WO2011007282A1 - Apparatus and method for safeguarding the operation of a fluid delivery device - Google Patents

Abstract

The apparatus allows the detection of light bubbles in the area of the pressurized fluid chamber or the nozzle of the micro-jet to detect bubbles by light scattering. Light is sent through the area of interest and detected behind it by a light detector. If the light intensity drops correspondingly a drop in the detector current is detected. This is indicative of unwanted bubbles. In this case the actuation of the electromechanical actuator to generate micro-jets may be stopped, alternatively or in additional signal may be output in order to inform a user to replace a fluid reservoir, or to simply issue an alarm. The fluid delivery device may comprise a durable and a disposable section, wherein the active parts such as power source, light source and light detector are integrated in the durable section and the disposable section comprises a nozzle and the fluid chamber which presents significant advantages, as the contact interface to the skin is frequently replaced and thus hygienic conditions are easy to maintain.

Description

Apparatus and method for safeguarding the operation of a fluid delivery device

FIELD OF THE INVENTION

The present invention generally relates to the field of needle-less drug delivery devices, and methods of making and operating such devices. In particular the present invention relates to transdermal delivery systems and methods of safeguarding them.

BACKGROUND OF THE INVENTION

WO 2008/142640 discloses a wearable drug delivery device. Here, in order to provide a wearable drug delivery device for long-term administration of drugs not employing a needle or cannula, it is suggested that a wearable drug delivery device comprises a tubular reservoir having an outlet end from which a drug may be expelled and a second end, a highspeed jet pump for transdermal, needle-less micro-jet drug delivery, being connected to the outlet end of the tubular reservoir, a venting valve being connected to the second end of the reservoir. An embodiment discussed in WO 2008/142640 incorporates a filling system which has a fluid sensor that allows for the detection of bubbles which may be injected from a syringe via a hypodermic needle into the tubular reservoir.

As gas bubbles in a volume associated with a jet nozzle take up volume and thus have an effect on the pressure that builds up in the context of forming micro-jets by an actuator during the jet generation, bubbles need to be avoided in order to safeguard an operation of a fluid delivery device relying on micro-jets.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus and method for safeguarding the operation of a fluid delivery device by making sure that sufficient pressure can be built up to generate a micro-jet. The present invention provides needle-less drug delivery devices, and methods of making and operating such devices. In particular the present invention provides transdermal delivery systems and methods of using them.

This object is achieved by an apparatus for safeguarding the operation of a fluid delivery device according to claim 1 and a method for safeguarding the operation of a fluid delivery device according to claim 14. Advantageous further developments of the invention are stated in the dependent claims.

In this text, transdermal implies all layers comprised in a mammal's skin underneath the stratum corneum which performs as the interface with the outside world. In order of increasing depth with regard to the stratum corneum, these layers are the epidermis, the dermis and the hypodermis, wherein the latter layer is also referred to as the subcutis or subcutaneous fat.

The apparatus according to the present invention presents the significant advantage that it places a detector in the area of the fluid chamber which is pressurized for generating the micro-jet and thus directly in the area that needs to be monitored. It uses a light source associated with a light detector in order to safeguard the operation of a fluid delivery device by detecting the signal from the light detector corresponding with or representative of gas bubbles in the fluid for safeguarding the operation of the fluid delivery device. By this arrangement an immediate monitoring of the critical area of the fluid delivery device is possible and a minimum technical effort in form of a light source is required, for instance a light emitting diode and a light detector, for instance a photodetector.

Expediently according to a further development of an embodiment of the apparatus according to the present invention a nozzle for ejecting a micro-jet is coupled to the fluid chamber. In this manner a fluid delivery device based on micro-jet is provided, using a minimum volume and which thus is highly integrated, and material to build the device can be saved.

Beneficially a further development of an embodiment of the apparatus according to the invention comprises an electromechanical actuator to pressurize the fluid chamber. Such devices are well-established and have the advantage when they are implemented as a piezoelectric device, that a controlled elongation or contraction of the crystal can be achieved by a defined increase of an applied voltage. They also are quick in their response and thus well suited for the generation of micro-jets.

