fibres lead to large pores which allows more cells to infiltrate more quickly into the scaffold and also to be ultimately released. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 105 pm with a standard deviation of ±10%. The tensile properties of electrospun Hydromed™, polycarbonate-based silicone polyurethane and a 4-5 pm average fibre diameter membrane containing an -1:1 ratio of both polymers were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in quadruplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. Figure 12 shows that the co-spun membrane is as stiff as the pure hydrophilic portion, which was unexpected according to theory benefits, as detailed above. Furthermore, the material has break strain as large as the pure hydrophobic portion, which was also unexpected. Example 4 The membranes were manufactured by simultaneously electrospinning a hydrophobic polycarbonate-based silicone polyurethane with a shore hardness of 55D (S-PU) (examples of this include Chronosil®, Mitsubishi Chemical Group, US; and Carbosil®, DSM, US) and a hydrophilic thermoplastic aromatic polyurethane (HT-PLI) (Hydrothane™ AR, Mitsubishi Chemical Group, US). Solutions containing 18.0% and 23.0% respectively of S-PU in a solvent system containing an 80 / 20 ratio of N, N-Dimethylformamide (DMF) (Sigma-Aldrich, UK) / Tetrahydrofuran (THF) (Sigma-Aldrich, UK) were made. Solutions containing 12.0 wt% and 14.0% of HT-PU in Hexafluoro-2-propanol (HFIP) (Sigma Aldrich, UK) were prepared. In a climate-controlled electrospinning machine (LE-100, Bioinica, Spain) with temperature and humidity set to 25°C and 30% respectively, two nozzle arrays were positioned on opposite sides of a rotating collector. The distance between each needle to the collector was ~20 cm. Example 4.1 The 18% S-PU solution was delivered at a constant feed rate of 5.5 ml / hr via a syringe pump and electrospun with an accelerating voltage of+16 kV. Simultaneously. The 12% HT-PU was delivered at a constant feed rate of 8 ml / hr via a syringe pump and electrospun with an accelerating voltage of+27 kV. The collector was charged at-3.5 kV. During jet initialisation the HT-PU jets showed poor stability and were prone to blocking up immediately in the absence of a gas shield. Thus, a HFIP gas shield was run through the HT-PU nozzle during jet initialisation at a set flow rate between 100-300 ml / min to stabilise the jets at this stage. Once stability was achieved, the gas shield could be turned off without affecting the stability of the jets. As a result, the gas shield was turned off prior to the start of the run proper to improve on the cost effectiveness and safety of the process by removing the need to rely on filling the electrospinning chamber with toxic gas for the duration of the run. Fibres were collected on a release paper sheet wrapped around the rotating collector.The collector was rotated at 50 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 20 mm / s. Electrospinning was performed for 50 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at ~10 mbar for ~24 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter, see figure 13, was -3.00 pm with a standard deviation of ±22%. This figure demonstrates that both fibre populations have average fibre diameters that are within 50% of each other. Furthermore, larger fibre diameters are demonstrated which has benefits, as detailed above Use of the gas shield, which is turned off after startup, may provide some of these benefits. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 62 pm with a standard deviation of ±12%. The tensile properties of electrospun hydrothane, polycarbonate-based silicone polyurethane and membrane containing an -1:1 ratio of both polymers with an average fibre diameter between 2-3 pm were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in quadruplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. The results of the tensile testing can be seen in figure 14. The combination dry is as strong as the pure hydrophobic portion, which was unexpected and beneficial, as further detailed above. Furthermore, the combination has higher break strain than both when dry, which was unexpected and beneficial, as further detailed above. The combination is strong enough when wet, which is beneficial in-vivo. The hydrophilicity of the membrane produced using this method is exemplified in figure 16, which shows the co-spun membrane when wet (left) vs dry (right). It is clear from this image that the appearance of the membrane is affected by its wetting, leading to a transparent membrane. This is unexpected behaviour from a material made from an -1:1 ratio of 0° water contact angle polymer and >90° water contact angle polymer. This material may have benefits for ophthalmological applications, as further explained in relation to Example 1 above. Example 4.2 The 23% S-PU solution was delivered at a constant feed rate of 7.3 ml / hr via a syringe pump and electrospun with an accelerating voltage of +17 kV. Simultaneously, the 14% HM-PU was delivered