HK1210006B - Laminar flow droplet generator device and methods of use - Google Patents

Description

Laminar flow droplet generator device and method of use

RELATED APPLICATIONS

The contents of U.S. application No.61/646721 (application date 5/14/2012 entitled "objector Device and Methods of Use") and U.S. application No.61/722600 (application date 11/5/2012 entitled "luminal Flow driver Generator Device and Methods of Use") are hereby incorporated herein by reference in their entirety.

Background

The use of a spray device to administer a product in the form of a mist or spray is a well-established field of use for safe and easy to use products. One important area where a spray device is required is the delivery of ophthalmic products. However, a major challenge in providing such devices is providing consistent and accurate delivery of the appropriate dose. In addition, multi-dose spray devices may become contaminated by interaction with the non-sterile external environment.

Thus, there is a need for a delivery device that delivers a safe, suitable and repeatable dose to a patient for ocular, topical, oral, nasal or pulmonary use.

Disclosure of Invention

The present invention relates in part to an ejector mechanism, ejector device and method for delivering a safe, proper and repeatable dose to a patient for ocular, topical, oral, nasal or pulmonary use. The present invention relates to an ejector device and a fluid supply system capable of supplying a defined volume of fluid in the form of a directed stream of droplets, which are characterised by providing a sufficient and repeatable high percentage of droplet deposition upon application.

According to the present invention, there is provided a piezoelectric injector device designed to minimise air ingress into the device upon actuation, as described in more detail below. The ejector mechanism may comprise a generator plate and a piezoelectric actuator operable to directly or indirectly oscillate the generator plate at a frequency so as to generate a directed stream of fluid droplets. The generator plate includes a fluid-facing surface, a droplet ejection surface, and a plurality of openings formed through a thickness of the generator plate between the surfaces. According to the invention, the generator plate and its plurality of openings are arranged to minimize the flow of air from the droplet ejection surface to the fluid facing surface through the plurality of openings during oscillation by promoting laminar flow of the liquid as it passes from the fluid facing surface to the droplet ejection surface.

Drawings

FIG. 1 illustrates example turbulent and laminar flows in accordance with aspects of the present invention;

FIG. 2 illustrates an example generator plate opening geometry, resulting in turbulent flow (left) and laminar flow (right), in accordance with aspects of the present invention;

FIG. 3 illustrates an example generator plate opening geometry, resulting in turbulent flow (left) and laminar flow (right), in accordance with aspects of the present invention;

FIG. 4 illustrates an example curvature of a laminar flow generator plate opening in accordance with aspects of the present invention;

FIG. 5 illustrates an example curvature of a laminar flow generator plate opening in accordance with aspects of the present invention;

FIG. 6 illustrates inlet length parameters for a tube/opening according to an embodiment of the present invention;

FIG. 7 illustrates a graph of initial turbulent inlet length as a function of Reynolds number, in accordance with aspects of the invention;

FIG. 8 illustrates one embodiment of a non-laminar flow NiCo injector in operation according to the present invention;

FIG. 9 illustrates another embodiment of a laminar flow NiCo injector in operation according to the present invention;

FIG. 10 illustrates one embodiment of a non-laminar PEEK injector in operation according to the present invention;

FIG. 11 illustrates another embodiment of a laminar flow PEEK injector in operation according to the present invention;

FIGS. 12-14 show three-dimensional views of the ejector surface of different embodiments of drop generator plates;

FIG. 15 shows a side view of a droplet generator plate orifice according to the present invention;

FIG. 16 illustrates a cross-sectional view of an injector device in accordance with aspects of the present invention;

FIGS. 17A and B show cross-sectional views of a drive injector plate for the injector device of FIG. 16;

FIG. 18 is a plan view of one embodiment of the injector mechanism of the present invention;

FIG. 19 is an exploded view of the symmetric injector mechanism of the present invention; and

FIG. 20 is a plan view of a symmetrical ejector mechanism of the invention.

Detailed Description

The present invention relates generally to piezoelectric injector devices, such as for fluid delivery, such as for delivering ophthalmic fluids to the eye. The ejector device may comprise an ejector assembly comprising an ejector mechanism and a fluid supply. In certain aspects, the ejector mechanism may comprise a piezoelectric actuator and a droplet generator plate operable to generate a directed stream of fluid droplets when the actuator is driven to directly or indirectly oscillate the generator plate. Fluids include, but are not limited to, suspensions or emulsions having viscosities in the range that can be formed into droplets using an ejector mechanism.

