Patent Description:
Drug delivery devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.

Drug delivery devices such like pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable drug delivery devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. Such injection devices should provide setting and subsequent dispensing of a dose of a medicament of variable size. Moreover, a dose setting as well as a dose dispensing procedure must be easy to operate and has to be unambiguous.

Typically, such devices comprise a housing or a particular cartridge holder, adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The device further comprises a drive mechanism, usually having a displaceable piston rod to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge is displaceable in a distal or dispensing direction and may therefore expel a predefined amount of the medicament via a piercing assembly, which is to be releasably coupled with a distal end section of the housing of the drug delivery device.

The medicament to be dispensed by the drug delivery device is provided and contained in a multi-dose cartridge. Such cartridges typically comprise a vitreous barrel sealed in distal direction by means of a pierceable seal and being further sealed in proximal direction by the piston. With reusable drug delivery devices an empty cartridge is replaceable by a new one. In contrast to that, drug delivery devices of disposable type are to be entirely discarded when the medicament in the cartridge has been dispensed or used-up.

It is generally desirable to determine the amount of medicament remaining in a cartridge while the cartridge is arranged inside a drug delivery device. It is generally known in the prior art to implement a capacitive measurement or capacitive determination of a filling level of a cartridge. For this either on the cartridge itself or at the interior of a cartridge holder section of the drug delivery device there are provided at least two electrodes. Since the dielectric properties of the liquid substance inside the cartridge clearly differ from those of other surrounding materials, such like the vitreous material the cartridge is made of the rubber-based material forming the proximal piston of the cartridge, the electrical capacity to be measured between the electrodes located on radially oppositely located sidewall portions of the cartridge correlates with the filling level of the cartridge and/or with the axial position of the piston inside the cartridge. The measurable electrical capacity between the electrodes is therefore a direct measure of the axial position of the cartridge's piston. In this way the measured capacity is directly indicative of the cartridge's filling level.

For instance, document <CIT> discloses a respective dispensing device having at least one pair of capacitive measuring electrodes that are arranged in the outer region of a medicament container for determining the permittivity of the respective medium in an intermediate region between the measuring electrodes. Furthermore, there is described a shield that is arranged around the container and which surrounds the measurement materials in a sheath-like manner.

The correct arrangement of capacitive electrodes at the outer circumference of such containers or cartridges is rather delicate and cumbersome. The electrodes must be correctly positioned and arranged relative to the cartridge. Once the electrodes have been correctly assembled they require electric contacting with a processor in order to provide measurement and data processing of measured capacity values. Only slight modifications or deviations of the relative positioning of at least two electrodes with respect to each other and/or with respect to the cartridge as well as only slight deviations or modifications of the electrical contact with a processor may have drastic consequences on the measurement results. Such high demands in regard to positioning precision and electrical contacting are hardly achievable in a mass manufacturing environment for producing cartridge- and/or drug delivery devices at low costs.

For conducting a measurement of a physical or chemical parameter of the cartridge on the basis of capacitive electrodes electrical energy must be provided. Passive solutions, e.g. on the basis of RFID transponder technologies are rather sophisticated and may be rather susceptible to electromagnetic or mechanical perturbations. Moreover, a measurement or monitoring of relevant parameters can only be conducted if a suitable energy source, typically in form of a RFID reader, is in close proximity to the cartridge or to the drug delivery device equipped with such a cartridge. In addition, the functionalities of such passive sensor systems with a wireless transfer of electromagnetic energy are rather limited with regard to their processing capabilities and storage capacity, e.g. storing sequences of physical or chemical parameters.

It is therefore an object of the present invention to provide an improved sensor for measuring at least one physical or chemical parameter of a cartridge, wherein said cartridge is filled with a liquid substance. The sensor should be manufacturable at low costs and should be configured as a disposable entity. Furthermore, the sensor and its interaction with a drug delivery device should provide a large range of functionalities as well as a rather large storage capacity for capturing and storing electronic data representing measured physical or chemical parameters. In addition, the sensor and its interaction with the drug delivery device should enable a constant or frequent measurement of physical or chemical parameters of the cartridge according to a predefined schedule and independent of an external reader or some other external electronic device configured to communicate with the sensor and/or with the drug delivery device.

<CIT> discloses a device which is used to determine the filling level of a substance in an ampoule comprising at least two electrodes between which the substance can be introduced.

Document <CIT>, which has been published after the effective filing date of the present application, discloses an electronic device and method for connecting electronic circuit board.

The disclosure relates to a sensor and a drug delivery device as defined by the features of the independent claims. Additional features and numerous examples are subject matter of the respective dependent claims.

In a first aspect a sensor for measuring at least one physical or chemical parameter of a cartridge or syringe is provided, wherein the cartridge or syringe is filled with a liquid substance. Typically, the cartridge is filled with a liquid medicament.

The sensor comprises a planar flexible foil that is arrangeable to an outer circumference of a barrel of the cartridge or syringe. Furthermore, the sensor comprises at least a first and a second measuring electrode arranged on said foil. The electrodes are typically spatially separated from each other in order to enable an arrangement of first and second electrodes at radially opposite sections of a sidewall of the cartridge. Generally, the measuring electrodes may be of arbitrary shape. When arranged or attached to the outer circumference of the sidewall of the barrel the first and the second measuring electrodes are separated from each other, so that at least a portion of the cartridge and the liquid substance contained therein is located between first and second measuring electrodes. Furthermore, the sensor also comprises at least a first and a second contact electrode arranged on said foil. The first contact electrode is electrically connected to the first measuring electrode and the second contact electrode is electrically connected to the second measuring electrode. In this way the two contact electrodes provide a well-defined electrical contact to an electric energy supply and to a processor or further signal processing means, such like a transceiver that are arranged inside a drug delivery device to provide wireless communication of the processor with external devices.

The first and second contact electrodes particularly provide a wired energy supply to the first and second measuring electrodes. In addition, first and second contact electrodes also provide a wired transfer of electrical signals obtained or generated by the first and/or second measuring electrodes.

First and second contact electrodes provide a well-defined electric interface between the measuring electrodes and at least an electric power supply. Typically, the electric power supply is located outside and remote from the sensor. It is typically arranged inside a drug delivery device or it is typically attached to an outside-facing portion thereof. When the sensor is attached or assembled to the cartridge and when said cartridge is placed inside a drug delivery device the first and second contact electrodes will get in electrical contact with an electric power supply so as to enable a measurement of a physical or chemical parameter of the cartridge.

According to an embodiment the sensor just consists of the planar flexible foil, first and second measuring electrodes and first and second contact electrodes. In this way all further components of a sensor assembly that are necessary for actually measuring the physical or chemical parameter of the cartridge are located remote, e.g. in or at the drug delivery device. Especially with reusable drug delivery devices the sensor can thus be easily implemented as a disposable sensor permanently fastened or fixed to a cartridge. Upon emptying of the cartridge the entire cartridge with the sensor attached thereto is to be discarded. Since the sensor comprises nothing but a planar flexible foil and numerous electrodes and since the sensor is void of any further semi-conducting structures or materials a rather eco-friendly disposal as well as a rather cost efficient production thereof can be provided.

