Device and system for detecting changes in the dielectric properties of a liquid in a drinking vessel, in particular for detecting foreign substances in beverages

Abstract

Device for detecting a change in a liquid in a drinking vessel, comprising: a) a drinking vessel for receiving a liquid, b) at least one electrical sensor arranged in such a way that an electric field passes at least partially through the liquid in the drinking vessel, c) a measuring unit for determining at least one electrical parameter of the sensor, d) an evaluation unit characterized in that the evaluation unit is configured to determine a baseline of the electrical parameter after the drinking vessel has been filled and to detect a time-persistent change of the parameter relative to the baseline, which indicates a change in the physical properties of the liquid, such as occurs when foreign substances are introduced.

Description

1. Technical field

[0001] The invention relates to a device and a system for detecting changes in the physical, in particular the dielectric, properties of a liquid in a drinking vessel. The invention is particularly useful for detecting possible tampering with beverages by foreign substances, such as occurs when sedatives (so-called date rape drugs) are administered. Measurement is carried out using electrical sensors that detect changes in the dielectric properties or the electrical impedance of the liquid. The sensors are preferably integrated into a drinking vessel. 2. State of the art

[0002] Date rape drugs, particularly those based on gamma-butyrolactone (GBL) and gamma-hydroxybutyric acid (GHB), pose a significant safety problem in the hospitality and nightlife sectors. GBL is readily available as an industrial solvent and is rapidly converted in the human body to GHB by lactonase enzymes, which acts as a central nervous system anesthetic.

[0003] In public venues such as bars, clubs, or at events, there is a risk that drinks may be tampered with. Known solutions are mostly based on chemical test strips, subsequent laboratory analysis, or optical reactions. These methods are not continuous, require reagents, or necessitate active user interaction.

[0004] All commercially available products for detecting date rape drugs in beverages, including test strips, coasters, wristbands, and straws, are based on wet chemical color reactions and primarily detect GHB and / or ketamine. While some rapid tests also claim to detect GBL, independent laboratory studies have failed to reliably demonstrate this at practically relevant concentrations. The only validated methods for direct GBL detection are laboratory techniques such as gas chromatography-mass spectrometry (GC-MS) or infrared spectroscopy, which are unsuitable for use in drinking vessels.

[0005] Sensory systems for liquid monitoring are known from industrial applications, such as capacitive sensors, impedance measurement systems, or LC oscillator-based circuits. However, these systems are not designed for use in drinking vessels and can only detect short-term changes in beverages to a limited extent. 3. Object of the invention

[0006] The object of the invention is to provide a device and a system that can automatically detect changes in the physical properties of a beverage without requiring chemical reagents, and that can be integrated into a drinking vessel, are reusable and suitable for use in catering establishments. 4. Solution - Description of the invention

[0007] The problem is solved by a device according to claim 1 and a system according to claim 16.

[0008] The invention utilizes the fact that introducing substances into a beverage causes a change in the effective dielectric properties of the liquid. Different liquids and dissolved substances exhibit different relative dielectric constants (εr). Water has εr ≈ 80, ethanol εr ≈ 24, and γ-butyrolactone (GBL) εr ≈ 42. Alcoholic beverages, depending on their composition, exhibit dielectric constants in the range of εr ≈ 45–75. The addition of GBL to a beverage therefore always leads to a change in the effective dielectric constant of the liquid.

[0009] This change can be detected using electrical sensors, for example by measuring the capacitance, impedance, resonant frequency of a resonant circuit, phase shift or quality factor of a sensor in contact with the liquid. 4.1 Setup of the device

