A nozzle for use in micropumps

Abstract

A nozzle (401) for use in micropumps comprises a first plate (402a) having a first substantially planar surface (403a); a second plate (402b) having a second substantially planar surface (403b); the first and second plates (402a, 402b) positioned so that the first (403a) and second (403b) planar surfaces are directly adjacent to one another, the substantially planar surfaces (403a, 403b) on both of the first (402a) and second (402b) plates etched to form open-topped channels (404a, 404b); the first and second plates etched and aligned so that the open-topped channels (404a, 404b) combine to form an enclosed passage or passages that run at least partly through the nozzle (401).

Description

[0001] A NOZZLE FOR USE IN MICROPUMPS

[0002] TECHNICAL FIELD

[0003] The present invention relates to a nozzle for use in micropumps for delivery of fluids. More particularly, the present invention relates to a nozzle for use in micropumps for delivery of fluids that comprises a pair of plates, each one of the pair having channels formed in / on the inner face. The present invention also relates to an inhaler device that comprises a nozzle for use in micropumps.

[0004] BACKGROUND

[0005] Micro liquid dispensing systems (‘micropumps’) are a type of device that is used for dispensing small quantities of fluids within a range of flow rates that is typically in the micro / millilitres per minute range. Such systems are of special interest for use as fluid delivery systems in applications such as drug delivery, where control and accuracy is important.

[0006] In inhalation drug delivery systems, micropumps are used to generate a spray of fine droplets for delivery to the lungs of a user. A typical known type of inhalation drug delivery system includes a nozzle (also known as a chip or filter) that contains a pattern of microchannels therethrough. In use, fluids pass into and out of the nozzle through the microchannels. Nozzles of this type are typically formed by sandwiching two large substrate sheets together - typically a glass substrate and a silicon substrate - so as to form a wafer, with the microchannels formed and located on one of the directly adjacent inner faces of the two substrates. This larger wafer is then cut into pieces so as to form a number of individual nozzles.

[0007] Within the nozzle, the microchannels define the flow of fluid through the nozzle and critical functional and performance attributes. In particular in addition to conveyance of fluid through the nozzle, the channels may have geometry that acts as a filtration mechanism, trapping undesirable particles to prevent them blocking exit orifices. The shape and characteristics of the fluid exiting the nozzle is also dependent on the shape of the microchannels, and the “jets” that form dictate the aerosol characteristics. Differences in the geometry of the microchannels directly affects the functional and performance characteristics and the microchannels are therefore formed as precisely as possible in order to accurately manage fluids inside the microchannels and exiting the microchannels.

[0008] The cross-sectional shape and size of a channel (microchannel) has a significant effect on the flow characteristics of a fluid within the channel, due to the distribution of shear stress and velocity profiles within the channel. For fluid flow, a round cross-section would provide optimum flow efficiency. However this optimum or ideal geometry is difficult to achieve using the manufacturing techniques currently available. As the aspect ratio (width:depth) increases, the overall efficiency of the microchannel for fluid flow through the microchannel decreases, for a given cross-sectional area.

[0009] In soft mist inhaler nozzles of the known type, it is normal to etch the nozzle jets into one of the substrates (leaving the other unetched), and the etch depth and the cross-sectional shape of the etched channel dictates the fluid flow through the microchannel, and the shape and velocity of fluid jets from exit orifices.

[0010] Channels having a rectangular cross-section can be relatively easily formed in a silicon substrate by using an anisotropic etching process such as for example Deep Reactive Ion Etching (DRIE). Other anisotropic etching methods can also be used. Anisotropic etching of this type when used on a silicon substrate will produce channels having a rectangular crosssection and sharp corners within the channel. By adjusting the DRIE process, deeper channels can be created, and given enough processing time, square (aspect ratio of 1 ) cross-sections can be achieved. However increasing the processing time increases the cost and as such microchannels with an aspect ratio of greater than 1 are commonly used as a compromise between the desired flow characteristics and manufacturing cost. In addition, channels with sharp corners have complex flow patterns near the corners. The flow velocity is highest at the centre of the channel, and decreases towards the walls. The presence of corners can lead to secondary flows (that is, minor flows superimposed on the primary flow direction, potentially affecting mixing and particle distribution in the channel).

[0011] DRIE is also generally less suitable for etching glass.

[0012] Rounded channels (e.g. channels with rounded corners / sides) offer a more uniform velocity profile and lower resistance to flow, due to the absence of sharp corners. Rounded channels offer a parabolic velocity profile for flow within the channel, with the maximum velocity at the centre

[0013] However, channels having rounded cross-sectional corners / sides can be formed more easily and with generally less cost than square channels, by using isotropic etching processes to etch glass substrates rather than using an anisotropic process such as the anisotropic processes described above that are used to etch silicon.

[0014] The isotropic etching process etches in all directions, such that the width of the microchannel is increased in each direction at a similar rate to the depth. The resulting geometry on a single etched channel therefore has an aspect ratio (width:depth) of at least 2.