Rather expensive and comparatively spacious components of a sensor assembly can be provided remote outside the sensor but inside or attached to a drug delivery device. Due to the reusable characteristics of such a device typical components of a sensor assembly, such like an electric energy supply, a transceiver for data transmission as well as a processor for signal processing of the signals obtained by the measuring electrodes can be arranged in and permanently attached to the drug delivery device and can be sequentially used with multiple sensors or cartridges equipped with such sensors.

According to another embodiment the first and the second contact electrodes are arranged at a longitudinal end section of the foil. Typically, the planar flexible foil extends in a plane defined by a longitudinal direction (z) and a lateral or circumferential direction (u). Longitudinal and lateral directions typically extend perpendicular with respect to each other. The planar flexible foil is configured to be wrapped around or to be attached to the outer circumference of a sidewall of the barrel of the cartridge. When wrapped around or attached to the cartridge the longitudinal direction of the foil typically extends parallel to the longitudinal or axial direction of the axially elongated cartridge whereas the lateral or circumferential direction of the planar flexible foil extends along the tubular or circular circumference of the cartridge's sidewall.

By arranging first and second contact electrodes at a longitudinal end section of the foil the contact electrodes form a distal or a proximal end of the planar flexible foil. When attached or arranged at the outer circumference of the barrel of the cartridge the first and second contact electrodes are arranged at or near a distal end or at or near a proximal end of the tubular-shaped cartridge. In this way only a distal or proximal end section of the planar flexible foil is occupied by first and second contact electrodes. Consequently, a residual and major portion of the planar flexible foil can be used for the arrangement of the at least first and second measuring electrodes.

According to a further embodiment first and second contact electrodes are arranged at a common longitudinal end section of the foil. For instance, first and second contact electrodes are both arranged near or at a distal end of the foil. Alternatively, the first and second contact electrodes are arranged near or at a proximal end section of the foil.

The terms proximal and distal refer to the intended orientation of the planar flexible foil and the respective cartridge inside the drug delivery device. The distal direction denotes a dispensing end of the drug delivery device. When the drug delivery device is implemented as an injection device the distal end of the drug delivery device faces towards an injection site of a patient. The proximal end or the proximal direction faces in the opposite direction. When implemented as an injection device, such like a pen-type injector, the proximal end of the drug delivery device is operable by a hand of a user so as to configure, to set and to conduct an injection procedure.

In another embodiment first and second contact electrodes are arranged at opposite longitudinal end sections of the foil. In such an embodiment it is conceivable that for instance the first contact electrode is located at a proximal end of the planar flexible foil whereas the second contact electrode is located at a distal end of the planar flexible foil. Here, the at least two contact electrodes form a longitudinal confinement of the planar flexible foil with the at least first and second measuring electrodes positioned therebetween. The specific arrangement and position of first and second contact electrodes on the foil depends on the specific implementation of the entire sensor assembly and the specific configuration of the cartridge and the respective drug delivery device. Typically, first and second contact electrodes are arranged in such a position on the planar flexible foil that an electrical contact is formed between the contact electrodes and the electric energy supply when the cartridge equipped with the planar flexible foil is correctly assembled inside the drug delivery device.

According to another embodiment the first and the second contact electrodes are separated in a longitudinal direction and extend substantially parallel in a lateral or circumferential direction. By separating first and second contact electrodes in longitudinal direction each contact electrode can be electrically connected separately to the electric energy supply, e.g. by means of first and second contact elements that are correspondingly positioned and arranged at a respective axial distance in or at the drug delivery device. Moreover, since first and second contact electrodes extend substantially parallel to each other in the lateral or circumferential direction a ringshaped contact electrode structure can be formed on the outer circumference of the cartridge when the planar flexible foil is wrapped around the sidewall of the cartridge's barrel.

Typically, the wrap of the planar flexible foil and the lateral or circumferential extension of first and second contact electrodes are such that each electrode almost forms a closed ring along the outer circumference of the cartridge's barrel, wherein said ring is located in a single transverse plane extending substantially perpendicular to the longitudinal or axial direction of the flexible foil's wrap or of the cartridge's barrel. In this way each one of the first and second contact electrodes forms a specific axial contact structure that is rotationally invariant as the cartridge is positioned at an arbitrary orientation in the drug delivery device.

According to a further embodiment first and second electrodes extend almost across the entire lateral dimension of the foil. Typically, the entire lateral dimension of the foil almost exactly matches and corresponds to the outer circumference of the barrel of the cartridge. Typically, the planar flexible foil is wrappable around the outer circumference of the barrel without overlap but by covering almost the entire outer circumference of the barrel. When first and second electrodes extend almost across the entire lateral dimension of the foil a substantially closed first and second electrode structure can be obtained. In this way a rotation invariant contact electrode structure can be provided on the outer circumference of the cartridge.

In other embodiment where for instance at least one of the first and second contact electrodes is wrapped around the cartridge in such a way that a small gap remains between oppositely located lateral ends of the contact electrodes the corresponding contact elements of the drug delivery device have a lateral extension exceeding the lateral gap size. In this way, an electrical contact between the contact elements and the contact electrodes is always provided with any arbitrary rotational orientation of the cartridge relative to the contact elements inside the drug delivery device.

In another embodiment the foil is substantially transparent. Furthermore, at least one of the first and second measuring electrodes or at least one of the first and second contact electrodes comprise a printed or coated conductive structure on the foil or in the foil.

The foil itself is typically electrically insulating. In this way the foil actually acts as a flexible planar substrate or as a mechanical support for both the at least first and second measuring electrodes as well as for the at least first and second contact electrodes. By having all electrodes printed or coated on or in the planar flexible foil the various electrodes, namely the first and second measuring electrodes as well as the first and second contact electrodes are inherently correctly positioned relative to each other. A relative position and/or relative orientation of first and second measuring electrodes as well as of first and second contact electrodes permanently persists and may only be subject to a well-defined modification as the initially planar flexible foil is wrapped around the outer circumference of the cartridge's barrel.

The electrodes may comprise a suitable conductive material, such like aluminum, gold, silver or mixtures and alloys thereof. The electrodes may be printed on the flexible foil, e.g. by way of screen printing. Alternatively, they may be coated on the planar flexible foil by any suitable thin film-depositing technology, such like sputtering, spray coating or by means of various chemical vapor-depositing techniques. The foil typically comprises or is made of a transparent polymer. The foil may comprise at least one or a combination of the materials: polycarbonate, polyamide or polyvinyl chloride (PVC).

According to a further embodiment the first and second measuring electrodes and the first and second contact electrodes are located on a common side of the foil. Alternatively, the first and second measuring electrodes are located on one side of the foil and the first and second contact electrodes are located on an opposite side of the foil. The first and second measuring electrodes are always located on the same side of the foil. Also, first and second contact electrodes are always located on the same and common side of the flexible foil.

The first and second contact electrodes are typically arranged on an outside-facing side of the planar flexible foil when the foil is wrapped around the outer circumference of the barrel of the cartridge. With such a configuration it is generally conceivable that the measuring electrodes are also located on the outside-facing side of the wrapped foil. When implemented as capacity measuring electrodes the planar flexible foil is dielectric or permeable to dielectric charges.

