Gas sensor with nanostructures

Abstract

The present invention relates to a sensor assembly for a gas sensor. The sensor assembly comprises an electronic board, such as a Printed Circuit Board, having a first board side and a second board side, opposite to the first board side, and a transducer comprising a substrate which has a first substrate side and a second substrate side, opposite to the first substrate side, wherein a plurality of nanostructures is deposited on the second substrate side. According to the invention, the second substrate side is attached to the first board side, so that the plurality of nanostructures face the first board side, and the sensor assembly is provided with one or more perforations, in order to allow a gas flow to reach the plurality of nanostructures. The present invention also refers to a method of manufacturing the sensor assembly and to a method of using it, for example in a sensor for detecting thermal runaways of batteries.

Description

[0001] GAS SENSOR WITH NANOSTRUCTURES

[0002] TECHNICAL FIELD

[0003] The present invention refers to the field of gas sensors. In particular, the present invention refers to the field of gas sensors exploiting nanostructures, such as nanotubes, for sensing.

[0004] STATE OF THE ART

[0005] Sensing chemical and biological species plays an important role in many industrial, agricultural, medical, and environmental processes. In some applications, the chemical and biological species may be for instance organic or inorganic gas molecules and the devices used for sensing may be gas sensors. For example, detection of runaway fumes emitted by Lithium-ion batteries provides a crucial measure for early detection of the phenomenon of thermal runaway.

[0006] Gas sensors that use nanotubes, such as carbon nanotubes, for detection of gas molecules are known at the state of the art.

[0007] An example of a gas sensor with nanotubes, also referred to as nanotube device, is disclosed in document WO 0144796 A1. The nanotube device of WO 0144796 A1 comprises at least one nanotube, preferably a carbon nanotube, which is electrically connected with its ends to first and second conducting elements, such as electrodes. The nanotube device may be used as a chemical or biological sensor. To tune the sensitivity of the device to a variety of molecular species the nanotubes may be modified by coating, or decorating with one or more sensing agents, to impart sensitivity to a particular species in its environment.

[0008] Another example of a gas sensor exploiting nanostructures for sensing is disclosed in document WO 03 / 046536 A1 . The chemical sensor device of WO 03 / 046536 A1 comprises a substrate and a sensor medium formed on the substrate, wherein the sensor medium comprises onedimensional nanoparticles made of semiconducting compounds having different selectivity towards a target molecule. The one-dimensional nanoparticles may be hollow or filled and may have the form of a nanotube or a nanowire. The sensor medium may be deposited as a film onto interdigitated electrodes, for instance made of gold, which were deposited onto an inert substrate.

[0009] In order to increase the duration and the accuracy of the chemical sensors, it is necessary to protect the nanotubes, or the other nanostructures, from mechanical impacts and / or direct contact with contaminants. Therefore, it is advantageous to apply a filter on the sensor substrate on which the nanotubes or nanostructures are deposited. However, application of a filter requires a material connection between the sensor substrate and the filter, such as gluing or welding, which can negatively affect the properties of the nanotubes, or nanostructures, for instance by providing excessive heating.

[0010] Due to the sensitive nature of nanostructures or nanotubes, in particular of carbon nanotubes, there is a need to develop sensing elements that are protected from mechanical impact and coarse contamination.

[0011] SUMMARY

[0012] It is thus an object of the present invention to provide an improved gas sensor which ensures a fast and precise detection of the gas molecules and a long duration of the device. It is also an object of the present invention to provide a method for assembling the gas sensor.

[0013] This object is achieved by providing an assembly for a gas sensor comprising an electronic board and a transducer with nanostructures, such as nanotubes, wherein the transducer is positioned upside down on the electronic board, so that the nanostructures face the electronic board.

[0014] According to a first aspect of the present invention, a sensor assembly for a gas sensor is provided, the sensor assembly comprising: an electronic board, such as a Printed Circuit Board (PCB), having a first board side and a second board side, opposite to the first board side; a transducer comprising a substrate having a first substrate side and a second substrate side, opposite to the first substrate side, wherein a plurality of nanostructures is deposited on the second substrate side;

[0015] Wherein the second substrate side is attached to the first board side so that the plurality of nanostructures faces the first board side, and

[0016] Wherein the sensor assembly is provided with one or more perforations in order to allow a gas flow to reach the plurality of nanostructures.