[0015] US7,896,264 describes and shows a microstructured nozzle used with an atomiser which produces an aerosol from a fluid containing a medicament. The nozzle consists of a number of channels produced by microstructuring a plate-shaped member or substrate. In the nozzle the channels are located between projections which are arranged side by side in rows and project from a base plate / substrate. This microstructured base plate / substrate is covered with a cover plate / substrate. The channels are narrowly defined in terms of shape, cross sectional area and length. The nozzle contains a filter as the primary structure and a secondary structure downstream of the filter.

[0016] As noted above, nozzles of this type are typically formed by sandwiching two large substrate sheets together to form a nozzle wafer (a nozzle wafer being a single large wafer from which smaller individual nozzles can be cut). The nozzle wafer is formed from a base plate / first substrate and a cover plate / second substrate. Typically, one substrate is glass and the other silicon - a ‘combination wafer’. Silicon is used because the anisotropic DRIE etching process can be used to form channels in / on the silicon, and this process provides accurate results as outlined above - the DRIE process provides channels having vertical side walls with a width defined by the mask (as opposed to isotropic etching where the width is increased during the etching process), and formed within tight tolerances. However, cutting / dicing a silicon / glass combination wafer can be problematic - both the glass and silicon substrates need to be cut very precisely in order to ensure that the final product is accurately sized and that both substrates are correctly aligned. For each of these materials by themselves, the cutting process would normally be carried out with both a saw specialised for that material and a process specialised for that material - different dicing / cutting parameters are required for the different materials (silicon and glass). However, in a combination nozzle wafer where one substrate is formed from glass and the other from silicon, these materials have to be cut simultaneously, and compromises to the cutting process must be made. Generally, in a combination wafer a single very thin high speed saw blade is used to cut the final product (e.g. the nozzle) from the wafer. This saw blade is either most suited / specialised for cutting one of the glass or the silicon, and as a consequence not optimal for cutting the other material. This can lead to undesirable results during the cutting process, such as delamination and cracking and chipping. For example, when a mixed silicon and glass material is cut, chipping along the edge of the cut can very easily occur. This can impact on the sealing ability of a nozzle cut from the wafer, and if chipping occurs at inlets or outlets of the microfluidic channels, the performance of the impinging jets can be also potentially be impaired.

[0017] As well as this, it can sometimes be necessary to add further items to the finished assembly, such as for example a washer, in order to prevent delamination and cracking in use. This adds to the complexity and cost of a micropump. SUMMARY

[0018] It is an object of the present invention to provide a nozzle for use in micropumps for delivery of fluids which goes some way to overcoming the abovementioned disadvantages or which at least provides the public or industry with a useful choice.

[0019] It is a further object of the present invention to provide an inhaler device that comprises a nozzle for use in micropumps which goes some way to overcoming the abovementioned disadvantages or which at least provides the public or industry with a useful choice.

[0020] Accordingly, in a first aspect the present invention may broadly be said to consist in a nozzle for use in micropumps, comprising: a first plate having a first substantially planar surface; a second plate having a second substantially planar surface; the first and second plates positioned so that the first and second planar surfaces are directly adjacent to one another, the substantially planar surfaces on one or both of the first and second plates etched to form open-topped channels, the first and second plates etched and aligned so that the open-topped channels combine to form an enclosed passage or passages that run at least partly through the nozzle.

[0021] In an embodiment, the first and second plates comprise glass plates, the channels having curved or radial sidewalls.

[0022] In an embodiment, the first plate is etched to form multiple side-by-side channels that partly overlap at their connecting edges to form a single passage.

[0023] In an embodiment, the second plate is etched to form multiple side-by-side channels that partly overlap at their connecting edges, the channels in the first and second plates aligned so as to form a single passage, the gap connecting the side-by-side channels having a cross-sectional area smaller than the cross-sectional area of any one of the channels.

[0024] In an embodiment, the channels in the second plate are formed so as to be substantially identical to the channels in the first plate.

[0025] In an embodiment, each of the first and second plates are etched to form channels, the first and second plates aligned so that a single passage is formed from the channels, the passage having an aspect ratio less than that of each of the channels.

[0026] In an embodiment, the channels on the first and second plates are substantially aligned to mirror each other.

[0027] In an embodiment, the channels on the first and second plates are aligned so as to form a gap connecting the channels, the gap having a cross-sectional area smaller than the cross- sectional area of a channel. In an embodiment, the first and second plates comprise silicon plates, the channels having a substantially rectangular cross-section.

[0028] In an embodiment, each of the first and second plates are etched to form channels, the first and second plates aligned so that a single passage is formed from the channels, the passage having an aspect ratio less than that of each of the channels.

[0029] In an embodiment, the channels on the first and second plates are substantially aligned to mirror each other.

[0030] With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

[0031] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0032] Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further aspects of the invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings which show an embodiment of the device by way of example, and in which:

[0035] Figure 1 shows a side view of a known type of manually-operated nebuliser / Soft Mist Inhaler that has an upper housing part and a lower housing part, the two housing parts rotated relative to one another in use to pump or prime the device for use, the upper housing part having a lid that can be opened and closed in use to allow a user to access a mouthpiece.