Piezoelectric drop generation and flow in microchannels depends on complex interactions between liquids flowing through micropores, fluid surface interactions, outlet orifice diameter, inlet cavity geometry, capillary length, mechanical properties of the ejector material, amplitude and phase of mechanical displacement, and displacement frequency of the ejector plate. Furthermore, fluid properties (such as viscosity, density and surface energy) play an important role in droplet formation. In accordance with certain aspects of the present invention, novel injector orifice structures and geometries have been developed that optimize droplet generation dynamics and microfluidic flow. For example, certain embodiments relate to computer controlled laser micromachining that provides precise control of the three-dimensional morphology of the injector surface and nozzle geometry. This provides independent control of fluid velocity amplification, resistance, turbulence, and valving of high viscosity fluids.

According to the present invention, there is provided a piezoelectric injector device designed to minimise the ingestion of air into the device when actuated, as will be described further below. As described above, the ejector mechanism comprises a generator plate and a piezoelectric actuator operable to directly or indirectly oscillate the generator plate at a frequency so as to generate a directed stream of fluid droplets. The generator plate includes a fluid-facing surface, a droplet ejection surface, and a plurality of openings formed through a thickness of the generator plate between the surfaces. As described in the various embodiments of the present disclosure, the generator plate and its plurality of openings are configured to minimize the flow of air from the droplet ejection surface to the fluid-facing surface through the plurality of openings during generation of the directed stream of droplets. As described herein, minimizing the air flow will locally result in a laminar flow of directed droplet streams. By way of background (but not by way of limitation, theory) the entry of air into the ejector device during operation may result in unexpected performance within the device, which may not only alter the operation of the device, but may also in many cases lead to failure. Furthermore (and not by way of limitation), the oscillating pump-like action of the ejection region of the ejector mechanism of the present invention creates a pressure gradient in the direction of droplet ejection and in the opposite direction of ejection. When the pressure gradient is aligned opposite to the direction of injection, air in the surrounding area may also enter the low-pressure area behind the active area through the injector opening.

However, air may be prevented from entering the system by the presence of fluid behind the injector opening, thereby preventing air from entering the system. In some cases, air may enter the system through a passage formed by a gap created during processing, which interferes with proper symmetric filling conditions. These treatments create regions of chaotic turbulence between the liquid and the air, which can create overpressure that envelopes the air that has entered the opening to create the bubbles.

One way air can enter the system by overcoming the resistance of the generator plate openings is by fluid turbulence on the fluid side of the ejector mechanism, which is created by sudden transitions in the fluid flow, for example when the fluid enters the fluid reservoir side of the generator plate. Fast moving fluids experience sudden flow changes due to large and sudden slope changes at the transition point. Referring to FIG. 1, a fluid "exceeds" a transition point region and shears the underlying fluid, causing a vortex or "jet pinch," which is a non-zero vorticity region. As shown in fig. 1, this results in a vorticity ω (which is a function of fluid velocity) having a value greater than 0. In contrast, when gradually transitioning, as shown in fig. 1, no shearing occurs and swirl is avoided (vorticity ω 0).

Referring to fig. 2, the generator plate on the left represents an abrupt transition, resulting in turbulent flow and chaotic spray, which enables outside air to enter the system through the generator plate openings during operation. The illustrated generator plate opening includes a shape with a large transition from the fluid reservoir side to the droplet ejection side, which promotes the formation of vortices, causing flow disruption and the formation of gaps within the opening. In contrast, the generator plate opening on the right has a gradual slope change from the fluid reservoir side to the droplet ejection side, resulting in laminar flow and efficient spraying.

The present invention relates generally to an ejector device, e.g. for fluid supply, for ocular, topical, oral, nasal or pulmonary use, more particularly for supplying ophthalmic fluids to the eye. In one embodiment, the ejector device comprises an ejector assembly comprising an ejector mechanism that generates a controllable stream of fluid droplets. The ejector mechanism may be a charge isolation mechanism. Fluids include, but are not limited to, suspensions or emulsions having viscosities in the range that can be formed into droplets using an ejector mechanism. The fluid may include drugs and pharmaceutical products.