[0017] The advantage of this solution is that the nanostructures deposited on the transducer substrate are protected against any mechanical impact or direct contact with contaminants present in the external environment. Therefore, the sensing process is more efficient and precise. The one or more perforations provided in the sensor assembly ensure that the gas flow can reach the nanostructures for the sensing process.

[0018] In the present invention, it is to be understood that the term “nanostructure” refer to any structure having at least one dimension in the nanoscale, such as nano-textured surfaces, nanotubes, nanoparticles, or the like. Nano-textured surfaces indicate nanostructures which have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have one or two dimensions on the nanoscale, i.e., the diameter of the tube may be between 0.1 and 100 nm, and its length may be longer than 100 nm. Nanoparticles, such as spherical nanoparticles, have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. Some illustrative and non-limiting examples of nanostructures may be nanotubes, Carbon nanotubes, fullerenes, graphene, or the like.

[0019] According to an embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein one or more of the perforations are provided in the electronic board in order to allow the gas flow to pass from the second board side to the first board side and reach the plurality of nanostructures.

[0020] The advantage of this configuration is that the nanostructures are protected against the external environment and, at the same time, the perforations formed in the electronic board allow the gas to be analyzed to pass through and to reach the nanostructures, from the bottom of the device, to enable sensing. In this way, the sensing process is accurate and efficient, because the flow of gas is precisely controlled.

[0021] The dimensions of the one or more perforations of the electronic board have to be designed so as to allow air molecules or other gas molecules to be detected to reach the transducer. At the same time, the dimensions of the one or more perforations of the electronic board have to be designed to block molecules that must not be detected.

[0022] According to preferred configurations, the one or more perforations provided in the electronic board may have a size comprised in the range between 1 pm and 20 pm, preferably between 10 pm and 15 pm. According to other preferred configurations, the one or more perforations provided in the electronic board may have a size comprised in the range between 10 mm and 20 mm, if an additional filter is also applied to the electronic board.

[0023] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein one or more of the perforations are provided in the substrate of the transducer in order to allow the gas flow to pass from the first substrate side to the second substrate side and reach the plurality of nanostructures.

[0024] The advantage of this configuration is that the nanostructures are protected against the external environment and, at the same time, the perforations formed in the transducer substrate allow the gas to be analyzed to pass through and reach the nanostructures, from the top of the device, to enable sensing. In this way, the sensing process is accurate and efficient, because the flow of gas is precisely controlled.

[0025] It is to be understood that, in the present disclosure, the sentence that “one or more perforations are provided in the transducer substrate” may indicate that the substrate of the transducer is perforated, or that the substrate of the transducer is made of an air permeable material.

[0026] In a similar way, the sentence that “one or more holes are provided in the filter” may indicate that holes are formed in the filter, or that the filter is made of an air permeable material.

[0027] According to an illustrative embodiment, the perforations may be formed both in the electronic board and in the transducer substrate.

[0028] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the perforations are formed both in the electronic board and in the transducer substrate, and the one or more of the perforations of the electronic board are aligned with one or more of the perforations of the transducer substrate.

[0029] The advantage of this configuration is that the gas can reach the nanostructures from both a top direction and a bottom direction with respect to the sensor assembly, and can easily flow from the bottom of the electronic board to the top of the transducer because the perforations are aligned.

[0030] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, further comprising separating means for separating the transducer from the electronic board and preventing direct contact between the plurality of nanostructures and the electronic board.

[0031] The advantage of this configuration is that the transducer is not directly in contact with the electronic board, hence the nanostructures are not damaged by friction or scraping between the transducer and the electronic board.

[0032] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, further comprising a filter attached to the second board side, the filter comprising a plurality of holes, for instance holes defining a lattice pattern.