[0036] Figure 2 shows a perspective view from one side and slightly above of the nebuliser / Soft Mist Inhaler of figure 1 , the lid shown slightly open. Figure 3 shows a perspective view of the nebuliser of figures 1 and 2 from a generally similar angle as that of figure 2 but with the lid closed, the outer casing elements of the nebuliser / Soft Mist Inhaler shown semi-transparent so as to show some internal detail of several of the main internal parts of the nebuliser.

[0037] Figure 4 shows a perspective cutaway side view of the upper end of the upper housing part of the nebuliser / Soft Mist Inhaler of figures 1 to 3, the upper housing part enclosed by a lid (shown in the closed position), the upper housing part comprising a mouthpiece and nozzle assembly, the nozzle assembly located within the mouthpiece.

[0038] Figure 5 shows a cutaway schematic side view of the nozzle assembly of figure 4, the nozzle assembly comprising a micropump that comprises a nozzle retainer, upper and lower seals, a nozzle chip / filter, a pre-filter and pre-filter holder, and a top nut that screws onto the upper end of an upper tube housing located within the upper housing so as to enclose these items.

[0039] Figure 6 shows a schematic end view of two sandwiched plates of the type that are used to form a nozzle chip / filter of the type used in the nebuliser / Soft Mist Inhaler of the preceding figures.

[0040] Figure 7 shows a schematic side view of one plate of a chip / filter of the type that is formed from two sandwiched plates, with the other plate not shown so that the internal structure of the chip / filter can be shown, this figure showing the general form of the structure of the channels inside the chip / filter.

[0041] Figure 8 shows a stylised cutaway end view of the flow channel cross-section of the chip / filter showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels or passages formed in the lower one of the layers, the channels shown as a stylised single passage in the figure, each of the layers formed from glass, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0042] Figure 9 shows a stylised cutaway end view of the single-etched chip / filter of figure 8, showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, multiple channels or passages formed in the lower one of the layers, the channels shown as a stylised pair of passages in the figure, each of the layers formed from glass, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0043] Figure 10 shows a stylised cutaway end view of a first embodiment of the chip / filter of the present invention, showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels or passages formed in each of the layers, the channels shown as a stylised single passage in the figure, the sides or edges of the channels substantially matched to form a single passage when the two wafers are brought together, each of the layers formed from glass, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0044] Figure 11 shows a stylised cutaway end view of a second embodiment that is a variation of the first embodiment of the chip / filter shown in figure 10, showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, multiple channels or passages formed in each of the layers, the channels shown as stylised single passages in the figure, the sides or edges of the channels substantially matched to form passage pairs when the two wafers are brought together, each of the layers formed from glass, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0045] Figure 12 shows a stylised cutaway end view of a prior art version of the chip / filter, showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, a channel or channels formed in each of the layers, the channels shown as stylised single passages in the figure, the channels offset on the sandwiched substrates when these are brought together to form the wafer, so that there is no fluid interchange or exchange between the channels, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0046] Figure 13 shows a stylised cutaway end view of a third embodiment showing detail of two glass layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels formed in each of the layers, the channels shown as a stylised single passage in the figure, the sides or edges of the channels partly or slightly overlapping to allow fluids to pass from one channel to the other where the channels overlap, an isotropic etching process used to form the channels so that the channels have rounded corners.

[0047] Figure 14 shows a stylised cutaway end view of a prior art form of chip / filter, showing detail of two layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels or passages formed in the lower one of the layers, the channels shown as a stylised single passage in the figure, the lower layer formed from silicon, an anisotropic etching process used to form channels having a rectangular cross section.

[0048] Figure 15 shows a stylised cutaway end view of a fourth embodiment of the chip / filter of the present invention, showing detail of two silicon layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels or passages formed in each of the layers, the channels shown as a stylised single passage in the figure, the sides or edges of the channels substantially matched to form a single passage when the two wafers are brought together, each of the layers formed from silicon, an anisotropic etching process used to form the channels so that these have substantially square or rectangular cross-sections.

[0049] Figure 16 shows a stylised cutaway end view of a fifth embodiment of the chip / filter of the present invention, showing detail of two silicon layers or plates sandwiched together with adjoining or directly adjacent inner faces, channels or passages formed in each of the layers, the sides or edges of the channels offset but partly or slightly overlapping to allow fluids to pass from one channel to the other where the channels overlap.

[0050] DETAILED DESCRIPTION

[0051] Embodiments of the invention, and variations thereof, will now be described in detail with reference to the figures.

[0052] As used in this specification, the term "micropump" refers to micro liquid dispensing systems employed to dispense a fluid in small quantities with increased accuracy, and which can control and manipulate small volumes of fluid (generally in micrometric volumes). The term "fluid" refers to a substance, typically a liquid, that undergoes a deformation in shape and / or volume when subjected to an external force. Examples of fluids include, but are not limited to, inhalation drug formulations. It will be appreciated that the micropump is required to deliver fluids such as these in small quantities, with accurate volume, and to precise locations.

