U.S. patent application number 13/712857 was filed with the patent office on 2013-06-13 for high modulus polymeric ejector mechanism, ejector device, and methods of use.
This patent application is currently assigned to CORINTHIAN OPHTHALMIC, INC.. The applicant listed for this patent is CORINTHIAN OPHTHALMIC, INC.. Invention is credited to Joshua Richard Brown, J. Sid Clements, Louis Thomas Germinario, Charles Eric Hunter, Iyam Lynch, Jonathan Ryan Wilkerson.
Application Number | 20130150812 13/712857 |
Document ID | / |
Family ID | 47505336 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130150812 |
Kind Code |
A1 |
Hunter; Charles Eric ; et
al. |
June 13, 2013 |
HIGH MODULUS POLYMERIC EJECTOR MECHANISM, EJECTOR DEVICE, AND
METHODS OF USE
Abstract
An ejector device and method of delivering safe, suitable, and
repeatable dosages to a subject for topical, oral, nasal, or
pulmonary use is disclosed. The ejector device includes a housing,
a reservoir disposed within the housing for receiving a volume of
fluid, and an ejector mechanism in fluid communication with the
reservoir and configured to eject a stream of droplets, the ejector
mechanism comprising an ejector plate coupled to a generator plate
and a piezoelectric actuator; the piezoelectric actuator being
operable to oscillate the ejector plate, and thereby the generator
plate, at a frequency and generate a directed stream of
droplets.
Inventors: |
Hunter; Charles Eric;
(Boone, NC) ; Germinario; Louis Thomas;
(Kingsport, TN) ; Wilkerson; Jonathan Ryan;
(Raleigh, NC) ; Lynch; Iyam; (Boone, NC) ;
Clements; J. Sid; (Boone, NC) ; Brown; Joshua
Richard; (Hickory, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORINTHIAN OPHTHALMIC, INC.; |
Raleigh |
NC |
US |
|
|
Assignee: |
CORINTHIAN OPHTHALMIC, INC.
Raleigh
NC
|
Family ID: |
47505336 |
Appl. No.: |
13/712857 |
Filed: |
December 12, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61569739 |
Dec 12, 2011 |
|
|
|
61591786 |
Jan 27, 2012 |
|
|
|
Current U.S.
Class: |
604/295 |
Current CPC
Class: |
B05B 17/0661 20130101;
A61F 9/0008 20130101; A61F 9/0026 20130101; B05B 17/0646 20130101;
B05B 17/0607 20130101 |
Class at
Publication: |
604/295 |
International
Class: |
A61F 9/00 20060101
A61F009/00 |
Claims
1. A device for delivering a fluid to a target, the device
comprising: a housing; a reservoir disposed within the housing for
receiving a volume of fluid; and an ejector mechanism in fluid
communication with the reservoir and configured to eject a stream
of droplets, the ejector mechanism comprising an ejector plate
coupled to a high modulus polymeric generator plate and a
piezoelectric actuator; the high modulus polymeric generator plate
including a plurality of openings formed through its thickness; and
the piezoelectric actuator being operable to oscillate the ejector
plate, and thereby the high modulus polymeric generator plate, at a
frequency and generate a directed stream of droplets.
2. The device of claim 1, wherein the plurality of openings are
configured to provide desired three-dimensional geometry and shape
and are formed via laser micromachining.
3. The device of claim 1, wherein one or more of said plurality of
openings are shaped so as to comprise a fluid entrance orifice, an
entrance cavity, a capillary channel, and a fluid exit orifice.
4. The device of claim 1, wherein the high modulus polymer
generator plate is formed from a material selected from the group
consisting of: ultrahigh molecular weight polyethylene (UHMWPE),
polyimide, polyether ether ketone (PEEK), talc-filled PEEK,
polyvinylidine fluoride (PVDF), and polyetherimide.
5. The device of claim 1, wherein the ejector plate has a central
open region aligned with the high modulus polymeric generator
plate, and the piezoelectric actuator is coupled to a peripheral
region of the ejector plate so as to not obstruct the plurality of
openings of the high modulus polymeric generator plate.
6. The device of claim 5, wherein the plurality of openings of the
high modulus polymeric generator plate are disposed in a center
region of the high modulus polymeric generator plate that is
uncovered by the piezoelectric actuator and aligned with the
central open region of the ejector plate.
7. The device of claim 6, wherein the high modulus polymeric
generator plate has a reduced size relative to the ejector plate,
and the size of the high modulus polymeric generator plate is
determined, at least in part, by the area occupied by the center
region and the arrangement of the plurality of openings.
8. The device of claim 1, having an average ejected droplet
diameter greater than 15 microns, the stream of droplets having low
entrained airflow such that the stream of droplets deposit on a
target during use.
9. An ejector mechanism configured to eject a stream of droplets,
the ejector mechanism comprising: an ejector plate coupled to a
high modulus polymeric generator plate and a piezoelectric
actuator; the high modulus polymeric generator plate including a
plurality of openings formed through its thickness; and the
piezoelectric actuator being operable to oscillate the ejector
plate, and thereby the high modulus polymeric generator plate, at a
frequency and generate a directed stream of droplets.
10. The ejector mechanism of claim 9, wherein one or more of said
plurality of openings are shaped so as to comprise a fluid entrance
orifice, an entrance cavity, a capillary channel, and a fluid exit
orifice.
11. The ejector mechanism of claim 9, wherein each of said
plurality of openings are shaped so as to comprise a fluid entrance
orifice, an entrance cavity, a capillary channel, and a fluid exit
orifice, and wherein each opening comprises an overall pitch
length.
12. The ejector mechanism of claim 9, wherein the high modulus
polymer generator plate is formed from a material selected from the
group consisting of: ultrahigh molecular weight polyethylene
(UHMWPE), polyimide, polyether ether ketone (PEEK), talc-filled
PEEK, polyvinylidine fluoride (PVDF), and polyetherimide.
13. The ejector mechanism of claim 9, wherein the ejector plate has
a central open region aligned with the high modulus polymeric
generator plate, and the piezoelectric actuator is coupled to a
peripheral region of the ejector plate so as to not obstruct the
plurality of openings of the high modulus polymeric generator
plate.
14. The ejector mechanism of claim 13, wherein the plurality of
openings of the high modulus polymeric generator plate are disposed
in a center region of the high modulus polymeric generator plate
that is uncovered by the piezoelectric actuator and aligned with
the central open region of the ejector plate.
15. The ejector mechanism of claim 14, wherein the high modulus
polymeric generator plate has a reduced size relative to the
ejector plate, and the size of the high modulus polymeric generator
plate is determined, at least in part, by the area occupied by the
center region and the arrangement of the plurality of openings.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of the filing date of
U.S. Provisional Application No. 61/569,739, filed Dec. 12, 2011,
and of U.S. Provisional Application No. 61/591,786, filed Jan. 27,
2012, contents of which are herein incorporated by reference in
their entireties.
BACKGROUND OF THE INVENTION
[0002] Using spray devices to administer products in the form of
mists or sprays is an area with large potential for safe,
easy-to-use products. A major challenge in providing such a device
is to provide consistent and accurate delivery of suitable
doses.
[0003] An important area where spray devices are needed is in
delivery of eye medications. The application of fluids, as in the
case of eye drops, has always posed a problem, especially for
children and animals who tend to blink or jerk at the critical
moment of administration, causing the droplet to land on the
eyelid, nose or other part of the face. The impact of a large drop
or drops of fluid on the eyeball, especially when the fluid is at a
different temperature, also tends to produce a blinking reaction.
Elderly also often lose the hand coordination necessary to get the
eye drops into their eyes. Stroke victims have similar
difficulties. Dropper delivery often requires a particular physical
position, such as tilting of the head or laying in a horizontal
position, neither of which might be practical.
[0004] Often, it is important that the subject administer the
correct dose the requisite number of times per day. However, in
practice, subjects that are prescribed eye medications for home use
tend to forget to dose, or dose excessively or cross-dose with
other medications. One of the compliance problems is that, even if
the subject is intent on following the treatment regimen, he or she
may not be compliant for any number of reasons.
[0005] Currently, many of these medications are administered by eye
droppers. Current eye drop devices often require either the head to
be tilted back, the subject to lie down or provide downward
traction on the lower eyelid, or a combination of traction and
tilting, since the delivery mechanism typically relies on gravity
for applying the medication. This is not only awkward, but involves
a fair amount of coordination, flexibility and cooperation on the
part of the subject to ensure that the medication gets into the eye
while avoiding poking the eye with the dropper tip. Current eye
dropper bottles pose the risk of poking the user in the eye,
potentially causing physical damage to the eye, and further,
exposing the tip to bacterial contamination due to contact with the
eye. As such, the subject runs the risk of contaminating the
medication in the eye drop bottle and subsequently infecting the
eye. Additionally, a large volume of the medication flows out of
the eye or is washed away by the tearing reflex. As a result, this
method of administration is also inaccurate and wasteful. Moreover,
the technology does not provide a satisfactory way of controlling
the amount of medication that is dispensed, nor does it provide a
way of ensuring that the medication that is dispensed actually
lands on the eye and remains on the eye.
[0006] Eye droppers also provide no way of verifying compliance by
a subject. Even if after a week of use the eye dropper bottle could
be checked for the total volume of medication dispensed, e.g., by
weighing the bottle, this does not provide a record of day-to-day
compliance. A subject may have missed one or more doses and
overdosed on other occasions. Also, the poor precision with which
eye droppers deliver drops to the eye makes it difficult to
determine whether the medication is actually delivered into the
eye, even though it may have been dispensed.
[0007] Accordingly, there is a need for a delivery device that
delivers safe, suitable, and repeatable dosages to a subject for
ophthalmic, topical, oral, nasal, or pulmonary use.