[0033] The advantage of this configuration is that the filter allows filtering out gas particles having a size larger than a predefined cut-off size. Therefore, the nanostructures can be protected against contamination with external compounds and the sensing process can be carried out in a precise and controlled way. Preferably, the filter is a membrane made of expanded polytetrafluoroethylene (ePTFE).

[0034] Some other illustrative but non-limiting examples of filtering materials are hydrophobic materials, such as polytetrafluoroethylene (PTFE), Ethylene tetrafluoroethylene (ETFE), polyvinylidene difluoride (PVDF), or hydrophilic materials.

[0035] Preferably, the filter is designed to filter out particles having a size larger than 500 nm.

[0036] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, further comprising a filter attached to the first substrate side, the filter comprising a plurality of holes defining a lattice pattern.

[0037] The advantage of this configuration is that the filter allows filtering out gas particles having a size larger than a predefined cut-off size. Therefore, the nanostructures can be protected against contamination with external compounds and the sensing process can be carried out in a precise and controlled way.

[0038] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein a size of each hole of the filter is smaller than a size of each of the one or more perforations.

[0039] The advantage of this configuration is that the filter allows filtering out gas particles having a size larger than a predefined cut-off size.

[0040] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the transducer is attached and connected to the electronic board by means of wire bonding.

[0041] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the transducer is attached and connected to the electronic board by means of adhesive bonding, such as bonding by means of an Adhesive Conductive Paste (ACP), or by means of an Adhesive Conductive Film (ACF).

[0042] The advantage of this configuration is that the ACP and the ACF layers provide both a mechanical and an electrical connection between the transducer and the electronic board. The mechanical and electrical connections realized by means of adhesive bonding are stable and secure.

[0043] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the nanostructures are nanotubes, preferably Carbon nanotubes (CNTs). The advantage of using CNTs for sensing is that the CNTs have a high surface-to-volume ratio, so the interaction between the sensor and the analyte gas is optimized. Furthermore CNTs can be functionalized with different molecules, thus enabling to modify their adsorption / desorption properties.

[0044] Preferably, CNTs have dimensions in the range comprised between 0.8 and 1.6 nm.

[0045] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the transducer is configured to convert a sensing signal generated by the nanostructures when reacting with a gas, into an electronic signal, such as a Voltage signal.

[0046] According to another embodiment of the first aspect of the present invention, a sensor assembly is provided, wherein the transducer is a flexible transducer comprising a plastic substrate with metal conductor lines arranged in an interdigitated way.

[0047] The advantage of having a flexible transducer is that it is easy to handle it and to attach it to the electronic board, such as a PCB.

[0048] The advantage of providing the electrodes of the transducer so that they comprise metal conductor lines arranged in an interdigitated way is that the width-to-length ratio of the electrodes is increased. Accordingly, when the nanostructures are deposited on the transducer substrate, the probability that they will cross the metal conductor lines, thus establishing an electrical connection between the electrodes, is increased.

[0049] According to another embodiment of the first aspect of the present invention, a gas sensor is provided, the gas sensor comprising: a sensor assembly as the ones defined above; one or more electronic components connected to the electronic board, wherein the one or more electronic components are configured to process an electronic signal generated by the transducer.

[0050] Preferably, the electronic components may be configured to perform the following functions: Analog Frontend, Wireless communication, energy harvesting, energy storage, power management, humidity sensing, temperature sensing, Micro Controller Unit, Memory, Serial Interface.

[0051] According to another embodiment of the first aspect of the present invention, a gas sensor is provided, wherein the gas sensor is an electronic nose sensor. The electronic nose sensor may be advantageously employed in different fields requiring gas sensing, such as in the medical field or in the automotive field.

[0052] According to a second aspect of the present invention, a method for manufacturing a sensor assembly as the ones described above is provided, the method comprising the following steps: a) providing an electronic board, such as a PCB, having a first board side and a second board side, opposite to the first board side; b) providing a transducer having a first substrate side and a second substrate side, opposite to the first substrate side, wherein a plurality of nanostructures is deposited on the second substrate side; c) flipping the transducer so that the nanostructures face the electronic board ; d) attaching the transducer to the electronic board.

