EP-4735874-A1 - MEASURING METHOD FOR SENSORS BASED ON POLYMER NANOCOMPOSITES, AND SENSOR BASED ON POLYMER NANOCOMPOSITES

Abstract

The invention relates to a measuring method for sensors based on polymer nanocomposites. The method involves a measuring device which is connected to the sensor, an analysis module, a parameter-identification module, and a monitoring module, wherein a. in a first step, at least three different frequencies are selected within a specified frequency range, and the impedance of the sensor, which is excited in the selected frequencies, is then measured in the selected frequency range by means of the measuring device, b. in a second step, the measured impedance values are analyzed in order to determine an impedance model of the sensor by means of the analysis module, c. in a third step, the optimal measuring parameter is identified on the basis of the impedance model by means of the parameter-identification module, said optimal measuring parameter having the highest degree of sensitivity and selectivity for the excitation of the sensor, and d. the optimal measuring parameter is used by the monitoring module for a real-time monitoring of the sensor reaction in one or a plurality of the selected frequencies. The invention additionally relates to a sensor based on polymer nanocomposites, comprising a polymer nanocomposite sensor layer, said nanocomposite sensor layer having electrically conductive nanoparticles which are integrated into a polymer matrix. The nanoparticles have at least one dimension which is shorter than 130 nm, and an electrode structure is in contact with the polymer nanocomposite sensor layer. Electric signals which are generated by the sensor in response to applied stimuli can be measured by means of the electrode structure.

Inventors

• RAMALINGAME, Rajarajan
• Kanoun, Olfa

Assignees

• Nanosen GmbH

Dates

Publication Date

20260506

Application Date

20240626

Claims (1)

1. Patent claims 1. Measuring method for sensors based on polymer nanocomposites, the method comprising a measuring device connected to the sensor, an analysis module, a parameter identification module and a monitoring module, characterized in that a. in a first method step, a selection of at least three different frequencies within a predetermined frequency range takes place and subsequently the impedance of the sensor excited at the selected frequencies is measured in the selected frequency range by means of the measuring device and that b. in a second method step, an analysis of the measured impedance values is carried out to determine an impedance model of the sensor by means of the analysis module and that c. in a third method step, the parameter identification module is used to identify the optimal measuring parameter on the basis of the impedance model, the optimal measuring parameter having the highest sensitivity and selectivity for the excitation of the sensor and that d. the optimal measuring parameter is used by the monitoring module for real-time monitoring of the sensor response at one or more of the selected frequencies. 2. Method according to claim 1, characterized in that the impedance measurement comprises the following steps: a. a time/frequency varying current or voltage signal which is treated using the Discrete Fourier Transform (DFT) to derive frequency-dependent components, b. processing the frequency-dependent components to calculate the frequency-dependent impedance spectrum Z(f), c. analysis of the impedance spectrum Z(f) by means of a signal processing unit to obtain the measurement parameters of the sensor. 3. Method according to claim 2, wherein the signal processing unit comprises an equivalent circuit model for extracting various electrical parameters and/or a neural network for extracting various features and applying machine learning models or a distributed relaxation time analysis for determining the distribution of the time constants or a differential impedance analysis for deriving a local equivalent circuit model. 4. Method according to claim 1, characterized in that the three or more selected frequencies are evenly distributed within the frequency range. 5. Method according to one of the preceding claims, characterized in that the impedance model comprises a series resistance (R s ), a parallel resistance (R p ) and a parallel capacitance (C p ). 6. Method according to one of the preceding claims, characterized in that the impedance model comprises a constant phase element (a) as a replacement for the parallel capacitance (C p ) in case of a depressed semicircular Nyquist plot. 7. Method according to one of the preceding claims, characterized in that the optimal measurement parameter is determined by evaluating the sensitivity and selectivity of each parameter in the impedance model. 8. Method according to one of the preceding claims, characterized in that the real-time monitoring of the sensor response in the selected frequencies is carried out using an embedded circuit. 9. Method according to one of the preceding claims, characterized in that the admittance and/or the permittivity and/or the dielectric constant and/or the capacitance of the sensor based on polymer nanocomposites is measured in the predetermined frequency range. 10. Sensor based on polymer nanocomposites for carrying out a measuring method according to claim 1 with a polymer nanocomposite sensor layer, characterized in that the nanocomposite sensor layer has electrically conductive nanoparticles embedded in a polymer matrix, the nanoparticles being smaller than 130 nm in at least one dimension, and that an electrode structure is in contact with the polymer nanocomposite sensor layer, electrical signals generated by the sensor in response to applied stimuli being measurable by means of the electrode structure. 11. Sensor according to claim 10, characterized in that the polymer matrix of the polymer nanocomposite sensor layer belongs to one or more of the following polymer groups: thermosetting, thermoplastic, cross-linked, elastomeric, biodegradable and conductive polymers. 12. Sensor according to claim 10 or 11, characterized in that the electrode structure is designed in the form of a parallel plate electrode structure in which the sensor layer is arranged between two electrode plates. 13. Sensor according to claim 10 or 11, characterized in that the electrode structure is in the form of an interdigital electrode structure in which the sensor layer is attached or deposited on the electrode to establish electrical contact. 14. Sensor according to one of the preceding claims, characterized in that the nanocomposite material is synthesized using techniques such as solution mixing, melt mixing, in-situ polymerization, electrospinning, layer-by-layer deposition and inclusion polymerization. 15. Sensor according to one of the preceding claims, characterized in that the nanocomposite sensor is manufactured using techniques such as spin coating, dip coating, spray coating, layer-by-layer deposition, filament winding, drop casting, mold casting, electrospinning, laser reduction, hold pressing, 3D printing, screen printing and inkjet printing. 16. Sensor according to one of the preceding claims, characterized in that the electrodes of the electrode structure are formed using techniques such as physical vapor deposition, chemical vapor deposition, screen printing, photolithography, inkjet printing, electroplating or laser ablation.

