Layer-by-layer deposition device

Abstract

The invention relates to a layer-by-layer deposition device. The layer-by-layer deposition device includes a first inlet that is configured to be fluidly connected to a first reservoir; a second inlet that is configured to be fluidly connected to a second reservoir; a unidirectional flow assembly that is fluidly connected to the first inlet and the second inlet; and a fluid conduit that is fluidly connected to each of the unidirectional flow assembly and a fluid outlet. The unidirectional flow assembly is configured to ensure unidirectional flow from each of the first inlet and the second inlet to the fluid outlet via the fluid conduit. The invention also relates to a kit of parts for assembly into a layer-by-layer deposition device and a layer-by-layer deposition method.

Description

LAYER-BY-LAYER DEPOSITION DEVICETECHNICAL FIELD OF INVENTION

[0001] The present invention relates to a layer-by-layer deposition device, for example a spray layer-by-layer deposition device and / or a hand held layer-by-layer deposition device. Aspects of the invention relate to a layer-by-layer deposition device; a kit of parts for assembly into a layer- by-layer deposition device; and a layer-by-layer deposition method.BACKGROUND

[0002] Various methods for applying layer-by-layer coatings to a surface are known, for example dip coating, spin coating and spray coating.

[0003] In dip coating methods, a pre-charged substrate to be coated is dipped into a reservoir of charged solution. As the substrate is dipped into the reservoir of charged solution, the layer is formed by electrostatic interaction between substrate and charged solution. The process is repeated until the desired number of layers is achieved.

[0004] Whilst dip coating methods are widely used, largely due to the simplicity of the immersive methodology, the process is very time consuming. This is because the time required to reach equilibrium adsorption for each coating step is relatively high compared to other techniques. Additional layers cannot be added until the existing layer has stabilised. For example, it can take two days to form 400 layers.

[0005] An alternative method for applying a layer-by-layer coating to a substrate is spin coating. In spin coating, a liquid is deposited and spread across a planar surface through rapid spinning of the substrate. Spin coating involves the rapid evaporation of solvent from the coating material, leading to the formation of films that are thicker than those resulting from the dipping technique. However, for spin coating it is difficult to homogenously coat irregularly shaped 2D substrates and impossible to coat 3D substrates.

[0006] A further method for layer-by-layer deposition is spray coating. Spray coating includes spraying a solution, generally an atomized solution, on a substrate. During spray coating, the substrate is typically fully enclosed within a housing to prevent the solution entering the surrounding environment. Spray coating does not provide a consistent homogeneous and stable layer every time. Moreover, there is a significant amount of wasted solution that does not attach to the substrate. This can greatly increase the costs associated with fabricating the thin-film.

[0007] It is an aim of the present invention to overcome one or more of the disadvantages associated with the prior art.

[0008] It would be useful, for example, to provide a device that enables layer-by-layer deposition methods to be used remotely from the laboratory environment and / or more quickly.BRIEF SUMMARY

[0009] Aspects and embodiments of the invention provide a layer-by-layer deposition device; a kit of parts for assembly into a layer-by-layer deposition device; and a layer-by-layer deposition method as claimed in the appended claims and as described below.

[0010] According to an aspect of the present invention there is provided a layer-by-layer deposition device, for example a portable layer-by-layer deposition device, including: a fluid inlet that is configured to be fluidly connected to a reservoir; a unidirectional flow assembly that is fluidly connected to the fluid inlet; and a fluid conduit that is fluidly connected to each of the fluid inlet and the unidirectional flow assembly; wherein the unidirectional flow assembly is configured to ensure unidirectional flow of a fluid from the fluid inlet to the fluid outlet via the fluid conduit.

[0011] According to an aspect of the present invention there is provided a layer-by-layer deposition device, for example a spray layer-by-layer deposition device, including: a fluid inlet that is configured to be fluidly connected to a reservoir; a unidirectional flow assembly that is fluidly connected to the fluid inlet; and a fluid conduit that is fluidly connected to each of the fluid inlet and the unidirectional flow assembly; wherein the unidirectional flow assembly is configured to prevent a flow of a fluid from the fluid conduit to the fluid inlet.

[0012] According to an aspect of the present invention there is provided a layer-by-layer deposition device including: a first inlet that is configured to be fluidly connected to a first reservoir; a second inlet that is configured to be fluidly connected to a second reservoir; a unidirectional flow assembly that is fluidly connected to the first inlet and the second inlet; and a fluid conduit that is fluidly connected to each of the unidirectional flow assembly and a fluid outlet; wherein the unidirectional flow assembly is configured to ensure unidirectional flow from each of the first inlet and the second inlet to the fluid outlet via the fluid conduit.

[0013] The layer-by-layer deposition device may be a spray layer-by-layer deposition device.

[0014] The layer-by-layer deposition device may include a first reservoir that is fluidly connected to the first inlet; and a second reservoir that is fluidly connected to the second inlet. The unidirectional flow assembly may be configured to ensure unidirectional flow of a first fluidfrom the first reservoir to the fluid conduit and unidirectional flow of a second fluid from the second reservoir to the fluid conduit.

[0015] The unidirectional flow assembly may include a pump that controls unidirectional flow of the first fluid from the first inlet to the fluid conduit and / or that controls unidirectional flow of the second fluid from the second inlet to the fluid conduit.

[0016] The pump may be a micropump, for example a positive displacement pump. The positive displacement pump may be a gear pump.

[0017] The unidirectional flow assembly may include a valve that cooperates with the pump to control unidirectional flow of the first fluid from the first inlet to the fluid conduit and / or to control unidirectional flow of the second fluid from the second inlet to the fluid conduit.

[0018] The valve may be a one-way valve, for example a check valve.

[0019] The one-way valve may be selected from a ball valve, a diaphragm valve, a swing check valve, a butterfly check valve, a stop-check valve, a lift-check valve, an in-line check valve, a duckbill valve, a reed valve, a solenoid valve.

[0020] In embodiments of the invention, a first inlet valve may be associated with the first inlet.

[0021] The first inlet may, for example, include a first inlet valve that is configured to ensure unidirectional flow of the first fluid from the first reservoir to the first inlet.

[0022] In embodiments of the invention, a second inlet valve may be associated with the second inlet.

[0023] The second inlet may, for example, include a second inlet valve that is configured to ensure unidirectional flow of the second fluid from the second reservoir to the second inlet.

[0024] One or both of the first inlet valve and / or the second inlet valve may be a one-way valve, for example a check valve.