As described in more detail herein, the ejector mechanism may form a directed stream of droplets, which may be directed at a target. The droplets may be formed in a size distribution, each distribution having an average droplet size. The average droplet size can 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, and the like. However, the average droplet size may be 2500 microns, depending on the intended use. Moreover, the droplets may have an average initial velocity of about 0.5m/s to about 100m/s, such as about 0.5m/s to about 20, such as 0.5 to 10m/s, about 1m/s to about 5m/s, about 1m/s to about 4m/s, about 2m/s, and the like. As used herein, spray size and initial velocity are the size and initial velocity of a droplet as it exits the ejector plate. A stream of droplets directed at the target will result in a certain mass percentage of the droplets (including their components) being deposited on the target.

As described herein, the ejector device and ejector mechanism of the present invention may be arranged to eject fluid of generally low to relatively high viscosity as a stream of droplets. For example, fluids suitable for use by the ejector device can have a very low viscosity, e.g., 1cP or less like water, e.g., 0.3 cP. Additionally, the fluid may have a viscosity in the range of up to 600 cP. More particularly, the fluid can have a viscosity range of approximately 0.3 to 100cP, 0.3 to 50cP, 0.3 to 30cP, 1cP to 53cP, and the like. In some embodiments, 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 of 1cP or more, ranging from about 1cP to about 600cP, about 1cP to about 200cP, about 1cP to about 100cP, about 10cP to about 100cP, and the like. In some embodiments, a solution or drug with suitable viscosity and surface tension can be used directly in the reservoir without changing. In other embodiments, additional materials may be added to adjust fluid parameters.

The droplets may be formed by the ejector mechanism from a fluid contained in a reservoir connected to the charge isolating ejector mechanism. The charge isolating sprayer mechanism and reservoir may be disposable or reusable, and the components may be packaged in the housing of the sprayer device, for example as described in U.S. provisional patent application nos. 61/569739, 61/636559, 61/636565, 61/636568, 61/642838, 61/642867, 61/643150, and 61/584060 and in U.S. patent application nos. 13/184446, 13/184468, and 13/184484, the contents of which are incorporated herein by reference. More particularly, exemplary injector devices and injector mechanisms are illustrated in U.S. application No.61/569739 (application Ser. No. 12/2011 entitled "injector Device, and Methods of Use"), U.S. application No.61/636565 (application Ser. No. 4/20/2012 entitled "Central-symmetry Lead free Ejector Mechanism, Ejector Device, and Methods of Use") and U.S. application No.61/591786 (application Ser. No. 1/27/2012 entitled "High Module Polymeric injector Device, Ejector Device, and Methods of Use"), the entire contents of each of which are incorporated herein by reference.

According to a particular embodiment of the invention, the openings of the generator plate of the invention are provided with such a shape that the gentle slope from the fluid facing surface to the droplet ejection surface varies. By way of background (but not by way of limitation, by theory), for fluids traveling in one direction, the optimal function is linear (e.g., pipe), and turbulence in the system is related to the Reynolds number, which is a function of velocity, pipe diameter, fluid density, and fluid viscosity. The reynolds number is the ratio between the inertial and viscous forces and is therefore a dimensionless number. When the reynolds number is less than 2300, the flow is considered substantially laminar and for values greater than 4000 turbulent. In the region between 2300 and 4000, the flow is considered to be "transitional", meaning that both laminar and turbulent flow is possible.

Wherein Re is a Reynolds number,

p is the density of the fluid and,

v is the velocity of the fluid

L is the tube diameter, and

η is the viscosity of the liquid.

In order to minimize the turbulent flow region formed due to the rapid transition (step) of the opening shape, the curvature may be a function with a smaller second derivative. According to one aspect of the invention, the second order curve providing the minimum for the second derivative is a circular shape, the function of which is expressed as follows. In this aspect, such curvature includes a shape having an outer inlet radius of curvature with a rounded shape from the fluid-facing surface to the droplet ejection surface.

Where R is the outer radius of the curve.

Referring to fig. 3, on the left side, an opening with an outer inlet curvature is shown, the opening being non-circular in shape. Such openings have a large abrupt change in the slope of the inlet curve, thus promoting turbulent flow and chaotic spray, which increases the ability of outside air to enter the system. On the contrary, on the right side is shown an opening according to an embodiment of the invention, wherein the outer inlet radius of curvature comprises a circular shape, which results in a laminar flow and minimizes the ability of outside air to enter the system.

