EP4776984A1

EP4776984A1 - Sensor assembly and method for wake up of a sensor assembly

Info

Publication number: EP4776984A1
Application number: EP24765678.8A
Authority: EP
Inventors: Kirill Sliozberg; Frederic Wehowski
Original assignee: Roche Diabetes Care GmbH
Current assignee: Roche Diabetes Care GmbH
Priority date: 2023-09-12
Filing date: 2024-09-09
Publication date: 2026-07-22
Also published as: KR20260065861A; TW202513002A; CN121843649A; WO2025056445A1

Abstract

A sensor assembly comprising at least one analyte sensor (110) configured for transdermal detecting at least one analyte is proposed. The analyte sensor (110) comprises at least two electrodes (116, 118). The sensor assembly (124) comprises at least one electronics unit (126) connectable to the analyte sensor (110). The electronics unit (126) comprises at least one wake up unit (128) configured for determining conductivity of the analyte sensor (110) and for triggering a wake up of the sensor assembly (124) depending on the determined conductivity of the analyte sensor (110).

Description

Sensor assembly and method for wake up of a sensor assembly

Technical Field

The invention relates to a sensor assembly and a method for wake up of a sensor assembly. The sensor assembly may specifically be configured for detecting at least one analyte in a body fluid of a subject. The devices may be applied in the field of continuous monitoring of the analyte, specifically in the field of home care and in the field of professional care, such as in hospitals. Other applications, however, are also feasible.

Background art

Monitoring one or more analyte concentrations such as one or more metabolite concentrations in a body fluid of a subject plays an important role in the prevention and treatment of various diseases. Such analytes can include by way of example, but not exclusively, glucose, lactate, cholesterol or other types of analytes and metabolites. Without restricting further possible applications, the invention will be described in the following text with reference to glucose monitoring. However, additionally or alternatively, the invention can also be applied to other types of analytes.

Continuous monitoring (CM) is increasingly becoming established as important method for managing, monitoring and controlling a diabetes state. Transdermal CM systems usually comprise a sensor, which is being inserted in the patient's skin and an electronic module, which controls the sensor and collects data. As the systems must be water-tight, the electronics, including battery, is sealed in the casing, so there is no way to keep the battery mechanically disconnected from the electronics, thus preventing its discharge over the storage period, which is typically about one year long. Therefor different methods are developed, to keep the electronics in a low power consumption mode during the storage, thus saving the battery charge. Keeping the electronics in the low power consumption mode demands some process and a signal source, to activate it, once the system has been applied and the measurement has to start.

Methods for activating CM systems are for example in EP3515287B1, US11350857B2, US20170172472A1. Several different methods are described, e.g. using a NFC antenna and external NFC reader, which activated the systems electronic by transferring power via NFC. Another way is using of electronic components, which are sensing magnetic fields. Such component is placed at PCBA of the system and a magnet is built-in in an external component, which is being removed during insertion of the CM system. The electronic is build and programmed to check for external magnetic field with some periodicity during the storage. However, the existing methods always require additional components, as the NFC antenna or some magnetic field sensors. Thus, there is a need of reducing the number of components in order to make the device simpler, cheaper and smaller.

Problem to be solved

It is therefore desirable to provide a sensor assembly and a method for wake up of a sensor assembly which at least partially address the above-mentioned technical challenges. Specifically, reducing the number of components in order to make the device simpler, cheaper and smaller is desirable.

Summary

This problem is addressed by a sensor assembly and a method for wake up of a sensor assembly with the features of the independent claims. Advantageous embodiments which might be realized in an isolated fashion or in any arbitrary combinations are listed in the dependent claims as well as throughout the specification.

As used in the following, the terms “have”, “comprise” or “include” or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions “A has B”, “A comprises B” and “A includes B” may both refer to a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

Further, it shall be noted that the terms “at least one”, “one or more” or similar expressions indicating that a feature or element may be present once or more than once typically will be used only once when introducing the respective feature or element. In the following, in most cases, when referring to the respective feature or element, the expressions “at least one” or “one or more” will not be repeated, non-withstanding the fact that the respective feature or element may be present once or more than once. Further, as used in the following, the terms "preferably", "more preferably", "particularly", "more particularly", "specifically", "more specifically" or similar terms are used in conjunction with optional features, without restricting alternative possibilities. Thus, features introduced by these terms are optional features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such way with other optional or non-optional features of the invention.

In a first aspect, a sensor assembly comprising at least one analyte sensor configured for transdermal detecting at least one analyte is disclosed.

The analyte sensor comprises at least two electrodes. The sensor assembly comprises at least one electronics unit connectable to the analyte sensor. The electronics unit comprises at least one wake up unit configured for determining conductivity of the analyte sensor and for triggering a wake up of the sensor assembly depending on the determined conductivity of the analyte sensor.

The term “sensor assembly” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a system comprising at least one sensor. The term “sensor” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary element or device configured for detecting at least one condition or for measuring at least one measurement variable.

The term “analyte sensor” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a sensor which is capable of qualitatively or quantitatively detecting the presence and/or the concentration of the at least one analyte. The term “detecting” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of determining a presence and/or a quantity and/or a concentration of the at least one analyte. Thus, the detection may be or may comprise a qualitative detection, simply determining the presence of the at least one analyte or the absence of the at least one analyte, and/or may be or may comprise a quantitative detection, which determines the quantity and/or the concentration of the at least one analyte. The analyte sensor may be an electrochemical sensor. The term “electrochemical sensor” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an analyte sensor which is adapted for a detection of an electrochemically detectable property of the analyte, such as an electrochemical detection reaction. Thus, for example, the electrochemical detection reaction may be detected by applying and comparing one or more electrode potentials. Specifically, the electrochemical sensor may be adapted to generate the at least one measurement signal which may, directly or indirectly, indicate a presence and/or an extent of the electrochemical detection reaction, such as at least one current signal and/or at least one voltage signal. The measurement may be a qualitative and/or a quantitative measurement. Still, other embodiments are feasible. As a result of the detection, at least one signal may be produced which characterizes an outcome of the detection, such as at least one measurement signal. The at least one signal specifically may be or may comprise at least one electronic signal such as at least one voltage and/or at least one current. The at least one signal may be or may comprise at least one analogue signal and/or may be or may comprise at least one digital signal.

The term “analyte” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a chemical and/or biological substance which takes part in the metabolism of the body of a subject. The analyte can be any electrochemically detectable species, including simple ions, such as potassium (potentiometric measurement), but also much more complex structures, like creatinine. Exemplarily, the analyte may be a metabolite or a combination of two or more metabolites. As an example, the analyte may be selected from the group consisting of glucose, ascorbate, ketones, lactate, triglycerides, cholesterol. A preferred analyte is glucose. Still, other analytes or combinations of two or more analytes may be detected.

The term “subject” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically relates to a human being or an animal, independent from the fact that the human being or animal, respectively, may be in a healthy condition or may suffer from one or more diseases. The subject may be a patient. As an example, the subject may be a human being or an animal suffering from diabetes. The subject may be a user, e.g. a patient, intending to monitor an analyte value, such as a glucose value, in the user’s body tissue and/or to deliver medication, such as insulin, into the user’s body tissue. However, in an embodiment, the user of the insertion device may be different from the subject. Additionally or alternatively, the invention may be applied to other types of users or patients.