[0025] One or both of the first inlet valve and / or the second inlet valve may be selected from a ball valve, a diaphragm valve, a swing check valve, a butterfly check valve, a stop-check valve, a lift-check valve, an in-line check valve, a duckbill valve, a reed valve, a solenoid valve.

[0026] The first inlet may include a first inlet actuator. The first inlet actuator may have a first configuration in which a fluid connection between the first inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the first inlet and the unidirectional flow assembly is closed.

[0027] When the first inlet actuator is in the first configuration and the fluid connection between the first inlet and the unidirectional flow assembly is open, the fluid connection between the second inlet and the unidirectional flow assembly may be closed.

[0028] The second inlet may include a second inlet actuator. The second inlet actuator may have a first configuration in which a fluid connection between the second inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the second inlet and the unidirectional flow assembly is closed.

[0029] When the second inlet actuator is in the first configuration and the fluid connection between the second inlet and the unidirectional flow assembly is open, the fluid connection between the first inlet and the unidirectional flow assembly may be closed.

[0030] The or each actuator may be a mechanical actuator, for example a manual switch or button.

[0031] The or each actuator may be an electric actuator, for example an electromagnetic actuator, such as an electromagnetic actuator including a solenoid.

[0032] The layer-by-layer deposition device may include a power supply and a controller. The controller may be operable to control the pump.

[0033] The power supply may include a battery.

[0034] The controller may be operable to control a pressure, for example in the fluid conduit.

[0035] The controller may be, for example, configured to control a voltage supplied to the pump from the power supply.

[0036] The controller may be operable to control a mass flow rate in the layer-by-layer deposition device. The controller may be, for example, configured to control the pump to fix the mass flow rate at a specific pressure.

[0037] The mass flow rate may be at least 2 grams per second, for example at least 2.2 grams per second.

[0038] The mass flow rate may be up to 3 grams per second, for example up to 2.5 grams per second.

[0039] The mass flow rate may be between 2 grams per second and 3 grams per second, for example between 2 grams per second and 2.5 grams per second.

[0040] The mass flow rate may be between 2.2 grams per second and 3 grams per second, for example between 2.2 grams per second and 2.5 grams per second.

[0041] The specific pressure may be up to 2 Megapascal (20 bar), for example up to 1 Megapascal (10 bar).

[0042] In embodiments, the controller may be operable to control an order in which the first fluid and / or the second fluid is ejected from the layer-by-layer deposition device.

[0043] The layer-by-layer deposition device may include a third inlet that is configured to be fluidly connected to a third reservoir; wherein the third inlet is fluidly connected to the unidirectional flow assembly.

[0044] The layer-by-layer deposition device may include a third reservoir that is fluidly connected to the third inlet. The unidirectional flow assembly may be configured to ensure unidirectional flow of a third fluid from the third reservoir to the fluid conduit.

[0045] The third inlet may include a third inlet valve that is configured to ensure unidirectional flow of the third fluid from the third reservoir to the third inlet.

[0046] The third inlet may include a third inlet actuator. The third inlet actuator may have a first configuration in which a fluid connection between the third inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the third inlet and the unidirectional flow assembly is closed.

[0047] The layer-by-layer deposition device may include a fourth inlet that is configured to be fluidly connected to a fourth reservoir; wherein the fourth inlet is fluidly connected to the unidirectional flow assembly.

[0048] The layer-by-layer deposition device may include a fourth reservoir that is fluidly connected to the fourth inlet. The unidirectional flow assembly may be configured to ensure unidirectional flow of a fourth fluid from the fourth reservoir to the fluid conduit.

[0049] The fourth inlet may include a fourth inlet valve that is configured to ensure unidirectional flow of the fourth fluid from the fourth reservoir to the fourth inlet.

[0050] The fourth inlet may include a fourth inlet actuator. The fourth inlet actuator may have a first configuration in which a fluid connection between the fourth inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the fourth inlet and the unidirectional flow assembly is closed.

[0051] The fluid outlet may include a nozzle, for example an atomising nozzle.

[0052] The nozzle may have an orifice. The orifice of the nozzle may have a diameter of at least 0.2 millimetres, for example at least 0.3 millimetres, for example at least 0.4 millimetres.

[0053] The diameter of the orifice of the nozzle may be less than or equal to 1 .2 millimetres, for example less than or equal to 1 .0 millimetres.

[0054] The diameter of the orifice of the nozzle may be between 0.2 millimetres and 1 .2 millimetres, for example between 0.2 millimetres and 1.1 millimetres, for example between 0.2 millimetres and 1 .0 millimetres.

[0055] The diameter of the orifice of the nozzle may be between 0.3 millimetres and 1 .2 millimetres, for example between 0.3 millimetres and 1.1 millimetres, for example between 0.3 millimetres and 1 .0 millimetres.

[0056] The diameter of the orifice of the nozzle may be between 0.4 millimetres and 1 .2 millimetres, for example between 0.4 millimetres and 1.1 millimetres, for example between 0.4 millimetres and 1 .0 millimetres.

[0057] The nozzle may include an impingement pin that is configured to atomise fluid into droplets.

[0058] The nozzle may be configured to produce one or more droplet.

[0059] The one or more droplet may have a diameter of less than or equal to 100 micrometres.

[0060] The diameter of the one or more droplet may be at least 70 micrometres.

[0061] The one or more droplet may have a force impact of less than or equal to 1 .5 x 10-6 Newtons.

[0062] The force impact of the one or more droplet may be at least 0.8 x 10-6 Newtons.

[0063] In embodiments of the invention, the layer-by-layer deposition device may be a portable layer-by-layer deposition device. The layer-by-layer deposition device may be, for example, a handheld layer-by-layer deposition device.

[0064] The layer-by-layer deposition device of any of the preceding aspects of the invention may include a manifold, wherein the manifold comprises the fluid inlet and a first portion of the unidirectional flow assembly; and a body including a second portion of the unidirectional flow assembly, the fluid conduit and the fluid outlet.

[0065] The layer-by-layer deposition device of any of the preceding aspects of the invention may include a manifold, wherein the manifold comprises the first inlet, the second inlet and a first portion of the unidirectional flow assembly; and a body including a second portion of the unidirectional flow assembly, the fluid conduit and the fluid outlet.

[0066] The manifold may include a or the third inlet.

[0067] The manifold may include a or the fourth inlet.

[0068] According to an aspect of the invention there is provided a kit of parts for assembly into the layer-by-layer deposition device of any of the preceding aspects of the invention.