Thus, laminar flow openings according to the present invention may be provided with a gradually changing curvature of the circle, which promotes laminar flow by minimizing vorticity and eliminating the presence of vortices. Referring to fig. 4 and 5, dimensions for constructing laminar flow generator plate openings are provided in accordance with aspects of the present invention. In fig. 4, the variables P, R and D represent the spacing between openings (pitch), the radius of curvature of the circular inlet shape, and the outlet diameter of the openings, respectively. In fig. 5, the additional variables De and σ are the inlet diameter and the ratio of the radius of curvature to the outlet diameter, respectively.

According to one aspect of the invention, the ratio σ (the ratio of the size of the radius of curvature to the size of the opening at the droplet ejection surface) determines suitable conditions for constructing a laminar flow ejector. In one embodiment, σ is selected to be equal to or greater than about 2.5 when the opening is greater than about 40 μm at the droplet ejection surface. In another embodiment, the ratio σ of the size of the radius of curvature to the size of the opening at the droplet ejection surface is selected to be greater than about 5 when the opening is less than about 40 μm at the droplet ejection surface. It should be noted that the height or thickness of the mesh (as determined by the generator plate) is not necessarily limited to the dimensions shown in fig. 5, and can be greater or less than the dimensions shown.

According to another aspect, the generator plate opening is provided with an inlet length or generator plate thickness that facilitates creating a laminar flow region. By way of background (but not by way of limitation, by theory), the fluid entering the tube (i.e., in the present invention, the fluid entering the generator plate openings) is subjected to a period of time (length) where laminar flow is not possible due to initial boundary conditions between the fluid and the tube/opening surfaces. This is shown in fig. 6. At the boundary, the inlet wall friction and viscous forces are primarily for the fluid closest to the surface. Under "no-slip" boundary conditions, the fluid immediately at the wall has zero tangential velocity, and the boundary layer exerts viscous drag on the adjacent fluid layer, which decreases with distance from the boundary layer. This causes the formation of layer-dependent velocity zones in the fluid, resulting in a non-uniform establishment of a final viscous boundary layer at equilibrium. The distance it takes for the boundary layer to build up as a constant layer is called the "inlet length". The "tack free" region is a region where the tack effect is negligible. Once the flow has passed the inlet length le, laminar flow can be achieved (laminar flow region is the region where Poiseuille flow is established). Poiseuille flow is a flow condition where the velocity profile is parabolic. The distance le is a function of the reynolds number Re and is given by the expression le ═ 0.06vd (Re), where v, d, and Re are the velocity of the fluid, the diameter of the nozzle, and the reynolds number, respectively. The laminar flow range as a function of reynolds number is for fluid that has passed through this initial inlet length le. In the following chart, the values for Reynolds number and inlet length will be calculated assuming a velocity of 2m/s, which 2m/s is selected according to the average droplet velocity calculated in one embodiment and the results for the embodiments are provided by Digital Holographic Microscopy (DHM), which measures the velocity for an effective membrane, in the range between 0.5-5 m/s. The injector diameter orifice size selected for the graph is 40 microns. Surface tension values are measured by a goniometer (contact angle analyzer), viscosity measurements will thus be made by a tuning fork "vibrating" viscometer, and density measurements are made by measuring a known amount of drug and weighing using a sensitive balance.

The results are shown in table 1 below.

As mentioned above, the reynolds number is the ratio between inertial and viscous forces, and when the reynolds number is less than 2300, the flow is considered substantially laminar and for values greater than 4000 turbulent. In the region between 2300 and 4000, the flow is considered to be "transitional", meaning that both laminar and turbulent flow is possible. However, as evidenced by the results in Table 1 and as shown later in FIG. 7, the Reynolds number also correlates to the inlet length le.

FIG. 7 shows the inlet length of the evolving flow as a function of Reynolds number, which is calculated for the velocity range of 1-10 m/s. Thus, it was found that for a 40 micron outlet diameter, an opening provided with an inlet length le (i.e. channel length) exceeding 150 microns would be better for creating laminar flow conditions, whereas for a 20 micron diameter hole, the inlet length le should exceed 100 microns. Thus, when a laminar flow ejector opening is constructed, the thickness (i.e., channel length) of the laminar flow ejector may be determined at least in part by the inlet diameter of the orifice. In certain aspects, a sufficient channel length to achieve laminar flow of the ejected fluid as it reaches the droplet ejection surface can be selected, as described herein.