[0010] The device according to the invention comprises: a) A drinking vessel for receiving a liquid. b) At least one electrical sensor arranged such that an electric field passes at least partially through the liquid in the drinking vessel. The sensor preferably comprises an electrode structure that is in direct or capacitive contact with the liquid. The electrode structure can be configured as an interdigital electrode, a planar electrode, annular electrode, or a co-planar electrode structure. In a preferred embodiment, the electrode structure consists of a chemically inert material such as gold, platinum, or another noble metal. c) A measuring unit for determining at least one electrical parameter of the sensor. The electrical parameter is preferably selected from the capacitance, impedance, resonant frequency, phase shift, and / or quality factor of a resonant circuit. In a preferred embodiment, the measuring unit comprises a capacitive digital-to-digital converter (CDC), in particular an LC oscillator IC, which detects the resonant frequency of an LC resonant circuit with a resolution of at least 24 bits, preferably 28 bits. d) An evaluation unit, preferably a microcontroller, which is configured to detect a change in the electrical parameter and to determine a change in the physical properties of the liquid from this. e) Preferably a wireless communication interface, in particular Bluetooth Low Energy (BLE), for transmitting measurement data and alarm signals to an external receiving system. f) A power supply, preferably a rechargeable battery. 4.2 Resonant Oscillating Circuit

[0011] In a preferred embodiment, the sensor is part of a resonant circuit. This circuit comprises an inductance L and a capacitance C, the capacitance being formed wholly or partially by the electrode structure in contact with the liquid. The circuit oscillates at a resonant frequency f = 1 / (2π√(LC)). A change in the dielectric constant of the liquid measurably alters the capacitance and thus the resonant frequency. 4.3 Reference sensor

[0012] In another embodiment, the device additionally includes a reference sensor. The reference sensor is positioned such that its electric field is not, or only partially, in contact with the liquid. Environmental influences such as temperature changes are compensated for by calculating the difference between the measuring sensor and the reference sensor. 4.4 Drinking vessel integration

[0013] The sensor is preferably integrated into the base or wall of the drinking vessel. In a preferred embodiment, the sensor is integrated into a printed circuit board (PCB) located in the base of the drinking vessel. The electronic components (measuring unit, evaluation unit, battery, and communication interface) are housed in a liquid-tight potting compound or a waterproof enclosure. The drinking vessel is preferably made of food-grade polycarbonate, Tritan, glass, or stainless steel and is dishwasher-safe. 4.5 Detection algorithm

[0014] The evaluation unit is designed to determine an event based on at least one of the following characteristics: amplitude of a change in the electrical parameter, temporal persistence of the change, rate of change, and / or change in the frequency spectrum. Preferably, after the container is filled, the evaluation unit determines a baseline for the electrical parameter and then continuously monitors deviations from this baseline. Baseline determination also enables automatic beverage classification. 4.6 Additional sensor versions

[0015] In an alternative or supplementary embodiment, the device may additionally or alternatively include an electrochemical sensor that operates on the basis of current-voltage measurements, in particular amperometry or cyclic voltammetry. This may include a working electrode coated with a conductive polymer, in particular polyaniline (PANI). 5. Advantages of the invention

[0016] The device functions as a detection system: it detects that the physical properties of a beverage have changed, as can occur when foreign substances are introduced. It does not perform forensic substance identification. a) Detection of changes in the physical properties of a liquid, such as those that occur when foreign substances are introduced, without chemical reaction and without consumable reagents. b) Passive real-time monitoring without active user intervention. c) Reusability of the sensor through the use of chemically inert electrode materials. d) Suitability of the drinking vessel for use in a dishwasher. e) Universal applicability to a wide variety of beverage types, as the physical measurement principle is independent of the substance. f) Scalability for catering establishments through wireless networking. 6. Example of implementation

[0017] The invention will now be explained in more detail using a preferred embodiment.

[0018] A drinking cup made of food-grade Tritan contains a potted electronic unit in its base. This unit comprises a circuit board with an FDC2214 capacitive digital converter (Texas Instruments), an ESP32 microcontroller with integrated BLE module, an 18 µH inductor, and a rechargeable lithium-polymer battery.

[0019] An interdigital electrode structure made of gold-plated copper on an FR-4 substrate is mounted on the inner wall of the beaker. The electrode has a finger width of 200 µm, a finger spacing of 200 µm, and an active area of ​​approximately 10 mm × 10 mm. The electrode, together with the 18 µH inductor, forms an LC parallel resonant circuit.

[0020] With an empty container (air, εr = 1), the resonant circuit oscillates at a frequency of approximately 5-10 MHz. When filled with water (εr ≈ 80), the resonant frequency drops significantly. A typical long drink (e.g., vodka and energy drink with approximately 6-7% ethanol and approximately 10% sugar, εr ≈ 68-71) establishes a characteristic baseline frequency.

