Vented multi-dose ocular fluid delivery system

Abstract

A device for delivery of a precise amount of pharmaceutical fluid to the eye is provided. The device includes an ampoule for storing a liquid and an aperture through which the liquid is discharged. The device further includes a vibrating membrane that includes a needle which protrudes from the membrane and extends to the aperture to form a needle valve. The needle valve provides hermetic closure of the aperture to enable preservative-free storage of the pharmaceutical fluid in the device. The system further includes an electromagnetic transducer to shift the membrane back and forth in order to discharge liquid through the nozzle. Finally, the system further includes a vent to permit air to enter the ampoule as fluid is ejected from the ampoule. Preferably this vent includes a filter to prevent ingress of microbes or other contaminants to the ampoule.

Description

FIELD OF THE INVENTION

This invention relates to topical ocular delivery of ophthalmic medications.

BACKGROUND

Currently, pharmaceutical fluids are typically delivered to the eye surface using a drop bottle. This method has multiple drawbacks: (1) Patients cannot aim well and often miss the eye; (2) Volume of a drop from a bottle is not well-defined and is too large (on the order of 50 μL) for the tear film on the cornea to absorb it—the tear film can hold no more than about 7 μL; (3) Very often patients blink during the drop delivery, so that part of the drop lands on the eyelid, and the rest is wiped off the cornea.

SUMMARY

We have developed a device that addresses these problems by (1) delivery of a precise amount of fluid; (2) with a micro-dose that the tear film can hold (<10 uL); (3) deliver it within the blink time (˜100 ms), and (4) using an optical aiming onto the cornea for precise self-administration.

For convenient aiming, the fluid ejector should be placed close to the eye, but not touch the eyelashes or eyebrow. Therefore, with reference to FIG. 1, the device 102 should be in the range of approximately L=1-10 cm from the eye, or more optimally 2-6 cm. On this figure, 102 is the fluid ejector, 104 is the emitted fluid stream and 106 is the patient's eye.

The cornea is about D=12 mm in diameter, i.e. 6 mm in radius. To ensure that the fluid is delivered approximately to the middle of the cornea, the jet 104 should not deflect under gravity by more than about half the cornea radius, i.e. no more than about h=3 mm. As shown in FIG. 1, vertical deflection h of the projectile ejected horizontally with velocity v over a distance L is: h=g*L/(2 v²). To ensure that vertical deflection does not exceed h, horizontal jet velocity should exceed v=L*(g/2 h)^0.5. For L=5 cm, g=9.8 m/s², h=3 mm, we obtain v=2 m/s. For L=5 cm and h=1 mm, velocity should be about v=3.6 m/s, and for L=10 cm, h=1 mm, velocity v=7.2 m/s. Therefore overall, jet velocity should be in the range of about 1-10 m/s, and more optimally 2-4 m/s. Velocities much higher than those may cause discomfort to the patient and even damage to the cornea.

The stream of fluid will reach the eye within a few milliseconds from the moment of dispensing (t=L/v, in the range of 1-100 ms). As soon as the fluid will touch the cornea, it will trigger the blink reflex, which typically takes about T=100 ms. To prevent the drug being blocked by the eyelid, the fluid should be delivered before the eye closure. For the required volume V to be delivered within the time T with the jet velocity v, the jet cross-sectional area should be S=V/(T*v). Since for a round aperture, S=π*d²/4, its diameter d=(4V/(πT*v))^0.5. For example, for v=2 m/s, T=100 ms, V=10 μL, we obtain d=250 μm. For v=1 m/s, d=350 μm, and for v=7 m/s, d=130 μm.

Therefore, the aperture diameter of the ejector should be in the range of approximately 200-600 μm, and more optimally 400-550 μm. Alternatively, several apertures could be used to produce several parallel streams for faster delivery.

Another key attribute of the system is the prevention of microbial ingress to the contained liquid during storage or use. As with any closed system, as liquid is ejected, air should be introduced to replace the ejected volume and thereby balance the pressure (venting). To preclude microbial ingress, the air is introduced via a special inlet preferably having a 0.2 um filter. Ideally, the device should operate such that liquid is ejected through the aperture any time it is opened, thereby preventing the air ingress through it.

An exemplary embodiment is an arrangement for storing and discharging liquid droplets having a housing including a chamber for holding liquid therein and having an intake port connected to an ampoule containing pharmaceutical fluid to be dispensed. The chamber includes a dispensing aperture plate which defines a frontal closure to the chamber and includes an aperture opening therein through which the liquid is discharged forwardly of the housing. The chamber further includes a vibrating membrane secured to the housing in pressure transmitting relation with the liquid in the chamber. The vibrating membrane is formed with a needle which protrudes from its center and extends to the aperture in the opposite side of the chamber, said needle closes the aperture to prevent outflow of liquid from the chamber and ingress of bacteria.

An electromagnetic transducer is attached to the housing, and when energized, pulls the membrane rearward against a spring in the chamber. When the electromagnetic transducer is turned off, the spring returns the membrane to its original position with the valve closed. When the electromagnetic transducer is energized with pulsatile or alternating current, the membrane is consequently oscillated, which in turn generates pressure on the liquid. At the correct frequencies, the pressure is sufficient to eject a stream of liquid from the aperture.