[0069] The kit of parts may include a manifold including the fluid inlet and a first portion of the unidirectional flow assembly; a body including a second portion of the unidirectional flow assembly, the fluid conduit and the fluid outlet; and a reservoir including a fluid.

[0070] According to an aspect of the invention there is provided a kit of parts for assembly into the layer-by-layer deposition device of any of the preceding aspects of the invention.

[0071] The kit of parts may include a manifold including the first inlet, a second inlet and a first portion of the unidirectional flow assembly; and a body within which a second portion of the unidirectional flow assembly, the fluid conduit and the fluid outlet are accommodated; a first reservoir including a first fluid; and a second reservoir including a second fluid.

[0072] The fluid, for example the first fluid, may be a first polyelectrolyte.

[0073] In embodiments including a second fluid, the second fluid may be a second polyelectrolyte.

[0074] The first polyelectrolyte may be different to the first polyelectrolyte.

[0075] One of the first polyelectrolyte and the second polyelectrolyte may be a positive polyelectrolyte.

[0076] In embodiments the other of the first polyelectrolyte and the second polyelectrolyte is a negative polyelectrolyte.

[0077] The kit of parts may include a third reservoir, for example wherein the third reservoir includes a third fluid.

[0078] The third fluid may be a third polyelectrolyte. The third polyelectrolyte may be different to the first polyelectrolyte and / or the second polyelectrolyte.

[0079] The kit of parts may include a fourth reservoir, for example wherein the fourth reservoir includes a fourth fluid.

[0080] The fourth fluid may be a fourth polyelectrolyte. The fourth polyelectrolyte may be different to the first polyelectrolyte and / or the second polyelectrolyte and / or the third polyelectrolyte.

[0081] The kit of parts may include a further reservoir, for example wherein the further reservoir includes a further fluid.

[0082] The further fluid may include one or more of: calcium, fibrogen, thrombin, fibrin sealant, keratinocytes, fibroblasts, pharmaceutical agents, antimicrobial agents, such as silver nanoparticles, antibacterial agents, peptides.

[0083] According to an aspect of the invention there is provided a layer-by-layer deposition method including providing the layer-by-layer deposition device of any of the preceding aspects of the invention.

[0084] The method may include spraying a fluid from a reservoir.

[0085] The method may include spraying a first fluid from the first reservoir; and / or spraying a second fluid from the second reservoir.

[0086] The step of spraying the first fluid from the first reservoir may be manual.

[0087] Additionally or alternatively, the step of spraying the second fluid from the second reservoir may be manual.

[0088] The step of spraying the first fluid from the first reservoir may be automatic.

[0089] Additionally or alternatively, the step of spraying the second fluid from the second reservoir may be automatic.

[0090] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the clauses, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim, accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.BRIEF DESCRIPTION OF THE DRAWINGS

[0091] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0092] FIG. 1 A shows a side view of a layer-by-layer deposition device according to an embodiment of the invention;

[0093] FIG. 1 B shows an exploded view of the layer-by-layer deposition device of FIG. 1 A;

[0094] FIG. 1 C shows an exploded view of part of the layer-by-layer deposition device of FIG.1 A;

[0095] FIG. 1 D shows a side section view of the layer-by-layer deposition device of FIG. 1 A;

[0096] FIG. 1 E shows an opposing side section view of the layer-by-layer deposition device of FIG. 1 A;

[0097] FIG. 1 F shows the fluid flow path of the layer-by-layer deposition device of FIG. 1 A;

[0098] FIG. 1 G shows a cross section view of a nozzle for use in the layer-by-layer deposition device of FIG. 1 A;

[0099] FIG. 1 H shows an exploded view of the nozzle of FIG. 1 G; and

[0100] FIG. 2 shows a flow diagram for a layer-by-layer deposition method according to an embodiment of the invention.DETAILED DESCRIPTION

[0101] A layer-by-layer deposition device; a kit of parts for assembly into a layer-by-layer deposition device; and a layer-by-layer deposition method in accordance with the present invention is described with reference to the accompanying drawings.

[0102] An embodiment of a layer-by-layer deposition device 100 and a kit of parts for assembly into a layer-by-layer deposition device 100 will be described with particular reference to FIG. 1A, FIG. 1 B, FIG. 1C, FIG. 1 D, FIG. 1 E, FIG. 1 F, FIG. I G and FIG. 1 H.

[0103] An embodiment of a layer-by-layer deposition method 200 will be described with reference to FIG. 2.

[0104] The layer-by-layer deposition device 100 is a portable, or hand held, spray layer-by-layer deposition device. Referring now to FIG. 1A, the layer-by-layer deposition device 100 includes a body 102 and a manifold 104.

[0105] As shown in FIG. 1 B, the body 102 is a hollow casing within which components of the layer-by-layer deposition device 100 are accommodated. The body 102 includes a handle portion 106 and a spray portion 108.

[0106] The handle portion 106 has a grip size of approximately 48 millimetres, and is ergonomically designed to ensure that it is easy for a user, having an average hand width, to hold and operate. The handle portion 106 includes an actuator 110, in the form of a manual switch or button and a battery compartment 112, within which a battery 114, for example a 9-Volt lithium- ion battery, may be accommodated.

[0107] With particular reference to FIG. 1 C and FIG. 1 D, the spray portion 108 includes a fluid outlet 1 16 that is configured to accommodate a nozzle 1 18. A fluid conduit 120, a pump 122 and a one-way valve 124, for example a check valve, are each accommodated within the hollow casing of the spray portion 108 of the body 102.

[0108] The layer-by-layer deposition device 100 is configured for use with a first reservoir 140, a second reservoir 142, a third reservoir 144 and a fourth reservoir 146.

[0109] Each of the first reservoir 140, the second reservoir 142, the third reservoir 144 and the fourth reservoir 146 includes a respective fluid (not shown). In other words, the first reservoir 140 includes a first fluid; the second reservoir 142 includes a second fluid; the third reservoir 144 includes a third fluid; and the fourth reservoir 146 includes a fourth fluid.

[0110] As shown in FIG. 1 C, the first reservoir 140 and the second reservoir 142 of this embodiment are positioned on a first side of the layer-by-layer deposition device 100.

[0111] As shown in FIG. 1 D, the third reservoir 144 and the fourth reservoir 146 of this embodiment are positioned on an opposing second side of the layer-by-layer deposition device 100.

[0112] Referring now to FIG. 1 E, the manifold 104 includes an upper manifold portion 126 that has a single outlet 128. The upper manifold portion 126 is configured for fluid connection to each of a first inlet 130, a second inlet 132, a third inlet 134 and a fourth inlet 136.

