US20130150812A1

US20130150812A1 - High modulus polymeric ejector mechanism, ejector device, and methods of use

Info

Publication number: US20130150812A1
Application number: US13/712,857
Authority: US
Inventors: Charles Eric Hunter; Louis Thomas Germinario; Jonathan Ryan Wilkerson; Iyam Lynch; J. Sid Clements; Joshua Richard BROWN
Original assignee: Corinthian Ophthalmic Inc
Current assignee: Eyenovia Inc
Priority date: 2011-12-12
Filing date: 2012-12-12
Publication date: 2013-06-13
Also published as: US20180116871A1; WO2013090468A1; EP2790620A1; US20130172830A1; CN104582647A; CN104487028A; US10646373B2; JP2015500132A; JP5960840B2; HK1208145A1; JP6105621B2; EP2790619A1; JP2015506731A; US20180085251A1; US10639194B2; WO2013090459A1

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.

Description

RELATED APPLICATIONS

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

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.
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.
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.
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.
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.
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

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.
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.
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.
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.
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.
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.
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

FIG. 1A shows a cross-sectional view of an implementation of an ejector assembly.

FIG. 1B shows a front view of an implementation of an ejector mechanism.

FIG. 1C shows an exploded view of an implementation of an ejector mechanism.

FIG. 1C-2 shows a schematic top view of an implementation of an active region of a high modulus polymeric generator plate.

FIGS. 1D-K show partial cross-sectional views showing examples of high modulus polymeric generator plate configurations.

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.

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.

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.

FIG. 5 illustrates a frequency scan of an ejection assembly vs. oscillation amplitude, according to an implementation of the disclosure.

FIG. 6 illustrates mass ejection vs. frequency for water using an ejector assembly according to an implementation of the disclosure.

FIGS. 7A-7B illustrate mass ejection vs. frequency for water and Restasis™ using an ejector assembly according to an implementation of the disclosure.

FIG. 8 illustrates exemplary generator plate structures according to an implementation of the disclosure.

FIG. 9 illustrates cross sectional views of a micromachined, laser ablated generator plate structures according to implementations of the disclosure.

FIG. 10 illustrates spatial distribution of select opening geometries (shown in FIG. 9), according to implementations of the disclosure.

FIG. 11 illustrates a view of the opening forming process using UV LIGA, according to implementations of the disclosure.

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.

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.

FIGS. 14A-B illustrate exemplary generator plate structures according to an implementation of the disclosure.

FIG. 15A-B illustrate a simulation of a pressure driven flow through in a capillary, according to implementations of the disclosure.

FIGS. 16A-16B illustrate ejected droplet velocity over time, according to implementations of the disclosure.

FIG. 17 illustrates a replicate analysis demonstrating the shear thinning behavior of Restasis.

FIG. 18 illustrates the same flow curve data as in FIG. 17, but plotted as shear stress versus shear rate.

FIGS. 19A-19C illustrate fluid resistance as a function of capillary length, according to implementations of the disclosure.

FIGS. 20A-20B illustrate spray performance as a function of opening placement on a generator plate, according to implementations of the disclosure.

FIGS. 21A-21B illustrate spray performance as a function of the number of openings on a generator plate, according to implementations of the disclosure.

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

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.
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.
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.
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:
drugs/fluids dynamic viscosity (cP) kinematic viscosity (cP) density

water 1.017 1.019 0.99821

Xalatan^TM 1.051 1.043 1.00804

Tropicamide 1.058 1.052 1.00551

Restasis^TM 18.08 17.98 1.00535

Viscosity measured at 20° C.
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.
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.
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 1648 a. 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.
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 1648 a. 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.
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.
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.
In the implementation of FIG. 1A, the ejector mechanism 1601 is activated by being vibrated by piezoelectric actuator 1604. Two electrodes 1606 a and 1606 b 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 1606 a and 1606 b 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 1606 a and 1606 b. 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 1606 a and the ejector plate 1602. Electrode 1606 a is in electrical contact with ejector plate 1602. When a voltage is applied across the electrodes 1606 a and 1606 b, 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.
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 1606 a and 1606 b, 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.
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.
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.
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.
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.)
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.
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.
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.
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 1606 a and 1606 b 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 1606 a and 1606 b 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.
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.
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.
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 μm to about 100 μm, about 20 μm to about 80 μm, about 20 μm to about 50 μm, about 30 μm to about 40 μm, etc. Opening height/thickness (i.e., high modulus polymeric generator plate thickness) may range from about 50 μm to about 500 μm, about 100 μm to about 200 μm, about 150 μm to about 200 μm, about 160 μm, etc. Selection of the aspect ratio of the openings may allow for formation of droplets of fluids having relatively high viscosities.
In certain implementations, the openings may have a generally cylindrical shape, that is, the diameter of the opening extending from surface 1622 a of high modulus polymeric generator plate 1632 to surface 1625 a 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 1622 a to 1625 a, 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 1626 a, an entrance cavity 1626 b, a capillary channel 1626 c, and a fluid exit orifice 1626 d, wherein the opening comprises an overall pitch length 1626 e.
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.
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.
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.


