A sensing system to detect the presence of NOX in an environment

Abstract

This invention presents a nitrogen oxide sensing system utilizing a polymeric film sensor comprising a plurality of sensing elements with embedded conductive particles. The system relies on detecting the electrical signal change when nitrogen oxides are introduced to the sensing elements. A multi-dimensional signal created by the plurality of sensing elements is processed with an AI model running processor that is trained on detecting nitrogen oxides in the environment. The processor integrates this data with environmental parameters to accurately determine the probability and concentration of nitrogen oxides, irrespective of the environment conditions where the system is deployed.

Description

A SENSING SYSTEM TO DETECT THE PRESENCE OF NOX IN AN ENVIRONMENTFIELD OF THE INVENTION

[0001] This disclosure relates to a system for detecting the presence of nitrogen oxides in an environment. Further, the disclosure also relates to a system for detecting the concentration of nitrogen oxides in the environment.BACKGROUND

[0002] Current nitrogen oxide sensors face several challenges, such as thermal stress causing sensitivity to decrease over time, precision measurement in different background environments with high humidity levels, maintaining sensitivity in confounding backgrounds and selectivity. Sensor array-based systems such as enose provide a solution to these problems, however, these arrays also go through drift over a period of time.SUMMARY

[0003] Disclosed herewith is a NOx (such as nitrous oxides, nitric oxides, and nitrogen oxides) sensing system using a sensor comprising an array of sensing elements. The array of sensing elements comprises polymeric films that are embedded with conductive particles. The plurality of sensing elements of the sensor is embedded with electrodes that communicate the change in at least one of the physical properties and chemical properties of the polymeric film to a processor. The processor uses the multidimensional data of the array of sensing elements and combines it with the operational environment data of the sensing system. From the combined data, the processor determined the probability of the presence of NOx and the concentration of NOx present in the operational environment of the sensing system.BRIEF DESCRIPTION OF DRAWINGS

[0004] FIG. 1 illustrates the sensing element undergoing physical and chemical change when exposed to a gasDETAILED DESCRIPTION

[0005] The invention discloses a sensing system that may be used to detect the presence of NOx in an operational environment of the sensing system. The sensing system comprises a sensor with an array of sensing elements, a processor, plurality of electrodes, a power supply, and a plurality of environmental sensors. The plurality of electrodes may be used to apply a voltage across the sensing elements of the array, from the power source. Further, the electrodes may be used to communicate the change in at least one of the physical properties and chemical properties of the plurality of sensing elements of the sensing element array to the processor, when the sensing system may be exposed to an environment that contains NOx.

[0006] In an embodiment of the invention, at least one of the physical properties and chemical properties of the sensors changes when the sensing elements array is exposed to an environment containing at least one of Nitrous oxides, Nitric oxides, and Nitrogen Oxides, hereinafter referred to as NOx. In yet another embodiment of the invention, at least one of the physical properties and chemical properties of the sensors changes when the sensing elements array is exposed to at least one of the families of compounds of NOy and NOz.

[0007] The sensing system may be used to detect the presence of NOx in the operation environment, wherein the NOx may be present in the form of a mixture of other environmental gases, such as nitrogen, hydrogen, oxygen, formaldehyde, and ammonia. Through the processor, the sensing may detect the presence of NOx from the mixture of at least one of the environmental gases by using one of the background rejection methods and algorithms, that may be present in one of the onboard sensing systems processors and a remote server, connected to the sensing system through one of the wired or wireless networks.

[0008] The disclosed sensing system comprises a plurality of environmental sensors, such as at least one temperature sensor, pressure sensor, humidity sensor, and wind speed sensor. The sensed / measured data from at least one of the environmental sensors, in the form of electrical signal, may be sent to the processor of the sensing system, to combine and process the environmental sensor data with the data from at least one of the sensors of the sensing elements array. The combined data may be processed by the processor, to robustly determine the presence of NOx in the operational environment, irrespective of the environmental conditions around the sensing system.

[0009] In an embodiment of the invention, the system comprises a clock and a time-stamping system, wherein the time stamping system may be a processor that assigns the time from the clock to the sensed data from the plurality of sensors of the sensing element array and plurality of environmental sensor. The time-stamped data from the plurality of sensors of the sensing element array and the plurality of environmental sensors may be sent to the processor, for combination and robustly deducing the presence of NOx in the operational environment.