The analyte sensor is configured for transdermal detecting the at least one analyte. The term “transdermal” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to suitability of the analyte sensor for being fully or at least partly arranged within the body tissue of a subject. The analyte sensor may be a fully or partially implantable analyte sensor. The analyte sensor may be a transcutaneous analyte sensor. The analyte sensor may be an in vivo sensor. The analyte sensor may be adapted for performing the detection of the analyte in a bodily fluid of the subject in a subcutaneous tissue, e.g. in an interstitial fluid. As further used herein, the term “bodily fluid”, generally, refers to a fluid, in particular a liquid, which is typically present in a body or a body tissue of the subject and/or may be produced by the body of the subject. The bodily fluid may be selected from the group consisting of blood and interstitial fluid. However, additionally or alternatively, one or more other types of bodily fluids may be used, such as saliva, tear fluid, urine or other body fluids.

The analyte sensor may comprise an insertable portion. The term “insertable portion” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a part or component of an element configured to be insertable into an arbitrary body tissue. Other parts or components of the analyte sensor may remain outside of the body tissue, e.g. counter electrode and/or reference electrode or combined counter/reference electrode may remain outside of the body tissue. The portion of the analyte sensor which is inserted is also called the in-vivo portion, the portion of the analyte sensor which may stay outside of the body tissue is also called the ex-vivo portion. For example, the in-vivo portion has a length in the range from 3 mm to 12 mm. The insertable portion may fully or partially comprise a biocompatible surface, which may have as little detrimental effects on the user or the body tissue as possible, at least during typical durations of use. For this purpose, the insertable portion may be fully or partially covered with at least one biocompatibility membrane layer, such as at least one polymer membrane or a gel membrane, which, on one hand, may be permeable for the body fluid or at least for the analyte as comprised therein and which, on the other hand, may retain sensor substances, such as one or more test chemicals within the analyte sensor, thus preventing a migration thereof into the body tissue.

The analyte sensor may comprise a carrier, e.g. a substrate. The term “carrier” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary element which is suitable to carry one or more other elements disposed thereon or therein. The term “substrate” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary flat element which has a lateral extension exceeding its thickness by at least a factor of 2, at least a factor of 5, at least a factor of 10, or even at least a factor of 20 or more. The substrate may have an elongated shape, such as a strip-shape and/or a bar-shape. The substrate, as an example, may comprise a shaft, specifically a shaft having an elongate shape. For example the shaft may have a shape selected from the group consisting of a strip, a needle, a tape. Also other shapes may be feasible. The substrate, may be a flexible substrate, i.e. a substrate which may be bent or deformed by forces which usually occur during wearing and insertion into the body tissue, such as forces of 10 N or less. The substrate may be made of or may comprise a deformable material, such as a plastic or malleable material and/or an elastic material. As an example, the substrate may be or may comprise a foil, such as a foil made of one or more of a paper material, a cardboard material, a plastic material, a metal material, a ceramic material or a glass material. As an example, the carrier or the substrate may comprise a polyimide foil. The substrate may comprise an electrically insulating material, such as an electrically insulating plastic foil. For example, the analyte sensor may be a needle-shaped or a strip-shaped analyte sensor having a flexible substrate and the electrodes disposed thereon. As an example, the analyte sensor may have a total length of 5 mm to 50 mm, specifically a total length of 7 mm to 30 mm. The term “total length” within the context of the present invention relates to the overall length of the analyte sensor which means a portion of the analyte sensor which is inserted and the portion of the analyte sensor which may stay outside of the body tissue.

The sensor assembly specifically may be a unitary system which may be handled as one single piece before use. For example, elements of the sensor assembly, such as the analyte sensor, an insertion cannula, an electronics unit, a housing and connector elements, may form a pre-assembled single unit. The term “preassembled” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the fact that an assembly process has already taken place. The components of the sensor assembly may be assembled, such as by being mechanically interconnected, thereby being mechanically ready for use, such as for being inserted into the body tissue of the subject for detection of the analyte. The pre-assembling may take place in a factory, thereby rendering the sensor assembly a factory-assembled functional module.

The analyte sensor may be inserted into the body tissue of the subject by using at least one insertion device, also denoted as inserter. The sensor assembly may comprise the insertion device. The sensor assembly may be configured for inserting the analyte sensor into the body tissue of the subject. The insertion may take place in such a way that the analyte sensor is fully or partially placed under the skin after insertion. The insertion may take place also in such a way that a part of the analyte sensor may protrude from the body tissue, through the skin, in order to be contacted on the outside of the body, such as electrically and/or fluidi- cally. After insertion of the analyte sensor into the body tissue, the sensor assembly may disassemble into a disposable handling component, e.g. including an inserter in a used state, and the analyte sensor with a body mount, wherein the body mount may be attached to the skin of the subject and wherein the analyte sensor may protrude into the body tissue.

The analyte sensor comprises at least two electrodes. However, embodiments are possible in which the analyte sensor comprises more than two electrodes, e.g. three or more. Moreover, embodiments are possible, in which the analyte sensor comprises one single or more electrode and at least one external electrode, contacting the skin surface. The term “electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an, generally arbitrary shaped, electrical conductor. An electrode immersed in an electrolyte solution can be simplified described by means of so-called Randle’s circuit. The simplest Randle’s circuit is described by two in series connected resistors Rl, R2 and one capacitor Cl in parallel to R2. The resistor Rl may represent so-called equivalent series resistance and includes resistance of the electrode itself, resistance of the electrolyte solution between the given electrode and another one against which these resistance values are being measured. The resistor R2 represents so-called charge-transfer resistance (RCT) and describes roughly the DC current, which flows through the interface electrode/electrolyte during a potentiostatic chronoam- perometric measurement. The Cl is so-called double layer capacitor and is formed by interface electrode/electrolyte. Physically, having an electrode immersed in the electrolyte solution, it is impossible to contact a connection point between R1 and R2 by some measuring device. The only accessible contacting points are at the one left from R1 and at the right from R2/C1. For resistance measurement, a voltage may be applied at the contacting points, which would lead to some current flow which may be measured. The resistance may be determined by dividing the applied DC voltage over the measured DC current and calculate the DC resistance according to Ohm’s law. The calculated resistance is the sum of the R1 and R2, as the DC current cannot flow through the Cl and, thus, it flows through the R1 and R2. If there is a need to measure R1 selectively, this can be done by measuring impedance. The impedance measured at some very high frequencies would correspond to the value of Rl, as the AC current would mainly flow through the Cl, thus avoiding R2 and the R2 would not contribute to the determined impedance.

For example, the analyte sensor may comprise at least one detection electrode, also denoted as working electrode, and at least one further electrode, e.g. a counter electrode and/or a reference electrode or a combined counter/reference electrode.