Beneficially a further development of an embodiment of the apparatus according to the present invention comprises two sections that are releasably connected to each other, wherein one is a durable or re-usable section and the other is a disposable section. Such an arrangement presents the advantage, that disposable items, such as the fluid container, the fluid chamber and the nozzle for instance can be arranged in the disposable part and lead thereby to advantages in terms of hygiene and sterility as they incorporate the device-skin interface, as well as in terms of a technical point of view. For example, the fluidic system is reset to a well-defined state once the disposable section is replaced. Thus the parameters that once are set to administer a fluid need not to be modified, once the disposable section is replaced.

Beneficially according to a further development of an embodiment of the apparatus according to the present invention the fluid chamber is arranged in the second section which is disposable. In this manner different fluids can be administered without having to perform complicated disinfecting and cleaning steps.

Advantageously according to a further development of an embodiment of the apparatus according to the present invention the light source and the light detector are arranged in the first section which is durable, i.e. is conserved or retained in re-use. In terms of the device and the associated costs, as well as the technical arrangement these devices cooperate and have a certain value and thus it is very useful to arrange them in the first and durable section which can be reused many times.

Beneficially according to a further development of an apparatus according to the present invention the second section cooperating with the first section containing the light detector and the light source comprises light guide means that are arranged in such a manner, that the light coming from the light source out of the first section is guided through the fluid chamber in the second section and from there to the light detector in the first section.

Beneficially a further development of an embodiment of the apparatus according to the present invention comprises a light guide that is arranged as indentation forming a reflecting plane and consequently a mirror for the light in the transparent material of the second section. Transparency as a property of the second section in this case is to be understood as being transparent for the certain wavelength of the optical radiation emitted by the light source. In this case it may be visible light for many polymers which may be used to manufacture the second section or it may be infrared in case of a semiconductor such as silicon forming the material of the second section.

Beneficially a further development of an embodiment of the apparatus according to the present invention comprises periscopic mirrors that are inserted in the second section and directly contact the first section. Such a configuration has the significant advantage, that the interfaces between the first section and the second section require no special treatment in order to allow for a low optical resistance, as the light guiding means are separate devices that can be reused and specially tailored for optimum optical properties.

Expediently a further development of an embodiment of the apparatus according to the present invention comprises control means connected to the light detector and responding to a certain condition in the detector current as a signal to safeguard the operation of the apparatus. Thus for instance a certain threshold can be predefined, which is monitored by the control means and in case a particular amount of bubbles in the fluid chamber reduces the light energy detected by the light detector in such a manner that the detector current transgresses a certain lower threshold an alarm may be signaled, or respectively the electromechanical actuator may be stopped from being actuated. The alarm signal may be optical, auditory or tactile for example.

Beneficially a further development of an embodiment of the apparatus according to the present invention has the control means connected to the pressurizing means, because in such a case, if an amount of bubbles is detected in the fluid chamber, the operation of the micro-jet pump, by controlling the pressurizing means can be adapted to the current situation.

Advantageously according to a further development of an embodiment of the apparatus according to the present invention the control means is also adapted to control the activation of the light source. In this manner beneficially in such a configuration the light source may only be activated shortly before a micro-jet is to be injected and thus power can be saved resulting in a longer operational period of the apparatus considering the limited battery capacity of the power source, without sacrificing any functionality.

In an advantageous manner, in a further development of an embodiment of the apparatus according to the present invention the control means is adapted to output an indication signal indicative of a predefined change in the detector current. In this way an easy configuration is provided by this embodiment that allows it to output an alarm signal or a display message, to for instance replace the second section in case a certain amount of bubbles has accumulated in the fluid chamber, corresponding to a significant drop in the detector current.

