NEBULIZER

Abstract

A nebulizer (10) comprising a housing which defines, a chamber that has an outlet to the chamber for the egress of atomised fluid particles from within the chamber. The nebulizer (10) further including solid substrate (11) within the chamber of the housing. A linear channel (12) being formed in the substrate (11) that has a closed base, opposite side walls and an opening that opens through an upper surface of the substrate (11). A vibration generator (17) being attached to the substrate (11) at a position spaced from the channel (12) for generating high frequency vibration that transmits through the substrate (11) to the channel (12) to atomise fluid within the channel (12). A feeding facility (15) being provided for feeding fluid to the channel (12).

Claims

1. A nebulizer comprising: a. a housing, i. the housing defining a chamber and having an outlet to the chamber for the egress of atomised fluid particles from within the chamber, b. a solid substrate within the chamber of the housing, c. a linear channel formed in the substrate that has a closed base, opposite side walls and an opening that opens through an upper surface of the substrate, d. a vibration generator attached to the substrate at a position spaced from the channel for generating high frequency vibration that transmits through the substrate to the channel to atomise fluid within the channel, e. a feeding facility for feeding fluid to the channel.

2. A nebulizer according to claim 1, the channel having a high aspect ratio in which the depth of the channel is much greater than the width.

3. A nebulizer according to claim 2, the aspect ratio of the channel being in the range of between 7:1 to 15:1.

4. A nebulizer according to claim 2, the depth of the channel being in the range of 10.5 micrometres for a channel that has an aspect ratio of 7:1 and a channel opening of 1.5 micrometres and up to a 300 micrometre for a channel that has aspect ratio of 15:1 and a channel opening of 20 micrometres.

5. (canceled)

6. (canceled)

7. (canceled)

8. (canceled)

9. (canceled)

10. A nebulizer according to claim 1, the substrate being a rigid substrate, in particular being formed from silicon.

11. (canceled)

12. A nebulizer according to claim 1, the surface of the channel being treated to render it hydrophilic, in particular by the application of O.sub.2 plasma to the channel surface.

13. (canceled)

14. A nebulizer according to claim 1, including multiple channels being formed in a parallel array or perpendicular to each other, or in a T or L formation for two channels, or in a C or square/rectangular formation for three or four channels.

15. (canceled)

16. (canceled)

17. (canceled)

18. A nebulizer according to claim 1, the vibration generator being a piezoelectric actuator that employs a piezoelectric disc that is actuated or excited electrically.

19. A nebulizer according to claim 18, the piezoelectric actuator generating actuation vibrations in a frequency range from 500 KHz to 5 MHz or from 5 MHz to 20 MHz.

20. (canceled)

21. A nebulizer according to claim 1, the vibration generator being placed on the upper surface of the substrate.

22. A nebulizer according claim 1, the vibration generator being placed on the lower or underneath surface of the substrate opposite to which the channel or channels open.

23. A nebulizer according to claim 21, the vibration generator being placed directly below the closed base of the channel.

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. A nebulizer according claim 1, the linear channel extending fully across the substrate from one side to the other and open through side edges of the substrate.

29. A nebulizer according claim 1, one end of the linear channel opening through one side edge of the substrate and the other and opposite end terminating within the substrate.

30. A nebulizer according any claim 1, both ends of the linear channel terminating within the substrate.

31. A nebulizer according claim 1, the feeding facility having a reservoir into which fluid is fed for subsequent passage or travel into the channel.

32. A nebulizer according to claim 30, the reservoir being formed in the substrate.

33. (canceled)

34. (canceled)

35. (canceled)

36. (canceled)

37. A nebulizer according claim 1, the feeding facility including a feed conduit or tube that facilitates feed of fluid directly into the channel.

38. A nebulizer according claim 1, the feeding facility including an external reservoir spaced from the substrate.

39. (canceled)

40. A nebulizer comprising: a. a solid substrate, b. a linear channel formed in the substrate that has a closed base, opposite side walls and an opening that opens through an upper surface of the substrate, c. a vibration generator attached to the substrate at a position spaced from the channel for generating high frequency vibration that transmits through the substrate to the channel to atomise fluid within the channel, d. a feeding facility for feeding fluid to the channel.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:

[0059] FIG. 1 is a perspective view of a nebulizer according to one embodiment of the invention.

[0060] FIG. 2 is a side view of a nebulizer according to another embodiment of the invention.