Flow rate	Fluid Resistance	Young-LaPlace equation

Q = Δ P/R	$R = \frac{8 µL}{π r 1^{4}}$	$ΔP = γ (\frac{1}{r 1} + \frac{1}{r 2})$

	μ = Fluid viscosity	γ = Fluid surface tension
	L = Capillary length	r1 = Capillary radius
	r1 = Capillary radius	r2 = Flute radius

The velocity of the fluid is thus:
$V (r) = \frac{π Δ p A_{in} ρ_{in}}{8 μ l A_{out} ρ_{out}} (R^{2} - r^{2})$
where R is the diameter of the channel and r is the volume of fluid within the channel.
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 μm to about 150 μm, about 70 μm to about 150 μm, about 70 μm to about 120 μm, etc. In certain implementations, the capillary channel may be between 120 μm and 150 μm, particularly for high viscosity fluids.
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 μm to about 500 μm. It is desirable that the coating adhere to the ejector plate 1602 sufficiently to prevent delamination when vibrating at a high frequency.
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.
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.
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™), polyether ether ketone (PEEK), talc-filled PEEK, polyvinylidine fluoride (PVDF, Kynar™), polyetherimide (Ultem™), and be coated as discussed herein.
By way of example, suitable materials include:


	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 ™, 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 ™	475,000	480,000	Heat Seal	Treatable	420/216	76	Resin FDA
(polyetherimide)							Compliant

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.
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 (4ω) 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.
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.
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 CO₂, 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 μm, capillary channel length of about 70 μm to about 120 μm, exit orifice of about 40 μm to 50 μm, e.g., 46 μm, and overall pitch of about 400 μm pitch.
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.
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.
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, 1622 a, 1625 a, 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.
Additionally, surface 1622 or 1622 a 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.
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 μm to about 500 μm. It is desirable that the coating adhere to the plate sufficiently to prevent delamination when vibrating at a high frequency.
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 1606 a and 1606 b 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.
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 μm to about 500 μm, as described above.
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 μm to about 400 μm, from about 20 μm to about 100 μm, from about 20 μm to about 50 μm, about 30 μm to about 50 μm, 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.
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.
The magnitude and frequency of the ejector plate vibration can also be controlled by controlling the voltage pulses applied to the electrodes 1606 a, 1606 b, 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 1606 a or 1606 b is grounded and voltage pulses, e.g., bipolar pulses, are applied to the other one of the electrodes 1606 a or 1606 b 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.
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.
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.
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.
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

Although many arrangements are possible, one implementation uses a piezoelectric-driven ejector mechanism which includes a 6 mm outer diameter, 300 μm thick PEEK generator plate that is bonded to a 20 mm outer diameter, 50 μm 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 ˜108 kHz, and a maximum amplitude of ˜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.
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 ˜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 ˜2 μm at the center, active region of the generator plate.

Example B

Spray Performance

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™ (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.
The mass ejection profile closely tracks the membrane oscillation amplitude with a maximum mass ejection at ˜110 kHz and maximum oscillation amplitude of ˜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 μm thick PEEK generator plate with 70 μm capillary channel length is illustrated, with an onset of maximum amplitude at 108 kHz and a maximum amplitude of 2.3 μm at 110 kHz, which coincides with a maximum water ejection mass (average over 5 ejections).

Example C

Effect of Capillary Length

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™ (dynamic viscosity=18.08 cP), a significant increase in the mass ejection peak (2.5×) for PEEK membranes with 120 micron long capillary channels vs. membranes with 70 micron long capillary channels is observed.
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.
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

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

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).
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).
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.
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

The purpose of the testing was to determine if the viscosity of the Restasis® 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.
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® 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° cone angle, 0.504 cone truncation (measuring gap), 0.29 ml fill volume. The testing was conducted 23±0.1° 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.
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.
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° 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.
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 mPa·s. Shear rate is expressed in 1/s (s⁻¹or 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)
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 ˜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.
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° C., of 111 mPa·s at 1 l/s while having a viscosity if 8 mPa·s at 1,000 l/s.

Example G

Effect of Capillary Channel Geometry and Placement

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.
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.


		R_hyd
shape	R_hyd expression	$[10^{11} \frac{Pa s}{m^{3}}]$	reference

circle	$\frac{8}{π} ηL \frac{1}{a^{4}}$	0.25	Eq. (2.30b)

ellipse	$\frac{4}{π} ηL \frac{1 + {(b / a)}^{2}}{{(b / a)}^{3}} \frac{1}{a^{4}}$	3.93	Eq. (2.29)

triangle	$\frac{320}{\sqrt{3}} ηL \frac{1}{a^{4}}$	18.48	Eq. (2.37)

two plates	$12 ηL \frac{1}{h^{3} w}$	0.40	Eq. (2.53)

rectangle	$\frac{12 ηL}{1 - 0.63 (h / w)} \frac{1}{h^{3} w}$	0.51	Eq. (2.49)

square	$\frac{12 ηL}{1 - 0.917 \times 0.63} \frac{1}{h^{4}}$	2.84	Exercise 3.4

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).
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 ˜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

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 ˜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.
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.

Claims

What is claimed is:

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;

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.