[0113] Each of the first inlet 130, the second inlet 132, the third inlet 134 and the fourth inlet 136 includes a respective inlet valve (not shown). In other words, the first inlet 130 includes a first inlet valve; the second inlet 132 includes a second inlet valve; the third inlet 134 includes a third inlet valve; and the fourth inlet 136 includes a fourth inlet valve. Each of the first inlet valve, the second inlet valve, the third inlet valve and the fourth inlet valve is a one-way valve, for example a check valve.

[0114] Each of the first inlet 130, the second inlet 132, the third inlet 134 and the fourth inlet 136 includes a respective actuator. In other words, the first inlet 130 includes a first inlet actuator 148; and the second inlet 132 includes a second inlet actuator 150 (see FIG. 1 C); and the third inlet 134 includes a third inlet actuator 154; and the fourth inlet 136 includes a fourth inlet actuator 152 (see FIG. 1 D).

[0115] The manifold 104 also includes a lower manifold portion 138 via which the first inlet 130 is fluidly connected to the first reservoir 140, the second inlet 132 is fluidly connected to thesecond reservoir 142, the third inlet 134 is fluidly connected to the third reservoir 144 and the fourth inlet 136 is fluidly connected to the fourth reservoir 146.

[0116] The layer-by-layer deposition device 100 may be assembled from a kit of parts, for example a kit of parts including the body 102 and the manifold 104.

[0117] A battery 1 14 is placed in the battery compartment 112 of the handle portion 106.

[0118] The components of the spray portion 108 are assembled such that a first (outlet) end of the one-way valve 124 is fluidly connected to an inlet of the pump 122 to form a unidirectional flow assembly.

[0119] A first (inlet) end of the fluid conduit 120 is fluidly connected to an outlet of the pump 122 and an opposing second (outlet) end of the fluid conduit 120 is fluidly connected to the fluid outlet 1 16 with which a nozzle 1 18 has been assembled. The nozzle 1 18 is described in greater detail below, with reference to FIG. 1 G and FIG. 1 H.

[0120] A body fluid path 156 is assembled between the unidirectional flow assembly, the fluid conduit 120 and the fluid outlet 1 16.

[0121] The hollow casing of the body 102 is closed and the fluid conduit 120, pump 122 and valve 124 enclosed within the body 102.

[0122] A first (outlet) end of each of the first inlet 130, the second inlet 132, the third inlet 134 and the fourth inlet 136 is fluidly connected to the upper manifold portion 126 and a second (inlet) end of each of the first inlet 130, the second inlet 132, the third inlet 134 and the fourth inlet 136 is fluidly connected to the lower manifold portion 138.

[0123] In this way, a first manifold fluid path and a second manifold fluid path are defined between the lower manifold portion 138 and the upper manifold portion 126. Similarly, a third manifold fluid path (not shown) and a fourth manifold fluid path (not shown) are defined between the lower manifold portion 138 and the upper manifold portion 126.

[0124] The manifold 104 is fluidly connected to the body 102 by fluidly connecting the single outlet 128 of the upper manifold portion 126 to a second (inlet) end of the one-way valve 124.

[0125] In this way the body fluid path 156 and each of the first manifold fluid path 158, the second manifold fluid path 160, the third manifold fluid path and the fourth manifold fluid path are fluidly connected.

[0126] Each of the first reservoir 140, the second reservoir 142, the third reservoir 144 and the fourth reservoir 146 is fluidly connected to the lower manifold portion 138.

[0127] The inlet valves ensure that fluid can pass from a reservoir through its respective inlet to the upper manifold portion 126, but cannot flow from the upper manifold portion 126 or any of the inlets to any of the reservoirs. In other words, the first inlet valve ensures unidirectional flow of the first fluid from the first reservoir 140 to the upper manifold portion 126; the second inlet valve ensures unidirectional flow of the second fluid from the second reservoir 142 to the upper manifold portion 126; the third inlet valve ensures unidirectional flow of the third fluid from the third reservoir 144 to the upper manifold portion 126; and the fourth inlet valve ensures unidirectional flow of the fourth fluid from the fourth reservoir 146 to the upper manifold portion 126.

[0128] The inlet actuators allow the flow of a fluid from a reservoir through its respective inlet to the upper manifold portion 126 to be enabled or prevented.

[0129] The first inlet actuator 148 has a first configuration in which the fluid connection between the first inlet 130 and the unidirectional flow assembly (via the upper manifold portion 126) is open and a second configuration in which the fluid connection between the first inlet 130 and the unidirectional flow assembly (via the upper manifold portion 126) is closed.

[0130] When the first inlet actuator 148 is in the first configuration, the first fluid can flow from the first inlet 130 to the unidirectional flow assembly via the upper manifold portion 126. When the first inlet actuator 148 is in the second configuration, however, the flow of the first fluid from the first inlet 130 to the unidirectional flow assembly via the upper manifold portion 126 is prevented.

[0131] In the same way, the second inlet actuator 150 has a first configuration in which the fluid connection between the second inlet 132 and the unidirectional flow assembly (via the upper manifold portion 126) is open and a second configuration in which the fluid connection between the second inlet 132 and the unidirectional flow assembly (via the upper manifold portion 126) is closed.

[0132] When the second inlet actuator 150 is in the first configuration, the second fluid can flow from the second inlet 132 to the unidirectional flow assembly via the upper manifold portion 126. When the second inlet actuator 150 is in the second configuration, however, the flow of the second fluid from the second inlet 132 to the unidirectional flow assembly via the upper manifold portion 126 is prevented.

[0133] Likewise, the third inlet actuator 154 has a first configuration in which the fluid connection between the third inlet 134 and the unidirectional flow assembly (via the upper manifold portion 126) is open and a second configuration in which the fluid connection betweenthe third inlet 134 and the unidirectional flow assembly (via the upper manifold portion 126) is closed.

[0134] When the third inlet actuator 154 is in the first configuration, the third fluid can flow from the third inlet 134 to the unidirectional flow assembly via the upper manifold portion 126. When the third inlet actuator 154 is in the second configuration, however, the flow of the third fluid from the third inlet 134 to the unidirectional flow assembly via the upper manifold portion 126 is prevented.

[0135] The fourth inlet actuator 152 also has a first configuration in which the fluid connection between the fourth inlet 136 and the unidirectional flow assembly (via the upper manifold portion 126) is open and a second configuration in which the fluid connection between the fourth inlet 136 and the unidirectional flow assembly (via the upper manifold portion 126) is closed.