The term “detection electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrode configured for performing at least one electrochemical detection reaction for detecting the at least one analyte. The working electrode may have an analyte detection agent being sensitive to the analyte to be detected. The term “analyte detection agent” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary material or a composition of materials adapted to change a detectable property in a presence of an analyte. This property may be an electrochemically detectable property. Specifically, the analyte detection agent may be a highly selective analyte detection agent, which only changes the property if the analyte is present in the body fluid whereas no change occurs if the analyte is not present. The degree or change of the property is dependent on the concentration of the analyte in the body fluid, in order to allow a quantitative detection of the analyte. As an example, the analyte detection agent may comprise an enzyme, such as glucose oxidase and/ or glucose dehydrogenase. The working electrode may further comprise a conductive working electrode pad. The conductive working electrode pad may be in contact with the analyte detection agent. Thus, the analyte detection agent may be coated onto the conductive working electrode pad. The analyte detection agent may form an analyte detection agent surface which may be in contact with the body fluid. As an example, the analyte detection agent surface may be an open analyte detection agent surface or may be covered by the above-mentioned membrane which is permeable to the analyte to be detected and/or to the body fluid or a part thereof, such that the analyte may interact with the analyte detection agent. For potential analyte detection agents and/or materials for the conductive working electrode pad, again, reference may be made to WO 2007/071562 Al and/or the prior art documents disclosed therein. Other embodiments, however, are feasible. The one or more working electrode pads specifically may be formed by a dot, line or grid which each can form a coherent area of an electrode material. If more than one dot, line or grid of the electrode material is superimposed, the sensor may provide more than one electrode pad. All electrode pads together may build the working electrode. The sensor may comprise the working electrode with a number of electrode pads in a range from 1 to 50, preferably from 2 to 30, preferably from 5 to 20 electrode pads.

The term “counter electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrode configured for performing at least one electrochemical counter reaction adapted for balancing a current flow required by the detection reaction at the detection electrode. The term “reference electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrode adapted for providing a constant electrode potential as a reference potential, in particular at least within tolerances, such as by providing a redox system having a constant electrode potential. The counter electrode and the reference electrode may be one of a common electrode or two separate electrodes. Again, for potential materials usable for the counter electrode and/or the reference electrode, reference may be made to WO 2007/071562 Al and/or the prior art documents disclosed therein. Other embodiments, however, are feasible. The working electrode may be sensitive for the analyte of interest at a polarization voltage which may be applied between the working and reference electrode and which may be regulated by a potentiostat. A measurement signal may be provided as an electric current between the counter electrode and the working electrode.

Each electrode may comprise a conductive pad or conductive element, such as a metal pad and/or a metal element and/or a pad or element made of a conductive inorganic or organic material such as carbon and/or a conductive polymer. The conductive pad or conductive element may be uncovered and/or may be covered with an additional material, such as a sensor chemical. The working electrode may comprise a working electrode pad and, optionally, at least one test chemical disposed thereon. The counter electrode may comprise a counter electrode pad. Additionally and optionally, one or more redox materials may be disposed thereon. The at least two electrodes of the analyte sensor may be embodied such that an electrochemical reaction may take place at one or more of the electrodes, such as one or more working electrodes. Thus, the electrodes may be embodied such that an oxidation reaction and/or reduction reaction may take place at one or more of the electrodes. The electrochemical detection reaction may be detected by comparing one or more electrode potentials, such as an electrostatic potential of a working electrode with an electrostatic potential of one or more further electrodes such as a counter electrode or a reference electrode.

The two or more electrodes may be used for one or more of an amperometric or potentiometric measurement. The potentiometric measurement may comprise measuring a potential by setting current, e.g. galvanostatic, where the current is kept constant, or galvanodynamic, where the current in time is intentionally change. The amperometric measurement may comprise measuring a current by setting a potential, e.g. potentioostatic, where the potential is kept constant, or potentiodynamic, where the potential in time is intentionally changed. An impedance measurement can be performed as potentiostatic method or as galvanostatic method, depending, on what is defined and what is measured. Moreover, OCP (open circuit potentiometry) may be used. In this case no current flow may be intentionally induced by the measurement electronics. These types of measurements generally are known to the skilled person in the art of analyte detection, such as from WO 2007/071562 Al and/or the prior art documents disclosed therein. For potential setups of the electrodes, electrode materials or measurement setups, reference may be made to this document. Analyte sensors are generally known in the art and include continuous glucose sensor systems or for example continuous ketone measurement. It shall be noted, however, that other setups, electrode materials or measurement setups may be used within the present invention.

The sensor assembly comprises at least one electronics unit connectable to the analyte sensor. The analyte sensor may be operably connected to the electronics unit. The term “electronics unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary unit, such as a unit which may be handled as a single piece, which is configured for performing at least one electronic function. For example, the electronics unit may have at least one interface for being connected to the analyte sensor. The analyte sensor may comprise one or more leads for electrically contacting the electrodes. The leads may, during insertion or at a later point in time, be connected to one or more electronic components. For example, the leads may already be connected to the electronics unit before insertion of the analyte sensor. The electronics unit may provide at least one electronic function interacting with the analyte sensor, such as at least one measurement function. The electronics unit may be configured for one or more of determining and/or controlling a detection of the analyte and/or transmitting measurement data to another component. Specifically, the electronics unit may be configured for one or more of performing a measurement with the analyte sensor, performing a voltage measurement, performing a current measurement, recording sensor signals, storing measurement signals and/or measurement data, transmitting sensor signals to another component. Thus, the electronics unit specifically may comprise at least one of: a voltmeter, an ammeter, a potentiostat, a voltage source, a current source, a signal receiver, a signal transmitter, an analog-digital converter, an electronic filter, a data storage device, an energy storage. For example, the electronics unit may be embodied as a transmitter or may comprise at least one transmitter configured for transmitting data to a remote computer or to a remote device. The sensor assembly further may comprise at least one electronic remote device configured to communicate and/or control with the sensor assembly. The electronic remote device may be selected from a personal computer, a wearable, a smartphone, a proprietary remote control, a tablet or a server.

The sensor assembly may comprise an electrical energy reservoir, such as at least one battery. The term “battery” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically relates to an arbitrary source of electric power comprising one or more electrochemical cells with external connections for powering an electrical device. When a battery supplies power, its positive terminal may be referred to as cathode and its negative terminal may be referred to as anode. The battery may specifically be a primary battery. The primary battery may be configured for being used once. The primary battery may also be referred to as single-use or disposable battery. The sensor assembly may comprise at least one connector element configured for establishing an electrical contact between the electrical energy reservoir and electronic components of the sensor assembly. For example, the battery may be a 3V or 1.5V battery.

Before use, the sensor assembly may be in an inactive status, e.g. during storage. The term “inactive status” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a status in which the electronic components of the sensor assembly are in a low power consumption mode and/or an energy save mode. Keeping the electronics in a low power consumption mode during the storage may allow saving battery charge. However, keeping the electronics in the low power consumption mode demands activation once the system has been applied and the measurement has to start. For this purpose, the sensor assembly may be configured for detecting a change in conductivity of the analyte sensor after insertion.

The electronics unit comprises at least one wake up unit configured for determining conductivity of the analyte sensor and for triggering a wake up of the sensor assembly depending on the determined conductivity of the analyte sensor.

The term “wake up” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process for activating the sensor assembly and/or for ceasing the inactive mode. The wake up may comprise one or more of initializing, initiating, starting, and turning on. The wake up may comprise at least one process for changing the status of the sensor assembly from the inactive mode to an activated mode. The term “activated mode”, also denoted as operating mode, as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a status in which the electronic components of the sensor assembly are configured for operation, e.g. for performing at least one measurement. In the activated mode, the electrical energy reservoir may be in a high power consumption mode. The wake up may comprise generating a wake up signal, e.g. to the electronics unit, and/or switching on at least one electronic component, e.g. by increasing power supply, flipping a switch, and/or generating an external energy input, e.g. in form of radiowaves into an antenna, and the like.