In another embodiment it is conceivable that the at least first and second contact electrodes are located on an outside-facing portion of the wrapped foil whereas the at least first and second measuring electrodes are located on an inside-facing portion of the wrapped foil. In such an embodiment it is conceivable that the planar flexible foil comprises a multilayer structure, wherein at least one conductor electrically connecting the first measuring electrode with the first contact electrode extends through the planar flexible foil.

In another embodiment the at least two measuring electrodes are configured as electrical capacity measuring electrodes or as temperature measuring electrodes. When implemented as electrical capacity measuring electrodes the first and the second measuring electrodes typically extend all along the longitudinal extension of the cartridge when the foil is wrapped around the cartridge's barrel. The measuring electrodes may comprise a substantially rectangular structure with a lateral or circumferential extension that is less than half of the circumference of the tubular-shaped barrel. Typically, first and second measuring electrodes are of substantially identical geometric shape.

Apart from a substantially rectangular structure the measuring electrodes may also comprise a tapered structure in axial direction. Moreover, the electrodes might be trapezoidal, triangular or may comprise a combination of a rectangular and a triangular shape. Especially by making use of electrodes having a geometric structure changing constantly in axial direction a respective linearly changing capacity signal is obtainable as for instance the piston of the cartridge is subject to a linear axial displacement in the course of a dispensing procedure. The geometric shape of the electrodes may hence improve the accuracy and precision of the capacity measurement.

Moreover, it is conceivable that there are arranged multiple measuring electrodes along the longitudinal extension of the planar flexible foil, wherein pairs of measuring electrodes located at the same or at overlapping longitudinal positions are pair-wise connectable to a specific processor. By means of multiple pairs of first and second measuring electrodes, wherein said pairs are arranged at different longitudinal positions along the outer circumference of the cartridge's barrel a spatial resolution of an electric capacity measurement and hence a rather high spatial resolution of a position of a piston can be measured and determined by a processor connectable to the various pairs of measuring electrodes.

When implemented as temperature measuring electrodes the electrodes may comprise pairs of heaters and thermistors that are pair-wise and alternately arranged in longitudinal direction along the cartridge's sidewall. Typically, the first measuring electrode may comprise several parallel oriented but longitudinally separated heaters whereas the second electrode may comprise correspondingly arranged thermistors placed longitudinally between the heaters of the first measuring electrode. By means of the first electrode thermal energy can be deposited to the sidewall of the cartridge and by means of the various thermistors, hence by means of the second electrode, temperature irregularities caused by the position of the piston inside the cartridge can be measured and determined. Typically, each branch of first and second electrodes forming a heater or a thermistor is separately connectable to a processor of the sensor assembly. In this way a thermal excitation and a heat transfer across the sidewall of the cartridge can be monitored with a spatial resolution in accordance to the distance of neighboring branches of first and second electrodes. When configured and implemented as temperature measuring electrodes the measuring electrodes act as a thermal sensing array or like a thermal flow sensor.

Implementation of such a temperature measuring arrangement is of particular benefit when sufficient electrical power can be supplied by the electric energy supply. By implementing the electric energy supply in the drug delivery device, e.g. in form of a battery, a solar cell or combinations thereof, sufficient electrical power for a temperature measurement can be easily provided in a rather cost efficient way.

According to another aspect the invention relates to a cartridge comprising a tubular-shaped barrel filled with a liquid substance, typically filled with a liquid medicament. The cartridge further comprises a sensor as described above which is wrapped around the outer circumference of the sidewall of the barrel.

The cartridge to which the sensor is arrangeable or attachable may comprise a tubular-shaped barrel, e.g. made of glass or some other material substantially inert to the liquid substance contained therein. The cartridge may comprise a distally-located and pierceable outlet sealed by a pierceable septum so as to obtain access to the interior of the cartridge by way of puncturing the distal seal by means of a piercing assembly, such like a double-tipped injection needle. Opposite the distal outlet the cartridge, in particular its tubular-shaped barrel, is typically sealed by a piston slidably displaceable inside the cartridge. The piston is slidably displaceable in distal direction relative to the barrel under the effect of a distally-directed driving force, typically exerted by a plunger or piston rod of the drug delivery device advancing in distal direction, thereby exerting a distally-directed pressure to said piston. The sensor is particularly dedicated to such cartridges but could also be used otherwise, e.g. for other types of medicament containers, including vials, ampoules, bottles or flexible bags.

The assembly of cartridge and sensor may be configured as a disposable unit, which after consumption or dispensing of the content of the cartridge is to be discarded in its entirety. Typically and since the flexible foil of the sensor is substantially transparent, a filling level of the cartridge is also visually inspectable even when the sensor, hence the flexible foil with electrodes thereon is attached to the cartridge. The electrodes may also be of transparent type. For instance, the electrodes may comprise or may consist of indium-tin oxide (ITO) that is conductive and substantially transparent. The visual inspectability of the interior of the cartridge even with the sensor completely covering the cartridge's sidewall is of particular benefit in order to provide an intuitive control whether the content of the cartridge, in particular the liquid medicament, might be subject to coagulation or flocculation or some other detrimental effects or phenomena.

In another embodiment the sensor is permanently attached to the cartridge and covers the complete tubular-shaped sidewall portion thereof. In such a configuration it may be of particular benefit when the sensor, in particular the planar flexible foil is provided with a visual scale that may be persistently printed on an upper side or lower side of the flexible foil. The scale may comprise various symbols, numbers or other signs in order to visually display a momentary filling level of the cartridge. By providing a scale, e.g. with numerous equidistantly arranged scale items typically separated along the axial or longitudinal direction of the flexible foil there is no longer a need to provide such scale items directly on the outer circumference of the, e.g. vitreous barrel. By providing a visual scale on the sensor, in particular on the flexible foil of the sensor and by attaching the sensor in a well-defined, precise and highly reproducible way on the outer circumference of the cartridge's barrel a rather cost efficient, straight forward and easy way of providing visually perceptible scale items on a vitreous barrel is provided.

According to a further embodiment the sensor, in particular its planar flexible foil is adhesively attached to the barrel of the cartridge. The adhesive agent for the adhesive attachment of sensor and cartridge may be provided on one side of the foil that faces radially inwardly as the foil is wrapped around the tubular-shaped cartridge.

The adhesive may be located on a side of the foil opposite to the first and second measuring electrodes. In such a configuration the measuring electrodes are located on an outside-facing side of the foil facing radially outwardly as the foil is wrapped around the cartridge. Alternatively, it is also conceivable that the measuring electrodes are located on an inside-facing portion of the wrapped foil. Then, the adhesive agent may be located longitudinally and/or circumferentially between the measuring electrodes. It is also conceivable, that the adhesive is located radially between the outer circumference of the barrel of the cartridge and the measuring electrodes of the sensor as the sensor is wrapped around the barrel.

According to another embodiment the contact electrodes of the sensor are located on an outwardly-facing side of the foil as the sensor is wrapped around the tubular-shaped barrel. In this way the contact electrodes are easily accessible from outside the cartridge for establishing an electrical connection between first and second measuring electrodes and at least the electric energy supply, the processor and/or a transceiver of the sensor assembly.