SUMMARY OF THE INVENTION
[0008] The present disclosure includes an ejector device and method
of delivering safe, suitable, and repeatable dosages to a subject
for ophthalmic, topical, oral, nasal, or pulmonary use. The present
disclosure also includes an ejector device and fluid delivery
system capable of delivering a defined volume of fluid in the form
of droplets having properties that afford adequate and repeatable
high percentage deposition upon application.
[0009] The present disclosure includes and provides an ejector
device for delivering a fluid to an eye of a subject, the device
comprising a housing, a reservoir disposed within the housing for
receiving a volume of fluid, and an ejector mechanism configured to
eject a stream of droplets having an average ejected droplet
diameter greater than 15 microns, with the stream of droplets
having low entrained airflow such that the stream of droplets
deposits on the eye of the subject during use.
[0010] The disclosure further includes and provides an ejector
mechanism configured to eject a stream of droplets, the ejector
mechanism comprising: an ejector plate coupled to a high modulus
polymeric generator plate and a piezoelectric actuator; the high
modulus polymeric generator plate including a plurality of openings
formed through its thickness; and the piezoelectric actuator being
operable to oscillate the ejector plate, and thereby the high
modulus polymeric generator plate, at a frequency and generate a
directed stream of droplets.
[0011] Another implementation of the disclosure provides a device
for delivering a fluid to a target, the device comprising: a
housing; a reservoir disposed within the housing for receiving a
volume of fluid; and an ejector mechanism in fluid communication
with the reservoir and configured to eject a stream of droplets,
the ejector mechanism comprising an ejector plate coupled to a high
modulus polymeric generator plate and a piezoelectric actuator. The
high modulus polymeric generator plate includes a plurality of
openings formed through its thickness; and the piezoelectric
actuator is operable to oscillate the ejector plate, and thereby
the high modulus polymeric generator plate, at a frequency and
generate a directed stream of droplets.
[0012] In certain implementations, the ejector plate has a central
open region aligned with the high modulus polymeric generator
plate, and the piezoelectric actuator is coupled to a peripheral
region of the ejector plate so as to not obstruct the plurality of
openings of the high modulus polymeric generator plate. The
plurality of openings of the high modulus polymeric generator plate
may be disposed in a center region of the high modulus polymeric
generator plate that is uncovered by the piezoelectric actuator and
aligned with the central open region of the ejector plate. In
certain implementations, the three-dimensional geometry and shape
of the openings, including orifice diameter and capillary length,
and spatial array on the high modulus polymeric generator plate may
be controlled to optimize generation of the directed stream of
droplets.
[0013] Another implementation includes a method for the fabrication
of a high modulus polymeric generator plate for ejecting high
viscosity fluids suitable for ophthalmic, topical, oral, nasal, or
pulmonary use comprising laser micromachining of high modulus
polymeric materials to form three-dimensional openings through the
thickness of the material, the openings comprising a fluid entrance
orifice, an entrance cavity, a capillary channel, and a fluid exit
orifice, wherein the opening comprises an overall pitch length.
[0014] Yet another implementation of the disclosure includes and
provides for a method of delivering a volume of ophthalmic fluid to
an eye of a subject, the method comprising ejecting a directed
stream of droplets of an ophthalmic fluid contained in a reservoir
from openings of an ejector plate, the droplets in the directed
stream having an average ejecting diameter in the range of 5-2500
microns, including but not limited to 20-400 microns, 20-200,
100-200, etc., and an average initial velocity in the range of
0.5-100 m/s, 1-100 m/s, including but not limited to, 2-20 m/s.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1A shows a cross-sectional view of an implementation of
an ejector assembly.
[0016] FIG. 1B shows a front view of an implementation of an
ejector mechanism.
[0017] FIG. 1C shows an exploded view of an implementation of an
ejector mechanism.
[0018] FIG. 1C-2 shows a schematic top view of an implementation of
an active region of a high modulus polymeric generator plate.
[0019] FIGS. 1D-K show partial cross-sectional views showing
examples of high modulus polymeric generator plate
configurations.
[0020] FIGS. 2A-2F illustrate exemplary CAD implementations and
laser micromachined high modulus polymeric generator plate
configurations, top and bottom views, and cross-sectional views of
related generator plates and openings, according to certain
implementations of the disclosure.
[0021] FIG. 3 illustrates modes of operation of an active region of
an implementation of a high modulus polymeric generator plate, and
digital holographic microscopy image of oscillation of the high
modulus polymeric generator plate according to an implementation of
the disclosure.
[0022] FIGS. 4A-B illustrate an active region of an implementation
of a high modulus polymeric generator plate, and a digital
holographic microscopy image of oscillation of the high modulus
polymeric generator plate according to an implementation of the
disclosure.
[0023] FIG. 5 illustrates a frequency scan of an ejection assembly
vs. oscillation amplitude, according to an implementation of the
disclosure.
[0024] FIG. 6 illustrates mass ejection vs. frequency for water
using an ejector assembly according to an implementation of the
disclosure.
[0025] FIGS. 7A-7B illustrate mass ejection vs. frequency for water
and Restasis.TM. using an ejector assembly according to an
implementation of the disclosure.
[0026] FIG. 8 illustrates exemplary generator plate structures
according to an implementation of the disclosure.
[0027] FIG. 9 illustrates cross sectional views of a micromachined,
laser ablated generator plate structures according to
implementations of the disclosure.
[0028] FIG. 10 illustrates spatial distribution of select opening
geometries (shown in FIG. 9), according to implementations of the
disclosure.
[0029] FIG. 11 illustrates a view of the opening forming process
using UV LIGA, according to implementations of the disclosure.
[0030] FIGS. 12A-12D illustrate exemplary CAD implementations and
laser micromachined high modulus polymeric generator plate
configurations, top and bottom views, and cross-sectional views of
related generator plates and openings, according to certain
implementations of the disclosure.
[0031] FIG. 13 illustrates a high speed image of a droplet spray
overlaid with a digital holographic image of a normal mode of
operation of exemplary ejector mechanisms of the disclosure.
[0032] FIGS. 14A-B illustrate exemplary generator plate structures
according to an implementation of the disclosure.
[0033] FIG. 15A-B illustrate a simulation of a pressure driven flow
through in a capillary, according to implementations of the
disclosure.
[0034] FIGS. 16A-16B illustrate ejected droplet velocity over time,
according to implementations of the disclosure.
[0035] FIG. 17 illustrates a replicate analysis demonstrating the
shear thinning behavior of Restasis.
[0036] FIG. 18 illustrates the same flow curve data as in FIG. 17,
but plotted as shear stress versus shear rate.
[0037] FIGS. 19A-19C illustrate fluid resistance as a function of
capillary length, according to implementations of the
disclosure.
[0038] FIGS. 20A-20B illustrate spray performance as a function of
opening placement on a generator plate, according to
implementations of the disclosure.
[0039] FIGS. 21A-21B illustrate spray performance as a function of
the number of openings on a generator plate, according to
implementations of the disclosure.
[0040] FIGS. 22A-22B illustrate spray performance as a function of
the polymer modulus of a generator plate, according to
implementations of the disclosure.
DETAILED DESCRIPTION
[0041] The present disclosure generally relates to ejector devices
useful, e.g., in the delivery of fluid for ophthalmic, topical,
oral, nasal, or pulmonary use, more particularly, for use in the
delivery of ophthalmic fluid to the eye. In certain aspects, the
ejector devices include an ejector assembly including an ejector
mechanism which generates a controllable stream of droplets of
fluid. Fluid includes, without limitation, suspensions or emulsions
which have viscosities in a range capable of droplet formation
using an ejector mechanism. Exemplary ejector devices and related
methods useful in connection with the present disclosure are
described in U.S. application Ser. No. 13/184,484 (Attorney Docket
Number 24591.003-US03), filed Jul. 15, 2011, entitled "Drop
Generating Device", U.S. application Ser. No. 13/184,446 (Attorney
Docket Number 24591.003-US01), filed Jul. 15, 2011, entitled
"Ophthalmic Drug Delivery" and U.S. application Ser. No. 13/184,468
(Attorney Docket Number 24591.003-US02), filed Jul. 15, 2011,
entitled "Method and System for Performing Remote Treatment and
Monitoring", which applications are each herein incorporated by
reference in their entireties.
[0042] As discussed further herein, the generation of droplets
using ejector devices of the disclosure depends on a complex
interaction between liquid flow through micro-orifices,
fluid-surface interactions, exit orifice diameter, entrant cavity
geometry, film thickness, capillary tube length, film mechanical
properties, amplitude and phase of mechanical displacement,
frequency of displacement, etc. Moreover fluid properties such as
viscosity, density, and surface energy play major roles in droplet
generation. In accordance with certain aspects of the disclosure,
ejector mechanism structures and generator plate opening geometries
that optimize droplet generation dynamics and microfluidic flow are
disclosed.
[0043] As explained in further detail herein, in accordance with
certain aspects of the present disclosure, the ejector mechanism
may form a directed stream of droplets which may be directed toward
a target. The droplets may be formed in a distribution of sizes,
each distribution having an average droplet size. The average
droplet size may be in the range of about 15 microns to over 400
microns, greater than 20 microns to about 400 microns, about 20
microns to about 80 microns, about 25 microns to about 75 microns,
about 30 microns to about 60 microns, about 35 microns to about 55
microns, about 20 microns to about 200 microns, about 100 microns
to about 200 microns, etc. However, the average droplet size may be
as large as 2500 microns, depending on the intended application.
Further, the droplets may have an average initial velocity of about
0.5 m/s to about 100 m/s, e.g., about 0.5 m/s to about 20 m/s,
about 0.5 to about 10 m/s, about 1 m/s to about 5 m/s, about 1 m/s
to about 4 m/s, about 2 m/s, etc. As used herein, the ejecting size
and the initial velocity are the size and initial velocity of the
droplets when the droplets leave the ejector plate. The stream of
droplets directed at a target will result in deposition of a
percentage of the mass of the droplets including their composition
onto the target.