Typical range of frequencies is in a range of 10 Hz to 500 Hz, more optimally 50 to 200 Hz. The diameter of the nozzle, velocity of the fluid ejection, and duration of the electromagnetic burst are preferably optimized to deliver the required amount of fluid within the required amount of time, as described above. Preferably the actuation pulse duration is 250 ms or less, and more preferably it is 100 ms or less. Here ‘actuation pulse duration’ refers to the length of time the electromagnetic transducer is energized so as to pull the needle out of the aperture in a single actuation pulse.

Other kinds of transducer can also be used to drive fluid ejection in this configuration, such as a coin vibration motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows geometry for delivering fluid to an eye of a patient.

FIG. 2 is an exterior view of an exemplary embodiment of the invention.

FIG. 3A is a cross section view of a first embodiment of the invention.

FIGS. 3B-C show operation of the embodiment of FIG. 3A.

FIGS. 4A-B show an example of venting.

FIG. 5 is a cross section view of a second embodiment of the invention.

FIG. 6 shows a conical spring.

DETAILED DESCRIPTION

FIG. 2 shows a perspective view of a first embodiment of the liquid ejection unit. The fluid ejection unit 200, is specifically but not exclusively suitable for use in delivering preservative-free pharmaceutical liquid to the surface of the eye. Liquid ejection device 200 comprises a thermoplastic body 206 formed with a liquid chamber and connected to a fluid supply ampule 202. The ejection unit includes nozzle 208 through which liquid 210 is dispensed as will explained in greater detail below.

FIG. 3A illustrates a cross-sectional view of the fluid ejection device. As mentioned earlier the fluid ejection device comprises a thermoplastic body 206 defining a chamber 316 connected to the fluid supply ampule 202 containing a fluid 302. The fluid ejection device includes a nozzle 208 through which liquid is ejected. The device further includes a membrane 308 at the opposite end of the chamber from the nozzle. Membrane 308 includes an integral needle 306 such that they are one component. The needle 306 and the membrane 308 are connected to an electromagnetic transducer 310 via a link member 318. Upon application of an electrical pulse to the electromagnetic transducer 310, electric current flows through the coil 312 and a magnetic force is developed which pulls plunger 314 backward against a spring 320.

On FIG. 3A, 304 shows the direction of fluid flow from ampule 202 to chamber 316. Vent tube 404 is described in greater detail below.

FIG. 3B shows the device of FIG. 3A following application of an electrical pulse to electromagnetic transducer 310. It can be seen that as a result from the magnetic force, plunger 314 is pulled into the electromagnetic transducer in the direction indicated by the arrow. Membrane 308 is connected to plunger 314 by linkage member 318 and is also pulled back. FIG. 3C shows the situation when the electromagnetic transducer 310 is de-energized. Here the spring 320 pushes the membrane 308 back to its original position, so the valve is closed and the chamber is hermetically sealed and prevents microbial ingress.

When the electromagnetic transducer 310 is energized with a pulsatile or alternating (AC) current, the oscillating membrane generates pressure in liquid resulting in a stream ejected from the aperture. Typically, the operating frequency is from 10 to 500 Hz and more specifically from 50 to 200 Hz. In an embodiment, the membrane 308 is made of silicon having hardness durometer between 50-70 (shore A), and the displacement of plunger 314 is about 200 um. Since the flow is produced only in the outward direction, it prevents microbial ingress even when the valve is open.

In the example of FIGS. 4A-B, the liquid ejection device includes a venting arrangement to equalize the pressure inside the ampoule 202 with the ambient atmospheric pressure. Here FIG. 4A is a cross section view along line E-E of FIG. 4B.

The venting system of this example includes an air inlet vent tube 404 that is extended beyond the liquid level of fluid 302 in the ampoule 202. It should be noted that the vent tube 404 is above the liquid level in any orientation of the device of FIGS. 4A-B. Vent tube 404 is connected to venting outlet 406, which is open to the atmosphere. In one embodiment, a filter 408 is placed in the venting outlet 406 such that the vented air flowing to the ampoule is filtered to prevent penetration of potential airborne contamination, such as microbes. Filter 408 will filter away particles with size >1 μm (more preferably >0.5 μm, still more preferably >0.2 μm). In this way the system can be isolated from microbial contamination, even though air 402 enters the ampule 202 as fluid is emitted.

In the preceding examples, diaphragm 308 is driven with a solenoid. In the example of FIG. 5, the diaphragm is driven by using a coin vibration motor. More specifically, 306 is a needle connected to a diaphragm 308 as described above. This assembly is overmolded with a magnetic steel pin 510. 502 is a coin vibrator motor (e.g., JINLONG MACHINERY & ELECTRONICS CO., LTD. model #C1026B002F). 504 is a plastic molded component which holds the motor 502 such that it can slide along rails (i.e., it is a motor holder). 506 is a plastic molded component that provides the above-mentioned rail guides for motor holder 504 to slide within. 510 is a magnetic steel pin which is molded into the membrane/needle assembly (308/306). 512 is the housing that holds all the components together.