Advantageously the method according to the present invention only requires a few steps to safeguard the operation of the fluid delivery device, in determining a light intensity of light passing through a fluid chamber and only powering the electromechanical actuator of the fluid delivery device, if sufficient the light intensity is detected.

Beneficially a further development of an embodiment of the method according to the present invention has a step to output an alarm or a display message to for instance replace the disposable section in case the detected light intensity is below a predefined threshold, corresponding to a significant amount of bubbles that have accumulated in the fluid chamber. BRIEF DESCRIPTION OF THE DRAWINGS

Below advantageous further developments of the invention will be further explained based on examples and embodiments depicted in drawings, wherein:

Fig. 1 shows an example of a release rate profile to be maintained by a fluid delivery device,

Fig. 2 shows a schematic example of an embodiment of an apparatus according to the present invention,

Fig. 3 shows an image of a nozzle region containing bubbles and no bubbles, Fig. 4 depicts an example of a detector current in response to an air bubble in the fluid chamber,

Fig. 5 shows an embodiment of a micro-jet injector characterized by a particular light guide,

Fig. 6 shows an alternative micro-jet injector characterized by another light guide, and

Fig. 7 shows a flow-chart of an embodiment of the method according to the present invention.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated. The term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

As Fig. 1 explains, an embodiment of an apparatus according to the present invention has a fluid delivery device that delivers micro -jets at certain intervals. The fluid delivery device may be a drug delivery device. The fluid delivery device may be a needleless transdermal drug delivery device. Micro-jets 260 and 270 are shown wherein with 260 an early microinjection is indicated and with 270 a late microinjection is marked. With 220 a time axis is indicated and with 210 the plasma level of the liquid to be administered in the blood plasma of a user is indicated. The curve indicated by 250 shows the current plasma level which is to be kept in between the lower threshold for the plasma level 230 and the upper threshold for the plasma level 240 in order to ensure the efficiency of the fluid.

All in all the injection diagram 200 may serve to explain the relation between the microinjections and the current plasma level 250. For instance, if the period between two subsequent microinjections is made longer, the current plasma level 250 will be on a lower level and subsequently transgress the lower threshold 230. On the other hand if the interval between two subsequent microinjections is shortened the plasma level will grow and subsequently transgress the upper threshold 240. Generally a volume of liquid that is delivered is computed by the volume that is administered by each microinjection multiplied with the number of microinjections, in case the operation of the microinjection device is safeguarded. In this case however a control device may count the number of microinjections that have already been performed in order to keep track of the current amount of fluid that has been injected. In case of a maintenance situation, or an irregularity occurring while administering the fluid, the current amount of fluid may be stored and once the operation of the fluid delivery device is resumed a pending number of microinjections will be released, until the predefined amount of fluid is delivered.

Fig. 2 shows a basic configuration of an embodiment of an apparatus according to the present invention, in form of a bubble detector 300. Bubble detector 300 can be included in embodiments of an apparatus according to the present invention that is a fluid delivery device that delivers micro-jets at certain intervals, e.g. the fluid delivery device may be a drug delivery device, such as a needle-less transdermal drug delivery device. In particular a light source 310 is shown, as well as a light detector 320, a first light guide 340 and a second light guide 330. Reference sign 305 is marking a nozzle that is integrated in a nozzle plate 360. Also a light beam 350 is shown, that starts at the light source 310 and is reflected by the first light guide 340 and the second light guide 330 until it arrives at the light detector 320.