[0053] According to an embodiment of the second aspect of the present invention, a method is provided, wherein the step d) comprises attaching the transducer to the electronic board by means of wirebonding, or adhesive bonding.

[0054] The advantage of these methods is that they allow manufacturing a sensor assembly according to the present invention.

[0055] The nanostructures may be deposited on the transducer according to any technique known at the state of the art.

[0056] According to a third aspect of the present invention, a method for detecting a thermal runaway of a battery by using a gas sensor as the ones described above is provided, the method comprising the following steps: a) Placing the gas sensor in proximity of a battery, such as a Lithium-ion battery; b) Detecting an amount of a predefined gas compound released by the battery; c) Generating an electronic signal proportional to the amount of the predefined gas compound by means of the gas sensor; d) Emitting a warning signal if the amount of the predefined gas compound exceeds a predefined threshold. The advantage of this method is that it allows using a sensor assembly according to the present invention.

[0057] Preferably, the detection range of the gas sensor is comprised between 0.2 m and 1 m.

[0058] FIGURES

[0059] Figure 1 schematically illustrates a side view of a gas sensor according to an embodiment of the present invention.

[0060] Figure 2 schematically illustrates the gas flow directions for enabling gas detection with a gas sensor according to an embodiment of the present invention.

[0061] Figure 3 schematically illustrates a side view of a gas sensor according to the prior art.

[0062] Figure 4 schematically illustrates a side view of a gas sensor according to another embodiment of the present invention.

[0063] Figure 5 schematically illustrates a side view of a gas sensor according to another embodiment of the present invention.

[0064] Figure 6 schematically illustrates a side view of a gas sensor according to another embodiment of the present invention.

[0065] DETAILED DESCRIPTION

[0066] In the following, the present invention is described with reference to particular embodiments, as illustrated in the enclosed figures. However, the present invention is not limited to the particular embodiments described in the following detailed description and shown in the figures. Instead, the described embodiments simply exemplify the different features of the present invention, the scope of which is defined in the claims. Further modifications and variations of the present invention will be clear to the skilled person.

[0067] In the following detailed description, the terms “right”, “left”, “top”, “bottom”, and variations thereon are employed with reference to the orientation shown in the figures.

[0068] Figure 1 schematically illustrates a side view of a gas sensor 100, according to an embodiment of the present invention.

[0069] The gas sensor 100 comprises a sensor assembly 50 including an electronic board 10 and a transducer 20. The electronic board 10 may be for instance a printed circuit board (PCB). The electronic board 10 has a first board side 10A (the top side of figure 1 ) and a second board side 10B (the bottom side of figure 1 ).

[0070] The transducer 20 comprises a substrate that has a first substrate side 20A (the top side of figure 1 ) and a second substrate side 20B (the bottom side of figure 1 ). The substrate comprises a sensor array 21 on which a plurality of nanostructures 26, such as nanotubes, is deposited.

[0071] The transducer 20 may be, for instance, a flexible transducer comprising a plastic substrate with metal conductor lines arranged in an interdigitated way, to increase the width-to-length ratio of the conductor lines. The gap between the lines may be covered with a network of functionalized nanostructures. The functionalized nanostructures may comprise nanotubes, for instance carbon nanotubes, or nanotubes functionalized with any other chemical compounds changing the resistance upon exposure to chemicals or gases.

[0072] The flexible transducer may be assembled on another flexible or rigid substrate in such a way that an electrical contact is established between the electronic board 10 and the transducer 20.

[0073] With continued reference to figure 1 , the transducer 20 is connected to the electronic board 10 by means of wire bonding, i.e. by means of two wires 22 connected to the electric pads 24A and 24B.

[0074] With continued reference to figure 1 , it is possible to see that a plurality of electronic components 40, 42, 44, and 46 is mounted on the electronic board 10. The electronic components 40, 42, 44, and 46 are configured to process the electronic signal generated by the transducer 20 after the sensing process has been carried out by means of the functionalized nanostructures 26. The electronic components may be for instance an Analog Frontend, a wireless communication unit, an energy harvesting component, an energy storage component, a power management component, a humidity sensing, a temperature sensing, a Micro Controller Unit (MCU), a memory, and / or a Serial Interface.