[0021] The addition of 2 ml of GBL (εr ≈ 42) to 250 ml of beverage reduces the effective dielectric constant of the liquid and leads to a measurable increase in the resonant frequency. The capacitive digital converter with 28-bit resolution and a sampling rate of 10 Hz detects this change in real time.

[0022] The detection algorithm on the microcontroller determines a stable baseline frequency within the first few seconds after filling, then continuously monitors the frequency deviation and sends an alarm signal via BLE to a base station if an adaptive threshold is exceeded.

Claims

Device for detecting a change in a liquid in a drinking vessel, comprising: a) a drinking vessel for holding a liquid, b) at least one electrical sensor arranged such that an electric field passes at least partially through the liquid in the drinking vessel, c) a measuring unit for determining at least one electrical parameter of the sensor, d) an evaluation unit, characterized in that the evaluation unit is configured to determine a baseline of the electrical parameter after the drinking vessel has been filled and to detect a time-persistent change of the parameter relative to the baseline, which indicates a change in the physical properties of the liquid, such as occurs when foreign substances are introduced. Device according to claim 1, characterized in that the electrical parameter is selected from: capacitance, impedance, resonant frequency, phase shift and / or quality factor of a resonant circuit. Device according to claim 1 or 2, characterized in that several electrical parameters are evaluated simultaneously. Device according to one of the preceding claims, characterized in that the sensor is part of a resonant oscillating circuit. Device according to claim 4, characterized in that the resonant oscillating circuit comprises an inductance and a capacitance, wherein the capacitance is formed wholly or partly by the electrode structure in contact with the liquid. Device according to one of the preceding claims, characterized in that the sensor comprises an electrode geometry selected from: interdigital electrode, planar electrode, ring-shaped electrode and / or co-planar electrode structure. Device according to one of the preceding claims, characterized in that the electrode structure consists of or is coated with a chemically inert material, in particular gold, platinum or another precious metal. Device according to one of the preceding claims, characterized in that the sensor is arranged such that the electric field is generated in an area which is completely surrounded by liquid when the drinking vessel is filled. Device according to one of the preceding claims, characterized in that a reference sensor is additionally provided, wherein the reference sensor is arranged such that its electric field is not or only partially in contact with the liquid. Device according to one of the preceding claims, characterized in that the evaluation unit is configured to determine an event based on at least one of the following features: amplitude of a change, temporal persistence of the change, rate of increase of the change and / or change of the frequency spectrum. Device according to one of the preceding claims, characterized in that the evaluation unit is configured to derive an automatic beverage classification from the baseline of the electrical parameter. Device according to one of the preceding claims, characterized in that the sensor is integrated into the base or wall of the drinking vessel. Device according to claim 12, characterized in that the sensor is integrated into a circuit board which is arranged in the base of the drinking vessel, and wherein the electronic components are housed in a liquid-tight potting compound. Device according to one of the preceding claims, characterized in that the device comprises a wireless communication interface, in particular Bluetooth Low Energy (BLE), for transmitting measurement data and alarm signals to an external receiving system. Device according to one of claims 1 to 14, characterized in that the drinking vessel is made of food-grade polycarbonate, Tritan, glass or stainless steel and is dishwasher-safe. System for monitoring a large number of beverages in a catering establishment, comprising: a) a plurality of devices according to any one of claims 1 to 15, b) a higher-level receiving system configured to wirelessly receive measurement data and alarm signals from the plurality of devices, c) a dashboard for real-time visualization of the security status of the monitored beverages, d) a notification system for alerting service personnel in the event of a positive detection result. System according to claim 16, characterized in that the higher-level receiving system comprises a database for logging detection events and is configured to derive beverage information from the baseline values ​​of the individual devices. Device according to one of the preceding claims, characterized in that the change in the electrical parameter reflects a change in the effective dielectric constant of the liquid, in particular a change caused by the introduction of a foreign substance whose dielectric constant differs from that of the liquid in the drinking vessel. Device according to claim 9, characterized in that the evaluation unit is configured to compensate for temperature-related changes in the electrical parameter by calculating the difference between the electrical parameter of the sensor and the electrical parameter of the reference sensor.