According to another aspect the invention further relates to a drug delivery device for administering a dose of a liquid medicament. The drug delivery device comprises a housing to accommodate a cartridge as described above, wherein the cartridge is filled with the liquid medicament and comprises a piston slidably received in the barrel of the cartridge. The drug delivery device further comprises a drive mechanism typically having a piston rod or a plunger to exert a distally-directed driving force on the piston of the cartridge for expelling of a dose of the liquid medicament via a distally-located outlet of the cartridge. The outlet of the cartridge is connectable with a piercing assembly, typically comprising a double-tipped injection needle by way of which fluid transferring access to the interior of the cartridge is obtainable and by way of which the medicament expelled from the cartridge can be directly injected into biological tissue.

Typically, the drug delivery device is configured as an injection device, such like a pen-type injector that provides individual and variable setting and subsequent dispensing of a dose of a medicament of variable and user-settable size.

Furthermore, the drug delivery device comprises an electrical energy supply electrically connectable to the first and second contact electrodes of the sensor when the sensor attached to the cartridge is located inside the drug delivery device. The drug delivery device further comprises a processor connected to the electrical energy supply. The processor is configured to obtain and to process electrical signals obtainable from the sensor as the sensor is supplied with electrical energy when in electrical contact with the electrical energy supply. The processor, e.g. configured as microcontroller, comprises a storage or a memory to store a sequence of measurement data. In addition, the processor is typically programmable so as to automatically conduct various measurement routines, e.g. in accordance with a predefined schedule. For instance, the processor may be programmed to conduct and to initiate temperature and/or content measurements of the cartridge at regular time intervals, such like several times a day, for instance every second hour. In this way environmental parameters, such like the temperature the cartridge is exposed to can be sequentially and constantly monitored.

In addition, the drug delivery device also comprises a transceiver connected to the processor. The transceiver is configured for wireless communication with an external device, such like a computer, a tablet computer, a mobile phone, a smartphone or a smartwatch or comparable personal electronic devices. The transceiver may be implemented as a radio-frequency (RF) transponder to communicate with the external electronic device via standardized communication protocols, such like Bluetooth, Wi-Fi or NFC. Alternatively, the transceiver may be implemented as an optical transmitter, e.g. operating in the infrared spectral range. In such a configuration the transceiver may comprise an IRDA interface. The arrangement of transceiver and processor may constitute or form an active RFID chip or an active RFID tag that is electrically powered by the electrical energy supply.

According to another embodiment the housing of the drug delivery device comprises a cartridge holder in which the cartridge is assembled. When implemented as a reusable device the housing of the drug delivery device typically comprises a proximally-located body releasably connectable to a distally-located cartridge holder. By disconnecting or by releasing cartridge holder and body a cartridge can be assembled inside the cartridge holder. As the medicament contained in the cartridge has been completely dispensed the cartridge can be replaced by a new one. For this the cartridge holder can be disconnected or released from the housing.

After exchanging an empty cartridge from the proximal end of the cartridge holder by a new one the cartridge holder can be re-attached or re-assembled to the body of the housing. Moreover, and according to a further embodiment, the drug delivery device is configured as a disposable device. Here, the cartridge with the sensor attached thereto is readily and initially arranged inside a cartridge holder, which cartridge holder is irreleasably and hence permanently connected to the body of the housing. In the present context an irreleasable connection means a connection non-detachable connection that is only separable by brute force methods and by destroying the integrity of at least one of cartridge holder and housing of the drug delivery device.

When implemented as a disposable device it is of particular benefit that electronic components of the sensor assembly, hence the processor, the electric energy supply as well as the transceiver are located in a separate accessory device that is detachably connectable to the housing of the drug delivery device. In this way the sensor assembly can be repeatedly used and attached to various disposable drug delivery devices on demand.

In another embodiment the transceiver and the processor are configured as a passive RFID chip or passive RFID tag. Here, the transceiver is operable and/or configured to withdraw and to obtain electrical energy from a RF field in the vicinity and to provide electrical energy to the processor and/or to the electrodes in order to conduct a measurement and/or to process measurement data obtained from the contact electrodes and/or to transmit the measured or processed data to another electronic device.

In effect, the sensor assembly can be implemented as a hybrid-type of active and passive RFID of NFC assembly. It may be constantly powered by the electrical energy supply, e.g. for a regular storage of data at predefined time intervals and independent of the presence of a RF field in close vicinity. In addition, the sensor assembly can be configured to obtain and to derive electrical energy via the transceiver when exposed to a RF field that may be provided and generated by an external electronic device, such like a smartphone. Such a passive behavior may be of particular use to save energy and to optimize the power management of the device. The battery lifetime could be prolonged in this way.

It is of particular benefit when the processor and the transceiver are configured to switch into a passive mode per default and to operate as long as possible on the basis of electrical energy derived from an applied RF field. In situations where a suitable RF field is not present the processor may conduct or trigger a measurement procedure on the basis of electrical energy obtained from the electrical energy supply, e.g. from a battery. It is also conceivable that the electrical energy supply, hence a battery, constantly keeps the processor powered, e.g. for monitoring the status or a dose history of the cartridge or syringe. Only when obtaining additional electrical power from a RF field the processor and the transceiver will then communicate wirelessly with an external electronic device. Such an approach would be fery energy efficient thus prolonging the lifetime of a battery.

According to a further embodiment the drug delivery device also comprises at least one operating element electrically connected to the energy supply to the processor or the transceiver to initiate a sensor-based measurement or to initiate a communication with an external electronic device by means of the transceiver. The operating element is user-actuatable. It may comprise a push button or a dial that is user-actuatable in order to trigger a measurement or a communication, e.g. a data exchange with the external electronic device. Additionally or alternatively, the operating element may be also software implemented in the external electronic device. Upon establishing a communication link between the external electronic device and the processor of the sensor assembly the operating element may be presented as a user selectable menu item, e.g. on a display of the external electronic device.

By means of the operating element a manual and user-actuatable measurement of the at least one physical or chemical parameter of the cartridge and in particular of the liquid substance contained therein can be triggered and initiated on request.

According to another embodiment the electrical energy supply comprises a compartment housing a battery and a first and a second contact element, each of which being electrically connectable to the battery. First and second contact elements further extend through a through opening of the housing to electrically connect with the first and with the second contact electrodes of the sensor, respectively. Typically, the compartment is accessible from outside via a detachable or releasable closure. Detaching or opening of the closure provides access to the interior of the compartment. In this way an empty battery could be exchanged or replaced by a new one. Additionally or alternatively, the battery may be rechargeable battery and the electrical energy supply may be further equipped with a solar cell or with some other kind of recharging means to accumulate, to generate and to store electrical energy in the battery.