Fig. 8-11 are experimental results showing the performance of the device for air intake during operation of an ejector having a droplet generator plate with regular non-laminar flow holes as opposed to a droplet generator plate with laminar flow holes. Droplet generator plates made of metal (NiCo, fig. 8 and 9) and polymer (PEEK, fig. 10 and 11) materials can be considered. In the embodiment of fig. 8, the actuator operates at 107kHz and the droplet generator plate is provided with non-laminar flow holes. In the embodiment of fig. 9, the actuator operates at 132kHz and the droplet generator plate is provided with laminar flow holes.

In the embodiment of fig. 10, the actuator operates at 110kHz using a droplet generator plate thickness of 100 μm. As in the embodiment of fig. 8, the holes in the droplet generator plate are regular, non-laminar flow holes. In the embodiment of fig. 11, the actuator operates at 111kHz using a droplet generator plate thickness of 100 μm. As in the embodiment of fig. 9, the droplet generator plate is provided with laminar flow holes. Thus, for each material, there are performance examples of non-laminar and laminar ejector designs constructed using the criteria described herein. The test was performed by having the device fitted with a translucent reservoir filled with water (water has a higher surface tension, as shown in table 1, which helps to form bubbles that provide the worst case for the test) and open to the atmosphere. The rear of the reservoir was imaged under peak spray conditions to track bubble formation within the system. The mounting conditions were the same as in all comparative examples. It has been found that for all tests, laminar design injectors (fig. 9 and 11) outperformed non-laminar injectors (fig. 8 and 10). Laminar flow ejector designs reduce the chance of outside air entering the system during operation by eliminating air gaps in the ejector openings (nozzles) by keeping them full of fluid during the spraying process.

The advantages of the masking system to prevent additional air ingestion include continuous operation of the device without failure due to excess air in the system, which causes unpredictable changes in pressure within the system. Excess air can also contaminate the fluid within the system, which is undesirable when administering pharmaceutical compositions, particularly those that are low preserved and non-preserved.

In a further aspect, to avoid liquid accumulation on the ejection surface of the droplet generator plate, the ejection surface may also be configured to define a channel surrounding at least a portion of one or more of the ejector orifices, as shown in fig. 12-14. The grooves may be such that substantially any fluid that may remain on the ejection surface collects in the grooves rather than blocking the ejection orifices. This can further reduce the accumulation of fluid on the ejection surface and interference with droplet ejection.

To further eliminate fluid beading and fluid accumulation on the ejection surface, certain aspects also involve the use of coatings on the surface of the ejector plate, such as gold coatings, silver coatings, antimicrobial coatings, and the like. In certain embodiments, a coating such as a gold coating may be deposited on the generator plate (e.g., a PEEK generator plate) in order to modify the surface (higher surface energy to increase hydrophilicity) so that the fluid flows more easily, to reduce the formation of beads or the like of fluid on the surface.

In still other aspects, the thickness of the droplet generator plate can also affect the laminar flow parameters, better laminar flow is achieved with thicker plates having longer capillary lengths, while also affecting plate oscillation, while thinner plates show better fluid ejection at higher frequencies. One embodiment was found to work well with a capillary length of 125 μm. A capillary tube or channel 1500 associated with the groove inlet section 1502 for laminar flow is shown in fig. 15.

The ejector assembly may include an ejector plate coupled to a drop generator plate and a piezoelectric actuator. For example, FIG. 16 illustrates an embodiment of an injector assembly 1600, the injector assembly 1600 including an injector mechanism 1601 and a reservoir 1620. The ejector mechanism 1601 may comprise an oscillating plate mechanism or system with ejector plates 1602 connected to a generator plate, or omitting the generator plate and simply defining a central drop generator region or ejector region 1632, the central drop generator region or ejector region 1632 comprising one or more openings 1626, the ejector plates being capable of being driven by a (e.g. piezoelectric) actuator 1604. For ease of reference, the drop generator region 1632 (whether it is integral with the ejector plate or connected to the ejector plate as a separate drop generator plate) will be interchangeable herein with the drop generator plate or drop generator region. The actuator 1604 causes the ejector plate 1602 to vibrate or otherwise move to supply fluid 1610 from the reservoir 1620 as individual droplets 1612 (desired droplets) from one or more openings 1626, or as a stream of droplets 1612 expelled from one or more openings 1626 in a direction 1614.