Fig. 2 also shows a control means 325 that has several control lines to communicate with the various devices depicted in the drawing. Control means 325 can be included in embodiments of an apparatus according to the present invention that is a fluid delivery device that delivers micro-jets at certain intervals, e.g. the fluid delivery device may be a drug delivery device, such as a needle-less transdermal drug delivery device. Reference sign 322 indicates a detector signal line to receive for instance a detector current that is responsive to the light intensity of the light beam 350. Furthermore an illumination control line 311 is shown, which allows it to control the activation of the light source 310 by the control means. Furthermore, a means to pressurize 308 is shown, which allows pressure to be exerted on the fluid chamber to eject a fluid jet from the nozzle 305. For instance, the means to pressurize may be implemented as piezo actuator and in case if a voltage is applied to the piezo actuator it changes its length and thus pushes the fluid in the fluid chamber 303 through the nozzle 305 generating a micro-jet. Alternative the means to pressurize are included within the scope of the invention, e.g. using thermal pulses. A control of the micro-jet formation by the means to pressurize 308 can be achieved by the control means 325 via the pressurizing control line 309. Further a power source 318 is shown serving to power the apparatus. Any suitable power source may be used like e.g. a battery, a solar cell, a fuel cell, or a generator like the ones used in wrist watches.

During the operation of the apparatus shown in Fig. 1 the means to pressurize 308 can be controlled by the control means 325 to generate micro-jets and subsequently inject fluid into a user in form of subsequent microinjections as shown in Fig. 1. A light beam 350 arriving from the light source 310 via the first light guide 340 and the second light guide 330 at the light detector 320 results in a certain light intensity corresponding to a certain detector current, which is processed at the control means 325. In case of bubbles building up in the fluid chamber 303 for instance due to running empty in a fluid reservoir which is not shown in the drawing, light coming from the light source will be scattered at the bubbles and thus the intensity of the light beam 350 arriving at the light detector 320 will drop, which leads to a lower detector current, that is recognized at the control means. In this case, if the detector current drops below a certain threshold which is e.g. predefined and monitored at the control means, an indication signal 327 may be generated, in order to sound an alarm, or to display a message on a display reminding a user to replace the fluid reservoir to safeguard the operation of the fluid delivery device. Furthermore a number of microinjections and the time of transgression of the threshold will be memorized in order to keep track of the amount of fluid that has been administered for a further point in time, when the administration of the fluid is resumed.

In this manner, a control means 325 can keep track of a total amount of fluid that has to be administered according to a prescription and start from a certain level until the total amount is delivered. In this case, it is important to understand, that a number of microinjections corresponds to a certain amount of fluid that is administered. Thus keeping track of a certain number of microinjections in terms of a malfunction makes it easy to resume the operation, and administer the remaining number of microinjections up to a total number that is predefined. Technically, an air pocket in the system will locally alter the index of refraction and thus will change the light scattering of light propagating through the fluid chamber. This allows to monitor the light intensity and thereby to detect air bubbles in the fluid chamber. The control means for instance may comprise a memory for all sorts of data and parameters related to the fluid delivery by microinjections. For instance it may comprise a preset in form of number of microinjections per time unit in order to maintain a certain current plasma level in the blood plasma of a user, of fluid to be delivered indicated by reference sign 250 in Fig. 1. Consequently, once a malfunction occurs, the control means also may have access to a clock, or an external time reference in order to measure the duration of the time of malfunction. After resuming the proper operation again, the control means may be adapted to compensate for the time of malfunction, by increasing the number of

microinjections per time unit, or the corresponding volume of a microinjection in order to increase the current plasma level in a shorter amount of time up to a prescribed level. Such a process may particularly be useful in case if the plasma level has dropped below the lower threshold.

Fig. 3 shows images of a nozzle environment in a fluid chamber of an embodiment of a fluid delivery device. These pictures are taken as shadow images of a translucent fluid chamber and an associated fluid nozzle, marked by reference numerals 303 and 305 respectively in Fig. 2. From the left hand side of Fig. 3 and the image 410 it is clear, that no bubbles are forming in the fluid chamber and in the nozzle. On the right-hand side of Fig. 3 in the image 420 however a first bubble 430 can be identified as shadow in the upper part of the fluid chamber and a second bubble 440 can be identified approaching the nozzle in the lower part of the image. Such bubbles being present in the fluid chamber or in the nozzle severely affect the performance of a fluid delivery device operating to regularly and periodically generate micro-jets expected to contain a certain fluid volume. As gases are much easier to compress than fluids, in case a pressure is exerted to the fluid present in the fluid chamber, instead of the fluid being expelled through the nozzle in a certain amount, that is proportional usually to the elongation of an electromechanical actuator pushing the fluid aside, the gas bubbles are compressed and almost no fluid is expelled, the speed of the micro- jet that is generated is not sufficient to penetrate the skin of a user, or no fluid jet is generated at all. Thus bubbles in the pressurized system severely deteriorate the functionality and the generation and formation of fluid jets of a fluid delivery device. In the presence of bubbles, no controlled environment is attainable. Thus bubbles when forming need to be detected, in order to safeguard the operation of a fluid delivery device.