The term “wake up unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a unit configured for wake up of the sensor assembly. The wake up unit may be configured for detecting an insertion of the analyte sensor, as will be described in more detail below.

The term “triggering a wake up” used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically relates to at least one action and/or reaction causing the assembly to wake up. The triggering of the wake up may happen in case of an occurrence or a fulfillment of at least one requirement, e.g. a change of conductivity of the analyte sensor by a predefined amount. The triggering may comprise one or more of causing, initiating, actuating, turning on the sensor assembly. The triggering may comprise timely and/or causally elements. For example, the wake up is triggered in case of a conductivity change from an initial conductivity value is determined. The wake up may be triggered in case of a conductivity change exceed at least one predefined limit. The predefined limit may depend on the sensor design and used materials. For example, the predefined limit may range from about 100 Q to 100 kQ, but may also exceed this range. For example, a typical DC resistance of a dry analyte sensor may be at least 1 GO, e.g. up to 100 GO. The DC resistance of an inserted analyte sensor may be in the range of 100 MO. An AC impedance may be in the range of 100 Q to several kQ.

The wake up unit may determine the conductivity of the analyte sensor repeatedly, e.g. every minute. Once a change in conductivity to a least a predefined amount is detected, the "main" electronics is activated. Alternatively, the wake up unit may determine the conductivity continuously, e.g. by continuously applying voltage.

The electronics unit may comprise at least one microcontroller unit configured for controlling operation of the analyte sensor. The wake up unit may be configured for generating at least one wake up signal depending on the determined conductivity and for providing the wake up signal to the microcontroller unit (MCU). The whole concept of detection of the conductivity can be performed without the MCU running. This can allow to save battery. The wake up signal may activate the MCU. The microcontroller unit may be configured for switching a status of the sensor assembly from the inactive status to the activated upon receiving the wake up signal.

The conductivity of the analyte sensor may be determined using at least one DC and/or AC measurement, in particular resistance or impedance measurement. Impedance may be a ratio of an AC voltage over the AC current caused by the AC voltage at different frequencies. One of the analyte sensor's properties, which drastically changes upon insertion is its impedance. As long as the sensor is dry, its impedance is virtually infinite at a very wide range of excitation frequencies. As long as the analyte sensor in this state, it can be represented by two or more solid electrodes, which are not interconnected to each other neither electrically, nor ionically. Once the analyte sensor is inserted, the electrodes are interconnected by the body fluids, e.g. the ISF. An impedance drop in the whole frequency range can be detected: at very low frequencies or with DC the measured impedance corresponds to the DC current of the amperometric sensor.

For example, the conductivity of the analyte sensor is determined using at least one impedance measurement.

The wake up unit may comprises at least one signal generator device. The term “signal generator device” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a device, for example a voltage source, being configured to generate a voltage signal. The signal generator device may be and/or may comprise at least one voltage source. The signal generator device may comprise at least one function generator selected from the group consisting of: at least one square wave generator and at least one sine wave generator. The AC voltage signal can have different shapes, such as sinusoidal or square wave or others. The AC voltage signal can have different durations, such as a continuous AC signal, or single square pulse, or fasttransient voltage signal or others. The term “AC voltage signal” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an voltage signal, e.g. continually, changing between positive and negative, e.g. by a predefined frequency. The frequency of the AC voltage signal may be from 10 mHz to 100 kHz.

The wake up unit may comprise at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor. The reference resistance may have a known resistance value such as an average value determined, specifically predetermined, from a plurality of reference measurements. The wake up unit may be configured for applying the AC voltage signal to the serially connected reference resistance and the analyte sensor. The wake up unit is configured for determining a voltage distribution over the analyte sensor and the reference resistance during the AC voltage signal. For example, a voltage measurement may be performed at the reference resistance. The relation between the applied and the measured voltage may be determined under consideration of the reference resistance. The wake up unit may be configured for activating the sensor assembly in case of a change in voltage distribution, in particular an impedance drop, to a least a predefined amount. In one embodiment, the impedance measurement may comprise a fast transient measurement. The signal generator device may comprise at least one pulse generator configured for generating a fast-transient voltage signal. The impedance measurement may comprise applying the fast-transient voltage signal to the serially connected reference resistance and the analyte sensor.

The term “fast-transient voltage signal” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to at least one arbitrary voltage signal, in particular an arbitrary voltage change in between two electrodes. The fast-transient voltage signal may have at least one fast transient signal flank, such as two very steep edges. The fast-transient voltage signal may comprise a square waveform and/or a sine wave form. For example, the fast-transient voltage signal may have a square wave form.

The fast-transient voltage signal may comprise a non-continuous signal such as a pulse. The term “pulse” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a signal having a transient change in the amplitude of the signal from a first value, also denoted baseline value, to a second value, followed by a return to the baseline value or at least approximately to the baseline value. The second value may be a higher or lower value than the baseline value. A pulse duration may be < 20 ps, more preferably < 10 ps. The duration of the single pulse must be sufficiently long to be able to record its propagation. The fast-transient voltage signal may comprise a pulse having two edges: a leading edge or front edge, which is a first edge of the pulse and a trailing edge or back edge, which is a second edge of the pulse.

The term “fast-transient” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to time range between first and second values of the signal flank.

The terms first and second “value” may refer to regions or points of the fast-transient voltage, in particular its amplitude. The first value may be the baseline value. The first value may be a local and/or overall minimum of the fast-transient voltage. The first value may be a first plateau of the fast-transient voltage. The first value may refer to a time point with no voltage is applied to the electrodes. The second value may be a local and/or overall extremum of the fast-transient voltage. The second value may be a second plateau of the fast-transient voltage, which may be reached during application of the fast-transient voltage. The second value may be extremum of the fast-transient voltage signal.

The term “signal flank” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to transition of a signal amplitude from low to high signal value or from high to low signal value. The signal flank may be a rising signal flank or a falling signal flank. The signal flank of the fasttransient voltage signal may have a change in signal from the first value of the signal flank to the second value of the signal flank in a microsecond to nanosecond range. The signal flank may also be referred to as edge. The fast-transient voltage signal may have a low-to- high transition of a signal amplitude, which is equivalent to rising or positive signal flank, or high-to-low transition of a signal amplitude, which is equivalent to falling or negative signal flank. The fast-transient voltage signal may have steep edges. Specifically, the fast transition square wave may have a change in voltage from the first value to the second value below or equal 20 ns. The change in voltage from the first value to the second value may be even faster and may be only limited by electronics such as by a fast-transient voltage signal generator (DAC, DO or others) or a read-out unit (voltage amplifier, ADC, or others). The duration of the single fast-transient voltage must be sufficiently long to record a response.

The fast-transient voltage signal may be applied to the electrodes with a known amplitude. The amplitude of the fast-transient voltage signal may vary in a broad range and must be optimized for a given set-up. Generally, the lower limit may be limited by the readout technique, which must record the response voltage, mostly by its input range and resolution and may require an additional sufficiently fast voltage amplifier.

The wake up unit may be configured for determining a voltage distribution over the analyte sensor and the reference resistance during the fast transient voltage signal. The relation between the applied and the measured voltage may be determined under consideration of the reference resistance. The wake up unit may be configured for activating the sensor assembly in case of a change in voltage distribution to a least a predefined amount.