In a further embodiment the compartment is integrated into a cartridge holder, in a protective cap detachably covering at least a distal end of the cartridge holder or the compartment is integrated in an accessory device detachably connectable to the housing. Typically, the accessory device may comprise at least one fastening clip by way of which the accessory device is detachably connectable to a particular portion of the housing of the drug delivery device. The accessory device is attachable to a body of the housing of the drug delivery device. Here, the accessory device may extend towards and to radially overlap with the cartridge holder of the housing of the drug delivery device. So when the compartment is integrated into the cartridge holder or in the accessory device it is the cartridge holder that comprises a through opening in a sidewall portion so that an electrical contact between first and second contact electrodes of the sensor attached to the cartridge and first and second contact elements of the electrical energy supply can be provided.

In an alternative embodiment the compartment is integrated into a protective cap detachably covering at least a distal end of the cartridge holder. Here, the protective cap as well as the cartridge holder comprise a through opening through which an electrical contact between first and second contact elements of the electrical energy supply and first and second contact electrodes of the sensor can be established, respectively.

The term 'sensor assembly' as used herein defines a system including the sensor with measuring electrodes and contact electrodes, an electric energy supply, a processor and a transceiver. Operation and completion of the sensor assembly is obtained as the cartridge equipped with the sensor is assembled inside the drug delivery device, thereby establishing electrical contact between the first and second contact electrodes and the electric energy supply.

Typically, at least the planar flexible foil with first and second measuring electrodes and with at least first and second contact electrodes is assembled and permanently fastened to the cartridge whereas other electronic components of the sensor assembly are assembled in the drug delivery device or wherein such electronic components are attached to the drug delivery device. In this way the sensor assembly can be split and separated among various components of the drug delivery device, namely the housing of the drug delivery device and the cartridge that may be replaceable or exchangeable.

The sensor and its planar flexible foil may be implemented as a kind of a label, which in addition to the measuring capability of at least one physical or chemical parameter of the cartridge is also operable to label or to distinguish the cartridge from other identically shaped cartridges. As the electric energy supply is integrated into the drug delivery device it does not have to be provided on said label. In this way the label can be kept small and requires only a minimum of space. Driving of the sensor by means of an electric energy source located remote from the sensor allows for a relatively complex and multifunctional sensor implementation.

The remotely-located electrical energy supply, e.g. comprising a battery, provides and enables sensor functionalities such like the creation of a dose history which may be stored in the processor or in a separate memory cell connected to the processor. On demand, a captured or recorded dose history can be transmitted to an external electronic device, such like a smartphone or a computer via the transceiver of the sensor assembly. It is generally to be mentioned that the sensor is not only capable to determine the filling level of the cartridge but that the electrodes thereof may be configured to conduct optical transmission measurements so as to inspect cloudiness, formation of aggregations, or the mixing status of constituted lyophilisates contained inside the cartridge. In such embodiments it is conceivable that at least one of the first and second measuring electrodes comprises a photo detector whereas the other one of first and second electrodes is implemented as a light transmitting device.

By arranging the electric energy supply and the transceiver in or on the drug delivery device the energy supply and the transceiver can be of reusable type whereas the sensor attached to the cartridge may be of disposable type. By establishing an electric contact between the electric energy supply and the sensor upon assembly of the cartridge inside the drug delivery device the processor can be permanently or frequently powered as long as the cartridge is positioned inside the drug delivery device. In this way the processor and the sensor can be operated to permanently collect and to permanently or frequently capture or store cartridge-related data during the entire lifetime of the cartridge. Such data may include the dose history as well as the temperature history of the cartridge. A wireless transmission of collected data may be frequently conducted either on external request or regularly according to a predefined schedule, e.g. stored in the processor.

Hormones are for example hypophysis hormones or hypothalamus hormones or regulatory active peptides and their antagonists as listed in <NPL>, such as Gonadotropine (Follitropin, Lutropin, Choriongonadotropin, Menotropin), Somatropine (Somatropin), Desmopressin, Terlipressin, Gonadorelin, Triptorelin, Leuprorelin, Buserelin, Nafarelin, Goserelin.

Antibodies are globular plasma proteins (~150kDa) that are also known as immunoglobulins which share a basic structure. As they have sugar chains added to amino acid residues, they are glycoproteins. The basic functional unit of each antibody is an immunoglobulin (Ig) monomer (containing only one Ig unit); secreted antibodies can also be dimeric with two Ig units as with IgA, tetrameric with four Ig units like teleost fish IgM, or pentameric with five Ig units, like mammalian IgM.

It will be further apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope of the invention as it is defined by the claims. Further, it is to be noted, that any reference numerals used in the appended claims are not to be construed as limiting the scope of the invention.

In the following, an embodiment of the display arrangement, the drive mechanism and the drug delivery device is described in detail by making reference to the drawings, in which:.

The drug delivery device <NUM> as illustrated for instance in <FIG> is implemented as a pen-type injector. The drug delivery device <NUM> is a handheld drug delivery device. It comprises a housing <NUM>, which housing <NUM> comprises various parts. As shown in <FIG>, the housing <NUM> actually includes or comprises a cartridge holder <NUM> and a body <NUM>. Both, the cartridge holder <NUM> as well as the body <NUM> are of substantially tubular shape. As illustrated in the various Figs. a proximal end of the cartridge holder <NUM> is connectable to a distal end of the body <NUM>. The cartridge holder <NUM> comprises a window <NUM> in a sidewall allowing to visually inspect the cartridge <NUM> to be assembled therein.

At its distal end the cartridge holder <NUM> comprises a threaded socket <NUM>. At its distal end face the cartridge holder <NUM> further comprises a through opening <NUM> through which a proximally-extending tipped end of a double-tipped injection needle may extend in order to pierce a distal seal <NUM> of the cartridge <NUM>. In <FIG> the proximal direction is denoted P and the distal direction is denoted D. The cartridge <NUM> as shown in <FIG> comprises a tubular-shaped barrel <NUM> having a tubular-shaped sidewall <NUM>, which in distal direction D extends into a stepped down neck portion <NUM>. At the distal end of the stepped down neck portion <NUM> there is provided a pierceable seal <NUM>, typically implemented as a pierceable septum.

The proximal end of the cartridge <NUM> is sealed by a piston <NUM> as illustrated in <FIG>. The piston <NUM> is frictionally engaged with the inside-facing portions of the sidewall <NUM> of the barrel <NUM> of the cartridge <NUM>. The piston <NUM> is slidably received inside the barrel <NUM> of the cartridge <NUM>. When assembled inside the cartridge holder <NUM> the vitreous barrel <NUM> of the cartridge <NUM> is visually inspectable through the window <NUM> of the cartridge holder <NUM>. The cartridge <NUM> is axially secured or axially fastened inside the cartridge holder <NUM> through an axial abutment of the radially narrowing neck portion <NUM> getting in axial abutment with a correspondingly-shaped diameter-reduced socket <NUM> of the cartridge holder <NUM>. The threaded socket <NUM> is threadedly engageable with a correspondingly-threaded needle hub that is releasably and detachably connectable to the cartridge holder <NUM> for dispensing of a dose of the medicament <NUM> located inside the cartridge.