Fig. 4 shows a detector current curve 500 as e.g. measured by the light detector marked in Fig. 3 by 320. Reference sign 510 indicates the detector current over time and 520 marks the time axis. With 530 a drop in the detector current caused by a bubble is marked. As mentioned before when explaining Fig. 2, bubbles in the fluid chamber scatter the light differently than the fluid itself does and thus less light arrives at the light detector in the presence of bubbles. This effect causes the drop in the detector current marked by 530. This drop can be used in the control means 325 shown in Fig. 2 to output an indication signal 325, to stop the means to pressurize 308 and to switch off the light source 310 until the fluid reservoir containing fluid to be injected is replaced.

Fig. 5 shows a micro-jet injector 600. When explaining Fig. 5 for the sake of efficiency only these parts of the drawing are explained that relate to new reference signs, other parts that have reference signs identical to the previous drawings that have been previously explained have the same function and relate to similar devices or parts of the micro-jet injector. Here an electromechanical actuator 630 is shown which corresponds to the means to pressurize 308 in Fig. 2. In this case it may be arranged as a piezo actuator which reacts to a voltage that is applied to it by an elongation. This elongation corresponds to a certain fluid volume that is expelled from the nozzle 305. In Fig. 5 also a reservoir 660 for fluid to be delivered is shown. In particular in this case the embodiment consists of a durable section 640 and a disposable section 650. Both sections 640 and 650 are connected in a releasable manner with means that are not shown in the drawing. In this case it is however important, that the connection means allow the light from the light source 310 to enter the second section 650. The second section 650 may be assembled from a cover plate 620 and a nozzle plate 360 in order to allow for an easier manufacturing of the device. In this case the embodiment comprises a first indentation mirror 617 and a second indentation mirror 615. Said indentation mirrors employ total internal reflection of the light issued to them. Here for instance by mechanically treating the surface of the nozzle plate in taking away material in a defined manner by for instance machining, or laser treatment, mirror surfaces can be generated at the interface between the nozzle plate 360 and the air. They reflect the light beam 350 to guide it from the light source 310 to the light detector 320 through the fluid chamber as previously explained. Another possibility is to manufacture the nozzle plate in the desired shape by e.g. injection molding.

Fig. 6 shows an alternative embodiment of a micro-jet injector as fluid delivery device in an embodiment of the present invention. Here in contrast to the

embodiment shown in Fig. 5, a first periscopic mirror 740 and a second periscopic mirror 730 are shown that are accompanied by a first barrier 750 and a second barrier 760. The first and the second barrier 750 and 760 may be fixedly connected to the first section 640 of the fluid delivery device, in order to allow for a precise positioning of the second section 650 of the fluid delivery device, which is disposable. These barriers serve to channel the light emitted from the light source through the respective mirror. The periscopic mirrors may be inserted from the lower side through the nozzle plate 360 and subsequently through the cover plate 620. This has the significant advantage that the interface between the cover plate 360 and the first section 640 needs no special optical treatment in order to lower the optical resistance to allow a sufficient amount of light to enter through the second section. In this case, only the replaceable parts, respectively the periscopic mirrors 740 and 730 need to be provided in a proper optical grade, which allows for a more cost-effective manufacturing. The shape of the periscopic mirrors 740 and 730 corresponds to the triangular indentation in the nozzle plate 360 used to generate the indentation mirror 617 and 615. As a light detector 320 also a photodiode may be used.