In some applications, ophthalmic fluids may be ejected toward the eye 1616, such as an eye of an adult or child or animal. The fluid may contain a medicament in order to treat discomfort, a condition or a disease of a human or animal (in the ocular or skin surface, or in nasal or pulmonary use).

The attachment of actuator 1604 to ejector plate 1602 can also affect the operation of jetting assembly 1600 and the generation of individual droplets or streams of droplets. In the embodiment of fig. 16, for example, the actuator 1604 (or a plurality of individual ejector components) may be connected to a peripheral region of the ejector plate 1602 on a surface 1622 opposite the reservoir 1620.

The central region 1630 of the ejector plate 1602 includes a drop generator region 1632, the drop generator region 1632 having one or more openings 1626 through which the fluid 1610 passes to form drops 1612. The ejection region (or drop generator) 1632 can occupy a portion of the central region 1630, such as the center, or the ejection orifice pattern of the drop generator region 1632 can occupy nearly the entire area of the central region 1630. Also, the open area 1638 of the reservoir housing 1608 may substantially correspond to the size of the ejection area 1632, or the open area 1638 may be larger than the ejection area 1632.

In this regard, the location of the openings can affect mass deposition, with a spray hole pattern generally near the center of the central region 1630 being preferred. Moreover, the structure and location of the piezoelectric actuator 1604 may affect operation, including the inner and outer diameters of the ejector plate 1602 and the thickness of the actuator 1604. In one embodiment, a 19mm outer diameter, 14mm inner diameter, 250 micron thickness actuator may be used for non-edge mounting applications.

As shown in fig. 16, the ejector plate 1602 is disposed over or in fluid communication with a reservoir 1620 containing fluid 1610. For example, the reservoir housing 1608 can be connected with the ejector plate 1602 at a peripheral region 1646 of the first major surface 1625 using a suitable seal or connection (e.g., an O-ring 1648 to seal against the reservoir wall 1650). Portion 1644 of reservoir housing 1608 can also be provided in the form of a collapsible bladder. However, the invention is not so limited and any suitable bladder or reservoir may be used.

Prior to energizing, injector assembly 1600 is set to a quiescent state. When a voltage is applied across electrodes 1606a and 1606B on opposing surfaces 1634 and 1636 of (e.g., piezoelectric) actuator 1604, ejector plate 1602 deflects to change between a relatively more concave shape 1700 and a relatively more convex shape 1701, as shown in fig. 17A and 17B, respectively.

When driven by an alternating voltage, actuator 1604 operates to reverse the convex and concave shapes 1700 and 1701 of ejector plate 1602, causing ejector plate 1602 to move (oscillate) periodically in an ejection region (drop generator) 1632. The droplets 1612 are formed at the holes or openings 1626, as described above, and the oscillating motion of the jetting region 1632 causes one or more droplets 1612 to be jetted in a fluid feed (jetting) direction 1614, such as in a single-droplet (desired-droplet) application, or as a stream of droplets.

The drive voltage and frequency may be selected to enhance the performance of the ejection mechanism, as described above. In certain embodiments, the oscillation frequency of actuator 1604 may be selected to be at or near the resonant frequency of the fluid-filled ejector mechanism, or at one or more frequencies selected such that ejector plate 1602 oscillates at resonance by superposition, interference, or resonant coupling.

When operating at or near resonance frequency (e.g., within the full width of half maximum resonance), ejector plate 1602 may amplify the displacement of ejector region (drop generator) 1632, thereby reducing the relative power requirements of the actuator (compared to a direct-coupled design). The damping coefficient of the resonant system (including ejector plate 1602 and drop generator 1632) may also be selected to be greater than the piezoelectric actuator input power in order to reduce fatigue and increase service life with substantially no failure.

An example of an eductor assembly is illustrated in U.S. provisional patent application No.61/569739 (having a filing date of 12/2011 entitled "injector Mechanism, injector Device, and Methods of Use," incorporated herein by reference). In one particular embodiment, Ejector plate Mechanism 1601 may include a rotationally Symmetric Ejector plate 1602 connected to a generator plate type actuator 1604, such as shown in fig. 18, and as described in U.S. provisional patent application No.61/636565 (application date 4/20/2012, entitled "central-Symmetric Lead free Ejector Mechanism, Ejector Device, and Methods of Use", also incorporated herein by reference). Although the invention is not so limited.