[0044] As described herein, the ejector device and ejector
mechanism of the disclosure may be configured to eject a fluid of
generally low to relatively high viscosity as a stream of droplets.
By way of example, fluids suitable for use by the ejector device
can have very low viscosities, e.g., as with water at 1 cP, or
less, e.g. 0.3 cP. The fluid may additionally have viscosities in
ranges up to 600 cP. More particularly, the fluid may have a
viscosity range of about 0.3 to 100 cP, 0.3 to 50 cP, 0.3 to 30 cP,
1 cP to 53 cP, etc. In some implementations, the ejection device
may be used to eject a fluid having a relatively high viscosity as
a stream of droplets, e.g., a fluid having a viscosity above 1 cP,
ranging from about 1 cP to about 600 cP, about 1 cP to about 200
cP, about 1 cP to about 100 cP, about 10 cP to about 100 cP, etc.
In some implementations, solutions or medications having the
suitable viscosities and surface tensions can be directly used in
the reservoir without modification. In other implementations,
additional materials may be added to adjust the fluid parameter. By
way of example, exemplary fluids are illustrated below:
TABLE-US-00001 drugs/fluids dynamic viscosity (cP) kinematic
viscosity (cP) density water 1.017 1.019 0.99821 Xalatan.sup.TM
1.051 1.043 1.00804 Tropicamide 1.058 1.052 1.00551 Restasis.sup.TM
18.08 17.98 1.00535
Viscosity measured at 20.degree. C.
[0045] Droplets may be formed by an ejector mechanism from fluid
contained in a reservoir coupled to the ejector mechanism. The
ejector mechanism and reservoir may be disposable or reusable, and
the components may be packaged in a housing. The housing may be
disposable or reusable. The housing may be handheld, miniaturized,
or formed to couple to a base, and may be adapted for communication
with other devices. Housings may be color-coded or configured for
easy identification. Ejector devices, in some implementations, may
include illumination means, alignment means, temperature control
means, diagnostic means, or other features. Other implementations
may be part of a larger network of interconnected and interacting
devices used for subject care and treatment. The ejector mechanism
may be, e.g., a piezoelectric actuator as described herein.
[0046] As discussed herein, in certain aspects, the ejector
mechanism may be piezoelectric. Referring to FIGS. 1A-C, an ejector
assembly 1600 may include an ejector mechanism 1601 and reservoir
1620. The ejector mechanism 1601 may include an ejector plate 1602
coupled to a high modulus polymeric generator plate 1632 including
one or more openings 1626, that can be activated by a piezoelectric
actuator 1604 which vibrates to deliver a fluid 1610, contained in
a reservoir 1620, in the form of ejected droplets 1612 along a
direction 1614. Again, the fluid may be an ophthalmic fluid that is
ejected towards an eye 1616 of a human adult, child, or animal.
Additionally, the fluid may contain an active pharmaceutical to
treat a discomfort, condition, or disease of a human or an
animal.
[0047] As shown in FIG. 1A, ejector plate 1602 is disposed over
reservoir 1620 which contains fluid 1610. Surface 1625 of ejector
plate 1602 is adjacent to the fluid 1610. Reservoir 1620 has open
region 1638 which is adjacent to surface 1625 and to openings 1626.
In this implementation, surface 1625 encloses the fluid 1610 in the
reservoir 1620. The reservoir 1620 may be coupled to the ejector
plate 1602 at a peripheral region 1646 of the surface 1625 of the
ejector plate 1602 using a suitable seal or coupling. By way of
example, the reservoir 1620 may be coupled via an O-ring 1648a.
Although not shown, more than one O-ring can be used. As known in
the art, the O-rings may have any suitable cross-sectional shape.
Furthermore, other couplers such as polymeric, ceramic, or metallic
seals can be used. Alternatively, the coupling can be eliminated
altogether and reservoir 1620 may be integrally connected to
ejector plate 1602, for example by welding or over molding. In such
an implementation, an opening through which fluid is supplied to
reservoir 1620 may be provided (not shown). Further still, the
couplings may be made removable, such as a hinge, or may be made
flexible or nonrigid connector, e.g., polymeric connector.
[0048] Other than the open region 1638, portions of the ejector
plate 1602 may be covered by an additional reservoir wall 1650. In
the implementation of FIG. 1A, wall 1650 does not directly contact
the ejector plate 1602, rather it is coupled to O-rings 1648a.
Alternatively, wall 1650 can be directly attached to ejector plate
1602. Furthermore, reservoir 1620 can be directly attached to
ejector plate 1602 and wall 1650 can be omitted altogether.
[0049] The configuration of the reservoir 1620, including the shape
and dimension, can be selected based on the amount of fluid 1610 to
be stored, as well as the geometry of the ejector plate 1602.
Alternative forms of reservoirs include gravity-fed, wicking, or
collapsible bladders which operate under pressure differentials.
These reservoirs may be prefilled, filled using a micro-pump or by
replacement of a cartridge. The micro pump may fill the reservoir
by pumping fluid into or out of a collapsible or noncollapsible
container. The cartridge may include a container which is loaded
into the reservoir. Alternatively, the cartridge itself may be
coupled to a disposable ejector assembly which is then replaced
within the housing after a specified number of discharges.
Exemplary reservoirs are illustrated in U.S. patent application
Ser. No. 13/184,484, filed Jul. 15, 2011, the contents of which are
herein incorporated by reference.
[0050] In some implementations, the reservoir 1620 includes through
holes 1642 (only one shown in FIG. 1A) to allow air to escape from
or enter the reservoir 1620 and keep the fluid 1610 in the
reservoir at the appropriate ambient pressure. The through holes
1642 have a small diameter so that the fluid 1610 does not leak
from the holes. Alternatively, no openings may be formed in the
reservoir 1620, and at least a portion, e.g., the portion 1644, or
the entire reservoir 1620 can be collapsible, e.g., in the form of
a bladder. The entire reservoir may also be made in the form of a
flexible or collapsible bladder. Accordingly, as the fluid 1610 is
ejected through openings 1626, the reservoir 1620 changes its shape
and volume to follow the changes in the amount of fluid 1610 in the
reservoir 1620.
[0051] In the implementation of FIG. 1A, the ejector mechanism 1601
is activated by being vibrated by piezoelectric actuator 1604. Two
electrodes 1606a and 1606b are formed on two opposite surfaces 1634
and 1636 of the piezoelectric actuator 1604 that are parallel to
the surface 1622 of the ejector plate 1602 and activate the
piezoelectric actuator 1604 to vibrate the ejector plate 1602 and a
high modulus polymeric generator plate 1632 (described in further
detail herein). The electrodes 1606a and 1606b can be attached to
the ejector plate or piezoelectric actuator in any known manner
including fixing by adhesive or otherwise bonding. They may also be
overmolded in place to ejector plate 1602. Wires or other
conductive connectors can be used to affect necessary electrical
contact between ejector plate 1602 and the electrodes 1606a and
1606b. Alternatively, the electrodes may be formed on the ejector
plate 1602 by plating or otherwise depositing. By way of example,
the electrodes are attached by adhesive 1628 which is applied
between the electrode 1606a and the ejector plate 1602. Electrode
1606a is in electrical contact with ejector plate 1602. When a
voltage is applied across the electrodes 1606a and 1606b, the
piezoelectric actuator 1604 deflects ejector plate 1602 and
likewise high modulus polymeric generator plate 1632 to change
shape to be more concave or convex.
[0052] An extensive range of voltages corresponding to different
piezoelectric materials are known in the art, but by way of
example, a voltage differential of between 5 and 60 V, 30 and 60 V,
e.g., 40 or 60 V may be applied to the electrodes. When the
direction of the voltage differential is reversed, for example to
-40 or -60, the plate will deflect in the opposite direction. In
this way, the piezoelectric actuator 1604 causes oscillation of
ejector plate 1602 and high modulus polymeric generator plate 1632
which constitutes the vibration that results in formation of the
droplets 1612 from fluid 1610. As the alternating voltage is
applied to electrodes 1606a and 1606b, the ejector plate 1602 and
the high modulus polymeric generator plate 1632 oscillate, causing
the fluid droplets 1612 to accumulate in the openings 1626 and
eventually be ejected from the openings 1626 along the direction
1614 away from the reservoir 1620. The frequency and wavelength of
oscillation may depend on many factors, including but not limited
to, the thickness, composition and morphology and mechanical
properties of the ejector plate 1602, the volume of the openings
1626, the number of openings 1626, composition and structure of the
piezoelectric actuator 1604, piezoelectric actuation driving
voltage, frequency and waveform, the viscosity of the fluid, the
stiffness of the ejector plate 1602, properties of the high modulus
polymeric generator plate 1632, temperature and other factors.
These parameters may be adjusted or selected to create the desired
droplet stream. The frequency of droplet ejection also depends on
many factors. In some implementations, the droplets 1612 are
ejected at a frequency lower than the pulse frequency to the
piezoelectric actuator 1604. For example, the droplets 1612 are
ejected every 1-1000 cycles, and more specifically 8-12 cycles, of
the ejector plate/high modulus polymeric generator plate
vibration.
[0053] Without intending to be limited by theory, piezoelectric
actuated generator plates possess a large number of eigenmodes that
define the shape that the generator plate assumes when in motion,
and the optimum eigenmode and shape provides the maximum
displacement over the generator plate's active area. Exciting a
given eigenmode requires placing the piezoelectric actuator at a
given location relative to the standing wave of the generator
plate. In this regard, the size and shape of a piezoelectric
actuator, e.g., thickness, outer dimension and inner dimension, may
determine, at least in part, its placement relative to the
generator plate. Further, placement and bonding of the
piezoelectric actuator on the generator plate may increase the
generator plate stiffness. However, movement of the portion of the
generator plate inside the inner dimension of the piezoelectric
actuator is generally not restricted by placement of piezoelectric
actuator.