[0010] The plurality of sensors of the sensing element array may comprise polymeric thin films. The polymeric thin films are deposited on a sensor site using processes such as the direct ink write process and drop-casting process. The thickness and width of the drop of polymeric material are chosen such that the sensitivity and functionality of the film are maintained in extreme working conditions, wherein the extreme working conditions may be defined based on the possible level of humidity, temperature, and atmospheric pressure, that the sensing system may encounter in the operating environment. The polymeric thin films are selected from a group of polymers wherein the polymers absorb or adsorb NOx from the operating atmosphere and undergo one of physical change or chemical change.

[0011] Further, the polymeric thin film of the plurality of sensors of the sensing element array may comprise conductive particles, converting the polymeric thin films to polymer composite thin films. The conductive particle may be one of silver, gold, carbon black, and carbon nanotubes. The conductive particle dimensions may range between 10 nanometers to 1 micron and preferably between 10 nanometers to 500 nanometers. The conductive particles are dispersed evenly in the polymeric thin film. In an embodiment of the invention, the conductive particles are present unevenly, with more concentration near the electrodes and the shortest path between the electrodes. Further, the concentration of the conductive particle may be selected to maintain the sensitivity and functionality of the polymeric thin film, and the operating environment of the sensing system.

[0012] The electrodes of the sensing system are embedded in the plurality of sensors of the sensing element array, wherein the electrodes may be used to apply a voltage across the polymeric thin films of the sensor. The electrodes may be used to connect the plurality of sensors of the sensing element array, with the power supply and with the processor of the sensing system.

[0013] In an embodiment of the invention, the electrodes are laid on a substrate layer and subsequently, the polymeric thin films with the conductive particles are deposited on the electrodes and substrate layer to form the sensing element. In yet another embodiment, the polymeric thinfilm containing conductive particles is deposited on a substrate layer and then the electrodes are laid on the polymeric thin film. Further, after laying the electrodes on the polymeric thin film that contains conductive particles, the second layer of conductive particles filled with polymeric thin film may be deposited on the electrodes layer to form one of the sensors of the array of sensors.

[0014] The electrodes embedded in the conductive particles containing polymeric thin films may apply a constant voltage across the polymeric thin film. During the exposure of NOx to the polymeric thin film, at least one of the physical and chemical properties of the polymeric thin film changes, which may cause a change in at least one of the resistance and capacitance of the polymeric thin film. The change in at least one of resistance and capacitance of the thin film is recorded across the plurality of sensors of the sensing element array and is sent to the processor for deducing the presence of NOx from the change in values of at least one of resistance and capacitance value across the polymeric thin films.

[0015] In an embodiment of the invention, a time-varying voltage is applied across the polymeric thin film and the change in at least one of resistance and capacitance across the polymeric thin film is recorded, during exposure of NOx to the polymeric thin film, for the time-varying voltage. The processor is then provided with the data of time-varying voltage data, along with the change in at least one resistance and capacitance across the polymeric thin film, to deduce the presence of NOx.

[0016] In yet another embodiment of the invention, the polymeric thin film may behave as a semiconductor, due to the introduction of charged carriers, such as holes, in the polymeric thin film, when the polymeric thin film is exposed to NOx. According to the embodiment, the generated charged carriers may be dynamically generated due to exposure to NOx and may disappear when the analyte is changed.

[0017] In yet another embodiment of the invention, presence of VOCs (volatile organic compounds) and other chemicals in the analyte may change the at least one of the physical properties and chemical properties of the polymeric

[0018] In an embodiment of the invention, the polymeric thin film of each of the sensors of the sensing element array may be made from the combination of a plurality of polymers, wherein the polymers may be block polymers, belonging to one of polystyrene, poly siloxane, poly acetate, saccharides, and poly ether families. In yet another embodiment of the invention, each sensor comprises a polymeric thin film, that is made from only one type of polymer, belonging to one of polystyrene, poly siloxane, poly acetate, saccharides, and poly ether families.

[0019] In an embodiment of the invention, the polymeric thin film of at least one of the sensors of the sensing element array may be made from one of Polystyrene-co-methyl styrene, Poly (dimethyl siloxane-co-diphenyl siloxane), Poly (vinyl acetate), Polystyrene-co-Acrylonitrile, Hydroxypropyl cellulose and Poly (methyl vinyl ether-co maleic acid).

[0020] The polymers of the polymeric thin films may be embedded with conductive particles before deposition of the polymeric thin films. The weight ratio of the conductive particles in the polymeric thin films may be 10%-30%, preferably 15%-20%, conductive particles to the polymer.