[0136] When the fourth inlet actuator 152 is in the first configuration, the fourth fluid can flow from the fourth inlet 136 to the unidirectional flow assembly via the upper manifold portion 126. When the fourth inlet actuator 152 is in the second configuration, however, the flow of the second fluid from the fourth inlet 136 to the unidirectional flow assembly via the upper manifold portion 126 is prevented.

[0137] In use, the fluid from each of the first inlet 130, the second inlet 132, the third inlet 134 and the fourth inlet 136 can enter the upper manifold portion 126 when the respective inlet actuator is in the first configuration (i.e. the fluid connection is open). Fluid within the upper manifold portion 126 can exit the upper manifold portion 126 via the single outlet 128.

[0138] The single outlet 128 of the upper manifold portion 126 is fluidly connected to the oneway valve 124, which in turn is fluidly connected to the pump 122.

[0139] The one-way valve 124 ensures that, in use, the flow of a fluid the single outlet 128 of the upper manifold portion 126 to the pump 122 is unidirectional. In other words, the one-way valve 124 prevents fluid from the pump 122 passing to the upper manifold portion 126 via the single outlet 128.

[0140] The pump 122 is fluidly connected to the fluid conduit 120, which is fluidly connected to the fluid outlet 1 16.

[0141] With reference to FIG. 1 G and FIG. 1 H, a nozzle 1 18 for use in the layer-by-layer deposition device 100 will be described. The nozzle 118 includes a nozzle body 162 having a bore orifice 164 and an outer thread 166 (by which the nozzle 1 18 is fluidly connected to the fluid conduit 120), a spring 168, a pen 170, and a nozzle cap 172 through which the pen 170 extends.The nozzle 1 18 is configured such that it can be cleaned without undue burden. In examples of the invention, the bore orifice has a size (diameter) of between 0.4 millimetres and 1 mm. The pen 170 is provided to increase the pressure of fluids passing through the nozzle 1 18 in order to provide a fine-mist spray. The outer thread 166 has a thread size (diameter) of 1 / 8 inch (3.175 millimetres).

[0142] The nozzle cap 172 can be replaced due to the ease of access. The viscosity range of the nozzle 118 can be adapted by varying the bore orifice 164 and the stiffness of the spring 168. The pen 170, the seal 174 and the spring 168 cooperate to prevent fluid dripping from the nozzle 1 18.

[0143] Referring now to FIG. 2, the layer-by-layer deposition method 200 includes providing, in a first step 202, a layer-by-layer deposition device 100 as described above.

[0144] The method includes include spraying 204 a first fluid from the first reservoir 140.

[0145] The method includes spraying 206 a second fluid from the second reservoir 142.

[0146] The method may further include spraying a third fluid from the third reservoir 144 and / or spraying a fourth fluid from a fourth reservoir 146.

[0147] The step 204 of spraying the first fluid from the first reservoir 140 may be manual. Alternatively, the step 204 of spraying the first fluid from the first reservoir 140 may be automatic.

[0148] The step 206 of spraying the second fluid from the second reservoir 142 may be manual. Alternatively, the step 206 of spraying the second fluid from the second reservoir 142 may be automatic.

[0149] Similarly, the steps of spraying a third fluid from the third reservoir and / or a fourth fluid from the fourth reservoir may be manual or automatic.

[0150] In embodiments of the invention, a pressure at which the fluid is suctioned is controlled by varying the voltage supplied to the pump 122.

[0151] In other embodiments of the invention, the speed at which the fluid is suctions is fixed to a specific pressure of up to 2 Megapascal (20 bar).

[0152] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

[0153] The first fluid, the second fluid, the third fluid and / or the fourth fluid for use with the layer-by-layer deposition device 100 of the invention may include one or more polyelectrolytes, for example for the deposition of multiple coatings for use in the medical and healthcare sectors.

[0154] The layer-by-layer deposition device 100 enables users to efficiently apply multiple, complimentary nano-coatings, which form a layer-by-layer assembly, to different surfaces,reducing the time required for the depositions of the coatings and minimising the waste generated during the coating process, offering portability and ease of operation.

[0155] Layer-by-layer deposition is a technique whereby polyelectrolytes, or electrostatic polymers, are built up in layers by the alternate deposition of oppositely charged materials. The layer-by-layer deposition device 100 of this embodiment enables the coating fluids to be sprayed at an appropriate distance from the surface to be coated, ensures unidirectional flow of each of the fluids within the layer-by-layer deposition device 100, is clean and easy-to-use.

[0156] The pump 122 which may be, for example, a micropump works with the one-way valve 124 to ensure that a vacuum is formed to pull fluid from the upper manifold portion 126 to the pump 122, and that the fluid cannot return backwards, thereby preventing cross-contamination of the different fluids in their respective reservoirs. In other words, the layer-by-layer deposition device 100 does not enable mixing of fluids within the layer-by-layer deposition device 100. The micropump may, in examples of the invention, be a gear-driven pump, to ensure a continuous motion is being applied to suction the fluid in a unidirectional manner.

[0157] The lower manifold portion 138 of this example is configured to provide a fluid connection to four reservoirs. It will be appreciated that, in other embodiments of the invention, the lower manifold portion may be configured to provide a fluid connection to any number of reservoirs, for example one, two, three, four, five, six or more reservoirs.

[0158] Advantageously, the layer-by-layer deposition device can be used with multiple reservoirs for spraying different polyelectrolytes, deposited sequentially or alternately to create nanocoatings based on the oppositely charged electrostatic interactions. The unidirectional flow assembly and inlet valves prevent any mixing of the complementary solutions within the layer-by- layer deposition device. The layer-by-layer deposition device enables the application of spray coatings that are versatile. The layer-by-layer deposition device also enables fast deposition speeds, for example each layer may be deposited within in a few nanoseconds, depending on the surface area to be coated. In this way, multiple layers can be built up in just a few minutes.

[0159] The manifold 104 of this example is configured to be operated manually using the actuator 1 10, using a manual switch or button. It will be appreciated that, in alternative embodiments of the invention, the manifold 104 may be configured to be operated automatically, for example using a button switch and a control screen via which an operator may open the valve and / or the actuator of any of the inlets with precision to control dosages (i.e. the volume of a fluid that is suctioned from a reservoir to the upper manifold portion 126 via its respective inlet).