at a constant feed rate of 12 ml / hr via a syringe pump and electrospun with an accelerating voltage of +29 kV. During jet initialisation the HT-PLI jets showed poor stability and were prone to blocking up immediately in the absence of a gas shield. Thus, a HFIP gas shield was run through the HT-PLI nozzle during jet initialisation at a set flow rate between 100-300 ml / min to stabilise the jets at this stage. Once stability was achieved, the gas shield could be turned off without affecting the stability of the jets. As a result, the gas shield was turned off prior to the start of the run proper to improve on the cost effectiveness and safety of the process by removing the need to rely on filling the electrospinning chamber with toxic gas for the duration of the run. Fibres were collected on a release paper sheet wrapped around the rotating collector. The collector was rotated at 50 rpm and longitudinal translation was also applied, using a programmable motorised stage with a translation speed of 40 mm / s. Electrospinning was performed for 14.5 minutes to fabricate the desired sheet thickness. The fibrous mat was dried in a vacuum oven at -10 mbar for ~24 hours at 25°C to reduce the amount of residual solvent remaining from the fabrication process. Fibre diameter and scaffold morphology characterisation were performed by scanning electronic microscopy (SEM) (Phenom G2 XL equipped with Fibremetric software, Phenom World, the Netherlands), using automated image characterisation of multiple images in order to determine the mean fibre diameter and the relative standard deviation. The Fibremetric software automatically identifies the location of the fibres within the captured SEM image and measures the diameter of each fibre 20 times at a specific location. Typically, around 100 of such measurements are performed per image. The diameter of the fibres can alternatively be obtained via manual measurements I analysis of multiple SEM images. The average fibre diameter, shown in figure 15, was -4.20 pm with a standard deviation of ±19%. This figure shows that both fibre populations have average fibre diameters that are within 50% of each other. There are larger fibres than in figure 13 with the benefits of this outlined above. Use of the gas shield which is turned off after startup may result in some of these benefits. Thickness of the sheet is measured using a digital micrometre (DIGIMICRO MH-15M with MS-5C DIGIMICRO Stand, Nikon Metrology Europe NV, Belgium). The average thickness of the material was 32 pm with a standard deviation of ±6%. The tensile properties of electrospun hydrothane, polycarbonate-based silicone polyurethane and membrane containing an -1:1 ratio of both polymers with an average fibre diameter between 4-5 pm were assessed using a materials testing machine (Model 5ST, Tinius Olsen Ltd., UK). Samples measured -10x50 mm and were taken in quadruplicate under both wet and dry conditions. Dry samples were clamped into the vice grips at a suitable grip separation length (e.g. 30 mm) and tested until break with a test speed of 10 mm / min and a preload of 0.02 N. Wet samples were first left in a water bath for -5 minutes and then tested using the same method as the dry samples. References Akhtar R, Sherratt MJ, Cruickshank JK, Derby B. Characterizing the elastic properties of tissues. Mater Today (Kidlington). 2011 Mar; 14(3):96-105. doi: 10.1016 / S1369-7021(11)70059-1. PMID: 22723736; PMCID: PMC3378034. Greiner A, Wendorff JH. Electrospinning: a fascinating method for the preparation of ultrathin fibers. Angewandte Chemie International Edition. 2007 Jul 23;46(30):5670-703. Gu, M., Wang, K., Li, W. et al. Preparation and characterization of PVA / PU blend nanofiber mats by dual-jet electrospinning. Fibers Polym 12, 65-72 (2011). Huhtamaki T, Tian X, Korhonen JT, Ras RH. Surface-wetting characterization using contact-angle measurements. Nature protocols. 2018 Jul; 13(7): 1521-38. Hussein, M.A.M.; Gunduz, O.; Sahin, A.; Grinholc, M.; El-Sherbiny, I.M.; Megahed, M. Dual Spinneret Electrospun Polyurethane / PVA-Gelatin Nanofibrous Scaffolds Containing Cinnamon Essential Oil and Nanoceria for Chronic Diabetic Wound Healing: Preparation, Physicochemical Characterization and In-Vitro Evaluation. Molecules 2022, 27, 2146. Larsen, G., Spretz, R. &Velarde-Ortiz, R. Use of Coaxial Gas Jackets to Stabilize Taylor Cones of Volatile Solutions and to Induce Particle-to-Fiber Transitions. Advanced Materials vol. 16 166-169 (2004). Martinez O. An efficient algorithm to calculate the center of the biggest inscribed circle in an irregular polygon. arXiv preprint arXiv:1212.3193. 2012 Dec 13. Tham, M. W. et al. Tensile properties prediction of natural fibre composites using rule of mixtures: A review. Journal of Reinforced Plastics and Composites vol. 38 211-248 (2018). Wlodarczyk J, Stojko M, Musial-Kulik M, Karpeta-Jarzabek P, Pastusiak M, Janeczek H, Dobrzynski P, Sobota M, Kasperczyk J. Dual-jet electrospun PDLGA / PCU nonwovens and their mechanical and hydrolytic degradation.