[0053] Terms such as ‘upper’, ‘lower’, ‘base’, and ‘cover" as used in this specification are context- dependent, and not absolute. For example, where ‘upper’ is used in the description of figure 4 above and in the detailed description below, this is within the context of the figure as shown. The nebuliser / Soft Mist Inhaler as shown in the figure can be used in any orientation and does not have to be used in the orientation shown.

[0054] As used in this specification, ‘substrate’ refers to a single piece of glass or silicon either etched or unetched, and (depending on the context as outlined in the relevant portion of the description) will usually refer to a single large sheet of glass or silicon that will be etched and then cut into smaller units.

[0055] ‘Wafer’ refers to a sandwich of two substrates formed as a result of a bonding process, a wafer containing multiple ones of the final product but not yet cut out from the wafer, and ‘nozzle’ or ‘chip / filter’ refers to an example of the final, finished product, following the final manufacturing step of dicing the wafer into separate items - that is, separate chips / filters or nozzles (‘nozzle’ and ‘chip / filter’ are used interchangeably, and ‘chip’, and ‘filter" may also be used separately from one another and in isolation).

[0056] ‘Layer’ or ‘plate’ as used in this specification refers in general to one of the two main pieces of the finished product (e.g. one of the two layers of the chip / filter). As used in this specification, the final finished product - the ‘chips / filters’ and / or ‘nozzles’ - are used to indicate items through which fluids flow, through an etched, moulded or engraved pattern of microchannels in the item. More specifically, the fluids flow through moulded or engraved microchannels that are formed in one or both of the directly adjacent or adjoining faces of two wafers that are sandwiched together to comprise part or all of the chip / filter.

[0057] Inhalation drug formulations frequently need to be provided as a spray with a droplet size small enough to penetrate to the lungs. A typical method for producing such a spray is to force fluid through chips / filters at high pressure, e.g. substantially between 10 to 59MPa. The fluid may be a pharmaceutical compound, dissolved in a suitable solvent (such as for example water or another acceptable low volatility substance). In the preferred embodiments as described and shown herein, the micropump is designed for use as part of an apparatus (a liquid delivery device) for delivering a substance used as a medication, i.e. the fluid is a chemical compound that has a physiological effect on the patient when administered.

[0058] General

[0059] For all of the embodiments described below, the invention is described as forming part of a liquid delivery device (the invention may also be considered as the liquid delivery device itself). Specifically for the embodiments described, the liquid delivery device is a nebuliser or inhaler (more specifically, a Soft Mist Inhaler).

[0060] A typical known type of nebuliser or inhaler in or with which the chip / filter of the present invention can be used is shown in figures 1 to 5. In these figures, a chip / filter forms part of the nebuliser / inhaler. This known type of chip / filter can be changed or swapped for the chip / filter of the present invention. Chips / filters according to embodiments of the invention, and variations of those embodiments, are described below. The chip / filter is referred to generally as chip / filter 101 , with the specific embodiments of the chips / filters of the present invention described separately and numbered appropriately as detailed below.

[0061] As shown in figures 1 to 5, the nebuliser 1 comprises an upper housing part 2 and a lower housing part 3. The upper housing part 2 contains a retaining structure / nozzle assembly (described in detail below) and a mouthpiece 5 within the lid. The lower housing part 3 contains a liquid reservoir (not shown), which typically comprises a cartridge that can be removed and replaced as required. A riser tube or capillary tube 6 extends between the reservoir and the nozzle assembly. A lid 4 is hingedly connected to the upper housing part, the lid configured so that when closed, the lid encloses the nozzle retaining structure / nozzle assembly.

[0062] In use, a user rotates the upper and lower housing parts 2, 3 relative to one another to pump or prime the device 1 for use. Liquid from the reservoir is sucked up the tube 6 towards the upper end of the tube. When a user then triggers the nebuliser (e.g. by pressing button 7), the tube 6 is forced rapidly upwards with the head of the tube 6 forcing liquid through the nozzle assembly, and then through the mouthpiece 5, for delivery to a user as a spray or aerosol of fine droplets.

[0063] For the purposes of this specification, references to orientations such as ‘upper, ‘lower’, ‘top’, ‘bottom’, ‘vertical’, ‘horizontal’ and similar or related references should be taken as meaning with respect to an orientation with the nebuliser stood upright with the mouthpiece at the upper end, even if in use the orientation would differ from this. These references to orientation should not be taken as absolute.

[0064] Nozzle Retaining Structure I Nozzle Assembly

[0065] Nozzle retaining structures I nozzle assemblies are shown in figures 4 and 5.

[0066] A typical known type of nozzle assembly comprises the following main parts: a filter holder 9; a pre-filter 10; an upper seal or nozzle seal 11 ; a lower seal 12; a chip / filter 101 ; a top nut 14, and; a nozzle retainer 15.

[0067] The filter holder 9, pre-filter 10, upper and lower seals 11 , 12, nozzle retainer 15 and chip / filter 101 are contained within the top nut 14. The top nut 14 is screwed to the top of an upper tube housing 8 (that contains the tube 6, with tube 6 moving axial ly / vertically within the tube housing 8), the top nut 14 and upper tube housing 8 mutually threaded to allow them to be screwed together.