In the particular configuration of FIG. 18, the generator plate type actuator 1604 includes one or more individual piezoelectric devices or other actuator elements, as described above, for driving the rotationally symmetric ejector plate 1602. The drop generator plate 1632 includes a pattern of openings 1626 in the central region 1630 and is driven by the ejector plate 1602 using suitable drive signal generator circuitry, as described below. Exemplary techniques for generating the drive voltages are illustrated in U.S. provisional patent application No.61/647359 (application date 5/15/2012, entitled "Methods, Drivers and Circuits for injection devices and Systems", incorporated herein by reference).

Fig. 19 is an exploded view of a symmetric injector mechanism 1601. In this embodiment, the ejector plate 1602 utilizes discrete (separated) drop generator plates 1632, as represented on the left and right sides of fig. 19 from a back surface (downward facing surface) 1625 and a front surface (upward facing surface) 1622, respectively. The drop generator plate 1632 is mechanically coupled to the ejector plate 1602 in a central bore 1652 and includes a pattern of openings 1626 arranged to generate a stream of fluid drops when driven by a generator plate type actuator 1604, as previously described.

Fig. 20 is a plan view of a symmetric ejector mechanism 1601. The ejector mechanism 1601 includes: an ejector plate 1602, the ejector plate 1602 being connected to a generator plate type actuator 1604 by a mechanical connection 1604C; and a drop generator plate 1632, the drop generator plate 1632 having a pattern of openings 1626 in a central region 1630. Injector mechanism 1601 may be connected to a fluid reservoir or other injection device component through a bore 1651 in a tab type mechanical connection element 1655, or using other suitable connections, as described above with reference to fig. 16.

As shown in fig. 20, ejector mechanisms 1601 and ejector plates 1602 may be defined by an overall dimension 1654, such as about 21mm, or from about 10mm or less to about 25mm or more (depending on the application). Suitable materials for ejector plate 1602 and drop generator 1632 include, but are not limited to: metals resistant to flexural stress and fatigue, such as stainless steel.

For orientation purposes, the various elements of the injector mechanism 1601 (as shown in fig. 18-20) may be described with respect to the position of the fluid 1610 or the reservoir 1620, as described above with reference to fig. 16. Generally, the proximal elements of the mechanism 1601 are disposed closer to the fluid reservoir 1620, and the distal elements are disposed further from the fluid reservoir 1620, as determined in the droplet stream or spray direction 1614.

The ejector assembly described herein may be incorporated into an ejector device. An example eductor apparatus is exemplified in U.S. patent application No.13/184484 (filed 2011, 7/15), the contents of which are incorporated herein by reference.

Various embodiments of the present invention have been described. The present invention contemplates that any feature of one embodiment can be combined with the features of one or more other embodiments. For example, any sprayer mechanism or reservoir can be used in combination with any of the described housings or housing features (e.g., covers, supports, shelves, lamps, seals and gaskets, filling mechanisms, or alignment mechanisms). Other variations of any of the elements of any of the embodiments herein are also within the purview of one of ordinary skill and are contemplated by the present invention. These variations include the choice of materials, coatings, or manufacturing methods. Any electrical and electronic technology can be used in any implementation (without limitation). Moreover, any network, remote access, subject monitoring, e-health, data storage, data collection, or internet functionality with respect to data captured by the device can be used in any and all embodiments, and can be implemented together. Moreover, additional diagnostic functions (e.g., testing or measuring performance of a physiological parameter) may also be included in the functionality of any of the embodiments. The performance of glaucoma or other ocular tests can also be performed by the device as part of their diagnostic function. Other manufacturing methods known in the art and not specifically listed herein can also be used to manufacture, test, repair, or maintain the device. Moreover, the device may include more complex imaging or alignment mechanisms than those described in the incorporated prior applications. For example, the device or base may be equipped with or connected to an iris or retinal scanner in order to generate a unique Id to match the device to the user, as well as to delineate between eyes. Alternatively, the device or base may include or be coupled with a complex imaging device for any suitable type of imaging or radiation application.

Although various embodiments have been described above by way of examples, it will be appreciated by those skilled in the art that variations and modifications may be effected within the spirit and scope of the application.