As the cartridge <NUM> is arranged and fixed inside the cartridge holder <NUM> and when the cartridge holder <NUM> is attached to the body <NUM> a drive mechanism <NUM> of the drug delivery device <NUM> located inside the body <NUM> is operable to exert distally-directed thrust to the piston <NUM> so that a well-defined dose of the liquid substance or medicament <NUM> can be expelled from the cartridge <NUM> via the injection needle or piercing assembly in fluid communication with the interior of the cartridge <NUM>.

Typically, the drive mechanism <NUM> comprises at least a piston rod to advance in distal direction D. The drive mechanism <NUM> may be implemented in many different ways. It may be fully mechanically implemented so that a driving force acting on the piston <NUM> is exclusively provided e.g.by a thumb of a user actually depressing a proximally protruding dispensing button <NUM> located at a proximal end face of the body <NUM>. In addition there may be provided a dose dial <NUM> by means of which a user may individually set a dose of variable size. Additionally, the drive mechanism <NUM> typically comprises a dose indicating window through which a rotatable dose indicating scale is visible.

Other implementations of the drive mechanism <NUM> may include a power-assisted dispensing. There, a driving force for advancing the piston rod in distal direction D may be provided or supported by a mechanical energy storage means, such like a spring, which may be pre-tensed upon a final assembly of the drug delivery device <NUM>. It is also conceivable, that a mechanical energy storage means, such like a spring is repeatedly biased during a dose setting procedure. In this case, dialing of the dose dial <NUM> serves to bias or to stress a dispensing spring. Further implementations of the drive mechanism <NUM> may include electromechanical means, such like electric drives that are operable to assist or to contribute to the advancing motion of the piston rod. Alternatively, the dispensing force acting on the piston or on the respective piston rod may be completely provided by a respective electrical drive.

As it is apparent from <FIG> and <FIG> there is provided a sensor <NUM> having a planar flexible foil <NUM> which is wrappable around the outer circumference of the barrel <NUM> of the cartridge <NUM>. The sensor <NUM> is part of a sensor assembly <NUM> and serves to measure at least one physical or chemical parameter of said cartridge <NUM>. Typically, the sensor <NUM> is implemented as a fill level sensor to measure the fill level of the cartridge, typically by way of determining and by way of measuring the actual axial position of the piston <NUM> inside the cartridge <NUM>. In addition or alternatively, the sensor <NUM> is implemented as a temperature sensor.

The sensor <NUM> comprises at least a first and a second measuring electrode <NUM>, <NUM>. The measuring electrodes <NUM>, <NUM> extend substantially parallel along a longitudinal direction (z). They are separated in circumferential direction (u) by a predefined distance that corresponds to the circumference of the sidewall <NUM> of the barrel <NUM> of the cartridge <NUM>. Typically, the lateral or circumferential distance between the parallel oriented first and second measuring electrodes <NUM>, <NUM> is selected such that when the sensor <NUM> is wrapped around the tubular portion of the sidewall <NUM> of the cartridge <NUM> first and second measuring electrodes <NUM>, <NUM> are diametrically oppositely-located on the outer circumference of the sidewall <NUM> of the cartridge <NUM>.

In this way, the cartridge <NUM> and the liquid substance <NUM> located therein are somewhat sandwiched between the first and the second measuring electrode <NUM>, <NUM>. The planar flexible foil <NUM> is typically transparent. It is also conceivable that the first and second measuring electrodes <NUM>, <NUM> are substantially transparent. In this way visual inspection of the vitreous and transparent cartridge <NUM> is not impeded when the sensor <NUM> is wrapped around the cartridge <NUM>. In addition to the at least first and second measuring electrodes <NUM>, <NUM> the sensor <NUM> further comprises a first and a second contact electrode <NUM>, <NUM> also arranged on said planar flexible foil <NUM>.

As it is shown in detail in <FIG>, first and second contact electrodes extend substantially perpendicular to the elongation of first and second measuring electrodes <NUM>, <NUM>. Moreover, first and second contact electrodes <NUM>, <NUM> extend along a longitudinal end section <NUM> of the planar flexible foil <NUM>. First and second contact electrodes <NUM>, <NUM> are actually separated by a small axial gap. Moreover, first and second contact electrodes <NUM>, <NUM> comprise a longitudinal straight-lined extension. When the sensor <NUM> is wrapped around the outer circumference of the sidewall <NUM> of the barrel <NUM> the first contact electrode106 as well as the second contact electrode <NUM> form a substantially closed ring structure. Such a ring structure allows for a rotation invariant arrangement of the cartridge <NUM> inside the cartridge holder <NUM> whilst guaranteeing an electric contact to an electric energy supply <NUM> as for instance shown in <FIG> or <FIG>.

The planar flexible foil <NUM> may be adhesively attached to the outer circumference of the sidewall <NUM> of the cartridge <NUM>. When attached to the cartridge <NUM> the first and second contact electrodes <NUM>, <NUM> are located on an outside-facing side 101b of the foil <NUM> so as to provide electric contacting from outside the sensor <NUM>. The measuring electrodes <NUM>, <NUM> may be located on the same side as the contact electrodes <NUM>, <NUM>. Alternatively it is conceivable that at least the first and the second measuring electrodes <NUM>, <NUM> are located on an inside-facing side 101a of the foil <NUM>. In such an embodiment the measuring electrodes <NUM>, <NUM> would get in direct mechanical contact with the outer circumference of the sidewall <NUM> of the cartridge <NUM>.

When the contact electrodes <NUM>, <NUM> and the measuring electrodes <NUM>, <NUM> are located on a common side 101b of the foil <NUM>, manufacturing and production of the sensor <NUM> can be implemented in a rather simple and cost efficient way. For instance, all electrically conductive structures, such like first and second measuring electrodes <NUM>, <NUM> as well as first and second contact electrodes <NUM>, <NUM> together with various conductors <NUM> extending therebetween can be printed or coated in a single step onto the planar flexible foil <NUM>.

The sensor <NUM> is a component of a sensor assembly <NUM>. The sensor assembly <NUM> comprises the sensor <NUM>, an electric energy supply <NUM>, a processor <NUM> and a transceiver <NUM>. In all embodiments as illustrated in the various Figures the sensor <NUM> only comprises the first and second measuring electrodes <NUM>, <NUM> as well as the at least first and second contact electrodes <NUM>, <NUM>. All residual components of the sensor assembly <NUM> are located and arranged in the housing <NUM> of the drug delivery device <NUM>. In some embodiments, the residual components of the sensor assembly <NUM> are attached or are attachable to the housing <NUM> of the drug delivery device <NUM>. The residual components may be arranged inside or at an accessory device <NUM> that might be fastened to the housing <NUM> of the drug delivery device <NUM>, e.g. by way of a fastening clip <NUM> as for instance shown in <FIG>.

At least the electric energy supply <NUM> is located on or in the housing <NUM> of the drug delivery device <NUM>. Typically, the electric energy supply <NUM> comprises at least one battery <NUM>, presently illustrated as a button battery.