[0068] As outlined above, the tube 6 moves along a passage within the upper tube housing 8, the passage aligned axially within the upper tube housing 8. The head of the tube 6 fits snugly within the passage. In use, fluid from the reservoir (not shown) travels through the hollow centre of the tube 6 (which forms a capillary tube), and during use is forced under pressure through the pre-filter 10, which is located directly above the top end of the passage. The prefilter 10 is held in place by the filter holder 9, with the filter holder 9 located above and directly adjacent to the top end of the tube housing 8. The lower seal 12 is located between the filter holder 9 and tube housing 8 so as to seal between the two and prevent fluid from leaking out through the seam or gap between the two.

[0069] The chip / filter 101 is located directly above the top end of the pre-filter 10, the chip / filter 101 located within and held in place by the upper seal 11 . The upper seal 11 locates into a recess within the nozzle retainer 15, which extends around the sides and top of the chip / filter 101 and upper seal 11. In use, fluids flow through a moulded or engraved pattern of microchannels in the chip / filter 101 to the outlet end, the outlet end of the chip / filter 101 comprising one or more spray jets. The top nut 14 and tube housing 8 are mutually threaded so that top nut 14 can be screwed onto the tube housing 8, so as to hold the lower seal 12, filter holder 9, filter 10, upper seal 11 , chip / filter 101 and nozzle retainer 15 in place within the top nut 14, the nut 14 substantially surrounding and enclosing the other elements of the nozzle retaining structure I nozzle assembly.

[0070] Chip / Filter

[0071] In the embodiments of the present invention, similar numbering is used for similar elements - e.g. the chip / filter is generally referred to as chip / filter 101 , and specific embodiments of the chips / filters of the present invention as described below are referred to as chip / filter 201 , 301 , etc.

[0072] ‘Chip / filter’ indicates an item through which fluids flow, through a moulded or engraved pattern of microchannels in the item. More specifically, the fluids flow through moulded or engraved microchannels that are formed in the chip / filter, from one end directly above the top end of the pre-filter 10, to the outlet end (e.g. nozzle jet 123). ‘Chip / filter’ as used in this specification indicates an item that has been formed by sandwiching two plates together, with the directly adjacent or adjoining faces of the two plates that are sandwiched together comprising part or all of the chip / filter, with microchannels formed and located on one or both of the directly adjacent inner faces of the two substrates.

[0073] The chip / filter is generally referred to as ‘chip / filter 10T. Similarly, the two layers or plates of the two halves that form the chip / filter are generally referred to as 102a, 102b, the inner faces of the two layers are generally referred to as 103a, 103b, etc.

[0074] For specific embodiments these items are referred to as upper and lower layers or plates 202a, 202b, 302a, 302b, faces 203a, 203b, etc.

[0075] This numbering convention is used for all the elements of the embodiments described and shown throughout this specification - all the individual elements of the embodiments shown and described are referred to generally / generically as ‘element 10X’, and for a specific element as ‘element 20X’, ‘element 30X’, etc.

[0076] In the plates of the embodiments of the present invention, both of the inner faces 103a, 103b are etched to form channels (microchannels), these channels open-topped or opening towards the inner face. In some embodiments, as described in detail below, the channels on the inner face of one plate are at least partly matched with the channels on the inner face of the other plate, so that when the two plates are brought together and joined, the channels match and merge (or at least partly overlap) so as to form a passage or passages through the chip / filter 101 where the passage as a whole is formed from multiple channels. The channels as shown in the figures and as described for each of the embodiments below are not intended to be exactly representative of the shape and configuration of the channels and plates - these are intended to be stylised representations to show the general relationships between the channels and plates, and to exemplify the relative positions and shapes of the channels and plates that can be achieved. The channels are referred to in the specific embodiments as channels or passages 204, 304, etc.

[0077] A side view of one plate of a typical chip / filter is shown schematically in figure 7, with the other plate not shown so that detail of the internal structure of the chip / filter can be seen. The figure is intended to be exemplary - to show the general layout and form only.

[0078] The plate of the chip / filter as shown in figure 7 has a series of pillars 120 spaced across one side or edge, the pillars forming inlet channels 121 therebetween through which the formulation to be dispensed enters the nozzle. Filtering region 122 is represented by a zigzag line in figure 7, but in the actual product this region is created by having a plurality of microchannels formed in the surface of the plate. The filtering region 122 filters out small particles from the formulation, and contamination from the assembly process, and prevents these particles and contamination from reaching and blocking the nozzle jet 123 (the passages that form the filter of the filtering region 122 are finer than the width / height of the nozzle jet 123).

[0079] Columns 124 between the filtering region 122 and the nozzle jet 123 are spaced and configured to even out the flow and increase the bond strength between the upper and lower plates. In the product, the columns 124 will each be smaller than shown in this schematic view, and more densely packed.

[0080] Glass-Glass Chips / Filters - General

[0081] In a first subset of embodiments, the chip / filter is formed from two glass plates - an upper glass plate and a lower glass plate.