Additionally or alternatively, for example, the conductivity of the analyte sensor is determined using at least one DC resistance measurement. The wake up unit may comprise at least one reference resistance connected in series with the analyte sensor. The electrical energy reservoir, such as at least one battery, may be configured for providing a DC voltage. Altematively, the wake up unit may comprise a voltage source for providing the DC voltage. The DC resistance measurement may comprise distributing a DC voltage to the analyte sensor and the reference resistance and measuring at least one voltage distribution over the analyte sensor and reference resistance. The DC voltage may be permanently applied before insertion, e.g. as battery voltage. This can allow ensuring safety for the analyte sensor. The wake up unit may be configured for activating the sensor assembly in case of a change in voltage distribution to at least a predefined amount. The DC voltage may be removed after activating the sensor assembly. The DC voltage used for wake up may be different from the polarization voltage used for analyte measurement.

The both above-mentioned techniques for determining conductivity, i.e. using a DC measurement and/or a AC measurement, work independently. The both above-mentioned techniques for determining conductivity work, whether the sensor acts as a galvanic element being in ISF, thus generation some current or voltage, or not, as the method measures conductivity and not voltage or current generated by the unpolarized sensor. The both above- mentioned techniques can also work with an external electrode(s).

In a further aspect of the present invention, a method for wake up of a sensor assembly according to the present invention, such as described in one or more of the embodiments enclosed herein, is disclosed. The method comprises determining conductivity of the analyte sensor and triggering a wake up of the sensor assembly depending on the determined conductivity of the analyte sensor. With respect to definitions and embodiments of the sensor assembly and determining of conductivity reference is made to the description of the sensor assembly described above or as described in more detail below.

The method steps may be performed in the given order. Further, one or more of the method steps may be performed in parallel and/or in a time overlapping fashion. Further, one or more of the method steps may be performed repeatedly. Further, additional method steps may be present which are not listed.

The conductivity of the analyte sensor may be determined using at least one DC resistance or AC impedance measurement.

For example, the conductivity of the analyte sensor is determined using at least one AC impedance measurement, wherein the method comprises i) generating and applying at least one AC voltage signal such as at least one fast-transient voltage signal by using at least one signal generator device such as a pulse generator of the wake up unit of the wake up unit, wherein the wake up unit comprises at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor, ii) measuring at least one voltage distribution over the analyte sensor and reference resistance during AC voltage signal, e.g. during the fast transient voltage signal, iii) activating the sensor assembly in case of a change in voltage distribution to a least a predefined amount.

For example, the conductivity of the analyte sensor is determined using at least one DC resistance measurement, wherein the method comprises a) distributing a DC voltage to the analyte sensor and a reference resistance connected in series with the analyte sensor; b) measuring at least one voltage distribution over the analyte sensor and reference resistance; c) activating the sensor assembly in case of a change in voltage distribution to at least a predefined amount.

The DC voltage is applied permanently. The DC voltage may be removed after activating the sensor assembly.

The method may be computer-implemented. The term "computer implemented method" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a method involving at least one computer and/or at least one computer network. The computer and/or computer network may comprise at least one processor which is configured for performing at least one of the method steps of the method according to the present invention. Specifically, each of the method steps is performed by the computer and/or computer network. The method may be performed completely automatically, specifically without user interaction.

Further disclosed and proposed herein is a computer program including computer-executable instructions for performing the method according to the present invention in one or more of the embodiments enclosed herein when the instructions are executed on a computer or computer network. Specifically, the computer program may be stored on a computer-readable data carrier and/or on a computer-readable storage medium. As used herein, the terms “computer-readable data carrier” and “computer-readable storage medium” specifically may refer to non-transitory data storage means, such as a hardware storage medium having stored thereon computer-executable instructions. The computer- readable data carrier or storage medium specifically may be or may comprise a storage medium such as a random-access memory (RAM) and/or a read-only memory (ROM).

Thus, specifically, one, more than one or even all of method steps as indicated above may be performed by using a computer or a computer network, preferably by using a computer program.

Further disclosed and proposed herein is a computer program product having program code means, in order to perform the method according to the present invention in one or more of the embodiments enclosed herein when the program is executed on a computer or computer network. Specifically, the program code means may be stored on a computer-readable data carrier and/or on a computer-readable storage medium.

Further disclosed and proposed herein is a data carrier having a data structure stored thereon, which, after loading into a computer or computer network, such as into a working memory or main memory of the computer or computer network, may execute the method according to one or more of the embodiments disclosed herein.

Further disclosed and proposed herein is a non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to the present invention.

Further disclosed and proposed herein is a computer program product with program code means stored on a machine-readable carrier, in order to perform the method according to one or more of the embodiments disclosed herein, when the program is executed on a computer or computer network. As used herein, a computer program product refers to the program as a tradable product. The product may generally exist in an arbitrary format, such as in a paper format, or on a computer-readable data carrier and/or on a computer-readable storage medium. Specifically, the computer program product may be distributed over a data network.

Finally, disclosed and proposed herein is a modulated data signal which contains instructions readable by a computer system or computer network, for performing the method according to one or more of the embodiments disclosed herein. Referring to the computer-implemented aspects of the invention, one or more of the method steps or even all of the method steps of the method according to one or more of the embodiments disclosed herein may be performed by using a computer or computer network. Thus, generally, any of the method steps including provision and/or manipulation of data may be performed by using a computer or computer network. Generally, these method steps may include any of the method steps, typically except for method steps requiring manual work, such as providing the samples and/or certain aspects of performing the actual measurements.

Specifically, further disclosed herein are:

- a computer or computer network comprising at least one processor, wherein the processor is adapted to perform the method according to one of the embodiments described in this description,

- a computer loadable data structure that is adapted to perform the method according to one of the embodiments described in this description while the data structure is being executed on a computer,

- a computer program, wherein the computer program is adapted to perform the method according to one of the embodiments described in this description while the program is being executed on a computer,

- a computer program comprising program means for performing the method according to one of the embodiments described in this description while the computer program is being executed on a computer or on a computer network,

- a computer program comprising program means according to the preceding embodiment, wherein the program means are stored on a storage medium readable to a computer,

- a storage medium, wherein a data structure is stored on the storage medium and wherein the data structure is adapted to perform the method according to one of the embodiments described in this description after having been loaded into a main and/or working storage of a computer or of a computer network, and

- a computer program product having program code means, wherein the program code means can be stored or are stored on a storage medium, for performing the method according to one of the embodiments described in this description, if the program code means are executed on a computer or on a computer network.

Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged: Embodiment 1. A sensor assembly comprising at least one analyte sensor configured for transdermal detecting at least one analyte, wherein the analyte sensor comprises at least two electrodes, wherein the sensor assembly comprises at least one electronics unit connectable to the analyte sensor, wherein the electronics unit comprises at least one wake up unit configured for determining conductivity of the analyte sensor and for triggering a wake up of the sensor assembly depending on the determined conductivity of the analyte sensor.

Embodiment 2. The sensor assembly according to the preceding embodiment, wherein the wake up is triggered in case of a conductivity change from an initial conductivity value is determined, wherein the wake up is triggered in case of a conductivity change exceed at least one predefined limit.