Needle 306 normally seals the aperture (i.e., the aperture is sealed except when fluid is being emitted), as described in greater detail above. A coin vibration motor has an eccentric weight off its axis of rotation (the axis of rotation is perpendicular to the plane of FIG. 5). Because the weight is off axis, as the motor rotates the unbalanced weight causes the motor to vibrate primarily in the plane of FIG. 5. By placing the coin vibration motor 502 in a plastic motor holder 504 which fits into corresponding rails (in member 506), the coin vibration motor is constrained so it can only move linearly (e.g., left to right on FIG. 5). As a result of this physical constraint, when the motor rotates, it is only allowed to oscillate left to right, rather than to vibrate in a plane. The coin vibration motor is coupled to the diaphragm 308, consequently as the motor oscillates left to right, the diaphragm is also vibrated left to right. The ejected fluid stream is generated in the same manner as described above—i.e., the needle 306 moves back and forth in the aperture to eject the liquid.

In an alternative embodiment, the coin vibration motor 502 can be coupled to the diaphragm via an optional magnet 508. Magnet 508 is fixed to motor holder 504 which is also affixed to the coin vibration motor 502. When the magnet 508 is close to the magnetic steel pin 510, the two latch together and the motor is thereby coupled to the diaphragm. This is an advantageous assembly feature, because the motor can be easily added to the system without the need for tight tolerances and the motor can be added at several different steps of the assembly process.

The example of FIG. 5 includes a disk-shaped spring 320. The spring is slightly deformed out of plane during assembly which serves to transmit force to needle 306. This force or load keeps the needle 306 pressed up against the orifice to close the flow path. Without the spring, the force required to push the needle open is very low and the device will readily leak. Additionally, the spring has a spring constant which is important for ensuring the correct frequency and amplitude of oscillation of the needle when the motor is energized. Also important is that without the spring it is only the stiffness of the diaphragm 308 which applies a load to keep the needle 306 in the closed position. The diaphragm can be made of an elastomer. For most elastomers mechanical properties vary significantly even with modest temperature changes. With the spring 320, a significant portion of the load applied to the needle 306 comes from the spring 320, not the diaphragm 308. Because the mechanical properties of spring steel (e.g., the material of the spring 320) are far more constant for the same temperature change, adding the spring makes the system performance more consistent.

In an alternative embodiment, the disc spring 320 of FIG. 5 is replaced with a conical spring. A conical spring is similar to a conventional compression spring made of wire, but instead of being wound with a constant diameter, the diameter gets progressively smaller so that the spring has the shape of a cone, not a cylinder. See FIG. 6. When a conical spring is fully compressed, the coils nest within each other so the spring can become flat, only being as thick as the diameter of the wire it is wound from. Thus a fully compressed conical spring can fit in a similar form factor as the disc spring 320 of FIG. 5 and can serve the same function. The conical spring is cheaper, and it is easier to get a wide range of spring constants and operating deflections compared to the disc spring, so it is a feature of presently preferred embodiments.

The tip of needle 306 and/or the aperture it engages with can include an anti-microbial material.

Claims

1. An apparatus for delivering a fluid to an eye of a patient, the apparatus comprising: a fluid package comprising a reservoir configured to hold a fluid, an aperture, and a needle configured to seal the aperture when fluid is not being ejected through the aperture;wherein the fluid package comprises a resilient diaphragm configured to provide a mechanical force to hold a tip of the needle in engagement with the aperture when fluid is not being ejected through the aperture;wherein the resilient diaphragm is connected to the needle;an actuator configured to eject the fluid through the aperture by providing a mechanical vibration at least to the needle; anda vent configured to allow air to enter the reservoir as fluid leaves the reservoir.

2. The apparatus of claim 1, further comprising a particle filter configured to remove particles larger than 0.2 μm from air that enters the reservoir via the vent.

3. The apparatus of claim 1, wherein the actuator includes an electromagnetic solenoid.

4. The apparatus of claim 1, wherein the actuator includes a coin vibration motor.

5. The apparatus of claim 1, wherein the fluid package comprises a resilient spring configured to provide an additional mechanical force to hold the tip of the needle in engagement with the aperture when fluid is not being ejected through the aperture.

6. The apparatus of claim 1, wherein the apparatus is configured to deliver a dose volume of 10 μl or less.

7. The apparatus of claim 1, wherein a diameter of the aperture is in a range between 200 μm and 600 μm.

8. The apparatus of claim 1, wherein a velocity of fluid ejected from the aperture is in a range from 1 m/s to 10 m/s.

9. The apparatus of claim 1, wherein an actuation pulse duration is 250 ms or less.

10. The apparatus of claim 1, wherein a repetition rate of actuation pulses is in a range from 10 Hz to 500 Hz.

11. The apparatus of claim 1, wherein the needle has a tip that engages with the aperture, and wherein the tip comprises an anti-microbial material.

12. The apparatus of claim 1, wherein the aperture comprises an anti-microbial material.

13. The apparatus of claim 1, wherein the aperture is in a front wall of the reservoir and wherein the diaphragm is in a rear wall of the reservoir.