[0075] According to the present invention, the transducer 20 is advantageously mounted on the electronic board 10 upside down, so that the plurality of nanostructures 26 face downwards, towards the electronic board 10. The electronic board 10 and the transducer 20 are advantageously separated from one another by means of separating means (not visible in the figures), in order to avoid a direct contact between the nanostructures 26 and the electronic board 10 and to avoid a possible damage of the nanostructures 26. In the embodiment of figure 1 , the electronic board 10 is advantageously perforated to allow a gas to flow upwards, towards the nanostructures 26. In other words, the electronic board 10 is provided with one or more perforations so that it is gas-permeable.

[0076] Preferably, a plurality of perforations 12 is formed in the electronic board 10. The perforations 12 do not compromise the structural integrity of the electronic board, but they do allow passage of gases.

[0077] In the embodiment of figure 1 , a filter 30 is advantageously mounted on the electronic board 10, on the side not covered by the transducer 20 (i.e. the bottom side). The filter 30 is provided with a plurality of holes 32, which filter out particles present in the environment, so that they do not reach the perforated electronic board 10, nor the transducer 20. Preferably, the holes of the filter 30 have a diameter which is smaller than the diameter of the perforations 12 of the electronic board 10.

[0078] The flow directions D1 , D2, and D3 of the gas analyzed by the gas sensor 100 are schematically shown with reference to figure 2. In figure 2, it is possible to see that the gas reaches the nanostructures 26 and the transducer 20 from the bottom, after passing through and being filtered by the filter 30 and the perforated electronic board 10. The gas reaching the nanostructures 26 induces a change in their resistance, which is detected by the sensor array 21.

[0079] Since the nanostructures 26 face the top side 10A of the electronic board 10, they are protected against contact with the environment on the top side. Accordingly, in the embodiment of figures 1 and 2, the gas cannot reach the nanostructures 26 from the top, but only from the bottom. In this way, the sensing process of the gas by means of the gas sensor 100 is carried out in a more controlled and reliable way. Moreover, thanks to the fact that the nanostructures 26 are covered by the sensor array 21 of the transducer 20, they are protected against mechanical stresses from the outside.

[0080] Figure 3 schematically illustrates a side view of a gas sensor 1000 according to the prior art, for comparison purposes. The gas sensor 1000 of the prior art comprises a sensor assembly 1050, which includes a transducer 1020 and an electronic board 1010. The transducer 1020 includes a sensor array 1021 , on which a plurality nanostructures 1026 is deposited. The electronic board 1010 has a top side 1010A and a bottom side 1010B. The transducer has a top side 1020A and a bottom side 1020B. The electronic board 1010 and the transducer 1020 of the state of the art do not comprise any perforations.

[0081] As visible in figure 3, the nanostructures 1026 are deposited on the top side 1020A of the transducer 1020 and the gas to be analyzed reaches the transducer 1020 from the top, for instance from directions D1 D2', and D3'. Hence, the nanostructures 1026 are exposed to the external environment and to possible mechanical stresses present in the external environment. Starting from the configuration of the gas sensor 1000 of figure 3, a possible solution for protecting the nanostructures 1026 and the sensor array 1021 could be that of placing a filter or barrier on top of the transducer 1020. However, this solution would require fixing the filter or the barrier to the top side 1020A of the transducer 1020, and / or to the top side 1010A of the electronic board 1010 by means of an adhesive material, thus applying a heating source to the transducer 1020. Therefore, placing a filter or a barrier on top of the transducer 1020 in order to protect the sensor array 1021 and the nanostructures 1026 would damage them in view of the heat exposure.

[0082] The gas sensor 100 according to the present invention solves this problem by flipping the transducer 20 and by mounting it to the electronic board 10 so that the nanostructures 26 and the sensor array 21 are faced downwards.