[0082] Each of the two glass plates has a surface that is configured to in use contact the equivalent surface on the other plate, so that the two equivalent inner surfaces on each of the plates form a pair of adjoining or directly adjacent inner faces. This arrangement is shown schematically in figure 6.

[0083] The same or a very similar manufacturing process is used for all of the embodiments where both plates are formed from glass (the ‘glass-glass’ embodiments). In these embodiments, the etching is carried out using an isotropic / wet etching process (that is, using an acid solution or chemical etchant). Isotropic / wet etching is preferred for glass because it offers better control over the etching rate and can achieve smoother surfaces, and isotropic / wet etching processes can be carried out at a batch level (whereas DRIE processes need to be conducted on individual wafers). A disadvantage of isotropic etching is that it results in shallow and wide channels due to width restrictions on the lithographic mask, and the etching spreading outwards as much as downwards / into the depth of the glass. In order to maintain a good aspect ratio, two-sided etching is advantageous.

[0084] As outlined above, wet etching or isotropic etching also usually results in etched channels with curved or radial sidewalls and lower aspect ratios than when etching is carried out using anisotropic techniques such as DRIE techniques.

[0085] An advantage of isotropic / wet etching on glass wafers is that the etching process can be carried out on large batches of substrates. Two finished, etched, substrates can then be brought together to form a wafer. The wafer is then cut into a number of separate nozzles. As both of the halves or parts of the wafer are formed from glass, cutting can be done with a cutting tool and process that is dedicated to the cutting of glass. Alternatively, cutting can be done with a laser.

[0086] For all of the embodiments, the two glass plates of the nozzles are cut from a larger wafer sheet or sheets using a single cutting tool that is optimised for both halves rather than just one.

[0087] The use of two glass substrates means that inspection of the substrates can be carried out more easily and quickly before these are joined / bonded, and the use of two substrate parts formed from the same material (glass) ensures that there is a stronger bond between them than for two parts made of different materials.

[0088] Specific embodiments of the glass-glass chip / filter of the present invention are described below with reference to the figures.

[0089] Single etched nozzle

[0090] Figure 8 shows the nozzle 201 which is formed from two plates 202a, and 202b. The two plates 202a, 202b are both formed from glass. However, it should be noted that other suitable materials that can be used for nozzles, and which can be isotropically etched, can also be used.

[0091] In use, the plates 202a, 202b are positioned (during an earlier step in the process where two substrates are brought together to form a wafer) so that the two equivalent surfaces 203a, 203b on each of the parts 202a, 202b form a pair of adjoining or directly adjacent inner faces.

[0092] The lower one of the plates 202b is etched (using an isotropic etching process) to form a channel 204 (it should be noted that the channel 204 is a single stylised passage as shown and described. However, this represents either or both of a single channel, or multiple channels formed in the plate, the channel or channels forming a passage or passages). The upper plate 202a is unetched.

[0093] The nozzle 201 produced using this process requires minimal alignment between the two substrates that are brought together to produce the plates 202a, 202b.

[0094] As shown in figure 8, a single channel 204 is formed, and the channel 204 only needs to be formed on a single plate 202b. However, the etch depth is shallow (lower aspect ratio) which has poorer fluid flow characteristics.

[0095] Multiple overlapping channels

[0096] Figure 9 shows a nozzle 301 , which is a variation of the nozzle shown in figure 8 . In this variation, the lower one of the plates 302b is etched to form multiple channels 304 side-by- side with one another. The channels partly overlap at their adjacent edges (as shown in the figure) so that a single passage is formed. Each channel has a common side or edge that it shares with the adjacent channel, but the common side / edge is formed so that it does not extend over the full depth or height of the channel, leaving a gap 305).

[0097] The gap 305 provides an advantage as it can be used as a filtering mechanism. In use, there is flow between the channels 304 via the gap 305, as shown by arrow 306. However, the gap 305 is smaller than the channels 304 (that is, the filtrational depth ‘F’ of the gap 305 is less than the depth ‘D’ of the channels 304), and therefore material which could flow relatively freely through the channels cannot pass through the gap 305, and is therefore filtered out of the stream passing through the nozzle / chip. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering.

[0098] The gap is capable of filtering out particles which are smaller than the wafer etch depth. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering.

[0099] It should be noted that the channels 304 as shown and described are stylised. There may be a single example or multiple examples of this arrangement in a nozzle.

[0100] Embodiment 1 - double etched nozzle with matched halves

[0101] As shown in figure 10, the nozzle 401 of a first embodiment is formed from two plates 402a, and 402b. The two plates 402a, 302b are both formed from glass. In use, the plates 402a, 402b are placed together so that the two equivalent surfaces 403a, 403b on each of the plates 402a, 402b form a pair of adjoining or directly adjacent inner faces.

[0102] In this embodiment, both the upper and lower plates 402a, 402b are etched to form upper and lower channels 404a, 404b. In this embodiment, each of the channels is substantially identical to the channel on the other wafer - the plates 402a, 402b mirror one another, having the same width and depth. A single passage is formed from the aligned, identical, upper and lower channels. The resulting aspect ratio of the channel formed from the combination of the two channels is lower than each individual channel - that is, an aspect ratio closer to 1 .