[0160] The manifold 104 described above includes an upper manifold portion 126 and a lower manifold portion 138. It will be appreciated that, in alternative embodiments of the invention, the manifold may include more portions or the manifold may be a single component. The inlets, the upper manifold portion and the lower manifold portion may, for example, be provided as a single component. Such an arrangement may be more compact and lower in weight.

[0161] Advantageously, the layer-by-layer deposition device 100 is a battery-powered airless spray device that is designed to be compact and lightweight, making it easy to transport and use in a variety of settings which may include, for example healthcare settings.

[0162] The size and force of the nanodroplets expelled from the device can also be controlled to minimise the impact force of the nanodroplets on a surface.

[0163] The layer-by-layer deposition device includes a nozzle that is easily accessible from the fluid outlet for quick cleaning and washing steps. In certain examples of the invention, the nozzle may be configured such that one side of the nozzle can be removed for cleaning without the need to dismantle the entire layer-by-layer deposition device. The nozzle is configured to produce a fine-mist spray of droplets having an average droplet size (diameter) of 90.06 ± 5.05 micrometres that are sprayed with a force of impact of 1 .1 1 E-6± 6.12E-7Newtons.

[0164] Certain embodiments of the invention are described in the following clauses:

[0165] Clause 1 . A layer-by-layer deposition device comprising: a first inlet that is configured to be fluidly connected to a first reservoir; a second inlet that is configured to be fluidly connected to a second reservoir; a unidirectional flow assembly that is fluidly connected to the first inlet and the second inlet and a fluid conduit that is fluidly connected to each of the unidirectional flow assembly and a fluid outlet; wherein the unidirectional flow assembly is configured to ensure unidirectional flow from each of the first inlet and the second inlet to the fluid outlet via the fluid conduit.

[0166] Clause 2. The layer-by-layer deposition device of clause 1 comprising: a first reservoir that is fluidly connected to the first inlet; and a second reservoir that is fluidly connected to the second inlet, wherein the unidirectional flow assembly is configured to ensure unidirectional flow of a first fluid from the first reservoir to the fluid conduit and unidirectional flow of a second fluid from the second reservoir to the fluid conduit.

[0167] Clause 3. The layer-by-layer deposition device of clause 2, wherein the unidirectional flow assembly comprises a pump that controls unidirectional flow of the first fluid from the firstinlet to the fluid conduit and / or controls unidirectional flow of the second fluid from the second inlet to the fluid conduit.

[0168] Clause 4. The layer-by-layer deposition device of clause 3, wherein the pump is a micropump.

[0169] Clause 5. The layer-by-layer deposition device of clause 3 or 4, wherein the pump is a positive displacement pump.

[0170] Clause 6. The layer-by-layer deposition device of clause 5, wherein the positive displacement pump is a gear pump.

[0171] Clause 7. The layer-by-layer deposition device of clause 3, wherein the unidirectional flow assembly comprises a valve that cooperates with the pump to control unidirectional flow from the first inlet to the fluid conduit and from the second inlet to the fluid conduit.

[0172] Clause 8. The layer-by-layer deposition device of clause 7, wherein the valve is a oneway valve.

[0173] Clause 9. The layer-by-layer deposition device of clause 8, wherein the valve is a check valve.

[0174] Clause 10. The layer-by-layer deposition device of clause 8 or 9, wherein the one-way valve is selected from a ball valve, a diaphragm valve, a swing check valve, a butterfly check valve, a stop-check valve, a lift-check valve, an in-line check valve, a duckbill valve, a reed valve, a solenoid valve.

[0175] Clause 1 1 . The layer-by-layer deposition device of any one of clauses 3 to 10, wherein the first inlet comprises a first inlet valve that is configured to ensure unidirectional flow of the first fluid from the first reservoir to the first inlet and / or wherein the second inlet comprises a second inlet valve that is configured to ensure unidirectional flow of the second fluid from the second reservoir to the second inlet.

[0176] Clause 12. The layer-by-layer deposition device of any one of clauses 3 to 1 1 , wherein the first inlet comprises a first inlet actuator, wherein the first inlet actuator has a first configuration in which a fluid connection between the first inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the first inlet and the unidirectional flow assembly is closed, and / or wherein the second inlet comprises a second inlet actuator, wherein the second inlet actuator has a first configuration in which a fluid connection between the second inlet and the unidirectional flow assembly is open and a secondconfiguration in which the fluid connection between the second inlet and the unidirectional flow assembly is closed.

[0177] Clause 13. The layer-by-layer deposition device of clause 12, wherein, when the first inlet actuator is in the first configuration and the fluid connection between the first inlet and the unidirectional flow assembly is open, the fluid connection between the second inlet and the unidirectional flow assembly is closed.

[0178] Clause 14. The layer-by-layer deposition device of clause 12 or 13, wherein, when the second inlet actuator is in the first configuration and the fluid connection between the second inlet and the unidirectional flow assembly is open, the fluid connection between the first inlet and the unidirectional flow assembly is closed.

[0179] Clause 15. The layer-by-layer deposition device of any one of clauses 12 to 14, wherein the or each actuator is a mechanical actuator.

[0180] Clause 16. The layer-by-layer deposition device of any one of clauses 12 to 14, wherein the or each actuator is an electromagnetic actuator

[0181] Clause 17. The layer-by-layer deposition device of clause 16, wherein the or each electromagnetic actuator comprises a solenoid.

[0182] Clause 18. The layer-by-layer deposition device of any one of clauses 7 to 17, comprising a power supply and a controller, wherein the controller is operable to control the pump.

[0183] Clause 19. The layer-by-layer deposition device of clause 18, wherein the power supply comprises a battery.

[0184] Clause 20. The layer-by-layer deposition device of clause 18 or 19, wherein the controller is operable to control a pressure in the fluid conduit.

[0185] Clause 21 . The layer-by-layer deposition device of clause 20, wherein the controller is configured to control a voltage supplied to the pump from the power supply.

[0186] Clause 22. The layer-by-layer deposition device of any one of clauses 18 to 21 , wherein the controller is operable to control a mass flow rate in the layer-by-layer deposition device.

[0187] Clause 23. The layer-by-layer deposition device of clause 22, wherein the controller is configured to control the pump to fix the mass flow rate at a specific pressure.

[0188] Clause 24. The layer-by-layer deposition device of clause 23, wherein the mass flow rate is at least 2 grams per second.

[0189] Clause 25. The layer-by-layer deposition device of clause 23 or 24, wherein the mass flow rate is at least 2.2 grams per second.

[0190] Clause 26. The layer-by-layer deposition device of any one of clauses 23 to 25, wherein the mass flow rate is up to 3 grams per second.

