Patent Application
20120012105
The present invention relates to an atomising device comprising an atomising body.
Atomising bodies and atomising devices are e.g. known from WO 02/18058.
The atomising bodies and devices as known in the art e.g. comprise a first membrane and a second membrane mounted to a support element comprising a fluid conduit (e.g. a cavity) arranged to guide a fluid from the first membrane to the second. In the embodiments as disclosed in the art, the support element has a cavity extending from a first surface of the support element to a second surface of the support element. The membranes are mounted to the resp. first and second surface thereby covering the cavity. In the embodiments as described, the first membrane operates as a nozzle to atomise a fluid from the cavity whereas the second membrane operates as a sieve to filter a fluid that is received in the cavity through the second membrane. The cavity arranged between the membranes can e.g. be obtained by mounting the membranes (e.g. micro-machined structures) to a support element containing the cavity. Such an element having a hole through it can be covered at both sides by a membrane. In order to manufacture an atomising body in such way, a minimal strength of the membranes is required to mount them to the element. Further, means have to be provided for the membranes to adhere to the element. The membranes can e.g. be glued to the element. The application of a glue may however be unwanted for some applications, e.g. medical applications. The minimal strength imposed upon the membranes in order to mount them to the element poses a limitation to the miniaturisation of the atomising head. It is further suggested in WO 02/18058 to provide the membranes to a solid support element and etch a cavity between the membranes through the pores of the membranes. Such an approach however may be cumbersome as the etching process through the available pores may take a long time.
In view of the above, it is an object of the present invention, to provide an alternative way of manufacturing an atomising body for use in an atomising device.
According to an aspect of the invention, there is provided a method of manufacturing an atomising body, the method comprising the steps of
The method of manufacturing an atomising body according to the invention departs from a support element which is provided with a first and second perforated membrane and a process orifice.
In accordance with the present invention, a perforated membrane is used to allow a fluid to enter the cavity of the atomising body or leave the atomising body. Applied in an atomising body according to the invention, a perforated membrane can e.g. be obtained by providing a layer on a support element and applying perforations to the layer. The required pattern of the perforation or perforations can be provided by a lithographic process. As an example, a membrane can be made from a silicon nitride layer. When the required pattern of perforations such as pores is provided (e.g. by a lithographic process), the perforation or perforations can be realised in the silicon nitride layer by e.g. an etching process. In an embodiment, the first membrane of the atomising body operates, in use, as a nozzle.
The second layer of the support element is provided with a process orifice and a second perforated membrane arranged adjacent the process orifice on a second layer used to etch a cavity in the support element. Within the meaning of the present invention, a process orifice is understood as a comparatively large perforation or perforations in the second layer, large compared to the size of the perforations of the first membrane or the perforations of the second membrane. By applying a comparatively large perforation, the etching process (e.g. a wet etching process using KOH or a reactive ion etching process using e.g. SF6 gas) of providing a cavity extending between the first and second layer of the support element is facilitated. It is acknowledged that etching processes are known in general. In order to generate a cavity between two layers of a support element by etching, the material between the two layers needs to be accessed by an etching substance. Within the meaning of the present invention, etching substance is used to designate a material or substance that can be applied to perform an etching process. Examples of such etching substance are KOH or TMAH. The etching substance can also comprise a plasma for etching the cavity. Examples of such a plasma are SF6 or CHF3. It has been devised that accessing the support element through the perforations of a membrane can be cumbersome and may not result in the required cavity (i.e. a cavity forming a fluid connection from the first layer to the second layer) being realised. Phrased differently, the pores as provided in a membrane may be insufficient to enable the required etching process. In practice, the etching process can come to a stop prior to the completion of the cavity.
The process orifice enables the etching substance to access the support element. This way the etching process does not have to rely on the etching substance entering the support element via the perforations of the first membrane or the second membrane. As a result of the etching process, a cavity forming a fluid connection from the process orifice to the first perforated membrane and from the first perforated membrane to the second perforated membrane is established. Such a cavity enables, during use of the atomising body as obtained by the manufacturing method, a fluid to enter the cavity through the process orifice and leave the cavity through the first perforated membrane.