Description

Measuring method for sensors based on polymer nanocomposites and sensor based on polymer nanocomposites The invention relates to a measuring method for sensors based on polymer nanocomposites and a sensor based on polymer nanocomposites according to the preamble of the first and eleventh patent claims. In the field of electrochemistry, the evaluation and performance analysis of various systems are based on the use of an equivalent impedance model. This model is usually achieved by applying electrochemical impedance spectroscopy (EIS), which is widely used in the investigation of sensors for medical applications, gas sensors and electrochemical systems such as batteries, fuel cells, corrosion processes and electrode/electrolyte interfaces. Conventionally, the EIS is measured over a wide frequency range, typically ranging from a few millihertz to a few megahertz. Based on the resulting Nyquist diagram, an equivalent impedance model is developed to represent the system under investigation. Curve fitting is then used to compare the data obtained from the model with the measured data. This makes it possible to assess how well the model agrees with the experimental results, and to evaluate the behavior and properties of the system. In certain cases, individual parameters of the model are also analyzed to show their influence on the measurement parameters. This contributes to a deeper understanding of the system response and the role of each parameter. In the field of electrical impedance spectroscopy, which goes beyond the field of electrochemistry, the focus is on analyzing the electrical properties of various systems, which include in particular resistive, capacitive and inductive components. This technique provides insights into the electrical behavior, material properties and response of the system under study. Impedance spectroscopy is partly used for the electrical characterization of sensors based on polymer nanocomposites, which can be used to measure physical stimuli such as force, pressure, strain, temperature and humidity. These sensors are characterized over a wide frequency range, ranging from a few hertz to several megahertz. The use of impedance spectroscopy is reported in the literature in two ways. Firstly, as a characterization tool to validate measured data against simulated data using an equivalent circuit model, or as a measurement technique where the entire impedance spectrum represents the excitation of the sensor. The classical approach of impedance spectroscopy, which involves sweeping a wide frequency range, is time consuming. The measurement process can take several seconds to minutes, making it impractical for real-time monitoring of the sensor response. This is due to frequency sampling, since impedance spectroscopy requires sampling over a large frequency range. This method involves taking impedance measurements at numerous points, which requires a significant amount of time and resources. The wide frequency range adds to the overall time of the measurement procedure. This limitation makes it difficult to capture dynamic changes in the sensor's behavior. In addition, the complexity of implementing impedance spectroscopy in an embedded system is a major disadvantage. The hardware and software requirements for accurately measuring impedance at multiple frequencies can be very extensive. This complexity of development, integration and maintenance increases the costs and technical requirements associated with integrating such a system into practical applications. Another disadvantage is the limitation to single-frequency measurements. Measuring only at a specific frequency can compromise the sensitivity and selectivity of the sensor. Different sensor parameters can have different frequency responses, and important information can be lost when analyzing sensor performance at a single frequency. A single-frequency measurement cannot fully capture the sensor's behavior. This can lead to inaccurate characterization and suboptimal performance, especially incomplete characterization and a deterioration in the sensitivity and selectivity of the sensor. Furthermore, the lack of real-time capability hinders application in dynamic environments where immediate and continuous monitoring of the sensor response is required. The inability to detect dynamic changes and fluctuations in sensor behavior limits effectiveness in certain applications. EP 3242128 A1 describes a method for monitoring a composite material, wherein the composite material consists of an epoxy resin filled with electrically conductive nanoparticles, wherein at least one electrical property, such as the impedance of the composite material, is influenced by mechanical deformation. The composite material is integrated into an electrical circuit which emits an electrical signal whose value depends on the electrical property of the composite material, so that a warning message is issued when a certain threshold is exceeded. The measur