[0103] It is preferred for this embodiment that the etching is carried out using an isotropic or wet etching process.

[0104] The nozzle 401 is produced by bringing together the two substrates that form the wafer, so that the channels 404a, 404b in the plates 402a, 402b that are created from the substrates align with one another to form a passage. A single optimised process can be used for cutting both wafers, which results in less chipping or similar issues at the edges of the cut.

[0105] Embodiment 2 - double etched nozzle with multiple overlapping channels

[0106] A second embodiment that is a variation of the first embodiment described above and shown in figure 10 is shown in figure 11. In this variation, the plates are etched to form multiple channels 504, with the channels on each of the plates 502a, 502b partly overlapping at their adjacent edges (each channel has a common side or edge that it shares with the adjacent channel, but the common side / edge is formed so that it does not extend over the full depth or height of the channel, leaving a gap 505).

[0107] The gap 505 provides an advantage as it can be used as a filtering mechanism. In use, there is flow between the channels 504 via the gap 505, as shown by arrow 506. However, the gap 505 is smaller than the channels 504 (that is, the filtrational depth ‘F’ of the gap 305 is less than the depth ‘D’ of the channels 304), and therefore material which could flow relatively freely through the channels 504 cannot pass through the gap 305, and is therefore filtered out of the stream passing through the nozzle / chip. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering.

[0108] The gap is capable of filtering out particles which are smaller than the wafer etch depth. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering.

[0109] The greater depth / height of the passages 504 formed from the aligned channels means that there can be better impingement by the liquid jets, and this results in smaller droplet size. The plates 502a, 502b mirror one another, the channels having the same width and depth, with flow passing from one passage formed by channels 504 to the other passage, via the gap 505.

[0110] Double etched nozzle with non-matching halves A known, prior art version of a chip / nozzle is shown in figure 12, the nozzle 601 of this version formed from two plates 602a, and 602b. The two plates 602a, 602b are both formed from glass. In use, the plates 602a, 602b are placed together so that the two equivalent surfaces 603a, 603b on each of the parts 602a, 602b form a pair of adjoining or directly adjacent inner faces.

[0111] In this version, both the upper and lower wafers 602a, 602b are etched to form upper and lower channels 604a, 604b. In this version, each of the channels can be identical in size and shape to the channel on the other wafer, or these can be formed differently on each plate.

[0112] In this version, it is preferred that the etching is carried out using an isotropic or wet etching process.

[0113] In this version, when the upper and lower wafers 602a, 602b are brought together, the channels 604a, 604b are fully offset from one another. In this version, the two channels 604a, 604b can be considered as a pair, so as to together form a single passage, but there is no direct fluid connection between the channels 604a, 604b.

[0114] Embodiment 3 - double etched nozzle with non-matching halves and partial overlap

[0115] A third embodiment of the nozzle of the present invention is shown in figure 13, where the upper and lower wafers 702a, 702b are brought together in such a manner that there is partial overlap between the channels 704a, 704b on the upper and lower plates - these are offset from one another to overlap at a common side or edge so as to form a single passage having a narrow gap 705 between the channels 704a, 704b to allow fluid flow between the channels. That is, there is fluid connection between the channels where they overlap. This gap 705 allows fluids to pass from one of the channels that forms the passage, to the other.

[0116] In a similar manner to that described above for the second embodiment, the gap 705 provides an advantage as it can be used as a filtering mechanism. In use, there is flow between the channels 704 via the gap 705, as shown by arrow 706. However, the gap 705 has a smaller cross-section than the channels 704 (that is, the filtrational depth ‘F’ of the gap 705 is less than the depth ‘D’ of the channels 704), and therefore material which could flow relatively freely through the channels 704 cannot pass through the gap 705, and is therefore filtered out of the stream passing through the nozzle / chip. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering and removes debris from the stream before this reaches the nozzle.

[0117] The gap is capable of filtering out particles which are smaller than the wafer etch depth. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering.

[0118] Silicon-Glass Chips I Filters - General

[0119] As noted in the background section, channels having a rectangular cross-section can be formed in a silicon substrate by using an anisotropic etching process such as Deep Reactive Ion Etching (DRIE). Anisotropic etching of this type when used on a silicon substrate will produce channels having a rectangular cross-section and sharp corners within the channel.

[0120] Nozzles with rectangular channels are formed by sandwiching two large substrate sheets together to form a nozzle wafer. Silicon is used for the substrate sheets because the anisotropic DRIE etching process can be used to form channels in / on the silicon, and this process provides accurate results as outlined above - the DRIE process provides channels having vertical side walls, and formed within tight tolerances.

[0121] Specific embodiments of the silicon-silicon chip / filter of the present invention are described below with reference to the figures.

[0122] Embodiment 4 - double etched nozzle

[0123] A fourth embodiment of the of the nozzle of the present invention is shown in figure 15.

[0124] In this embodiment, two silicon layers or plates 802a, 802b are sandwiched together with adjoining or directly adjacent inner faces. Channels 804a, 804b are formed in each of the layers, with the edges of the channel on one layer substantially aligned with the edges of the channel on the other layer so as to form a single passage having a substantially square or rectangular cross-sectional profile. The resulting aspect ratio of the channel formed from the combination of the two channels is lower than each individual channel - that is, an aspect ratio closer to 1 .