In order to manufacture the process orifice or the membranes that e.g. operate as a nozzle or a sieve, etching processes such as isotropic and anisotropic etching can be applied.
In case the first perforated membrane is to be applied as a nozzle, a fluid entering the cavity of the atomising body through the process orifice can e.g. be filtered by providing a cover covering the process orifice, the cover e.g. being made or comprising a porous material. The second perforated membrane of the atomising body can e.g. operate as a sieve.
The manufacturing method according to the invention thus provides a process orifice that facilitates accessing a volume of the support element arranged between the membranes. As such, the process orifice is arranged adjacent to the second perforated membrane. By providing the process orifice, an access is generated that enables an etchant to remove part of the support element that is located between the first and second membrane.
In accordance with the present invention, a cavity extending from a first perforated membrane to a second perforated membrane is provided by etching the support element to enable a fluid flow between the first and second membrane. By doing so, no manipulation of the membranes (i.e. the mounting of the membranes to a supporting structure) is required to obtain a cavity enclosed by two membranes. As a consequence, the strength requirements for the membranes can be less stringent thus allowing the application of very thin membranes (0.5 to 5 μm thick). The application of these thin membranes may result in a reduced pressure drop over the membranes thus allowing a lower operating pressure to be applied.
Atomising bodies as obtained by the manufacturing method according to the invention may advantageously be applied in an atomising device. As such according to an aspect of the invention, there is provided an atomising body comprising
Within the meaning of the present invention, the process orifice of the atomising body according to the invention is understood as a comparatively large perforation or perforations, large compared to the size of the perforations of the first membrane. As an example, the perforations of the first membrane may have a size (e.g. a diameter) varying from 0.5 to 10 micron whereas the process orifice can comprise one or more perforations having a size>10 μm in diameter. The size of the process orifice enables the transport of etching substance into the atomizing body and/or the transport of reactants out of the atomizing body.
In an embodiment, the atomising body further comprises a cover for covering the process orifice. Such a cover can e.g. be made from a porous material and, in use, operate as a sieve, prohibiting particles to enter the cavity through the process orifice.
In a preferred embodiment, the cross-section of the process orifice is smaller than an area covering the first perforated membrane. This may e.g. provide the advantage of enabling the etching process without increasing the overall size of the atomising body. It may also minimize the ‘dead volume’ of liquid inside the atomizing body, which enables priming out air bubbles. Selecting the appropriate size for the process orifice can thus be considered a trade-off between selecting the process orifice sufficiently large to enable the etching of the cavity and sufficiently small to keep the overall size of the atomising body as small as possible.
According to a further aspect, of the invention, there is provided an atomising device comprising an atomising body and a supporting structure, the atomising body comprising:
and wherein the atomising body is attached to a surface of the supporting structure, thereby substantially covering the process orifice.
An atomising device according to the invention comprises a supporting structure and an atomising body. The supporting structure can e.g. comprise an inlet for receiving a fluid and providing the fluid, e.g. under pressure, to the atomising body. In use, the fluid received can e.g. enter the atomising body through the second membrane e.g. a sieve. The second membrane may thus operate as a filter to prohibit particles, that may block the downstream first perforated membrane, to enter the cavity of the atomising body. The fluid received in the cavity can leave the atomising body through the first membrane which can e.g. comprise a nozzle orifice thereby forming a vapour or a mist. Within the present application, terms such as vapour, spray, aerosol or mist are deemed to be equivalent as are terms as atomising, vaporising, spraying and nebulising. The second perforated membrane may also act as a microbial filter, to prevent microbes to pass through the atomising body upstream towards a fluid container. The second membrane may block microbes when the perforations are smaller than 2 micron, preferably smaller than 1 micron, preferably smaller than 0.5 micron, preferably smaller than 0.25 micron.
The supporting structure of the atomising device according to the invention further comprises a surface for covering the process orifice of the atomising body. By covering the process orifice, fluid is substantially prohibited from entering or leaving the atomising body without passing through the filter membranes of the atomising body.
The supporting structure of the atomising device can e.g. have a tubular shape.