[0054] In accordance with certain aspects of the disclosure, with
reference to FIGS. 1B-1C, a first surface 1622 of ejector plate
1602 may be coupled to high modulus polymeric generator plate 1632.
The ejector plate 1602 may generally comprise a central open region
1652 configured to align with the high modulus polymeric generator
plate 1632. The high modulus polymeric generator plate 1632 may
then be coupled with the ejector plate 1602 such that a center
region 1630 of the high modulus polymeric generator plate 1632
aligns with the central open region 1652 of the ejector plate 1602.
The center region 1630 of the high modulus polymeric generator
plate 1632 may generally include one or more openings 1626, and
alignment of the central open region 1652 of the ejector plate 1602
and the center region 1630 of the high modulus polymeric generator
plate 1632 including the one or more openings 1626 allows for
through communication of the one or more openings 1626.
[0055] In certain aspects, the central open region 1652 of the
ejector plate 1602 may be smaller than the high modulus polymeric
generator plate 1632 to provide sufficient overlap of material so
as to allow for coupling of the ejector plate 1602 and the high
modulus polymeric generator plate 1632. However, the central open
region 1652 of the ejector plate 1602 should, in certain
embodiments, be sized and shaped so as to not interfere with or
obstruct the center region 1630 (and thereby one or more openings
1626) of the high modulus polymeric generator plate 1632.
[0056] By way of non-limiting example, the central open region 1652
of the ejector plate may be shaped in a manner similar to the high
modulus polymeric generator plate 1632, and may be sized so as to
have, e.g., about 0.5 mm to about 4 mm, about 1 mm to about 4 mm,
about 1 mm to about 2 mm, etc., of overlap material available for
coupling of the high modulus polymeric generator plate 1632 to the
ejector plate 1602 (e.g., overlap on all sides). For instance, the
central open region 1652 of the ejector plate may be shaped as a
square, a rectangle, a circle, an oval, etc., in a manner to
generally match the shape of the high modulus polymeric generator
plate 1632, and sized such that the central open region 1652 is,
e.g., about 0.5 mm to about 4 mm smaller in overall dimensions
(i.e., the diameter of a circle is about 0.5 to about 4 mm smaller,
the major and minor axes of an oval are about 0.5 to about 4 mm
smaller, the length of the sides of a square or rectangle are about
0.5 to about 4 mm smaller, etc.)
[0057] In certain embodiments, the high modulus polymer generator
plate may be sized and shaped so as to have an overall outer
dimension (OD) of about 4 mm to about 8 mm, e.g., 4 mm, 5 mm, 6 mm,
etc. The ejector plate may be sized and shaped so as to have an
overall outer dimension (OD) of about 18 mm to about 24 mm, e.g.,
20 mm, 21 mm, 22 mm, 23 mm, etc., and an inner dimension (ID)
(i.e., of the central opening) configured to provide sufficient
overlap with the OD of the generator place. For instance, the ID of
the ejector plate may be about 3 mm to about 16 mm, e.g., 4 mm, 6
mm, 12 mm, 14 mm, 16 mm, etc.
[0058] High modulus polymeric generator plate 1632 may be coupled
to ejector plate 1602 using any suitable manner known in the art,
depending on the materials in use. Exemplary coupling methods
include use of adhesive and bonding materials, e.g., glues,
epoxies, bonding agents, and adhesives such as loctite E-30CL or
Loctite 480 or 380 epoxies or other suitable super glue such as
Loctite ultra gel, welding and bonding processing, e.g., ultrasonic
or thermosonic bonding, thermal bonding, diffusion bonding, laser
welding or press-fit etc.
[0059] Surface 1622 of ejector plate 1602 may be coupled to a
piezoelectric actuator 1604, which activates high modulus polymeric
generator plate 1632 to form the droplets upon activation. The
manner and location of attachment of the piezoelectric actuator
1604 to the ejector plate 1602 affects the operation of the ejector
assembly 1600 and the creation of the droplet stream. In the
implementation of FIGS. 1B-C, the piezoelectric actuator 1604 may
be coupled to a peripheral region of surface 1622 of plate 1602,
while high modulus polymeric generator plate 1632 is coupled to
surface 1622 so as to align with central open region 1652 of
ejector plate 1602, as described above. Piezoelectric actuator 1604
is generally coupled to ejector plate 1602 so as to not cover or
obstruct center region 1630 (and thereby one or more openings 1626)
of the high modulus polymeric generator plate 1632. In this manner,
fluid 1610 may pass through openings 1626 to form droplets 1612. In
certain embodiments, the piezoelectric actuator may be shaped to
generally correspond in shape with the generator plate. By way of
example, the piezoelectric actuator may be sized to have an overall
outer dimension (OD) of about 8 mm to about 24 mm, e.g., 8 mm, 10
mm, 12 mm, 14 mm, 16 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, etc.,
and an inner dimension (ID) of about 4 mm to about 18 mm, e.g., 4
mm, 10 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, etc.
[0060] As the ejector assembly 1600 is used for delivering
therapeutic agents or other fluids to the desired target, e.g., the
eye, the ejector assembly 1600 may be generally designed to prevent
the fluid 1610 contained in the reservoir 1620 and the ejected
droplets 1612 from being contaminated. In some implementations, for
example, a coating (not shown) may be formed over at least a
portion of the exposed surface(s) of the piezoelectric actuator
1604, the ejector plate 1602, the high modulus polymeric generator
plate 1632, etc. The coating may be used to prevent direct contact
of the piezoelectric actuator 1604 and the electrodes 1606a and
1606b with the fluid 1610. The coating may be used to prevent
interaction of the ejector plate 1602 or high modulus polymeric
generator plate 1632 with the fluid, or it may be used to protect
the piezoelectric actuator 1604 and electrodes 1606a and 1606b from
the environment. For example, the coating can be a conformal
coating including a nonreactive material, e.g., polymers including
polyamide imide (PAI), polyether ether ketone (PEEK), polypropylene
(PP), or high density polyethylene (HDPE), or an inert material
selected from the group consisting of gold (Au), platinum (Pt),
palladium (Pd), titanium nitride (TiN), chromium nitride (CrN),
diamond like carbon/amorphous carbon, chromium carbon nitride, and
aluminum (Al). Coatings are described in further detail herein.
[0061] The high modulus polymeric generator plate 1632 may be a
perforated plate that contains at least one opening 1626. The one
or more openings 1626 form the droplets as fluid 1610 is passed
through. The high modulus polymeric generator plate 1632 may
include any suitable configuration of openings, one configuration
being depicted in FIG. 1B. By way of example, the openings may be
formed as a grid, a spiral, or in a rectangular, rectilinear, or
other pattern. The pattern may be regular or irregular. The pattern
may maintain a uniform spacing of openings, or the spacing may be
varied. For example, the density of openings may increase or
decrease towards the center of the plate. The pattern may also
cover all or part of the plate, i.e., center region 1632 may cover
all or part of the high modulus polymeric generator plate, etc.
[0062] The openings 1626 may be formed through the thickness of the
high modulus polymeric generator plate 1632 in any suitable
three-dimensional geometry, shape or volume, including orifice
diameter and capillary length, and spatial array on the high
modulus polymeric generator plate. The formation and arrangement of
the openings may be controlled so as to optimize generation of the
directed stream of droplets. Further, the openings may be formed
with an appropriate aspect ratio (i.e., height/thickness of opening
vs. diameter of opening) selected and configured to efficiently
eject droplets based, at least in part, on fluid properties.
[0063] Without being limited by theory, higher aspect ratio
openings produce a higher pressure gradient in the fluid being
ejected, and therefore may be generally preferred for higher
viscosity fluids. By way of example, in certain implementations,
the high modulus polymeric generator plates may have openings with
aspect ratios between about 1 and about 10, about 1 and about 5,
about 1 and about 4, etc. Such aspect ratios may be obtained by
varying opening height/thickness (i.e., high modulus polymeric
generator plate thickness) and opening diameter. By way of example,
opening diameter may range from about 20 .mu.m to about 100 .mu.m,
about 20 .mu.m to about 80 .mu.m, about 20 .mu.m to about 50 .mu.m,
about 30 .mu.m to about 40 .mu.m, etc. Opening height/thickness
(i.e., high modulus polymeric generator plate thickness) may range
from about 50 .mu.m to about 500 .mu.m, about 100 .mu.m to about
200 .mu.m, about 150 .mu.m to about 200 .mu.m, about 160 .mu.m,
etc. Selection of the aspect ratio of the openings may allow for
formation of droplets of fluids having relatively high
viscosities.
[0064] In certain implementations, the openings may have a
generally cylindrical shape, that is, the diameter of the opening
extending from surface 1622a of high modulus polymeric generator
plate 1632 to surface 1625a of high modulus polymeric generator
plate 1632 remains generally constant. Nevertheless, the openings
need not be limited to this cylindrical shape and may be fluted,
tapered, conical, oval, hourglass, etc. In other implementations,
the openings may comprise a general entrance cavity region (e.g., a
cylindrical, fluted, tapered, conical, hour glass, etc., shaped
cavity region) leading to a capillary channel and exit orifice.
See, e.g., FIGS. 1D-K. By way of example, a tapered opening may
extend the entire thickness from surface 1622a to 1625a, or it may
extend partway with a capillary channel extending to an exit
orifice. The opening may also be beveled on one or both sides. The
bevel may have an angled edge or a curved edge. The cross section
of the opening may be round, or may have any other suitable shape.