[0125] Embodiment 5 - double etched nozzle

[0126] A fifth embodiment of the of the nozzle of the present invention is shown in figure 16.

[0127] In this embodiment, two silicon layers or plates 902a, 902b are sandwiched together with adjoining or directly adjacent inner faces. Channels 904a, 904b are formed in each of the layers, with the upper and lower wafers 902a, 902b brought together in such a manner that there is partial overlap between the channels 904a, 904b on the upper and lower plates - these are offset from one another to overlap at a common side or edge so as to form a single passage having a narrow gap 905 between the channels 904a, 904b to allow fluid flow between the channels. That is, there is fluid connection between the channels where they overlap. This gap 905 allows fluids to pass from one of the channels that forms the passage, to the other. The gap 905 provides an advantage as it can be used as a filtering mechanism. In use, there is flow between the channels 904 via the gap 905, as shown by arrow 906. However, the gap 905 has a smaller cross-section than the channels 904 (that is, the filtrational depth ‘F’ of the gap 905 is less than the depth ‘D’ of the channels 904), and therefore material which could flow relatively freely through the channels 904 cannot pass through the gap 905, and is therefore filtered out of the stream passing through the nozzle / chip. This helps to ensure that the jet orifices of the nozzle don’t become blocked, as the overlap provides fine filtering and removes debris from the stream before this reaches the nozzle.

[0128] For all of the embodiments described above and as shown in the figures, it should be noted that the channels shown and described are stylised examples. In a nozzle as manufactured, there may be a single example or multiple examples of this arrangement in the nozzle, and the nozzle can contain one or more of the embodiments as described and shown. It should also be noted that all nozzles will have multiple passages passing therethrough between their inlet end and their outlet end, and that the single passages shown and described will form a part of the overall channel and passage arrangement within the nozzle.

[0129] For all of the embodiments above, it should be noted that these can be ‘mixed and matched’ within a single chip / filter. For example, one part of the chip / filter could contain a channel arrangement according to one of the specific embodiments shown in the figures and described above, with another part of the chip / filter containing another of the specific embodiments. The materials can also be mixed and matched, with glass-glass substrates (as for embodiments one to ten), silicon-silicon substrates (as for embodiments 11 to 14), orglass-silicon substrates - that is, it is possible to match a silicon substrate with an anisotropically-formed channel having a more rectangular profile, with a glass substrate having a rounder isotropically-formed channel.

[0130] For all of embodiments above, these can be described as ‘multiple channel passages’. Each passage is formed from multiple channels - either channels on the same substrate that partly overlap at their adjacent edges as in the second embodiment shown in figure 9, or channels that are formed on each substrate that form a single passage.

Claims

Claims1. A nozzle, comprising: a first plate having a first substantially planar surface; a second plate having a second substantially planar surface; the first and second plates positioned so that the first and second planar surfaces are directly adjacent to one another, the substantially planar surfaces on one or both of the first and second plates etched to form open-topped channels, characterised in that the first and second plates are etched and aligned so that the open-topped channels combine to form an enclosed passage or passages that run at least partly through the nozzle.

2. A nozzle as claimed in claim 1 wherein the first and second plates comprise glass plates, the channels having curved or radial sidewalls.

3. A nozzle as claimed in claim 1 or claim 2 wherein the first plate is etched to form multiple side-by-side channels that partly overlap at their connecting edges to form a single passage.

4. A nozzle as claimed in claim 3 wherein the second plate is etched to form multiple side- by-side channels that partly overlap at their connecting edges, the channels in the first and second plates aligned so as to form a single passage, the gap connecting the side-by-side channels having a cross-sectional area smaller than the cross-sectional area of any one of the channels.

5. A nozzle as claimed in claim 4 wherein the channels in the second plate are formed so as to be substantially identical to the channels in the first plate.

6. A nozzle as claimed in claim 1 or claim 2 wherein each of the first and second plates are etched to form channels, the first and second plates aligned so that a single passage is formed from the channels, the passage having an aspect ratio less than that of each of the channels.

7. A nozzle as claimed in claim 6 wherein the channels on the first and second plates are substantially aligned to mirror each other.

8. A nozzle as claimed in claim 1 or claim 2 wherein the channels on the first and second plates are aligned so as to form a gap connecting the channels, the gap having a cross- sectional area smaller than the cross-sectional area of a channel.

9. A nozzle as claimed in claim 8, wherein the first and the second plates comprise silicon plates.

10. A nozzle as claimed in claim 1 wherein the first and second plates comprise silicon plates, the channels having a substantially rectangular cross-section.

11. A nozzle as claimed in claim 10 wherein each of the first and second plates are etched form channels, the first and second plates aligned so that a single passage is formed from the channels, the passage having an aspect ratio less than that of each of the channels.

12. A nozzle as claimed in claim 10 or claim 11 wherein the channels on the first and second plates are substantially aligned to mirror each other.

Images