The assembly or mounting of an atomising body in an atomising device such that a process orifice of the atomising body is substantially closed or covered can be realised in various ways. Therefore, according to a further aspect of the invention, there is provided a manufacturing method for an atomising device, the method comprising the steps of
Attaching the atomising body to the supporting structure can e.g. be done by applying a glue to the surface of the supporting structure or by bonding.
In a preferred embodiment, the supporting structure is made from a thermoplastic and the attaching of the atomising body to the structure is realised by heating the atomising body in order to adhere the atomising body to the structure at least at the surface. By heating the atomising body, parts of the supporting structure that are in heat exchanging contact with the atomising body will melt and may, as a result thereof adhere to the atomising body.
Attaching the atomising body to the supporting structure in this manner does not require the use of additional components or materials such as glue. Avoiding such components or materials can facilitate the acceptance of the atomising device for pharmaceutical or medical applications because, for these applications, each material that may come in contact with a drug substance or patient needs to be safe, tested and certified.
The atomising body or atomising device according to the invention may e.g. be powered by a manual spray pump or a spring driven pump mechanism. The fluid can also be powered by a pressurised container, either with a continuous valve or a metered valve. Such inhalers can e.g. combine an atomising body, operating as a spray nozzle, a valve that can be actuated by a user and a pressurised container for providing a fluid to the atomising body. The valve can e.g. be a continuous valve or a metered valve. Therefore, according to an aspect of the invention, there is provided an inhaler comprising
In an embodiment of the present invention, an inhaler is provided comprising:
In the embodiment, the volume reduction can e.g. substantially continuous and directly affects the amount of fluid (i.e. the dose) that is administered. In such an inhaler, the dose administered thus depends on the user action on the container. As such, only the total dose as available in the container is fixed, whereas the different doses that are applied sequentially in order to empty the container, can be adjusted/selected by the user by appropriate action on the container. In an embodiment, the container can comprise a syringe or syringe-like device for containing the fluid.
Various embodiments covering the different aspects of the present invention are described below with reference to the following drawings wherein corresponding reference numbers indicate corresponding parts or elements.
a-1b schematically depict atomising bodies as known in the art.
a-2f schematically illustrated an embodiment of the manufacturing process of an atomising body according to the present invention.
a schematically depicts a top view of a filter membrane and two process orifices arranged on opposite sides of the membrane.
b schematically depicts another top view of a filter membrane and four process orifices arranged adjacent the membrane.
a-5c schematically illustrate another embodiment of the manufacturing process of an atomising body according to the present invention.
a-9b schematically depict cross-sectional views of part of other atomising devices according to the invention.
a schematically depicts a known atomising body as disclosed in WO 02/18058. WO 02/180058 discloses atomising bodies comprising a support element 100, a nozzle plate 110 and a filtration plate 120 as indicated in
a-2f schematically depict different processing steps of an embodiment of the manufacturing method to obtain an atomising body according to the invention. The manufacturing method as illustrated can depart from a structure 300 comprising a support element 310 having a first layer 320 on a first surface 330 of the support element and a second layer 340 on a second surface 350 of the support element, the first layer comprising a first perforated membrane 360 and the second layer comprising a second perforated membrane 370. Such a structure can e.g. be obtained by the following process:
1 departing from a support element such as silicon, the silicon is covered on two surfaces with a layer of silicon nitride to obtain the layers 320 and 340,
The first and second membranes are perforated structures that are intended for use as a nozzle and a sieve or filter respectively once the atomising body is manufactured. The first membrane, to be used as a nozzle may, as an example, be provided with one or more protrusions or orifices, e.g. having a diameter of 0.5 to 10 micron. The orifices may e.g. have a substantially circular shape or may e.g. have a rectangular slit-shape. In an embodiment, the nozzle comprises an array of approx. 300 orifices or pores. The second membrane, to be used as a filter or sieve, can e.g. comprise an array of pores, typically approx. 10000 pores of 0.2 to 5 micron in size.
According to the embodiment of the manufacturing method of the invention, a process orifice is further provided on at least one of the first or second layer, the orifice being arranged adjacent the first or second membrane.