[0191] Clause 27. The layer-by-layer deposition device of any one of clauses 23 to 26, wherein the mass flow rate is up to 2.5 grams per second.

[0192] Clause 28. The layer-by-layer deposition device of clause 23, wherein the mass flow rate is between 2 grams per second and 3 grams per second.

[0193] Clause 29. The layer-by-layer deposition device of clause 23, wherein the mass flow rate is between 2 grams per second and 2.5 grams per second.

[0194] Clause 30. The layer-by-layer deposition device of clause 23, wherein the mass flow rate is between 2.2 grams per second and 3 grams per second.

[0195] Clause 31 . The layer-by-layer deposition device of clause 23, wherein the mass flow rate is between 2.2 grams per second and 2.5 grams per second.

[0196] Clause 32. The layer-by-layer deposition device of any one of clauses 23 to 31 , wherein the specific pressure is up to 2 Megapascal (20 bar).

[0197] Clause 33. The layer-by-layer deposition device of clause 332, wherein the specific pressure is up to 1 Megapascal (10 bar).

[0198] Clause 34. The layer-by-layer deposition device of any one of clauses 18 to 33, wherein the controller is operable to control an order in which the first fluid and / or the second fluid is ejected from the layer-by-layer deposition device.

[0199] Clause 35. The layer-by-layer deposition device of any one of clauses 1 to 34, comprising: a third inlet that is configured to be fluidly connected to a third reservoir; wherein the third inlet is fluidly connected to the unidirectional flow assembly.

[0200] Clause 36. The layer-by-layer deposition device of clause 35, comprising: a third reservoir that is fluidly connected to the third inlet; and wherein the unidirectional flow assembly is configured to ensure unidirectional flow of a third fluid from the third reservoir to the fluid conduit.

[0201] Clause 37. The layer-by-layer deposition device of clause 36, wherein the third inlet comprises a third inlet valve that is configured to ensure unidirectional flow of the third fluid from the third reservoir to the third inlet.

[0202] Clause 38. The layer-by-layer deposition device of clause 36 or clause 37, wherein the third inlet comprises a third inlet actuator, wherein the third inlet actuator has a first configuration in which a fluid connection between the third inlet and the unidirectional flowassembly is open and a second configuration in which the fluid connection between the third inlet and the unidirectional flow assembly is closed

[0203] Clause 39. The layer-by-layer deposition device of any one of clauses 1 to 38, wherein the fluid outlet comprises a nozzle.

[0204] Clause 40. The layer-by-layer deposition device of clause 39, wherein the nozzle is an atomising nozzle.

[0205] Clause 41 . The layer-by-layer deposition device of clause 40, wherein the nozzle has an orifice, and the orifice of the nozzle has a diameter of at least 0.2 millimetres.

[0206] Clause 42. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is at least 0.3 millimetres.

[0207] Clause 43. The layer-by-layer deposition device of clause 41 or 42, wherein the diameter of the orifice of the nozzle is at least 0.4 millimetres.

[0208] Clause 44. The layer-by-layer deposition device of any one of clauses 41 to 43, wherein the diameter of the orifice of the nozzle is less than or equal to 1 .2 millimetres.

[0209] Clause 45. The layer-by-layer deposition device of any one of clauses 41 to 44, wherein the diameter of the orifice of the nozzle is less than or equal to 1 .0 millimetres.

[0210] Clause 46. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.2 millimetres and 1.2 millimetres.

[0211] Clause 47. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.2 millimetres and 1.1 millimetres.

[0212] Clause 48. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.2 millimetres and 1.0 millimetres.

[0213] Clause 49. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.3 millimetres and 1.2 millimetres.

[0214] Clause 50. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.3 millimetres and 1.1 millimetres.

[0215] Clause 51 . The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.3 millimetres and 1.0 millimetres.

[0216] Clause 52. The layer-by-layer deposition device of clause 41 , wherein the diameter of the orifice of the nozzle is between 0.4 millimetres and 1.2 millimetres.

[0217] Clause 53. The layer-by-layer deposition device of clause 41, wherein the diameter of the orifice of the nozzle is between 0.4 millimetres and 1.1 millimetres.

[0218] Clause 54. The layer-by-layer deposition device of clause 41, wherein the diameter of the orifice of the nozzle is between 0.4 millimetres and 1.0 millimetres.

[0219] Clause 55. The layer-by-layer deposition device of any one of clauses 39 to 54, wherein the nozzle comprises an impingement pin that is configured to atomise fluid into droplets.

[0220] Clause 56. The layer-by-layer deposition device of clause 55, wherein the nozzle is configured to produce one or more droplet, and wherein the one or more droplet has a diameter of less than or equal to 100 micrometres.

[0221] Clause 57. The layer-by-layer deposition device of clause 56, wherein the diameter of the one or more droplet is at least 70 micrometres.

[0222] Clause 58. The layer-by-layer deposition device of clause 56 or 57, wherein the one or more droplet has a force impact of less than or equal to 1.5 x 10-6 Newtons.

[0223] Clause 59. The layer-by-layer deposition device of clause58, wherein the force impact of the one or more droplet is at least 0.8 x 10-6 Newtons.

[0224] Clause 60. The layer-by-layer deposition device of any one of clauses 1 to 59, wherein the layer-by-layer deposition device is a portable layer-by-layer deposition device.

[0225] Clause 61 . The layer-by-layer deposition device of any one of clauses 1 to 60; comprising a manifold, wherein the manifold comprises the first inlet, the second inlet and a first portion of the unidirectional flow assembly; and a body including a second portion of the unidirectional flow assembly, the fluid conduit and the fluid outlet.

[0226] Clause 62. A kit of parts for assembly into the layer-by-layer deposition device of any one of clauses 2 to 60, the kit of parts comprising: a manifold comprising the first inlet, the second inlet and a first portion of the unidirectional flow assembly; a body within which the fluid conduit and a second portion of the unidirectional flow assembly are housed; the first reservoir comprising the first fluid; and the second reservoir comprising the second fluid.

[0227] Clause 63. The kit of parts of clause 62, wherein the first fluid is a first polyelectrolyte and the second fluid is a second polyelectrolyte, wherein the first polyelectrolyte is different to the first polyelectrolyte.

[0228] Clause 64. The kit of parts of clause 63, wherein one of the first polyelectrolyte and the second polyelectrolyte is a positive polyelectrolyte.

[0229] Clause 65. The kit of parts of clause 64, wherein the other of the first polyelectrolyte and the second polyelectrolyte is a negative polyelectrolyte.