Claims

1. A fibrous composite material comprising:a first electrospun polymer fibre population; anda second electrospun polymer fibre population dispersed within at least part of the first electrospun polymer fibre population,wherein the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 1:5 to 9:5;wherein the first electrospun polymer fibre population comprises a hydrophilic polyurethane;wherein the second electrospun polymer fibre population comprises a synthetic, non-degradable, hydrophobic polymer; andwherein the first electrospun polymer fibre population and the second electrospun polymer fibre population are water insoluble.

2. The fibrous composite material according to claim 1 wherein the hydrophobic polymer comprises a polymer from the following group: polyurethane, Polyethylene terephthalate, Polyvinylidene fluoride, Polyacrylonitrile, Polycarbonate, Poly(methyl methacrylate), Polyvinyl chloride, Acrylonitrile butadiene styrene, Polystyrene, Polysulfone, Polyimide, Polyamide, Polyvinyl butyral, and Poly(Glycerol Sebacate).

3. The fibrous composite material according to claim 1 or 2, wherein the ratio of the average fibre diameter of the first electrospun population to the average fibre diameter of the second population is in the range 3:10 to 17:10; preferably in the range 2:5 to 8:5; even more preferably in the range 1:2 to 3:2.

4. The fibrous composite material according to any preceding claim, wherein the first electrospun polymer fibre population and the second electrospun polymer fibre population each have an average fibre diameter greater than 1 pm.

5. The fibrous composite material according to any one of the preceding claims, wherein the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population is between 90:10 to 10:90 by weight, preferably 50:50 by weight.

6. The fibrous composite material according to any one of the preceding claims, wherein the first electrospun polymer fibre population is non-degradable.

7. The fibrous composite material of any preceding claim which is in the form of a sheet having a total thickness between 20 and 5000 micrometers.

8. The fibrous composite material of any preceding claim, wherein the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population by weight varies through the length, width, and / or thickness of the material.

9. The fibrous composite material of claim 8, wherein the ratio of the first electrospun polymer fibre population to the second electrospun polymer fibre population by weight varies through the thickness of the material from 90:10 at a first face of the material to 10:90 at a second face of the material which is opposite to the first face, or wherein the ratio by weight of the first electrospun polymer fibre population and the second electrospun polymer fibre population is homogenous through the thickness of the material.

10. The fibrous composite material of any one of the preceding claims, wherein the material further comprises one or more additional electrospun polymer fibre populations.

11. The fibrous composite material of any one of the preceding claims, wherein the water contact angle of the material on at least one face of said material is in the range of 0 to 90 degrees.

12. The fibrous composite material of any one of the preceding claims, which comprises pores having an average pore size between 50 nm to 200 pm.

13. The fibrous composite material of any one of the preceding claims for use in therapy.

14. The fibrous composite material of claim 13, wherein the fibrous composite material is for use in soft tissue regeneration, soft tissue reconstruction, coverings for metal stents and frames, orthopedic applications and / or ophthalmic applications.

15. A stent comprising a stent frame and a stent cover, wherein the stent cover comprises the fibrous composite material according to any one of claims 1 to 14.

16. A wound dressing comprising the fibrous composite material according to any one of claims 1 to 14.

17. The fibrous composite material of claims 1 to 12 for use in a filter or a separation membrane.

18. The fibrous composite material of claims 1 to 12 for use in apparel.

19. A piece of apparel comprising the fibrous composite material according to any one of claims 1 to 12.

20. A method for producing a fibrous composite material as defined in any of claims 1 to 12, comprising electrospinning a first precursor polymer solution from a first sourceand electrospinning a second precursor polymer solution from a second source,onto a collector to form the fibrous composite material which comprises a second electrospun polymer fibre population dispersed within at least part of a first electrospun polymer fibre population.

21. A method according to claim 20 wherein a gas shield is provided around the first source, preferably wherein the gas shield is activated during the electrospinning of the first precursor polymer solution and then deactivated before the electrospinning of the first precursor polymer solution is complete.

22. A method according to claim 21 wherein the first electrospun polymer fibre population has an average fibre diameter of greater than 1 pm.

23. A method for producing a fibrous composite material, comprising the steps of:providing an electrospinning device comprising a collector, a first needle, and a second needle,wherein the collector has a rotating mandrel, the first needle is in fluid communication with a first reservoir containing a first precursor polymer solution, and the second needle is in fluid communication with a second reservoir containing a second precursor polymer solution,wherein the rotating mandrel is oppositely charged as compared to the first needle and the second needle,wherein the first needle is disposed on an opposite side of the rotating mandrel to the second needle in the rotational axis direction, wherein the first and second needle are each 5 to 50 cm away from the rotating mandrel;wherein the mandrel is provided with a voltage of -60 to +60 kV;providing a gas shield around the first needle prior to delivering, at a constant feed rate between 0.1 and 100 ml / hr, the first precursor polymer solution at an accelerating voltage of -60 to +60 kV;delivering, at a constant feed rate between 0.1 and 100 ml / hr, the second precursor polymer solution at an accelerating voltage in the range -60 to +60 kV;de-activating the gas shield around the first needle during delivery of the first precursor polymer solution to the rotating mandrel.

Images