[0083] Figure 4 schematically illustrates a side view of a gas sensor 100, according to another embodiment of the present invention. The gas sensor 100 of figure 4 corresponds to the gas sensor 100 described with reference to figures 1 and 2, and it differs from the latter in that the connection between the transducer 20 and the electronic board 10 is realized by means of conductive bonding, for instance by means of one or more layers of adhesive conducting paste (ACP), or adhesive conductive film (ACF) 28A and 28B that are placed between the transducer 20 and the electronic board 10. Also in the embodiment of figure 4, the electronic board 10 is advantageously perforated so as to allow a flow of the gas from the bottom to the top of the sensor 100. Also in the embodiment of figure 4, a filter 30 is advantageously mounted on the bottom side of the electronic board 10.

[0084] Figure 5 schematically illustrates a side view of a gas sensor 100, according to another embodiment of the present invention. The gas sensor 100 of figure 5 corresponds to the gas sensor 100 described with reference to figures 1 and 2, and it differs from the latter in that the transducer 20 comprises a plurality of perforations 23. In other words, in the gas sensor 100 of figure 4, both the electronic board 10 and the transducer 20 comprise perforations 12 and 23. The perforations 12 and 23 are advantageously aligned so that they allow the gas to flow and reach the nanostructures 26 from both the top direction and bottom direction. In this way, sensing is carried out in the controlled and precise way in a larger amount of gas with respect to the other embodiments can reach the nanostructures 26 and be sensed. The perforations 12 and 23 formed in the electronic board 10 and in the transducer 20 may be realized by means of any perforating technique known at the state-of-the-art. As visible in figure 4, a filter 30 is advantageously mounted on the bottom side of the electronic board 10 in the gas sensor 100.

[0085] Figure 6 schematically illustrates a side view of a gas sensor 100, according to another embodiment of the present invention. The gas sensor 100 of figure 6 corresponds to the gas sensor 100 described with reference to figures 1 and 2, and it differs from the latter in that it does not comprise a filter 30 attached to the bottom side of the electronic board 10. In the gas sensor 100 of figure 6, the perforated electronic board 10 acts as a filter. Accordingly, the gas reaches the nanostructures 26 from the bottom, after passing through the perforations 12 made in the electronic board 10. The perforations 12 may be advantageously sized so as to filter out molecules or chemical compounds having a predefined size or diameter.

[0086] It is to be understood that the present invention is not limited to the embodiments shown in figures 1 , 2, 4, 5, and 6, and that the technical features described with reference to the figures may be combined in different ways. For example, the gas sensors 100 of figures 5 and / or 6 may also be provided with a different connection between the transducer 20 and the electronic board 10. For instance, in the gas sensors 100 of figures 5 and / or 6, the wire bonding connection 22 may be replaced with a conductive bonding connection, and a layer of an adhesive conductive paste (ACP) or layer of an adhesive conductive film (ACF) may be placed between the transducer 20 and the electronic board 10 to ensure a mechanical and electrical connection between the two components.

[0087] For example, in the embodiment of figure 5, wherein the transducer 20 is provided with perforations 23, an additional filter 34 (not shown) may be advantageously mounted on the top side of the perforated transducer 20. The additional filter 34 may be provided with a plurality of holes 32, which filter out particles present in the environment, so that they do not reach the perforated transducer 20. Preferably, the holes of the additional filter 34 may have a diameter which is smaller than the diameter of the perforations 23 of the transducer 20.

[0088] Moreover, even if it is not shown in the figures, it is to be understood that a configuration may also be possible, wherein the electronic board 10 is not provided with perforations and only the transducer 20 is provided with perforations 21 so as to be gas-permeable.

[0089] The transducer 20 may comprise, for instance, a perforated substrate, or it may be formed by a gas-permeable material.

[0090] A possible use of the gas sensor 100 according to the present invention is to detect thermal runaway of lithium batteries. However, it is to be understood that the gas sensor 100 is not limited to this particular use, but may be applied also in other fields, such as in a biomedical field. Preferably, the gas sensor 100, when used for detecting thermal runaway of lithium batteries, comprises a transducer 20 with a network of carbon nanotubes deposited on the sensor array 21 .