A few examples may be round, oval, rectangular or polygonal. The
openings may be regularly shaped or irregularly shaped. The shape
may be symmetric or asymmetric. The shape and aspect ratio of the
openings may impact ejection of droplets, and may be optimized so
as to efficiently eject fluids of varying viscosities, etc. In an
exemplary implementation of FIG. 1L, the openings 1626 may comprise
a fluid entrance orifice 1626a, an entrance cavity 1626b, a
capillary channel 1626c, and a fluid exit orifice 1626d, wherein
the opening comprises an overall pitch length 1626e.
[0065] As indicated herein, the size, shape, and aspect ratio of
the openings 1626 affect the size and shape of the droplets and the
droplet stream created by the ejector mechanism 1601. It may also
affect the density distribution throughout the droplet stream.
Thus, the size, shape, and aspect ratio of the openings as well as
their pattern may be selected and configured to produce the desired
properties of the droplet stream, based in part on fluid
properties, in accordance with certain aspects of the present
disclosure.
[0066] As with the size and shape of the openings 1626, the size
and shape of the central region 1630 can be selected based on the
desired properties of the droplet stream. As shown in FIG. 1C-2, by
way of example, the openings 1626 are arranged in a circular
pattern in the active region of high modulus polymeric generator
plate 1632, but other patterns may also be used as explained above.
The distance l between adjacent openings 1626 may be any suitable
value, including 1 micron to a few mm, e.g., 150 microns to 300
microns. In one particular implementation, l is chosen to be 200
microns. Additionally, also as explained above, the separation of
the openings 1626 need not be uniform.
[0067] Again, droplet stream generation depends on a complex
interaction between fluid flow through openings, aspect ratios of
openings, exit and entrance orifice diameter, entrance cavity
geometry, capillary channel length, generator plate material
composition and mechanical properties, amplitude and phase of
generator plate displacement, frequency of displacement of
generator plate, and fluid properties such as viscosity, density,
and surface energy, for example. For instance, without intending to
be limited by theory, fluid flow rate in microchannels and
capillary channels is dependent on the pressure difference between
the capillary channel and exit face as described by the
Young-LaPlace equation, divided by the resistance of the fluid flow
within the capillary channel. As such, the three-dimensional
geometry of the capillary channel and orifice diameters of the
openings of the generator plate can impact fluid flow rates through
the openings.
TABLE-US-00002 Flow rate Fluid Resistance Young-LaPlace equation Q
= .DELTA. P/R R = 8 L .pi. r 1 4 ##EQU00001## .DELTA.P = .gamma. (
1 r 1 + 1 r 2 ) ##EQU00002## .mu. = Fluid viscosity .gamma. = Fluid
surface tension L = Capillary length r1 = Capillary radius r1 =
Capillary radius r2 = Flute radius
[0068] The velocity of the fluid is thus:
V ( r ) = .pi. .DELTA. p A in .rho. in 8 .mu. l A out .rho. out ( R
2 - r 2 ) ##EQU00003##
where R is the diameter of the channel and r is the volume of fluid
within the channel.
[0069] In some implementations, the length of the capillary channel
may be selected so as to optimize flow and ejected mass of fluid
forming the droplet stream. By way of example, capillary channels
may range from 0 .mu.m to about 150 .mu.m, about 70 .mu.m to about
150 .mu.m, about 70 .mu.m to about 120 .mu.m, etc. In certain
implementations, the capillary channel may be between 120 .mu.m and
150 .mu.m, particularly for high viscosity fluids.
[0070] In some implementations, the ejector plate 1602 may be
formed of a metal, e.g., stainless steel, nickel, cobalt, titanium,
iridium, platinum, or palladium or alloys thereof. Alternatively,
the plate can be formed of suitable material, including other
metals or polymers, such as polyether ether ketone (PEEK) or
talc-filled PEEK, and be coated as described herein. The plate may
be a composite of one or more materials or layers. The plate may be
fabricated for example by cutting from sheet metal, pre-forming,
rolling, casting, photoetching, laser cutting or otherwise shaping.
The coatings may also be deposited by suitable deposition
techniques such as sputtering, vapor deposition including physical
vapor deposition (PAD), chemical vapor deposition (COD), or
electrostatic powder deposition. The protective coating may have a
thickness of about less than 0.1 .mu.m to about 500 .mu.m. It is
desirable that the coating adhere to the ejector plate 1602
sufficiently to prevent delamination when vibrating at a high
frequency.
[0071] Referring to FIGS. 1B-C, in one implementation, the ejector
plate 1602 and high modulus polymeric generator plate 1632 may have
concentric circular shapes. In certain aspects, the ejector plate
may be larger than the high modulus polymeric generator plate, so
as to accommodate coupling of the high modulus polymeric generator
plate and other components (e.g., piezoelectric actuator, etc.)
described herein. Likewise, in certain implementations, the high
modulus polymeric generator plate 1632 may have a reduced size or
diameter (in the implementation of a circular configuration)
relative to the ejector plate 1602. In certain aspects, the overall
size or diameter of high modulus polymeric generator plate 1632 may
be, at least in part, determined by the size of center region 1630
and by the arrangement of openings 1626.
[0072] However, both plates may independently have other shapes,
e.g., an oval, square, rectangular, or generally polygonal shape,
and may be the same or different. Overall size and shape may be any
suitable size and shape, and may be selected based on ejector
device design parameters, e.g., size and shape of an outer device
housing, etc. Additionally, the plates need not be flat, and may
include a surface curvature making it concave or convex. The
piezoelectric actuator 1604 may be of any suitable shape or
material. For example, the actuator may have a circular, oval,
square, rectangular, or a generally polygonal shape. The actuator
1604 may conform to the shape of the ejector plate 1602, high
modulus polymeric generator plate 1632, or regions 1630/1652.
Alternatively, the actuator 1604 may have a different shape.
Furthermore, the actuator 1604 may be coupled to the ejector plate
1602 or surface 1622 of the ejector plate 1602 in one or more
sections. In the example shown in FIGS. 1B-C, the piezoelectric
actuator 1604 is illustrated in the shape of a ring that is
concentric to the ejector plate 1602, high modulus polymeric
generator plate 1632, and regions 1630/1652.
[0073] In some implementations, the high modulus polymeric
generator plate 1632 may be formed from any suitable polymeric
material having a modulus of elasticity suitable to provide
sufficient tensile strength and flexibility to allow fabrication of
the one or more openings as well as vibration by the piezoelectric
actuator during use. Such materials may generally include those
with a modulus above about 100,000 psi, between about 100,000 psi
and about 700,000 psi, etc. (e.g., high modulus polymeric
materials). Exemplary materials include, ultrahigh molecular weight
polyethylene (UHMWPE), polyimide (Kapton.TM.), polyether ether
ketone (PEEK), talc-filled PEEK, polyvinylidine fluoride (PVDF,
Kynar.TM.), polyetherimide (Ultem.TM.), and be coated as discussed
herein.
[0074] By way of example, suitable materials include:
TABLE-US-00003 Modulus Modulus Coated Melt FDA Tensile Flexural
Seal/ (1 or Degrees Thickness Compliant/ Material (psi) (psi) Bond
2 side) F/C (um) Approved UHMWPE 105,000 Fusion Treatable 273-134
76 FDA & Weld/Heat USDA Seal Approved Kynar .TM., Solef 250,000
260,000 Fusion Treatable 329-338 Resin FDA (Polyvinylidine Weld
(165-170) Compliant Fluoride) Kapton ~350,000 652F 1 or 2 N/A 25,
50, FDA (polyimide) 20PSI 76, 127 Certified 20 Sec Grade PEEK
390,000 530,000 Si Treatable 644/340 76 FDA (polyether ether
Adhesive/ Certified ketone Mechanical Grade Ultem .TM. 475,000
480,000 Heat Seal Treatable 420/216 76 Resin FDA (polyetherimide)
Compliant
[0075] The high modulus polymeric generator plate may be a
composite of one or more materials or layers. The openings in the
plate may be formed using suitable methods including but not
limited to drilling by mechanical or thermal stamping or optical
means, such as laser drilling or ablation. More particularly, in
certain implementations, the openings may be formed via laser
machining. Without being limited, laser machining of polymeric
materials provides an efficient means of fabricating the high
modulus polymeric generator plate described herein by offering
accurate control of the three-dimensional geometry and spatial
array of openings. Exemplary laser micromachining technology may
utilize high power lasers, such as Excimer lasers, to ablate
polymeric materials, for example, while under computer control. The
manipulation of laser position, pulse duration and power provides
for accurate three-dimensional structuring of openings. Exemplary
methods for laser micromachining and ablation are disclosed, e.g.,
in U.S. Pat. No. 5,296,673, U.S. Pat. No. 4,414,059, and Andreas
Ostendorfa, et al., Proceedings of SPIE Vol. 4633 (2002), 128-135,
the contents of which are herein incorporated by reference.
[0076] In one implementation, laser micromachining and
UV-laser-assisted micromachining of polymeric materials may be used
to form a high modulus polymer generator plate of this disclosure.
In certain aspects, polymeric materials, such as polyether ether
ketone (PEEK), talc-filled PEEK, polysulfone (PSU) and polyimide
(PI) may be selected, due in part to their chemical stability and
corresponding absorbance with KrF-Excimer laser radiation
(wavelength 248 nm) as well as frequency quadrupled (4.omega.)
Nd:YAG laser radiation (wavelength 266 nm). Patterns and complex
shapes may be formed on masks projected onto the target material to
ablate patterns onto the target and to obtain the desired pattern.
The projected mask pattern may be linearly demagnified from the
mask through a lens and onto the target for ablation, for example,
to obtain resolutions from 1 to 10 microns, e.g., 2 microns. Direct
optical imaging of complex structures may also be formed on masks
and allows use of motorized masks, which in turn provides a means
of rotating masks and which further enables complex mask structures
to be changed with high precision and without stopping the ablation
process.