[0021] During the exposure to NOx, the polymeric thin film of at least one of the sensors of the sensing element array under the process of at least one of physisorption and chemisorption, wherein the amount of at least one of physisorption and chemisorption by each of the polymeric thin film of at least one of the sensors of the sensing element array depends on the type of polymer of the polymeric thin film and the amount and type of conductive particles in the polymeric thin film.

[0022] During the process of at least one of physisorption and chemisorption, the polymeric thin film of at least one of the sensors of the sensing element array expands, and the distance between the conductive particles changes, which may result in a change in at least one of electrical resistance and electrical conductance (herein after also referred to as electrical response or electrical signal) across the polymeric thin film. In an embodiment of the invention, the polymeric thin film of at least one of the sensors of the sensing element array contract, resulting in decreasing the distance between the conductive particles. The change in the distance between the conductive particles due to contraction of the polymeric thin film may result in a change in at least one of electrical resistance and electrical conductance across the polymeric thin film.

[0023] Each of the sensors of the sensing element array may be spatially located to prevent the effect of the presence of one sensor on another due to any one of heat conductance, air flow, contraction, expansion, and strain. In an embodiment of the invention, 32 sensors are used to make the sensing element array wherein the 32 sensors of the sensing element array are arranged along a plurality of rows and columns. In yet another embodiment of the invention, the sensors of the sensing element array may be arranged along the perimeter of a circle or an ellipse. The substrate of each of the sensors of the sensing element array may be at the same height or different height, to prevent the effect of the presence of one sensor on the sensitivity and functionality of the other.

[0024] In an embodiment of the invention, a heater may be embedded in the substrate of the sensing element array wherein the heater heats the polymeric thin film, thereby starting the process of NOx desorption from the polymeric thin films. The heater is powered by the power supply of the sensing system.

[0025] In yet another embodiment of the invention, each sensor of the sensing element array may be provided with a dedicated heater, wherein the heating of each sensor of the sensing element array is individually controlled based on the type of polymer of the polymeric thin film of the sensor. The power to the heating element may be provided from the power supply of the sensing system or a dedicated power supply, exclusive of the sensing system.

[0026] The plurality of environment sensors of the sensing system may include at least one of temperature sensor, atmospheric pressure sensor, humidity sensor, and air velocity sensor. The plurality of sensors may continuously record the environmental conditions of the operating environment of the sensing system. The plurality of environments may record the operating environment temperature, pressure, humidity, air velocity, the temperature of the sensor of the sensing element array, and humidity around each of the sensors of the sensing element array.

[0027] The time-stamped data of the plurality of environment sensors is sent to the processor of the sensing system along with the time-stamped data from the sensors of the sensing element array of the sensing system for combining the data from the plurality of sensors and processing the data from deducing presence and concentration of NOx in the operating environment of the sensing system, without the influence of factors such as atmospheric temperature, humidity, pressure or wind velocity.

[0028] In an embodiment of the invention, the raw data from the plurality of environment sensors, the plurality of sensors of the sensing element array, and the clock may be provided to the processor of the sensing system, which may time stamp each stream of incoming data from the plurality of sensors and use the time-stamped data for deducing the presence and concentration of NOx in the operating environment of the sensing system.

[0029] The presence of a plurality of polymers in the sensing element array and their response to NOx exposure creates a multi-dimensional response wherein each dimension represents the response of polymeric thin film of one of the sensors of the sensing element array. At any given time, the multi-dimensional response results in a manifold. Each of the manifolds for the multidimensional response represents a characteristic change (physical and chemical) in the polymericthin films of the sensors of the sensing element array. The processor of the sensing system processes the manifold of the multi-dimensional response to deduce the presence and concentration of NOx in the operating environment of the sensing system.,

[0030] The time-stamped manifold of the multidimensional response may represent a concentration of NOx in the operating environment of the sensing system wherein the concentration may start from 0% upwards and upwards of 0% may be deduced as the presence of NOx while simultaneously denoting the concentration of NOx in the operating environment of the sensing system.

[0031] The processor of the sensing system may be provided with an artificial intelligence model to comprehend the stream of time-stamped multi-dimensional data from the plurality of environmental sensors and sensors of the sensing element array of the sensing system. The artificial intelligence model is trained using the introduction of NOx in an environment and calibrating the response of the artificial intelligence model with the concentration of NOx that is introduced during training.

[0032] The Artificial intelligence model may tag one of the multi-dimensional responses of the plurality of sensors of the sensing system, the change in multidimensional response of the plurality of sensors of the sensing system, and the rate of change of the multi-dimensional response of the plurality of sensors of the sensing system, as the concentration of NOx.