[0061] FIG. 3 is a photograph in cross-sectional side view of a prototype nebulizer according to the invention.

[0062] FIG. 4 is a graph created from prototype testing in relation to nebulizers according to the invention that are excited at different frequencies.

[0063] FIG. 5 graphically illustrates the typical size distribution of droplets for a 20 μm wide, 200 μm deep channel in a substrate that is excited at 675 MHz.

[0064] FIGS. 6(a) to 6(c) are a series of still images taken from high speed imagery looking down on 13.75 μm wide channels etched into a a silicon wafer during nebulisation.

[0065] FIG. 7 is a still image of the atomized droplets produced in a nebulizer that has a channel that is 20 μm wide and 200 μm deep that is excited at 675 MHz.

DETAILED DESCRIPTION

[0066] FIG. 1 illustrates a nebulizer 10 according to one embodiment of the present invention. The nebulizer 10 is shown without a housing being depicted, so that the features of the nebulizer 10 can be easily shown. Accordingly, the nebulizer 10 of FIG. 1 is formed from a substrate 11 that is rectangular in configuration and includes a linear channel 12 that extends laterally across the substrate 11 between respective long sides 13 and 14 of the substrate 11. It can be seen that the channel 12 extends through the long side 13 at one end, and extends into a generally circular reservoir 15 at the other end. The channel 12 extends for a short extent on the opposite side of the reservoir 15 to extend through the opposite long side 14. The channel 12 includes a closed base and opposite side walls and an opening that opens through the upper surface 16 of the substrate 11. The dimensions of the channel 12 are greatly exaggerated in FIG. 1 for the purpose of illustration. As will be appreciated from the discussion earlier herein, the opening of the channel 12 through the upper surface 16 of the substrate 11 can have a width transverse to the length from about 1.5 micrometres to about 20 micrometres. The depth of the channel can be from about 10.5 micrometres up to about 300 micrometres.

[0067] A vibration generator 17 is mounted on the upper surface 16 of the substrate 11 at a position spaced from the channel 12 and is in the form of a piezoelectric actuator. The piezoelectric actuator is a piezoelectric block. The actuator 17 is connected in a normal manner to cables 18 that attach to separate electrodes of the actuator 17 and that supply electric current to the actuator 17 for the purpose of exciting the actuator 17. Upon the actuator 17 being excited, high frequency vibrations are generated that transmit through the substrate 11 in the direction towards the channel 12 as shown by the arrows A. The vibrations reach the channel 12 and cause atomisation of fluid within the channel 12.

[0068] FIG. 2 illustrates an alternative arrangement of a nebulizer 20 according to another embodiment of the present invention. The nebulizer 20 is again shown without a housing being depicted. The nebulizer of FIG. 2 is shown from the side and includes a square or rectangular substrate 21 and linear channel 22 that extends laterally across the substrate 21. The channel 22 is fed by a generally circular reservoir which is not shown, but which can be assumed to be the same as or similar to the reservoir 15 of FIG. 1. Thus, the channel 22 extends through opposite sides of the substrate 21. The channel 22 includes a closed base and opposite side walls and an opening that opens through the upper surface 23 of the substrate 21. The dimensions of the channel 22 are greatly exaggerated in FIG. 2 as they were in FIG. 1 for the purpose of illustration.

[0069] A vibration generator 24 is mounted on the lower or underneath surface 25 of the substrate 21 at a position spaced from the closed base of the channel 22. The vibration generator 24 is again in the form of a piezoelectric actuator. The actuator 24 is connected in a normal manner to cables (not shown) that supply electric current to the actuator 24 for the purpose of exciting the actuator 24. Upon the actuator 24 being excited, high frequency vibrations are generated that transmit through the substrate 21 in the direction towards the channel 22. Obviously the distance shown for the vibrations to travel to reach the channel 22 is much shorter than illustrated in FIG. 1, but the thickness of the substrate 21 can be selected to provide an appropriate distance for vibration propagation. In the same manner as FIG. 1, the vibrations reach the channel 22 and cause atomisation of fluid within the channel 22.

[0070] The vibration generator 24 is placed directly below the closed base of the channel 22. In alternative arrangements, the vibration generator 24 can be offset from the channel 22 but still located on the underneath surface 25 of the substrate 21.