[0077] In certain implementations, a computer aided design (CAD)
drawing may be used to design a mask used to control the spatial
distribution of a generator plate array and to fabricate the
internal three-dimensional geometry of the opening orifices. By way
of non-limiting example, FIGS. 2A-2F and FIG. 12A-12D illustrate an
exemplary CAD drawing of generator plate desired opening
geometries, and corresponding generator plates and openings. Top
and bottom views, as well as cross-sectional views are illustrated
with openings having varying capillary channel lengths (e.g., FIGS.
2C and 2D). As shown, the openings may comprise a fluid entrance
orifice, an entrance cavity, a capillary channel, and a fluid exit
orifice. The entrance and exit sides of the generator plate are
separately illustrated in FIGS. 2E and 2F. With reference to FIG.
12, FIGS. 12A and 12D illustrate exemplary fluted openings of a
generator plate, and FIGS. 12B-12C illustrate the entrance and exit
sides of a generator plate. Such an exemplary CAD configuration may
be used to design a mask and for computer control of micromachining
process.
[0078] This mask technique may be further used for patterning large
complex structures. CAD data may also be used to control the laser
beam by beam shaping using cylindrical lenses and thereby to
control the machined three-dimensional structure by controlling the
laser fluence at the target to control the removal of
photodecomposition products by ablation. Control of ambient
environment through use of oxygen purge promotes formation of
volatile photo-degradation products such as CO.sub.2, CO, etc.
Furthermore, curved grooves and grooves with a variation of cross
section may be fabricated using this process. By way of
non-limiting example, with reference to FIG. 1K, the CAD drawing
may be comprised of an opening with an entrance diameter of about
300 .mu.m, capillary channel length of about 70 .mu.m to about 120
.mu.m, exit orifice of about 40 .mu.m to 50 .mu.m, e.g., 46 .mu.m,
and overall pitch of about 400 .mu.m pitch.
[0079] FIG. 8 further shows exemplary generator plate structures
which may serve as inputs for fabrication, e.g., via excimer laser
ablation. Using excimer laser ablation as a tool for
microfabricating generator plate nozzle structures, all of the
design parameters described in FIG. 10 can be independently
controlled and modified. FIG. 9 illustrates cross sectional views
of a micromachined, laser ablated generator plate structures. All
are micromachined from virgin PEEK with exception of (9) which is
talc filled (20%). In addition, the spatial distribution of the
nozzle array on the generator plate (membrane) can be controlled
(FIG. 11). FIG. 10 illustrates spatial distribution of select
opening geometries (shown in FIG. 9), shown as an array on the
generator plate (membrane). These are viewed with the fluid
entrance opening facing up.
[0080] The two-dimensional array displayed in FIGS. 9 and 10
provide an example of the flexibility that excimer laser ablation
provides for microfabrication and surface structuring of polymers.
Alternative processes for forming openings of a generator plate
include the LIGA process. (E. W. Becker, et al., Microelectron.
Eng. 4 (1986) 35-56), processes based on UV lithography, UV LIGA
(H. Miyajima et al., J. Microelectrochem. Syst. 4 (1995) 220-229;
C. H. Cheng, et al., J. Microchem. Microeng. 15 (2005) 843-848).
Reference to FIG. 11 provides a view of the opening-forming process
using UV LIGA. Opening formation via UV LIGA employs an
electroforming step in which the metal is deposited via
electroforming onto the photoresist mold (C. H. Cheng, et al). The
overdeposition results in the formation of a parabolic hole which
is the opening.
[0081] In some implementations, the ejector plate 1602 and/or high
modulus polymeric generator plate 1632 may be coated with a
protective coating that is anti-contamination and/or
anti-microbial. The protective coating can be conformal over all
surfaces of the ejector plate and/or high modulus polymeric
generator plate, including surfaces defining the openings 1626,
portions of the openings (outer surface, inner surface, etc.). In
other implementations, the protective coating can be applied over
selected surfaces, e.g., the surfaces 1622, 1625, 1622a, 1625a, or
surface regions, e.g., parts of such surfaces. The protective
coating can be formed of a biocompatible metal, e.g., gold (Au),
iridium (Ir), rhodium (Rh), platinum (Pt), palladium (Pd), titanium
nitride (TN), chromium nitride (CrN), amorphous carbon,
nickel-platinum alloy, nickel-palladium alloy, chromium carbon
nitride, aluminum (Al), or alloys thereof, or a biocompatible
polymer, polyamide imide, polyether ether ketone (PEEK),
polypropylene (PP), or high density polyethylene (HDPE).
Antimicrobial materials include metals such as silver, silver
oxide, selenium or organic chlorides or organometallics such as
alkylbenzyldimethylammonium (benzalkonium) chloride, or transition
metal complexes of 1,1'-diacetylferrocene-derived
thiocarbohydrazone, for example, or polymers such as
carboxyl-containing ethylenecopolymers such as
poly(ethylene-co-acrylic acid) (E/AA), and 8-hydroxyquinolinium
ionomers. The protective coating can be in direct contact with the
fluid 1610 or the droplets 1612. The coating may provide an inert
barrier around the fluid or may inhibit microbial growth and
sanitize the fluid 1610 and/or the droplets 1612.
[0082] Additionally, surface 1622 or 1622a of ejector plate 1602 or
high modulus polymeric generator plate 1632 may be coated with a
hydrophilic or hydrophobic coating. Additionally, the coating may
be coated with a protective layer. The surface may also be coated
with a reflective layer. A coating layer may be both protective and
reflective. Alternatively, the surface may have been formed to be
reflective. For example, the surface may be made of stainless,
nickel-cobalt, or other reflective material. A surface may have
been formed or polished to be reflective. In addition to making the
surface reflective, the surface may also be backlit on its surface
or around its perimeter. In ophthalmic applications, a reflective
surface aids the user in aligning the ejector assembly with the
eye.
[0083] If desired, surfaces of the ejector assembly may include
coatings that may be pre-formed by dipping, plating, including
electroplating, or otherwise encapsulating, such as by molding or
casting. The coatings may also be deposited by suitable deposition
techniques such as sputtering, vapor deposition, including physical
vapor deposition (PAD) and chemical vapor deposition (COD), or
electrostatic powder deposition. The protective coating may have a
thickness of about less than 0.1 .mu.m to about 500 .mu.m. It is
desirable that the coating adhere to the plate sufficiently to
prevent delamination when vibrating at a high frequency.
[0084] Piezoelectric actuator 1604 may be formed from any suitable
material known in the art. By way of example, in some
implementations, the piezoelectric actuator can be formed from lead
zirconate titanate (Pb[Zr(x)Ti(1-x)]O3) (PZT), barium titanate
(BaTiO3), bariumzirconate titanate (Ba(Zr,Ti)O3), BiFeO3-based
ceramic, bismuth sodium titanate (BNT) material or a bismuth
potassium titanate (BKT) material or polymer-based piezoelectric
materials, such as polyvinylidine fluoride. The electrodes 1606a
and 1606b can be formed of suitable conductors including gold,
platinum, or silver. Suitable materials for use as the adhesive
1628 can include, but not be limited to, adhesives such as loctite
E-30CL or Loctite 480 or 380 epoxies or other suitable super glue
such as Loctite ultra gel-epoxies, silver-epoxy or nickel-epoxy
paste. One example of a conductive adhesive includes an epoxy paste
formulated using Ni powder and Loctite E-30CL. The reservoir 1620
may be formed of a polymer material, a few examples of which
include Nexcel Latitude ML29xxC, Rollprint-ClearFoil V, low density
and high density polyethylene (LDPE, HDPE), or ethylene vinyl
acetate/polyvinylidene chloride (EVA/PVDC) coextruded films.
[0085] In certain aspects of the disclosure, the ejector mechanism
may be configured so as to facilitate actuation of the ejector
plate, and thereby the high modulus polymeric generator plate, by
the piezoelectric actuator. As described above, the high modulus
polymeric generator plate may be configured to optimize ejection of
a fluid of interest. For example, the aspect ratio of the openings
of the high modulus polymeric generator plate may be selected
based, in part, on fluid properties, such that the general
thickness of the high modulus polymeric generator plate ranges from
about 50 .mu.m to about 500 .mu.m, as described above.
[0086] Without being limited by theory, in certain implementations,
actuation of the ejector mechanism may be optimized using
configurations including a high modulus polymeric generator plate
coupled to an ejector plate, as described herein. In addition,
reducing the surface area of the high modulus polymeric generator
plate (i.e., the central region having one or more openings)
likewise reduces manufacturing costs, reduces potential related
manufacturing defects, and increases manufacturing efficiencies and
output. In certain aspects, the ejector plate may be sized and
shaped in a manner to facilitate actuation of the ejector mechanism
(i.e., actuation of the ejector plate and thereby the high modulus
polymeric generator plate). By way of example, configurations of
the ejector plate may effectuate actuation of the ejector mechanism
through selection of properties (e.g., size, shape, material, etc.)
that facilitate flex of the ejector plate, and thereby vibration of
the high modulus polymeric generator plate. For instance, the
ejector plate may have a thickness generally ranging from about 10
.mu.m to about 400 .mu.m, from about 20 .mu.m to about 100 .mu.m,
from about 20 .mu.m to about 50 .mu.m, about 30 .mu.m to about 50
.mu.m, etc. Again, without being limited by theory, in certain
implementations, direct actuation of a relatively thinner ejector
plate (compared to the high modulus polymeric generator plate), may
be more optimal.
[0087] In accordance with certain implementations of the
disclosure, the configuration of the ejector plate and the high
modulus polymeric generator plate may be selected such that the
center region of the high modulus polymeric generator plate
including openings (e.g., the "active region" of the high modulus
polymeric generator plate) produces a symmetric oscillation with a
normal mode of oscillation. Without being limited by theory, in
certain implementations, configurations of the ejector plate and
high modulus polymeric generator plate may be selected such that
0,2 normal mode and 0,3 normal mode of oscillation of the active
region of the high modulus polymeric generator plate is observed.