Embodiment 3. The sensor assembly according to the preceding embodiment, wherein the electronics unit comprises at least one microcontroller unit configured for controlling operation of the analyte sensor, wherein the wake up unit is configured for generating at least one wake up signal depending on the determined conductivity and for providing the wake up signal to the microcontroller unit, wherein the microcontroller unit is configured for switching a status of the sensor assembly from an inactive status to an activated mode upon receiving the wake up signal.

Embodiment 4. The sensor assembly according to any one of the preceding embodiments, wherein the conductivity of the analyte sensor is determined using at least one DC and/or AC measurement, in particular resistance or impedance measurement.

Embodiment 5. The sensor assembly according to any one of the preceding embodiments, wherein the conductivity of the analyte sensor is determined using at least one impedance measurement, wherein the wake up unit comprises at least one signal generator device, wherein the wake up unit comprises at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor, wherein the wake up unit is configured for applying an AC voltage signal to the serially connected reference resistance and the analyte sensor, wherein the wake up unit is configured for determining a voltage distribution over the analyte sensor and the reference resistance during the AC voltage signal, wherein the wake up unit is configured for activating the sensor assembly in case of a change in voltage distribution to a least a predefined amount. Embodiment 6. The sensor assembly according to the preceding embodiment, wherein the signal generator device comprises at least one pulse generator configured for generating a fast-transient voltage signal, wherein the wake up unit comprises at least one reference resistance connected to the pulse generator and connected in series with the analyte sensor, wherein the impedance measurement comprises applying the fast-transient voltage signal to the serially connected reference resistance and the analyte sensor, wherein the wake up unit is configured for determining a voltage distribution over the analyte sensor and the reference resistance during the fast transient voltage signal, wherein the wake up unit is configured for activating the sensor assembly in case of a change in voltage distribution to a least a predefined amount.

Embodiment 7. The sensor assembly according to the preceding embodiment, wherein the fast-transient voltage signal comprises a single pulse or series of pulses, wherein the duration of each pulse is < 20 ps, preferably < 10 ps.

Embodiment 8. The sensor assembly according to any one of the four preceding embodiments, wherein the conductivity of the analyte sensor is determined using at least one DC resistance measurement, wherein the wake up unit comprises at least one reference resistance connected in series with the analyte sensor, wherein the DC resistance measurement comprises distributing a DC voltage to the analyte sensor and the reference resistance and measuring at least one voltage distribution over the analyte sensor and reference resistance, wherein the wake up unit is configured for activating the sensor assembly in case of a change in voltage distribution to at least a predefined amount.

Embodiment 9. The sensor assembly according to any one of the preceding embodiments, wherein the wake up unit is configured for detecting an insertion of the analyte sensor.

Embodiment 10. The sensor assembly according to any one of the preceding embodiments, wherein the analyte sensor is a two-electrode sensor or a three-electrode sensor.

Embodiment 11. A method for wake up of a sensor assembly according to any one of the preceding embodiments, the method comprises determining conductivity of the analyte sensor and triggering a wake up of the sensor assembly depending on the determined conductivity of the analyte sensor. Embodiment 12. The method according to the preceding embodiment, wherein the conductivity of the analyte sensor is determined using at least one DC resistance or AC impedance measurement.

Embodiment 13. The method according to any one of the preceding embodiments referring to a method, wherein the conductivity of the analyte sensor is determined using at least one AC impedance measurement, wherein the method comprises i) generating and applying at least one AC voltage signal such as at least one fasttransient voltage signal by using at least one signal generator device such as a pulse generator of the wake up unit, wherein the wake up unit comprises at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor, ii) measuring at least one voltage distribution over the analyte sensor and reference resistance during the AC voltage signal, e.g. during the fast transient voltage signal, iii) activating the sensor assembly in case of a change in voltage distribution to a least a predefined amount.

Embodiment 14. The method according to any one of the preceding embodiments referring to a method, wherein the conductivity of the analyte sensor is determined using at least one DC resistance measurement, wherein the method comprises a) distributing a DC voltage to the analyte sensor and a reference resistance connected in series with the analyte sensor; b) measuring at least one voltage distribution over the analyte sensor and reference resistance; c) activating the sensor assembly in case of a change in voltage distribution to at least a predefined amount.

Embodiment 15. The method according to the preceding embodiment, wherein the DC voltage is removed after activating the sensor assembly.

Embodiment 16. The method according to any one of the preceding embodiments referring to a method, wherein the method is computer-implemented.

Embodiment 17. A computer program comprising instructions which, when the program is executed by the sensor assembly according to any one of the preceding embodiments referring to a sensor assembly, cause the sensor assembly to perform the method according to any one of the preceding embodiments referring to a method.

Embodiment 18. A computer-readable storage medium comprising instructions which, when the instructions are executed by the sensor assembly according to any one of the preceding embodiments referring to a sensor assembly, cause the sensor assembly to perform the method according to any one of the preceding embodiments referring to a method.

Embodiment 19. A non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to any one of the preceding embodiments referring to a method.

Short description of the Figures

Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

In the Figures:

Figure 1 shows schematically a biological end of an analyte sensor;

Figure 2 shows two simulated impedance spectra of analyte sensors represented as Randle's circuits in the frequency range from 10 mHz to 100 kHz;

Figure 3 shows a sensor assembly for determining conductivity by using an AC measurement; and

Figure 4 shows a sensor assembly for determining conductivity by using an DC measurement. Detailed description of the embodiments

In Figure 1, upper part, highly schematically, a biological end of an insertable portion of an analyte sensor 110 is shown. The analyte sensor 110 is an element of a sensor assembly 124, as shown in Figures 3 and 4. The analyte sensor 110 may be configured for transdermal detecting at least one analyte. In the embodiment of Figure 1, the analyte sensor 110 is an amperometric sensor and comprises two-electrodes. The analyte sensor 110 may comprise a carrier, e.g. a substrate 114. The substrate 114 may have an elongated shape, such as a stripshape and/or a bar-shape. The substrate 114 may comprise an electrically insulating material, e.g. as shown in Figure 1 a plastic foil. Each side of the substrate 114 may be coated by some conductive layer 115, e.g. carbon. The electrodes comprise at least one working electrode (WE) 116 and at least one further electrode (CE/RE) 118, e.g. a counter electrode and/or a reference electrode or a combined counter/ reference electrode. In Figure 1, one side is the working electrode 116 and the other side is a combined counter-reference electrode 118. Sensing chemistry 112 may be applied at the working electrode 116 and some Ag/AgCl 113 may be applied at the counter/ reference electrode 118. An insulating layer 122 may be applied. A diffusion limiting membrane 120 may be arranged at the top by e.g. dip coating.