[0091] Lithium-ion batteries are widely employed for powering electric vehicles due to their high energy and power densities. The thermal runaway of lithium-ion batteries is the phenomenon of chain exothermic reactions within the battery. These reactions cause a sharp rise in the internal battery temperature causing the inner structures of the battery to destabilize and degrade, which eventually leads to the failure of the battery.

[0092] As the temperature of the battery increases, multiphase fumes are released, which include gases, liquids, and particles. Safety vents may be included in Li-ion batteries to vent these fumes and reduce the risk of explosive hazards. Therefore, it could be useful to study the fumes that are released during thermal runaway.

[0093] During use, the gas sensor 100 according to the present invention is placed in proximity of the lithium battery and is activated. The fumes emitted by the lithium battery may be detected by means of the gas sensor 100 having a sensor array 21 functionalized with carbon nanotubes. The fumes may flow from the bottom of the gas sensor 100, pass through the filter 30 and / or the perforated electronic board 10, and then reach the carbon nanotubes of the transducer 20.

[0094] The fumes may include gas compounds such as hydrogen or carbon oxide, and these gas compounds may be detected by the transducer 20, by means of the functionalized carbon nanotubes deposited on the sensor array 21 . The chemical reaction of the functionalized carbon nanotubes may be converted into an electronic signal by means of the transducer 20; this electronic signal may then be transmitted to the electronic board 10 and may be further processed by the electronic components 40, 42, 44, and 46. The processed electronic signal generated by the gas sensor 100 may be further analyzed by a computer, for instance by means of machine learning algorithms, in order to identify the gas component emitted by the lithium battery and characterize or identify the thermal runaway process. Preferably, the gas sensor 100 may be coupled to another device for emitting a warning signal if an amount of the predefined gas compound exceeds a predefined threshold.

[0095] Even if the present invention has been described with reference to the embodiments described above, it is clear to the skilled person that it is possible to apply different modifications, variations and improvements of the present invention in light of the teachings described above and the field, and within the scope of the enclosed claims, without departing from the scope and purpose of the present invention. Finally, those fields considered known to the skilled person have not been described to avoid covering in a useless way the described invention.

[0096] REFERENCE NUMBERS

[0097] 10: electronic board

[0098] 10A: first board side

[0099] 10B: second board side

[0100] 12: perforations in the electronic board

[0101] 20: transducer

[0102] 20A: first substrate side

[0103] 20B: second substrate side

[0104] 21 : sensor array

[0105] 22: wire-bonds

[0106] 23: perforations in the transducer substrate

[0107] 24A, 24B: electric pads

[0108] 26: nanostructures

[0109] 28A, 28B: adhesive conductive bonds

[0110] 30, 34: filter

[0111] 32: filter holes

[0112] 40, 42, 44, 46: electronic components

[0113] 50: sensor assembly

[0114] 100: gas sensor

[0115] 1000: gas sensor according to prior art

[0116] 1010: electronic board according to prior art 1010A: first board side according to prior art

[0117] 101 OB: second board side according to prior art

[0118] 1020: transducer according to prior art

[0119] 1020A: first substrate side according to prior art

[0120] 1020B: second substrate side according to prior art

[0121] 1021: sensor array according to prior art

[0122] 1022: wire-bonds according to prior art

[0123] 1024A, 1024B: electric pads according to prior art

[0124] 1026: nanostructures according to prior art

[0125] 1050: sensor assembly according to prior art

[0126] D1 , D2, D3: gas flow directions

[0127] D1’, D2’, D3’: gas flow directions according to prior art

Claims

CLAIMS1 . A sensor assembly (50) for a gas sensor comprising:An electronic board (10), such as a Printed Circuit Board “PCB”, having a first board side (10A) and a second board side (10B), opposite to said first board side (10A);A transducer (20) comprising a substrate having a first substrate side (20A) and a second substrate side (20B), opposite to said first substrate side (20A), wherein a plurality of nanostructures (26) is deposited on said second substrate side (20B);Wherein said second substrate side (20B) is attached to said first board side (10A) so that said plurality of nanostructures (26) face said first board side (10A), andWherein said sensor assembly (50) is provided with one or more perforations (12; 23) in order to allow a gas flow to reach said plurality of nanostructures (26).