Fig. 7 shows an example of an embodiment of a method 800 according to the present invention. At 805 the flow starts, at 810 the light of a light source is switched on.

Subsequently at 815 an intensity of light is detected at a light detector and it is determined if the intensity is above a threshold. In case the intensity would be below a threshold which is predefined, this would lead to the conclusion that bubbles had formed scattering the light away. As bubbles are deteriorating the operation of a pump for generating micro-jets, subsequent action is required. In case the intensity is not high enough thus at 820 a signal is generated informing about a malfunction, respectively asking to replace a disposable part of a fluid delivery device, for instance replacing a reservoir containing the fluid to be delivered. On the other hand however if the intensity is sufficient, at 830 an electromechanical actuator may be powered in order to generate a fluid jet to perform a microinjection. At 840 the process is stopped.

Claims

CLAIMS:

1. Apparatus (300) for safeguarding the operation of a fluid delivery device (600, 700) comprising:

a light source (310),

a light detector (320),

- a fluid chamber (303), and

first means to pressurize (308) coupled to the fluid chamber (303) for fluid delivery;

wherein the light source (310) is arranged for illuminating the fluid chamber (303) and wherein the light detector (320) is arranged for detecting light (350) sent from the light source (310) through the fluid chamber (303), and for outputting a signal (530) for safeguarding the operation of the fluid delivery device.

2. Apparatus (300) according to claim 1, comprising a nozzle (305) coupled to the fluid chamber (303) for fluid delivery.

3. Apparatus (300) according to claim 1, wherein the first means (308) is arranged as electromechanical actuator (630).

4. Apparatus (300) according to claim 1, comprising two sections (640, 650), wherein a first section (640) is durable, wherein a second section (650) is disposable and wherein the second section (650) is made from transparent material.

5. Apparatus (300) according to claim 4, wherein the fluid chamber (303) is arranged in the second section (650).

6. Apparatus (300) according to claim 4, wherein the light source (310) and the light detector (320) are arranged in the first section (640).

7. Apparatus (300) according to claim 6 in combination with claim 5 comprising: a first light guide (340) for guiding light (350) from the light source (310) through the fluid chamber (303), and

a second light guide (330) for guiding light coming from the fluid chamber (303) to the light detector (320).

8. Apparatus (300) according to claim 7, wherein the first (340) and second (330) light guide are arranged as indentation in the second section (650) shaped as a reflection plane in the form of a first (617) and second (615) mirror.

9. Apparatus (300) according to claim 7, wherein the first (340) and second (330) light guide are arranged as a first (740) and a second (730) periscopic mirror inserted in the second section (650).

10. Apparatus (300) according to claim 1, comprising control means (325) connected to the light detector (320) by a detector signal line (322) for monitoring a detector current (510) as signal (530) for safeguarding the operation.

11. Apparatus (300) according to claim 10, wherein the control means (325) is connected to the pressurizing means (308) by a pressurizing control line (309) and wherein the control means is adapted to control the pressurizing means (308) in dependency of the detector current.

12. Apparatus (300) according to claim 10, wherein the control means (325) is connected by an illumination control line (311) to the light source (310) and wherein the control means is adapted to control the activation of the light source (310) by the illumination control line (311).

13. Apparatus (300) according to claim 10, wherein the control means (325) is adapted to output an indication signal (327) to indicate a predefined change in the detector current.

14. Method (800) for safeguarding the operation of a fluid delivery device (600, 700), comprising a first step (815) for detecting a light intensity of light passing through a fluid chamber, a second step for powering an electromechanical actuator (630) to pressurize fluid in the fluid chamber for safeguarding the operation is detected if the detected light intensity is above a predefined threshold.

15. Method (800) according to claim 14, comprising a further step (820) for generating a signal to safeguard the operation if the detected light intensity is below the predefined threshold.