Claims (14)

1. A device for generating a directed stream of droplets, 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 a reservoir and arranged to generate a directed stream of droplets of the fluid, the ejector mechanism comprising a generator plate and a piezoelectric actuator;

wherein the generator plate comprises a fluid-facing surface, a droplet ejection surface, and a plurality of openings formed through a thickness of the generator plate between the fluid-facing surface and the droplet ejection surface;

wherein the piezoelectric actuator is operable to directly or indirectly oscillate the generator plate at a frequency so as to generate a directed stream of droplets of said fluid;

the plurality of openings of the generator plate gradually varying in slope from the fluid facing surface to the droplet ejection surface to provide a radius of curvature of the external inlet, the external inlet having a circular shape to reduce air flow from the droplet ejection surface to the fluid facing surface through the plurality of openings in generating the directed stream of droplets by causing the plurality of openings to be arranged to provide the fluid with a laminar flow as the fluid passes through the openings; and

the ratio of the size of the radius of curvature to the size of the opening at the droplet ejection surface is: greater than 2.5 when the opening is greater than 40 μm at the droplet ejection surface; or greater than 5 when the opening is less than 40 μm at the droplet ejection surface.

2. The apparatus of claim 1, wherein: the external inlet into each opening from the fluid facing surface is a fluted inlet section providing a gradual transition from the fluid facing surface into the opening.

3. The apparatus of claim 1, wherein: a groove is defined around the at least one opening on the droplet ejection surface.

4. The apparatus of claim 1, wherein: each external inlet is a fluted inlet portion and each opening further defines a channel extending to the droplet ejection surface, the channel being configured to have a sufficient length to obtain laminar flow of the fluid before the fluid reaches the droplet ejection surface.

5. The apparatus of claim 1, wherein: the ejector mechanism further includes an ejector plate connected to the generator plate and a piezoelectric actuator operable to oscillate the ejector plate at a frequency to oscillate the generator plate to generate the directed stream of droplets.

6. The apparatus of claim 5, wherein: the ejector plate has a central open region aligned with the generator plate, and the piezoelectric actuator is connected to a peripheral region of the ejector plate so as not to obstruct the plurality of openings of the generator plate.

7. The apparatus of claim 6, wherein: the plurality of openings of the generator plate are arranged in a central region of the generator plate, which is not covered by the piezoelectric actuator and is aligned with the central open region of the ejector plate.

8. The apparatus of claim 7, wherein: the generator plate has a reduced size relative to the ejector plate, and the size of the generator plate is determined at least in part by the area occupied by the central region and the structure of the plurality of openings.

9. The apparatus of claim 1, wherein: the ejector mechanism is arranged to eject a directed stream of droplets such that at least 75% by mass of the ejected droplets are deposited on the target.

10. The apparatus of claim 1, wherein: the ejector mechanism is arranged to eject a stream of droplets having an average ejected droplet diameter in the range of 20 to 400 microns.

11. The apparatus of claim 1, wherein: the ejector mechanism is arranged to eject a stream of droplets having an average initial ejection velocity in the range of 0.5m/s to 10 m/s.

12. A method of reducing air ingress into a fluid ejector assembly during operation, comprising: providing a fluid ejector assembly to obtain laminar flow of a fluid prior to ejection from the fluid ejector assembly, the fluid ejector assembly comprising: a droplet generator plate having a fluid-facing surface, a droplet ejection surface, and a plurality of openings formed through a thickness of the droplet generator plate between the fluid-facing surface and the droplet ejection surface; the method includes providing an inlet on the fluid facing surface to each opening that transitions gradually from the fluid facing surface to the droplet ejection surface to provide a radius of curvature of the external inlet, the external inlet having a circular shape to reduce air ingress into the fluid ejector assembly during operation by providing the openings to provide fluid with laminar flow as the fluid passes through the openings, wherein: the ratio of the size of the radius of curvature to the size of the opening at the droplet ejection surface is: greater than 2.5 when the opening is greater than 40 μm at the droplet ejection surface; or greater than 5 when the opening is less than 40 μm at the droplet ejection surface.

13. The method of claim 12, wherein: the inlet is a groove inlet and the opening further defines a channel extending from the groove inlet to the droplet ejection surface, the channel having a length sufficient to obtain laminar flow of the fluid when the fluid reaches the droplet ejection surface.

14. The method of claim 13, wherein: the channel length is about 125 μm.