2. The sensor assembly (50) of claim 1 , wherein one or more of said perforations (12) are provided in said electronic board (10) in order to allow said gas flow to pass from said second board side (10B) to said first board side (10A) and reach said plurality of nanostructures (26).

3. The sensor assembly (50) of claim 1 or 2, wherein one or more of said perforations (23) are provided in said substrate of said transducer (20) in order to allow said gas flow to pass from said first substrate side (20A) to said second substrate side (20B) and reach said plurality of nanostructures (26).

4. The sensor assembly (50) of claim 3 when depending on claim 2, wherein one or more of the perforations (12) of said electronic board (10) are aligned with one or more of the perforations (23) of said substrate of said transducer (20).

5. The sensor assembly (50) of any of claims 1 to 4, further comprising separating means for separating said transducer (20) from said electronic board (10) and preventing direct contact between said plurality of nanostructures (26) and said electronic board (10).

6. The sensor assembly (50) of any of claims 1 to 5, further comprising a filter (30) attached to said second board side (10B), said filter (30) comprising a plurality of holes (32), for instance holes defining a lattice pattern.

7. The sensor assembly (50) of any of claims 1 to 6, further comprising a filter (34) attached to said first substrate side (20A), said filter (34) comprising a plurality of holes (32), for instance holes defining a lattice pattern.

8. The sensor assembly (50) of claim 6 or 7, wherein a size of each hole (32) of said filter (30; 34) is smaller than a size of each of said one or more perforations (12; 23).

9. The sensor assembly (50) of any of claims 1 to 8, wherein said transducer (20) is attached and connected to said electronic board (10) by means of wire bonding.

10. The sensor assembly (50) of any of claims 1 to 8, wherein said transducer (20) is attached and connected to said electronic board (10) by means of adhesive bonding, such as bonding by means of an Adhesive Conductive Paste, or by means of an Adhesive Conductive Film.11 . The sensor assembly (50) of any of claims 1 to 10, wherein said nanostructures (26) are nanotubes, preferably Carbon nanotubes.

12. The sensor assembly (50) of any of claims 1 to 11 , wherein said transducer (20) is configured to convert a sensing signal, generated by said nanostructures when reacting with a gas, into an electronic signal, such as a Voltage signal.

13. The sensor assembly (50) of any of claims 1 to 12, wherein said transducer (20) is a flexible transducer comprising a plastic substrate with metal conductor lines arranged in an interdigitated way.

14. A gas sensor (100) comprising: the sensor assembly (50) of any of previous claims; one or more electronic components (40, 42, 44, 46) connected to said electronic board (10), wherein said one or more electronic components (40, 42, 44, 46) are configured to process an electronic signal generated by said transducer (20).

15. The gas sensor (100) of claim 14, wherein said gas sensor (100) is an electronic nose sensor.

16. Method of manufacturing the sensor assembly (50) of any of claims 1 to 13, said method comprising:a) providing an electronic board (10), such as a PCB, having a first board side (10A) and a second board side (10B), opposite to said first board side (10A); b) providing a transducer (20) comprising a substrate having a first substrate side (20A) and a second substrate side (20B), opposite to said first substrate side (20A), wherein a plurality of nanostructures (26) is deposited on said second substrate side (20B) c) flipping said transducer (20) so that said nanostructures (26) face said electronic board (10); d) attaching said transducer (20) to said electronic board (10).

17. The method of claim 16, wherein said step d) comprises attaching said transducer (20) to said electronic board (10) by means of wire-bonding, or adhesive bonding.

18. Method for detecting a thermal runaway of a battery by using the gas sensor (100) of claim 14 or 15, said method comprising: a) Placing said gas sensor (100) in proximity of a battery, such as a Lithium-ion battery; b) Detecting an amount of a predefined gas compound released by said battery; c) Generating an electronic signal proportional to said amount of said predefined gas compound by means of said gas sensor (100); d) Emitting a warning signal if said amount of said predefined gas compound exceeds a predefined threshold.

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