[0033] According to an embodiment of the invention, at least one of deep learning methods, such as artificial neural networks, deep neural networks, convolutional neural networks, and recurrent neural networks may be used by the processor of the sensing system to process the stream of the multi-dimensional response of the plurality of sensors of the sensing system.

[0034] In yet another embodiment of the invention, at least one of long short-term memory, gated recurrent model, time series forecasting, transformers, autoregressive integrated moving average, and seasonal autoregressive integrated moving average may be used by the processor of the sensing system to process the stream of the multi-dimensional response of the plurality of sensors of the sensing system

[0035] In an embodiment of the invention, the processor for the sensing system may be provided on a remote server, that may be connected to the sensing system using wireless or wireline communication. The wireless communication may use one of WIFI, Bluetooth, Zigbee, and NFC 3G, LTE, 4G, and 5G communication protocols to communicate with the remote server. In yetanother embodiment of the invention, the wireline communication system may connect the sensing system with one of the nodes of the access network, aggregate network, and core network to communicate with the remote server. The wired communication enablers may be one of the electrical conductors and optical conductors.

[0036] The power supply of the sensing system may comprise a plurality of batteries, that may supply power to at least one of the plurality of sensors of the array of sensors, a plurality of environment sensors, the clock, and the heater. In an embodiment of the invention, an AC power supply may be used to provide electrical power to the models of the sensing system.

[0037] The sensing system may be provided with a notification model that may be used to provide notification to a user regarding the presence and concentration of NOx in the operating environment of the sensing system. The sensing system may communicate with the wireless devices of a user, to provide the notification, wherein the wireless device may be one of home assistance, smartphone, and notebook. The sensing system may communicate with the heating, ventilation, and air conditioning model, to mitigate the increase in the concentration of NOx in the environment.

Claims

CLAIMS1. A system for detecting presence and concentration of nitrogen oxides in an environment, the system comprising: a polymer composite sensor including a plurality of polymer composite sensing elements, each of the sensing element being configured to generate an electrical signal in response to an interaction with gases present in an environment; a plurality of environmental sensors configured to generate an electrical signal in response to a measure of a temperature, pressure, and humidity of the environment; and a processor configured to execute an artificial intelligence (Al) model, the model being trained to detect a change in a multi-dimensional signal generated by the plurality of sensing elements and the environment sensors and correlating the change in response with the at least one of presence and change in concentration of nitrogen oxides present in the environment of the nitrogen oxides in the environment.

2. The system of claim 1, wherein a plurality of sensing elements of the sensors comprises one of Polystyrene-co-methyl styrene, Poly (dimethyl siloxane-co-diphenyl siloxane), Poly (vinyl acetate), Polystyrene-co-Acrylonitrile, Hydroxypropyl cellulose and Poly (methyl vinyl ether-co maleic acid).

3. The system of claim 1, wherein the polymers of the sensing elements are electrically functionalized by adding conductive particles in the polymer, and wherein a weight ratio of the conductive particles to the polymer is in a range of 10%-30%, preferable 15% - 20%.

4. The system of claim 1, wherein the sensing elements generate an electrical signal when interacting with at least one of oxides of nitrogen, nitric oxide and nitrogen dioxide.

5. The system of claim 1, wherein the processor combines a relative humidity measure signal with the polymer composite sensing elements and wherein the Al model is trained to detect a change in a multi-dimensional signal generated by the sensing elements in a plurality of humidity ranges.

6. The system of claim 1, wherein the Al model of the processor is trained to detect nitrogen oxides from an environment that comprise of a mixture of plurality of gasses and volatile organic compounds, wherein the artificial intelligence model is trained identify a conductivity increase across the plurality of sensing elements electrical signal and correlate the conductivity increase with the presence and concentration of nitrogen oxides in the environment.

7. A method for detecting presence and concentration of nitrogen oxides in an environment, the method comprising: generating an electrical signal through a plurality of sensing element of a sensor, in response to an interaction of gases present in an environment; generating an electrical signal through a plurality of environment sensors in response to a temperature, humidity and pressure measures of the environment; combining the generated electrical signal from the plurality or sensing elements of the sensor and environment sensors into a multidimensional signal; and processing the multidimensional signal using an artificial intelligence model that is trained to detect a change in multi-dimensional response and correlate the change in response with at least one of presence and concentration of nitrogen oxides in the environment.

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