An electrode immersed in an electrolyte solution can be simplified described by means of so-called Randle’s circuit. The simplest Randle’s circuit is described by two resistors and one capacitor interconnected. Each of both electrodes 116, 118 can be described as Randle’s circuit in the first approximation. The simplest Randle’s circuit is described by two in series connected resistors Rl, R2 and one capacitor Cl in parallel to R2. The resistor R1 may represent so-called equivalent series resistance and includes resistance of the electrode itself, resistance of the electrolyte solution between the given electrode and another one against which these resistance values are being measured. The resistor R2 represents so-called charge-transfer resistance (RCT) and describes roughly the DC current, which flows through the interface electrode/electrolyte. Cl is the so-called double layer capacitor and is formed by interface electrode/electrolyte. Physically, having an electrode immersed in the electrolyte solution, it is impossible to contact a connection point between Rl and R2 by some measuring device. The only accessible contacting points are at the one left from Rl and at the right from R2/C 1. For resistance measurement, a voltage may be applied at the contacting points, which would lead to some current flow which may be measured. The resistance may be determined by dividing the applied DC voltage over the measured DC current and calculate the DC resistance according to Ohm’s law. The calculated resistance is the sum of the Rl and R2, as the DC current cannot flow through the Cl and, thus, it flows through the Rl and R2. If there is a need to measure R1 selectively, this can be done by measuring impedance. The impedance measured at some very high frequencies would correspond to the value of Rl, as the AC current would flow through the Cl, thus avoiding R2 and the R2 would not contribute to the determined impedance. The Rl is so-called equivalent series resistance (ESR) and it comprises all serially connected high-frequency impedances as those cannot be separately measured by impedance measurement.

In the lower part of Figure 1 a simplified equivalent circuit of such the analyte sensor 110 is depicted, comprising corresponding charge transfer resistances at the both sensor sides, substrate, membrane and electrolyte resistivity as well as double layer capacitances. The working electrode 116 comprises the substrate resistance Rsub, double layer capacitance CDL in parallel to the charge transfer resistance RCT and membrane resistance Rmem. The combined counter-reference electrode 118 also comprises substrate resistance Rsub’, the own double layer capacitance CDL’ in parallel to the charge transfer resistance RCT’ and the membrane resistance Rmem’. Furthermore, there is solution resistance Rsoi between both electrodes 116, 118. The ESR can be determined as follows

ESR Esub T E_subl + Rmem T Rmem' T Rsol -

Figure 2 depicts two simulated impedance spectra of analyte sensors 110 represented as Randle's circuits in the frequency range from 10 mHz to 100 kHz. The circles denote a set of values representing roughly impedance spectrum of a dry analyte sensor 110. As all resistances values are very high (here RCT and ESR are taken as half of GO per each) end the CDL is infinitely small, the impedance in the simulated frequencies range corresponds more or less to the sum of both above resistances. Once the analyte sensor 110 is inserted this can be seen in the corresponding impedance spectrum (squares). At low frequencies the impedance corresponds to the sum of RCT and ESR, pre-requisite for the measurable Rct is proper polarization of the working electrode 116. At high frequencies, like 50-100 kHz, the impedance corresponds to ESR, including ionic resistivity of the ISF. The high-frequency portion of the impedance spectrum will show the maximum change upon insertion, as it drops from quasi-infinity to, depending on sensors design, few hundreds or thousands of ohms. Furthermore, the high-frequency measurement does not demand any DC excitation, as it would be the case for the low-frequency impedance.

The known methods for wake up of a sensor assembly demand complex electronics and consumes much power. The sensor assembly 124 allows for a simple and low power method using the sensor impedance change. As shown in Figures 3 and 4, the sensor assembly 124 comprises at least one electronics unit 126 connectable to the analyte sensor 1110. The electronics unit 126 comprises at least one wake up unit 128 configured for determining conductivity of the analyte sensor 110 and for triggering a wake up of the sensor assembly 124 depending on the determined conductivity of the analyte sensor 110.

As further shown in Figures 3 and 4, the sensor assembly 124 may comprise an electrical energy reservoir 130, such as at least one battery. For example, the battery may be a 3V or 1.5V battery. Before use, the sensor assembly 124 may be in an inactive status, e.g. during storage. In the inactive status, the electronic components of the sensor assembly 124 are in a low power consumption mode and/or an energy save mode. Keeping the electronics in a low power consumption mode during the storage may allow saving battery charge. However, keeping the electronics in the low power consumption mode demands activation once the system has been applied and the measurement has to start. For this purpose, the sensor assembly 124 may be configured for detecting a change in conductivity of the analyte sensor after insertion. The wake up unit 128 is configured for determining conductivity of the analyte sensor 110 and for triggering a wake up of the sensor assembly 124 depending on the determined conductivity of the analyte sensor 110. For example, the wake up is triggered in case of a conductivity change from an initial conductivity value is determined. The wake up is may be in case of a conductivity change exceed at least one predefined limit. The predefined limit may depend on the sensor design and used materials. For example, the predefined limit may range from about 100 Qto 100 kQ, but may also exceed this range. For example, a typical DC resistance of a dry analyte sensor 110 may be at least 1 GO, e.g. up to 100 GO. The DC resistance of an inserted analyte sensor 110 may be in the range of 100 MO. An AC impedance may be in the range of 100 Q. The wake up unit 128 may determine the conductivity of the analyte sensor 110 repeatedly, e.g. every minute. Once a change in conductivity to a least a predefined amount is detected, the "main" electronics is activated.

The electronics unit 126 may comprise at least one microcontroller unit (MCU) 132 configured for controlling operation of the analyte sensor 110. The wake up unit 128 may be configured for generating at least one wake up signal depending on the determined conductivity and for providing the wake up signal to the MCU 132. The whole concept of detection of the conductivity can be performed without the MCU 132 running. This can allow to save battery. The wake up signal may activate the MCU 132. The MCU 132 may be configured for switching a status of the sensor assembly 124 from the inactive status to the activated upon receiving the wake up signal. The conductivity of the analyte sensor may be determined using at least one DC and/or AC measurement, in particular resistance or impedance measurement.

For example, the conductivity of the analyte sensor is determined using at least one impedance measurement. Figure 3 shows an sensor assembly 124 for determining conductivity by using an AC measurement, in particular by using a fast-transient technique based on a fast transient voltage signal. The fast-transient may be an impedance measurement at virtually infinite frequency and is, therefore, selective for equivalent serial resistance. Advantage of this method compared to a simple static DC resistance measurement unfolds in electrochemical systems, as those can be often represented as Randle’s circuit. Since the Randle’s circuit includes a capacitor in parallel to the charge transfer resistance (RCT), the short voltage pulse allows bypassing the RCT and the whole measurement corresponds to impedance measurement of ESR. Or, in other words, since the fast-transient measurement “sees” capacitances as shunts, RCT and RCT’ are short circuited and do not contribute to the measured impedance. All depicted serially connected resistances (resistance of the conductive layer of each electrode, resistance of the chemistry layers, resistance of the membrane, resistance of the electrolyte - here ISF) are measured by impedance. Moreover, this technique has the advantage of allowing for low-power implementation thereof. Furthermore, the circuitry is very simple and the measured impedance value corresponds to a single frequency impedance measurement at a very high frequency, thus the measurement is selective for ESR, where the changes are also most pronounced. Furthermore, there is no need for sensor polarization, as CT is not measured there.

Figure 3 shows a very low power implementation schematic. A pulse generator 134 is generating, for example, one 20 ps pulse every second (e.g. allowing the system making one detection per second). This signal is connected to a high value reference resistor R (for example 2.2MQ). The other side of the reference resistor R is connected to the WE electrode 118.