The mode is associated with a maximum amplitude and displacement of
the active region, wherein the mode is designated as (d,c) where d
is the number of nodal diameters and c is the number of nodal
circles.
[0088] The magnitude and frequency of the ejector plate vibration
can also be controlled by controlling the voltage pulses applied to
the electrodes 1606a, 1606b, e.g., a voltage differential of 40 or
60 V may be applied to the electrodes. As discussed above, the
pulses are created by voltage differentials that deflect ejector
plate 1602, and thereby high modulus polymeric generator plate
1632. In some implementations, one of the electrodes 1606a or 1606b
is grounded and voltage pulses, e.g., bipolar pulses, are applied
to the other one of the electrodes 1606a or 1606b e.g., to vibrate
the ejector plate 1602. By way of example, in one implementation,
the piezoelectric actuator 1604 can have a resonant frequency of
about 5 kHz to about 1 MHz, about 10 kHz to about 160 kHz, about
50-120 kHz to about 50-140 kHz, etc., e.g., 108-130 kHz. The
applied voltage pulses can have a frequency lower, higher, or the
same as the resonant frequency of the piezoelectric actuator
1604.
[0089] In certain implementations, delivery time of the droplets is
about 0.1 ms to about several seconds. Without wishing to be bound
by theory, it is believed that human eyes take about 300 ms to
about 400 ms between blinks. Therefore, for implementations where
delivery is desired to be between blinks, the delivery time may be
about 50 ms to about 300 ms and more particularly 25 ms to 200 ms.
In one implementation, the delivery time is 50 ms to 100 ms. In
this way, the ejected droplets can be effectively delivered and
deposited in the eye during a blinking cycle of the eye. In some
implementations, for example over-the-counter saline dispensers,
the delivery time can be as long as several seconds, e.g., 3-4
seconds, spanning several blink cycles. Alternatively, a single
delivery can be administered by several bursts or pulses of droplet
ejection. Additionally, and not intending to be limited by theory,
pulsing may be used to reduce the peak amplitude of the droplet
airstream by spreading the impulse out over time. Therefore, the
pressure of the ejection on the target may be mitigated.
Furthermore, pulsing may also reduce droplet agglomeration and
result in less entrained air generation. By way of example, pulses
of 25 ms can be administered with stop times of 25 ms separating
the pulses. In one implementation, the pulses may be repeated for a
total of 150 ms total time.
[0090] The ejector assembly described herein may be incorporated
into an ejector device and system. Exemplary ejector devices and
systems are illustrated in U.S. application Ser. No. 13/184,484,
filed Jul. 15, 2011 and U.S. Application No. 61/569,739, filed Dec.
12, 2011, the contents of which are herein incorporated by
reference for the purpose of such disclosures.
[0091] Many implementations of the invention have been disclosed.
This disclosure contemplates combining any of the features of one
implementation with the features of one or more of the other
implementations. For example, any of the ejector mechanisms or
reservoirs can be used in combination with any of the disclosed
housings or housing features, e.g., covers, supports, rests,
lights, seals and gaskets, fill mechanisms, or alignment
mechanisms. Further variations on any of the elements of any of the
inventions within the scope of ordinary skill is contemplated by
this disclosure. Such variations include selection of materials,
coatings, or methods of manufacturing. Any of the electrical and
electronic technology can be used with any of the implementations
without limitation. Furthermore, any networking, remote access,
subject monitoring, e-health, data storage, data mining, or
internet functionality is applicable to any and all of the
implementations and can be practiced therewith. Further still,
additional diagnostic functions, such as performance of tests or
measurements of physiological parameters may be incorporated into
the functionality of any of the implementations. Performance of
glaucoma or other ocular tests can be performed by the devices as a
part of their diagnostic functionality. Other methods of
fabrication known in the art and not explicitly listed here can be
used to fabricate, test, repair, or maintain the device.
Furthermore, the device may include more sophisticated imaging or
alignment mechanisms. For example, the device or base may be
equipped with or coupled to an iris or retina scanner to create a
unique identification to match a device to the user, and to
delineate between eyes. Alternatively, the device or base may be
coupled to or include sophisticated imaging devices for any
suitable type of photography or radiology.
[0092] To assist in understanding the present invention, the
following Example is included. The experiments described herein
should not, of course, be construed as specifically limiting the
invention and such variations of the invention, now known or later
developed, which would be within the purview of one skilled in the
art are considered to fall within the scope of the invention as
described herein and hereinafter claimed.
EXAMPLES
Example A
Modes of Operation
[0093] Although many arrangements are possible, one implementation
uses a piezoelectric-driven ejector mechanism which includes a 6 mm
outer diameter, 300 .mu.m thick PEEK generator plate that is bonded
to a 20 mm outer diameter, 50 .mu.m thick 304 stainless steel
ejector plate annulus. The ejector plate annulus includes a 4 mm
diameter central opening which is aligned with the PEEK generator
plate, and a 16 mm outer diameter, 8 mm inner diameter
piezoelectric actuator is attached directly to the ejector plate. A
modulation frequency of approximately 108 kHz to over 140 kHz is
applied to the piezoelectric actuator, causing the ejector plate to
oscillate. Digital holographic microscopy images are captured to
observe oscillation of the high modulus polymeric generator plate.
By way of example, with reference to FIG. 5, a frequency scan of
the implemented ejection assembly vs. oscillation amplitude was
performed to provide for identification of optimal resonant
frequency and range of frequencies at which the maximum out of
plane displacement of the generator plate is achieved. Out of plane
oscillation amplitude of the generator plate as a function of drive
frequency and excitation with a sine wave at 60 Vpp is illustrated
in FIG. 5, with an onset of maximum amplitude of oscillation at
.about.108 kHz, and a maximum amplitude of .about.2.3 microns at
110 kHz. Overlaid onto the amplitude profile in FIG. 5 is the sine
wave of the 60 Vpp used to drive the piezoelectric actuator.
[0094] The piezoelectric-actuated PEEK membrane displays a periodic
oscillation which spans a frequency range from about 108 kHz to
over 140 kHz and a maximum oscillation amplitude of .about.2
microns at 110 kHz. Dynamic imaging of oscillation modes confirms
the normal modes of oscillation as 0,1 and 0,2 in the active
ejector region of the PEEK membrane. FIG. 3 illustrates Digital
Holographic Microscopy of an ejector assembly comprising a
generator plate formed from PEEK operating at a modulation
frequency=110 kHz. Phase series display periodic oscillations of
the PEEK generator plate at resonance (1-6). With reference to FIG.
4A (Phase) and FIG. 4B (Topograph), Digital Holographic Microscopy,
phase and amplitude images display the topography at resonance (110
kHz) and resultant symmetric oscillation of the PEEK membrane are
illustrated. Computer simulation confirms experimental observation
of the normal modes of oscillation 0,1 and 0,2 in bonded PEEK
membrane. This mode is associated with a maximum amplitude and a
measured displacement of .about.2 .mu.m at the center, active
region of the generator plate.
Example B
Spray Performance
[0095] Ejector assembly performance may be evaluated over a range
of fluid viscosities from low viscosity, e.g., using distilled
water (viscosity 1.017 cP), to high viscosity, e.g., using
medications such as an ophthalmic emulsion of cyclosporine such as
Restasis.TM. (dynamic viscosity=18.08 cP). By way of example,
ejector assembly performance may be evaluated by analyzing fluid
mass ejection as a function of actuation frequency.
[0096] The mass ejection profile closely tracks the membrane
oscillation amplitude with a maximum mass ejection at .about.110
kHz and maximum oscillation amplitude of .about.2 microns at 110
kHz. Ejection of low viscosity fluids (water) was observed with
capillary lengths of both 70 and 120 microns. With reference to
FIG. 6, mass ejection vs. frequency for water using a 300 .mu.m
thick PEEK generator plate with 70 .mu.m capillary channel length
is illustrated, with an onset of maximum amplitude at 108 kHz and a
maximum amplitude of 2.3 .mu.m at 110 kHz, which coincides with a
maximum water ejection mass (average over 5 ejections).
Example C
Effect of Capillary Length
[0097] In certain implementations of ejector mechanisms of the
disclosure, capillary length of the openings of the generator plate
may affect spray performance. As illustrated in FIGS. 7A-7B, mass
ejection vs. frequency reveals a shift in frequency, to lower
frequencies, for water ejected from PEEK membranes having 120
micron long capillary channels. However, for high viscosity fluids
such as Restasis.TM. (dynamic viscosity=18.08 cP), a significant
increase in the mass ejection peak (2.5.times.) for PEEK membranes
with 120 micron long capillary channels vs. membranes with 70
micron long capillary channels is observed.
[0098] More particularly, FIG. 7A illustrates ejection of Newtonian
fluids (water), while FIG. 7B illustrates ejection of Non-Newtonian
fluids (Restasis). FIG. 7A shows that an increase in capillary
length leads to an increase in resistance and load on the fluid as
it exits the opening. This mass loading effect leads to a shift in
the peak ejection frequencies. FIG. 7B shows that mass ejection
through a capillary is affected by capillary length.
[0099] As shown, the increase in capillary length from 70 microns
to 120 microns and associated change in entrance cavity contour
leads to about a 2.5 fold increase in ejected mass. The increase in
fluid acceleration along the capillary (e.g., as shown in FIG. 15),
coupled with the 7.5 fold reduction in diameter from the entrance
cavity to the exit orifice, leads to an increased pressure gradient
and subsequent increase in shear force. The result is a decrease in
viscosity of the fluid and an increase in ejected volume.