In order to etch a cavity extending between the two membranes, an etching substance is applied to the process orifices, as indicated by the arrows 380 in
a schematically depicts a top view of a possible configuration of two process orifices 550, 560 and a membrane 570 arranged between them. In the configuration as shown, the membrane is a two-dimensional array of substantially circular pores.
The manufacturing method as illustrated above employs two process orifices arranged on opposing sides of one of the membranes. It should be emphasised that other arrangements are possible as well and provide similar benefits in facilitating the etching process. Examples of such arrangements are:
As an example,
Rather than departing from a structure 300 comprising a support element 310 having a first layer 320 on a first surface 330 of the support element and a second layer 340 wherein the first layer comprises a first perforated membrane 360 and the second layer comprising a second perforated membrane, the manufacturing method according to the invention may equally depart from a structure 300 comprising a support element 310 having a first layer 320 on a first surface 330 of the support element and a second layer 340 on a second surface 350 of the support element wherein the first layer comprises a first perforated membrane 360 and the second layer comprising a process orifice 375. Two possible arrangements as schematically depicted in
As already mentioned above, it may be advised to provide a sieve or filter to filter a fluid that enters the cavity. In the embodiments departing from an support element having a second membrane, the second membrane can e.g. be used to filter the fluid. With respect to the embodiment as shown in
In order to be applied in an atomising device, the atomising body can be provided with a cover covering the process orifice or orifices.
In order to assemble the cover to the atomising body, various methods can be applied. As an example, the atomising body and cover can be assembled using ‘direct bonding’. The direct bonding occurs when two clean and smooth surfaces are brought closely together, and are held together by the so-called Van Der Waal's forces. The bonding can be stimulated or improved by adding heat and/or electricity. The latter process also being known as anodic bonding.
As an alternative, the cover can be glued to the atomising body. It can however be noted that, for pharmaceutical or medical applications, the bonding methods are preferred as they avoid the use of glue.
An other method that avoids the use of glue but which does not rely on direct bonding is the application of a thermoplastic as a cover material. The thermoplastic cover can be rigidly mounted to the atomising body by heating the atomising body or parts of the body close to the plastic cover. By heating the atomising body, part of the plastic cover close to the atomising body can (partly) melt and thus become a melted fluid plastic. The melted plastic may flow and substantially close the process orifice or orifices. When subsequently, the plastic cools down, it will become solid again. Shrinkage of the plastic may cause a secure seal.
The method of closing the process orifices by melting and subsequently solidifying a plastic part may have the advantage over the direct bonding methods that no close direct contact is required between the atomising body and the cover. As the membranes of the atomising body are fragile structures, in particular after the creation of the cavity between the membranes, bringing a cover in close contact to the membrane in order to realise a direct bonding, may result in damaging the membrane. As a result, the membrane's function as a nozzle or sieve can be compromised.
Once a cover is provided, the atomising body including the cover can be mounted to a supporting structure thereby forming an atomising device.
Instead of providing a cover to an atomising body in order to substantially close a process orifice of the atomising body, the process orifice of the atomising body can be sealed off during the assembly of the atomising device. In order to realise this, an atomising device is manufactured by assembling a supporting structure having a surface and an atomising body and whereby the surface of the supporting structure is shaped in such manner that when the atomising body is mounted to it, the process orifice is substantially closed off. By doing so, the step of separately mounting a cover to the atomising body, as explained above, is no longer required. A further advantage of covering the process orifice by a surface of the supporting structure of the atomising device is that it reduces the number of components required to assemble an atomising device according to the invention.
The atomising device according to the invention may, as an example, be applied in an inhaler as schematically depicted in
In
Exemplary embodiments of the present invention have been described above. It should be noted that the embodiments are merely intended to illustrate the invention, the scope of the invention only being limited by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002787 | Apr 2009 | NL | national |
This application is the National Stage of International Application No. PCT/NL2010/000070, filed Apr. 22, 2010, which claims the benefit of Netherlands Application No. 2002787, filed Apr. 23, 2009, the contents of which is incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL2010/000070 | 4/22/2010 | WO | 00 | 9/19/2011 |