If the analyte sensor 110 is dry, its impedance is very high, higher than 100MQ. When the output of the pulse generator 134 is at 0 (most of the time), the voltage on both side of the reference resistor R is 0. The output of the Nand gate N1 is 1, the RS flip-flop stays with an output at 0 and no wake-up signal is given to the MCU 132. When a pulse is coming (one time per second), the voltage on both side of the resistor R is close to the battery voltage. The output of the Nand gate N1 is 1, the RS flip-flop stays with an output at 0 and no wakeup signal is given to the MCU 132. If the analyte sensor 110 is wet, its impedance drops below 100 kQ. The voltage at the right part of the reference resistor R is now under the threshold of the input of the Nand gate N2 during a pulse. Both inputs of the Nand gate N1 are at 1, its output is 0. This is setting the output Q of the RS flip-flop at 1 and waking up the MCU 132. The MCU 132 asks the pulse generator 134 to put its output in three state mode to avoid to perturbate the normal functioning of the potentiostat (with the RST pin that also reset the RS flip-flop). A small low pass filter 136 is used at one of the inputs of the Nand gate N1 to avoid glitches at the output of N1 during the rising edge of the pulse (both inputs are moving around the same time). This low pass filter 136 could be constituted of only one resistor and taking advantage of the input capacitance of the gate. *

Additionally or alternatively, for example, the conductivity of the analyte sensor 110 is determined using at least one DC resistance measurement, e.g. as shown in the embodiment of Figure 4. The schematic shown in Figure 4 may be purely static and no pulse generator is required. As long as the analyte sensor 110 is dry, its impedance is very high, over 100 MO. For example, R1 can have a value around 2.2MQ, however, other values are possible. When the MCU 134 is sleeping, the pin Out is at logical 1. VGS of the P mosfet may be close to 0 V and the wake-up pin is also at 0. When the analyte sensor 110 is wet, it is generating a negative voltage between WE 116 and CE 118 of around lOOmV (the potential of CE 118 is lower than the one at WE 116). The voltage at the right part of R1 is strongly dropping. The VGS of the P mosfet is now under the threshold of the transistor (e.g. around -0.5 to -1 Volt) and the top point of R2 and the wake-up pin are now at the battery voltage. The MCU 134 wakes up and put the Out pin in three state (or analog input) to avoid to perturbate the normal functioning of the potentiostat.

List of reference numbers analyte sensor sensing chemistry

Ag/AgCl substrate conductive layer working electrode, WE further electrode membrane insulating layer sensor assembly electronics unit wake up unit energy reservoir microcontroller unit pulse generator low pass filter

Claims

1. A sensor assembly (124) comprising at least one analyte sensor (110) configured for transdermal detecting at least one analyte, wherein the analyte sensor (110) comprises at least two electrodes (116, 118), wherein the sensor assembly (124) comprises at least one electronics unit (126) connectable to the analyte sensor (110), wherein the electronics unit (126) comprises at least one wake up unit (128) configured for determining conductivity of the analyte sensor (110) and for triggering a wake up of the sensor assembly (124) depending on the determined conductivity of the analyte sensor (110).

2. The sensor assembly (124) according to the preceding claim, wherein the wake up is triggered in case of a conductivity change from an initial conductivity value is determined, wherein the wake up is triggered in case of a conductivity change exceed at least one predefined limit.

3. The sensor assembly (124) according to the preceding claim, wherein the electronics unit (126) comprises at least one microcontroller unit (132) configured for controlling operation of the analyte sensor (110), wherein the wake up unit (128) is configured for generating at least one wake up signal depending on the determined conductivity and for providing the wake up signal to the microcontroller unit (132), wherein the microcontroller unit (132) is configured for switching a status of the sensor assembly (124) from an inactive status to an activated mode upon receiving the wake up signal.

4. The sensor assembly (124) according to any one of the preceding claims, wherein the conductivity of the analyte sensor (110) is determined using at least one DC and/or AC measurement.

5. The sensor assembly (124) according to any one of the preceding claims, wherein the conductivity of the analyte sensor (110) is determined using at least one impedance measurement, wherein the wake up unit (128) comprises at least one signal generator device, wherein the wake up unit (128) comprises at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor (110), wherein the wake up unit (128) is configured for applying an AC voltage signal to the serially connected reference resistance and the analyte sensor (110), wherein the wake up unit (128) is configured for determining a voltage distribution over the analyte sensor (110) and the reference resistance during the AC voltage signal, wherein the wake up unit (128) is configured for activating the sensor assembly (124) in case of a change in voltage distribution to a least a predefined amount.

6. The sensor assembly (124) according to the preceding claim, wherein the signal generator device comprises at least one pulse generator (134) configured for generating a fast-transient voltage signal, wherein the wake up unit (128) comprises at least one reference resistance R connected to the pulse generator (134) and connected in series with the analyte sensor (110), wherein the impedance measurement comprises applying the fast-transient voltage signal to the serially connected reference resistance R and the analyte sensor (110), wherein the wake up unit (128) is configured for determining a voltage distribution over the analyte sensor (110) and the reference resistance R during the fast transient voltage signal, wherein the wake up unit (128) is configured for activating the sensor assembly (124) in case of a change in voltage distribution to a least a predefined amount.

7. The sensor assembly (124) according to the preceding claim, wherein the fast-transient voltage signal comprises a single pulse or series of pulses, wherein the duration of each pulse is < 20 ps, preferably < 10 ps.

8. The sensor assembly (124) according to any one of the preceding claims, wherein the conductivity of the analyte sensor (110) is determined using at least one DC resistance measurement, wherein the wake up unit (128) comprises at least one reference resistance R1 connected in series with the analyte sensor (110), wherein the DC resistance measurement comprises distributing a DC voltage to the analyte sensor (110) and the reference resistance R1 and measuring at least one voltage distribution over the analyte sensor (110) and reference resistance Rl, wherein the wake up unit (128) is configured for activating the sensor assembly (124) in case of a change in voltage distribution to at least a predefined amount.

9. The sensor assembly (124) according to any one of the preceding claims, wherein the wake up unit (128) is configured for detecting an insertion of the analyte sensor (110).

10. The sensor assembly (124) according to any one of the preceding claims, wherein the analyte sensor (110) is a two-electrode sensor or a three-electrode sensor.

11. A method for wake up of a sensor assembly (124) according to any one of the preceding claims, the method comprises determining conductivity of the analyte sensor (110) and triggering a wake up of the sensor assembly (124) depending on the determined conductivity of the analyte sensor (110).

12. The method according to the preceding claim, wherein the conductivity of the analyte sensor (110) is determined using at least one DC resistance or AC impedance measurement.

13. The method according to any one of the preceding claims referring to a method, wherein the conductivity of the analyte sensor (110) is determined using at least one AC impedance measurement, wherein the method comprises i) generating and applying at least one AC voltage signal such as at least one fasttransient voltage signal by using at least one signal generator device of the wake up unit (128), wherein the wake up unit (128) comprises at least one reference resistance connected to the signal generator device and connected in series with the analyte sensor (110), ii) measuring at least one voltage distribution over the analyte sensor (110) and reference resistance during the AC voltage signal, iii) activating the sensor assembly (124) in case of a change in voltage distribution to a least a predefined amount.

14. The method according to any one of the preceding claims referring to a method, wherein the conductivity of the analyte sensor (110) is determined using at least one DC resistance measurement, wherein the method comprises a) distributing a DC voltage to the analyte sensor (110) and a reference resistance connected in series with the analyte sensor (110); b) measuring at least one voltage distribution over the analyte sensor (110) and reference resistance; c) activating the sensor assembly (124) in case of a change in voltage distribution to at least a predefined amount.

15. The method according to the preceding claim, wherein the DC voltage is removed after activating the sensor assembly (124).