[0230] Clause 66. The kit of parts of any one of clauses 62 to 65, comprising a third reservoir, wherein the third reservoir comprises a third fluid.

[0231] Clause 67. The kit of parts of clause 66, wherein the third fluid is a third polyelectrolyte and wherein the third polyelectrolyte is different to the first polyelectrolyte and the second polyelectrolyte.

[0232] Clause 68. The kit of parts of clause 66 or 67, comprising a fourth reservoir, wherein the fourth reservoir comprises a fourth fluid.

[0233] Clause 69. The kit of parts of clause 68, wherein the fourth fluid is a fourth polyelectrolyte, wherein the fourth polyelectrolyte is different to the first polyelectrolyte, the second polyelectrolyte and the third polyelectrolyte.

[0234] Clause 70. The kit of parts of any one of clauses 62 to 68, comprising a further reservoir, wherein the further reservoir comprises a further fluid.

[0235] Clause 71 . The kit of parts of clause 70, wherein the further fluid comprises one or more of: calcium, fibrogen, thrombin, fibrin sealant, keratinocytes, fibroblasts, pharmaceutical agents, antimicrobial agents, such as silver nanoparticles, antibacterial agents, peptides.

[0236] Clause 72. A layer-by-layer deposition method comprising: providing the layer-by-layer deposition device of any one of clauses 2 to 61 , spraying a first fluid from the first reservoir; and spraying a second fluid from the second reservoir.

[0237] Clause 73. The layer-by-layer deposition method of clause 72, wherein the step of spraying the first fluid from the first reservoir is manual.

[0238] Clause 74. The layer-by-layer deposition method of clause 72 or 73, wherein the step of spraying the second fluid from the second reservoir is manual.

[0239] Clause 75. The layer-by-layer deposition method of clause 72, wherein the step of spraying the first fluid from the first reservoir is automatic.

[0240] Clause 76. The layer-by-layer deposition method of clause 72 or 75, wherein the step of spraying the second fluid from the second reservoir is automatic. 1

Claims

CLAIMS1 . A layer-by-layer deposition device comprising: a first inlet that is configured to be fluidly connected to a first reservoir; a second inlet that is configured to be fluidly connected to a second reservoir; a fluid conduit that is fluidly connected to each of the first inlet and the second inlet by a unidirectional flow assembly; and a fluid outlet that is fluidly connected to the fluid conduit; wherein the unidirectional flow assembly is configured to ensure unidirectional flow of a fluid from each of the first inlet and the second inlet to the fluid conduit.

2. The layer-by-layer deposition device of claim 1 , comprising: a first reservoir that is fluidly connected to the first inlet; and a second reservoir that is fluidly connected to the second inlet, wherein the unidirectional flow assembly is configured to ensure unidirectional flow of a first fluid from the first reservoir to the fluid conduit and unidirectional flow of a second fluid from the second reservoir to the fluid conduit.

3. The layer-by-layer deposition device of claim 1 or 2, wherein the unidirectional flow assembly comprises a pump that controls unidirectional flow from the first inlet to the fluid conduit and / or from the second inlet to the fluid conduit.

4. The layer-by-layer deposition device of claim 3, wherein the unidirectional flow assembly comprises a valve that cooperates with the pump to control unidirectional flow from the first inlet to the fluid conduit and / or unidirectional flow from the second inlet to the fluid conduit.

5. The layer-by-layer deposition device of any one of claims 1 to 4, wherein the first inlet comprises a first inlet actuator, wherein the first inlet actuator has a first configuration in which a fluid connection between the first inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the first inlet and the unidirectional flow assembly is closed.

6. The layer-by-layer deposition device of claim 5, wherein, when the first inlet actuator is in the first configuration and the fluid connection between the first inlet and the unidirectional flow assembly is open, the fluid connection between the second inlet and the unidirectional flow assembly is closed.

7. The layer-by-layer deposition device of any one of claims 1 to 5, wherein the second inlet comprises a second inlet actuator, wherein the second inlet actuator has a first configuration in which a fluid connection between the second inlet and the unidirectional flow assembly is open and a second configuration in which the fluid connection between the second inlet and the unidirectional flow assembly is closed.

8. The layer-by-layer deposition device of claim 7, wherein, when the second inlet actuator is in the first configuration and the fluid connection between the second inlet and the unidirectional flow assembly is open, the fluid connection between the first inlet and the unidirectional flow assembly is closed.

9. The layer-by-layer deposition device of any one of claims 3 to 8, comprising a power supply and a controller, wherein the controller is operable to control the pump.

10. The layer-by-layer deposition device of claim 9, wherein the controller is operable to control a pressure in the fluid conduit.11 . The layer-by-layer deposition device of claim 10, wherein the controller is configured to control a voltage supplied to the pump from the power supply.

12. The layer-by-layer deposition device of any one of claims 9 to 11 , wherein the controller is operable to control a mass flow rate of a fluid in the layer-by-layer deposition device.

13. The layer-by-layer deposition device of claim 12, wherein the controller is configured to control the pump to fix the mass flow rate at a specific pressure.

14. The layer-by-layer deposition device of claim 13, wherein the mass flow rate is at least 2 grams per second.

15. The layer-by-layer deposition device of claim 13 or 14, wherein the mass flow rate is up to 3 grams per second.

16. The layer-by-layer deposition device of any one of claims 13 to 15, wherein the specific pressure is up to 2 Megapascal (20 bar).

17. The layer-by-layer deposition device of any one of claims 9 to 16, wherein the controller is operable to control an order in which the first fluid and / or the second fluid is sprayed from the layer-by-layer deposition device.

18. The layer-by-layer deposition device of any one of claims 1 to 17, wherein the fluid outlet comprises a nozzle, for example wherein the nozzle is an atomising nozzle.

19. A kit of parts for assembly into the layer-by-layer deposition device of any one of claims 1 to 18, the kit of parts comprising: a manifold comprising the first inlet and the second inlet; and a body comprising the unidirectional flow assembly, the fluid conduit and the fluid outlet.

20. The kit of parts of claim 19, comprising: a first reservoir that is configured for fluid connection to the first inlet via the manifold, the first reservoir comprising a first fluid; and a second reservoir that is configured for fluid connection to the second inlet via the manifold, the second reservoir comprising a second fluid; for example wherein the first fluid is a first polyelectrolyte and the second fluid is a second polyelectrolyte, wherein the first polyelectrolyte is different to the first polyelectrolyte.

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