The sensor assembly <NUM> is completed and becomes operable as the cartridge <NUM> equipped with the sensor <NUM> is correctly assembled inside the drug delivery device <NUM>, in particular inside the cartridge holder <NUM>. Then, the electric energy supply <NUM> is electrically connected to the sensor <NUM>. At least two contact elements <NUM>, <NUM> provided in or on the housing <NUM> of the drug delivery device <NUM> extend through a through opening <NUM> of the housing <NUM> and get in direct electrical contact with the contact electrodes <NUM>, <NUM> on the outer circumference of the cartridge <NUM> as it is for instance illustrated in <FIG>. There, the contact element <NUM> implemented as a contact spring extends through a through opening <NUM> of the sidewall of the cartridge holder <NUM> and gets in direct mechanical and electrical contact with the first contact electrode <NUM>.

The further contact element <NUM> will get in electric contact with the second contact electrode <NUM> accordingly. Since first and second contact electrodes <NUM>, <NUM> are separated in axial or longitudinal direction (z) also the radially-inwardly protruding portions of the contact springs of first and second contact elements <NUM>, <NUM> will be located axially offset with respect to each other. The axial position of the contact elements <NUM>, <NUM> directly matches and corresponds to the axial position of first and second contact electrodes <NUM>, <NUM> on the outer circumference of the cartridge <NUM>.

As the contact elements <NUM>, <NUM> are in electrical contact with the battery <NUM> the sensor <NUM> can be supplied with electrical energy upon establishing said electric contact between the contact elements <NUM>, <NUM> and the respective contact electrodes <NUM>, <NUM>.

The sensor assembly <NUM> further comprises a processor <NUM>, which in the present embodiment is located in or on the housing <NUM> of the drug delivery device <NUM>. In addition, the sensor assembly <NUM> comprises a transceiver <NUM> that is located and arranged in or on the housing <NUM> of the drug delivery device <NUM>. In the present embodiment the transceiver <NUM> is permanently connected to the processor <NUM> and optionally also to the battery <NUM> of the electric energy supply <NUM>. It is upon a correct assembly of the cartridge <NUM> inside the housing <NUM> that an electrical contact between the measuring electrodes <NUM>, <NUM> and the processor <NUM> is established. The processor <NUM> may be permanently electrically connected to the transceiver and/or to the battery <NUM>.

In any case and since the battery <NUM> of the electric energy supply <NUM> is located on or in the housing <NUM> it is remote from the sensor <NUM>. The design of the sensor <NUM> can thus be simplified and a low cost sensor can be implemented while offering a large spectrum of functionalities that will be possible with a battery-driven processor <NUM>.

As it is further illustrated in <FIG> the electric energy supply <NUM> comprises a compartment <NUM> located on the outer circumference of a proximal portion of the cartridge holder <NUM>. The compartment <NUM> actually accommodates the battery <NUM>, the contact elements <NUM>, <NUM>, the processor <NUM> and the transceiver <NUM>. The compartment <NUM> is closable by a closure <NUM>, implemented as a detachable or as a pivotable lid. On a user's request the closure <NUM> can be opened so as to provide access to the interior of the compartment <NUM>. In this way, an empty battery <NUM> may be replaced by a new one. Making use of a separate compartment <NUM> for at least a part of the electric components of the sensor assembly <NUM> further allows to provide a wired interface on the outer circumference of the housing <NUM> of the drug delivery device <NUM>.

Instead of a wireless transceiver <NUM> it is conceivable to provide a standardized wired connector by way of which a wired data transmission may be established to an external electronic device <NUM>. The sensor assembly <NUM> may be further equipped with an operating element <NUM> as indicated in <FIG>, which operating element <NUM> may be accessible from outside the drug delivery device <NUM>. The operating element <NUM> may be electrically connectable or may be permanently electrically connected to the processor <NUM>, to the transceiver <NUM> or to the battery <NUM>. By way of actuating the operating element <NUM> a measurement process conducted by the processor <NUM> and/or a data transmitting operable by the transceiver <NUM> can be triggered. Even though not explicitly shown, the operating element <NUM> can be also implemented with the drug delivery device <NUM> and <NUM> as illustrated in <FIG>.

The transceiver <NUM> is typically implemented as a wireless transceiver or transponder operable to exchange data and to communicate with an external electronic device <NUM>, such like a mobile phone, a smartphone, a smartwatch, a tablet computer or any other kind of computer or communication system.

The sensor <NUM> as for instance shown in <FIG> is typically implemented as a capacitance measuring sensor. For this, the at least first and second measuring electrodes <NUM>, <NUM> extend almost along the entirety of the longitudinal extension of the flexible foil <NUM>. The electrical capacitance to be measured between these two measuring electrodes <NUM>, <NUM> when wrapped around the cartridge <NUM> depends on the axial position of the piston <NUM> exhibiting an electric susceptibility or permittivity that is distinguishable from the electric susceptibility of the liquid substance <NUM> located inside the cartridge <NUM>.

The alternative embodiment of a sensor <NUM> as shown in <FIG> is implemented as a temperature sensor. There, the first measuring electrode <NUM> comprises various heaters 102a and the second measuring electrode <NUM> comprises multiple thermistors 104a. As shown in <FIG>, the various heaters 102a and thermistors 104a are alternately arranged in longitudinal direction (z) so as to form an alternating array of heaters 102a and thermistors 104a in longitudinal or axial direction. In this way, the sensor <NUM> is implemented as a thermal flow sensor. When connected to the electric energy supply <NUM> the heaters 102a may selectively or simultaneously induce a small but distinct heating of a respective portion of the sidewall <NUM> of the cartridge <NUM>. This change in temperature is detectable by the array of thermistors 104a. In this way and due to the different thermal conducting properties of the piston <NUM> and the liquid substance <NUM> contained therein the longitudinal position of the piston <NUM> inside the cartridge <NUM> could be also determined by way of a temperature measurement. Alternatively and additionally a temperature level the entire cartridge <NUM> is exposed to can be determined even without making use of a series of heaters 102a.

In <FIG> another embodiment of attaching the sensor <NUM> to a cartridge <NUM> is illustrated. There, and contrary to the embodiment as shown in <FIG> the sensor <NUM> is flipped by <NUM>° so that the first and second contact electrodes <NUM>, <NUM> are located near a distal end of the cartridge <NUM>. This configuration of sensor <NUM> and cartridge <NUM> is particularly provided for the embodiment of the drug delivery device <NUM> as shown in <FIG>. In comparison to the embodiment of the drug delivery device <NUM> as shown in <FIG> only a protective cap <NUM> of the housing <NUM> as well as the cartridge holder <NUM> are subject to modification while the residual components, in particular the body <NUM> of the drug delivery devices <NUM>, <NUM> are left unchanged.

As it is apparent from a comparison of <FIG> and <FIG> with the drug delivery device <NUM> it is the protective cap <NUM> that is equipped with the electric energy supply <NUM>. As shown in <FIG> there is provided a compartment <NUM> on the outer circumference near a distal end of the protective cap <NUM>. As described already in connection with the electric energy supply <NUM> of the drug delivery device <NUM> also with the drug delivery device <NUM> as shown in <FIG> the compartment <NUM> houses the battery <NUM> as well as first and second contact elements <NUM>, <NUM> extending through a through opening <NUM> of the sidewall of the protective cap <NUM>. The cartridge holder <NUM> also comprises a window <NUM> in its sidewall. The window <NUM> extends in longitudinal direction and almost across the entire longitudinal extension of the tubular-shaped cartridge holder <NUM>.