[0071] FIG. 3 is a photograph taken with a microscope and illustrates an actual prototype nebulizer according to the invention which is shown in side cross-section. The nebulizer 30 has a substrate 31, a channel 32 and an upper surface 33. The dark section above the surface 33 is background and is not part of the nebulizer 30. The channel 32 has a closed base 34, opposite side walls 35 that are generally parallel and a lateral opening 36 that opens through the upper surface 33. The substrate 31 is a silicon wafer and the channel 32 is formed by deep reactive ion etching. The internal surface of the channel 32 has been rendered hydrophilic by the use of the application of O.sub.2 plasma.

[0072] The dimensions of the channel 32 are given in FIG. 3. Thus, the transverse width of the channel 32 is 19.59 μm, while the length or height of the channel 32 extending downwardly from the upper surface 33 to the close base 34, is 265.41 μm. These measurements will give context to the nebulizers 10 and 20 illustrated in FIGS. 1 and 2, in terms of dimensional size.

[0073] FIG. 4 is a graph created from prototype testing in relation to nebulizers according to the invention that are excited at different frequencies. The Y-axis gives the diameter in μm of the droplet size that is produced, while the X-axis gives the vibration frequency that is applied to the substrate by the vibration generator. The graph shows that a range of the droplet sizes are produced at a particular frequency, The graph also illustrates the use of two different sized channels and substrate thicknesses, whereby the channel dimensions given is the lateral opening dimension of the channels through the upper surface of the substrate in which the channels are formed and the substrate dimension is the thickness of the substrate between the upper and lower surfaces of the substrate. Thus, the results relate to different channels having respective lateral openings of 20 μm and 5 μm and substrate5 thicknesses of 525 μm and 225 μm.

[0074] The graph shows that there is a highly advantageous result produced by the present invention. The graph for the 20 μm channel shows that the droplet size does not vary greatly at a particular frequency. For the 20 μm channel, at each of the approximate 1 MHz, 1.3 MHz and 1.6 MHz points, the extent to which there is variation in droplet size is approximately the same and within the range of about 0.5 μm. For the 5 μm channel, at each of the approximate 1 MHz and 4.15 MHz points, the variation in droplet size is approximately between 0.5 μm and 0.9 μm. That level of variability is very low and the consistency is very good.

[0075] This result is that the mean diameters of the droplets that are produced by a nebulizer according to the present invention, can be maintained within a small range of different sizes. Thus, the particles are generally of the same size. This differs from nebulizers according to the prior art, in which there is much greater variation in the diameter of droplets produced. Thus, the present invention provides high levels of control over the mean diameter of the droplets produced. This is highly advantageous for aerosol drug delivery into the lungs, as the size of delivered droplets determines where in the lung the droplets are deposited as well as influencing the therapeutic effectiveness of the drug. As shown in FIG. 4, the size of the particles can be tuned on-demand by changing the frequency of actuation.

[0076] As previously described, from measurements of the droplet size relative to the driving frequency of the high frequency vibration, as well as imagery that has been observed of the fluid/air interface, capillary waves form at the fluid/air interface at the opening of a channel formed in the substrate. The use of a vibration generator such as a piezoelectric actuator which is capable of exciting a substrate at a range of frequencies, different sizes of droplets can be produced from the same nebulizer. Physical properties affecting capillary wavelength at the fluid/air interface include 1) the density of the two fluids in contact, 2) the surface tension and 3) the driving wavelength. FIG. 5 graphically illustrates the typical size distribution of droplets for a 20 μm wide, 200 μm deep channel in a substrate that is excited at 675 MHz.

[0077] FIGS. 6(a) to 6(c) is a series of still images taken from high speed imagery looking down on 13.75 μm wide channels etched into a a silicon wafer during nebulisation. FIG. 6(a) shows a water filled channel with no frequency generation. No capillary waves are apparent on the surface of the water. In FIG. 6(b), a 675 MHz frequency generation has been applied to the substrate, creating capillary waves on surface of the water. In FIG. 6(c) the wavelength of the capillary waves of FIG. 6(b) are shown, and these have been measured to be approximately 9.5 μm.

[0078] FIG. 7 is a still image of the atomized droplets produced in a nebulizer that has a channel that is 20 μm wide and 200 μm deep that is excited at 675 MHz. The nebulizer produces droplets approximately 7 μm in diameter. High speed imagery used to measure these droplets detected a droplet velocity about 0.6-1 m.s.sup.−1 vertically.

[0079] Where any or all of the terms “comprise”, “comprises”, “comprised” or “comprising” are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

[0080] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.