Example D
Effect of Eigenmode
[0100] In certain implementations of ejector mechanisms of the
disclosure, the eigenmode of the generator plate may affect the
shape of the generator plate, and the resulting spray, during
excitation. FIG. 13 shows a high speed image frame representative
of an ejected spray from a ejector mechanism of the disclosure
overlaid with digital holographic image captured from a similar
ejector mechanism, which displays the normal mode of generator
plate oscillation at 140 kHz.
Example E
Simulation of Pressure Driven Flows
[0101] Forces acting on fluids include, pressure gradient, friction
forces and volume forces. The magnitude and time during which such
forces act on a fluid may be controlled by, e.g., changing the
fluid entrance diameter, fluid exit diameter, capillary length, and
material properties (mechanical, chemical and surface topography).
By way of example, flow simulation through an opening of a
generator plate may be modeled based on, e.g., the opening designs
of FIGS. 14A-14B (100 um thick PEEK; 40 micron diameter exit
orifice and 240 micron diameter entrance orifice), using PEEK
material properties and fluid viscosities of 1 Pa-s, and 18 Pa-s
(to simulate viscosities of water and Restasis, respectively).
[0102] FIG. 15 shows a simulation of a pressure driven flow through
in a capillary. The flow simulation was solved assuming an
oscillating pressure from 0 to 2000 Pa and an oscillating frequency
of 120 kHz. The simulation includes both low viscosity (1 mPa-s),
Newtonian (FIG. 15A) and high viscosity (18 mPa-s), non-Newtonian
fluids (FIG. 15B).
[0103] In the simulation of low viscosity (1 mPa-s), Newtonian
(water) (FIG. 15A) and high viscosity (18 mPa-s), non-Newtonian
fluids (Restasis) (FIG. 15BB), the maximum velocity is located at
the nozzle ejector exit region where the orifice is at its minimum
cross section. The fluid velocity, while inside the exit orifice
before emerging as a spray is from 60 to 65 meters/sec (m/s). The
computed velocity for water as it emerges from the nozzle orifice
has a velocity from 5 to 10 m/s, while the exit velocity for
Restasis is from 5 to 20 m/s.
[0104] These simulated ejected velocities compare favorably with
measured velocities for water and Restasis ejected from a NiCo
ejector. With reference to FIGS. 16A-16B, high speed videography
(not shown) was used to capture and measure single droplet speed as
it emerged from the opening. (20 mm, OD NiCo membrane with 40
micron exit holes and 160 micron thick, and actuated with a 16 mm,
OD and 8 mm, ID piezoelectric element (PZT) at an excitation
voltage of 90Vpp and at a frequency of 132 kHz). These data show
the ejected speed for water as from 1 to 7 m/s (FIG. 16B), while
Restasis emerged from the nozzle at speeds from 5 to 20 m/s (FIG.
16A).
Example F
Shear Rate Dependence Viscosity
[0105] The purpose of the testing was to determine if the viscosity
of the Restasis.RTM. was shear independent (Newtonian) or shear
dependent (non-Newtonian). For Newtonian fluids, the pressure drop
increases linearly with flow rate and the measured viscosity does
not depend upon applied deformation rate or stress. Non-Newtonian
fluids or complex fluids, however, can display shear thinning or
shear thickening, and the pressure drop versus flow rate data must
be analyzed using Weissenberg-Rabinowitch-Mooney equation.
[0106] The shear rate dependence of Restasis was measured by
rheometery. This method is commonly used to measure the way a
liquid, suspension or slurry flows in response to applied forces.
An MCR 302 rheometer by Anton Paar was used to characterize the
flow properties of three 0.4 ml vials of Restasis.RTM. lot 74381.
The rheometer configuration utilized was as follows: MCR 302
rheometer; P-PTD200/80 Peltier controlled lower plate chamber; and
CP50-0.5 measuring cone (50 mm diameter; 0.5.degree. cone angle,
0.504 cone truncation (measuring gap), 0.29 ml fill volume. The
testing was conducted 23.+-.0.1.degree. C. Within the time scale of
one single flow curve, the samples were not volatile and did not
appear to sediment therefore no precautions were necessary with
respect to evaporation control or mixing.
[0107] For sample loading, the vial cap was removed in the full 0.4
ml dose was squeezed onto the rheometer's lower plate. A sharp
point was used to pop any entrapped air bubbles visible in the
sample. Entrapped air in a sample will impact accuracy and
reproducibility in viscosity measurements. While the fill volume
for the measuring cone used was 0.29 ml, the full 0.4 ml dose was
used. Attempting to trim the excess sample would possibly introduce
error and disturb structure within the sample around the edge of
the cone.
[0108] A thirty second hold after sample loading and attainment of
the measuring gap was used to a) ensure the sample temperature was
at equilibrium at 23.degree. C. and b) ensure that any structural
damage occurring during loading was allowed to recover. A flow
curve is a steady shear (rotational) test is conducted by ramping
the shear rate and measuring shear stress required to obtain the
applied shear rates in the given sample. From this, viscosity is
determined as the ratio of shear stress to shear rate.
[0109] Flow curve results may be plotted as Viscosity versus Shear
Rate which is called a viscosity curve. They may also be plotted as
Shear Stress versus Shear Rate which is called simply a flow curve.
Generated flow curves present viscosity in mPas. Shear rate is
expressed in 1/s (s.sup.-1 or reciprocal second) and shear stress
is expressed in Pa (pascal). Instrument calibration was verified
prior to testing using traceable viscosity standard Cannon S200
(results not shown)
[0110] FIG. 17 shows a replicate analysis of three samples
demonstrate the shear thinning behavior of Restasis, i.e. as shear
rate is increased the sample viscosity decreases. The drop in
measured viscosity for each sample is dramatic. Slight variation in
the measured viscosity is most likely a result of the presence of
entrapped air bubbles in the Restasis emulsion which could not be
removed and/or the inability to dose out precisely the same volume
for each sample loading. FIG. 18 displays the same flow curve data
as in FIG. 17, but plotted as shear stress versus shear rate. The
samples did exhibit a weak yield point at shear rates of
.about.0.15 l/s and corresponding stress of 0.05 Pa, which is
expected in an emulsion. A yield stress means that a certain amount
of applied stress must occur in order to overcome the internal
structure in the samples so that flow may begin.
[0111] The flow curves indicate that this material exhibits
complex, shear thinning behavior. Describing this sample by a
single viscosity value requires identification of the shear rate at
that point. In the case of non-Newtonian materials, viscosity is
not a material function thus the conditions under which the
viscosity was measured must be stated. It was found that Restasis
has a viscosity, at 23.degree. C., of 111 mPas at 1 l/s while
having a viscosity if 8 mPas at 1,000 l/s.
Example G
Effect of Capillary Channel Geometry and Placement
[0112] In certain implementations of ejector mechanisms of the
disclosure, capillary channel geometry and placement may affect
spray performance. FIGS. 19A-19C show that fluid resistance
displays a linear relationship as a function of capillary
length.
[0113] The hydraulic resistance for straight channels with
different cross sectional shapes is shown below. The numerical
values are calculated using the following parameters:=1 mPa s
(water), L=1 mm, a=100 um, b=33 um, h=100 um, and w=300 um.
TABLE-US-00004 R.sub.hyd shape R.sub.hyd expression [ 10 11 Pa s m
3 ] ##EQU00004## reference circle ##STR00001## 8 .pi. .eta.L 1 a 4
##EQU00005## 0.25 Eq. (2.30b) ellipse ##STR00002## 4 .pi. .eta.L 1
+ ( b / a ) 2 ( b / a ) 3 1 a 4 ##EQU00006## 3.93 Eq. (2.29)
triangle ##STR00003## 320 3 .eta.L 1 a 4 ##EQU00007## 18.48 Eq.
(2.37) two plates ##STR00004## 12 .eta.L 1 h 3 w ##EQU00008## 0.40
Eq. (2.53) rectangle ##STR00005## 12 .eta.L 1 - 0.63 ( h / w ) 1 h
3 w ##EQU00009## 0.51 Eq. (2.49) square ##STR00006## 12 .eta.L 1 -
0.917 .times. 0.63 1 h 4 ##EQU00010## 2.84 Exercise 3.4
[0114] With reference to FIGS. 20A-20B, (6 mm, OD, 100 u thick PEEK
membrane 20 mm, mounted on a 20 mm, OD. and 4 mm, ID, 50 u thick
stainless steel (304 or 316L) annulus and actuated by a 14 mm, OD
and 13 mm, ID piezoelectric element (PZT)), placement of openings
in the generator plate has a effect on spray performance. As shown
in FIG. 20A, circular symmetric placement of openings leads to
about a 2-3 fold increase in spray volume (mass deposition), as
compared to a square opening array (FIG. 20B).
[0115] FIG. 21A-21B shows spray performance is also increased by
increasing the number of openings in a generator plate. The effect
of increased number of ejector holes per unit area of the active
area is demonstrated in FIG. 21A, with a 3 fold increase in ejected
mass at .about.130 kHz when the number of holes are increased from
69 to 177 holes. FIG. 21B illustrates normalization of ejected
volume (mass) per unit number of holes, showing the number of holes
as the multiplicative factor.
Example H
Effect of Polymer Modulus
[0116] In certain implementations of ejector mechanisms of the
disclosure, polymer modulus may affect spray performance. FIG.
22A-22B shows that an increase in tensile modulus from 363 kpsi to
696 kpsi for virgin PEEK and 20% talc-filled PEEK leads to .about.2
fold increase in performance in the 100 kHz to 150 kHz excitation
frequency range. This increase in spray performance tracks with the
corresponding increase in tensile modulus.
[0117] Although the foregoing describes various embodiments by way
of illustration and example, the skilled artisan will appreciate
that various changes and modifications may be practiced within the
spirit and scope of the present application.
* * * * *