Also here, the distal end of the cartridge holder <NUM> comprises a threaded and stepped down socket <NUM> that serves as an axial abutment for the radially narrowing shoulder portion of the cartridge <NUM> when assembled inside the cartridge holder <NUM>. As shown in detail in <FIG> the cartridge holder <NUM> also comprises a distal through opening <NUM>, through which the pierceable and distal seal <NUM> of the cartridge <NUM> is accessible. In the embodiment as shown in <FIG> the first and second contact electrodes <NUM>, <NUM> of the sensor <NUM> will be accessible through the window <NUM> of the cartridge holder <NUM>. For this purpose the window <NUM> is configured as a recess in the sidewall of the cartridge holder <NUM>.

Since the first and second contact electrodes <NUM>, <NUM> form an almost closed annular structure on the outer circumference of the sidewall <NUM> of the cartridge <NUM>, the cartridge <NUM> can be arranged in any arbitrary angular orientation inside the cartridge holder <NUM> with regard to its longitudinal axis as an axis of rotation. In order to provide a well-defined electric contact between the battery <NUM>, hence between the contact elements <NUM>, <NUM> and the sensor <NUM> it is required that the protective cap <NUM> is arranged in a well-defined orientation onto the cartridge holder <NUM>.

It is of particular benefit, when the cartridge holder <NUM> and the protective cap <NUM> are equipped with at least one symmetry-breaking feature as it is for instance shown in the embodiment of the drug delivery device <NUM> according to <FIG>. There, the protective cap <NUM> comprises a recess <NUM> at its proximal end that serves to receive the radially outwardly protruding compartment <NUM> located on the outer circumference of a proximal portion of the cartridge holder <NUM>. A similar symmetry-breaking feature is also implemented with the cartridge holder <NUM> and the protective cap <NUM> of the drug delivery device <NUM> as shown in <FIG>. Apart from that the electric contacting through the through opening <NUM> between the first and second contact elements <NUM>, <NUM> is substantially the same as already described in connection with the drug delivery device <NUM>.

By means of the closure <NUM> the compartment <NUM> is closeable or sealable. So the interior of the compartment <NUM> as well as the interior of the protective cap <NUM> can be effectively protected against environmental influences, such like dust or humidity.

In the further embodiment of a drug delivery device <NUM> as shown in <FIG> substantially the same cartridge holder <NUM> and the same protective cap <NUM> as already described in connection with the drug delivery device <NUM> according to <FIG> are provided. Here, at least some of the electronic components of the sensor assembly <NUM>, namely the battery <NUM>, the contact elements <NUM>, <NUM>, the processor <NUM> and the transceiver <NUM> are located and arranged in or on an accessory device <NUM> that is detachably connectable to the outer circumference of the tubular-shaped body <NUM> of the drug delivery device <NUM>.

The accessory device <NUM> serves as an electric energy supply <NUM>. It comprises a compartment <NUM> to house at least the battery <NUM>. In the illustrated embodiments, the compartment <NUM> also houses the processor <NUM> and the transceiver <NUM> as well as the electric contact elements <NUM>, <NUM>. The accessory device <NUM> comprises a fastening clip <NUM> that provides a positive engagement of the tubular-shaped body <NUM> of the drug delivery device <NUM> with the accessory device <NUM>. In addition to the compartment <NUM> the accessory device <NUM> comprises a longitudinal extension <NUM> extending in distal direction D. The contact elements <NUM>, <NUM> are located at a distal end of the extension <NUM>.

As it is shown in <FIG> the distal end of the accessory device <NUM> is arrangeable in a radially overlapping way to a proximal portion of the cartridge holder <NUM>. As shown in <FIG> the cartridge holder <NUM> comprises a through opening <NUM> near its distal end through which the radially inwardly extending contact elements <NUM>, <NUM> of the accessory device <NUM> can extend so as to establish an electrical contact with the contact electrodes <NUM>, <NUM> of the sensor <NUM> attached to the cartridge <NUM>. The geometric shape of the extension <NUM> is configured to match with the recess <NUM> of the protective cap <NUM>. As it is shown in <FIG> the first and second contact elements <NUM> are located at a lower side <NUM> of the extension <NUM> of the accessory device <NUM> so as to extend through the through opening <NUM> of the cartridge holder <NUM> when the drug delivery device <NUM> is fully assembled. In this way the contact elements <NUM>, <NUM> get in electric contact with the first and second contact electrodes <NUM>, <NUM> of the sensor <NUM>.

Since the extension <NUM> of the accessory device <NUM> ongitudinally or axially extends across the interface of body <NUM> and cartridge holder <NUM> the body <NUM> can remain completely unchanged compared to a conventional drug delivery device being void of a sensor assembly <NUM>. For the implementation of an electric contact between the sensor <NUM> located inside the drug delivery device <NUM> and the accessory device <NUM> detachably arrangeable on the outer circumference of the body <NUM> only minor modifications have to be made to the cartridge holder <NUM>. With the accessory device <NUM> at least some or all electronic components of the sensor assembly <NUM> can be provided in a separate device, thus leaving the structure of the drug delivery device <NUM> substantially unchanged. Since the accessory device <NUM> is detachably connectable to the housing <NUM> of the drug delivery device <NUM> it is repeatedly usable with a multiplicity of drug delivery devices <NUM> that may be implemented as disposable devices.

Claim 1:
A sensor for measuring at least one physical or chemical parameter of a cartridge (<NUM>) filled with a liquid substance (<NUM>) and comprising a tubular-shaped barrel (<NUM>) sealed by a piston (<NUM>) slidably displaceable inside the cartridge (<NUM>), wherein the piston (<NUM>) exhibits an electric susceptibility or permittivity being distinguishable from the electric susceptibility of the liquid substance (<NUM>) inside the cartridge (<NUM>), the sensor comprising:
- a planar flexible foil (<NUM>) attachable to an outer circumference of the barrel (<NUM>) of the cartridge (<NUM>), and
- at least a first and a second measuring electrode (<NUM>, <NUM>) arranged on said foil (<NUM>) and configured as electrical capacity measuring electrodes to measure an electrical capacitance between the first and second capacity measuring electrodes (<NUM>, <NUM>) when wrapped around the cartridge, which electrical capacitance depends on an axial position of the piston (<NUM>), characterized by
- at least a first and a second contact electrode (<NUM>, <NUM>) arranged on said foil (<NUM>),
- wherein the first contact electrode (<NUM>) is connected to the first measuring electrode (<NUM>) and wherein the second contact electrode (<NUM>) is connected to the second measuring electrode (<NUM>),
- wherein the first and second contact electrodes (<NUM>, <NUM>) are configured to provide a wired energy supply to the first and second measuring electrodes (<NUM>, <NUM>), and
- wherein the first and second contact electrodes (<NUM>, <NUM>) are configured to provide a wired transfer of electrical signals obtained or generated by at least one of the first and second measuring electrodes (<NUM>, <NUM>) to a processor (<NUM>) or transceiver (<NUM>).