Gas sensor system

Abstract

There is provided a gas sensor system for detecting the presence of one or more chemical agents in a gas. The gas sensor system comprises a wearable gas sensor comprising at least one gas flow path arranged such that gas to be analysed can flow from an input port to an output port via the or each gas flow path. The gas sensor comprises a plurality of discrete sensing portions each in fluidic communication with one or more of the gas flow paths and comprising one of a plurality of different types of metal-organic frameworks MOFs. Each type of MOF is responsive to one or more chemical agents. The gas sensor comprises a detection assembly arranged to measure a material property of with at least some of the discrete sensing portions. The gas sensor system comprises a control system arranged to detect one or more chemical agents in the gas flow path based at least in part on one or more values for the material property as measured by the detection assembly.

Description

[0001] GAS SENSOR SYSTEM

[0002] Field of the invention

[0003] The present invention relates to a gas sensor system for detecting the presence of one or more chemical agents contained in a gas. Methods and computer programme products are also disclosed.

[0004] Background

[0005] There is a need to protect personnel from harmful or hazardous agents. Harmful agents could include chemical agents, for example, such as Toxic Industrial Chemicals (TICs) and Chemical Warfare Agents (CWAs). Events involving chemical agents can be unpredictable and are often characterised by great uncertainty and enormous need for information, particularly in the management phase. The threat posed by chemical agents has increased significantly in recent years.

[0006] One problem is the persistent threat of the use of chemical agents in warfare or in acts of terrorism. Chemical warfare agents have a huge potential for damage and can put entire units out of action in a short period of time. Patients contaminated with such warfare agents are extremely resource-intensive, and there is a limit to how many patients can be treated at the same time. Mass damage is defined by simultaneous combat injuries where the resources for treatment are insufficient. When CWAs are used in an area of operation, there is always risk of mass casualty. Chemical agents could include, but are not limited to, organophosphates. Such agents pose a significant threat due to their high toxicity and potential for extensive damage. As well as direct weaponry, chemical agents can also pose a threat as a result of other malicious activity. This activity could include, for example, the bombing of chemical plants.

[0007] Furthermore, chemical agents can pose a threat when entering the environment naturally or accidentally. For example, several serious accidents have occurred involving highly toxic, extremely flammable chemicals in industrial plants and during transport by road and rail, both in Norway and abroad.

[0008] In all of these situations, it is important to have simple and effective protection available to soldiers and / or civilians. Effective detection of harmful agents such as chemical agents is critical for the protection of both military and civilian populations in said hazardous environments and / or during chemical attacks or incidents. Current solutions for the identification of chemical agents are semi-mobile, for example the size of a tablet and upwards to fully equipped armoured vehicles. Currently, multiple different solutions are need for detection of multiple different types of chemical agent. A single solution cannot easily be adapted in the field to detect different agents on an as-need basis. Furthermore, current warning equipment typically requires its own trained and dedicated personnel and is therefore limited to where this is located at any given time. This limits the amount of information available and does not provide individualised information to personnel (e.g. soldiers or civilians). This can also lead to delays in individuals receiving information in relation to the presence of an agent or an agent-based incident more generally.

[0009] The present invention attempts to address at least some of these points.

[0010] Summary of Invention

[0011] The present invention is defined by the appended claims and in the following.

[0012] In a first aspect, a gas sensor system is provided. The gas sensor system is for detecting the presence of one or more chemical agents contained in a gas. The gas sensor system comprises at least one gas flow path or channel. Each gas flow path or channel is arranged such that the gas that is to be analysed can flow from an input port to an output port (of the system) via each gas flow path. The input port and output port may be referred to, respectively, as a gas input port and a gas output port. In some embodiments, the input port and the output port are defined in a housing of the gas sensor system, for example a housing of a gas sensor device of the system.

[0013] The gas sensor system comprises a plurality of discrete sensing portions. Each of the plurality of discrete sensing portions is in fluidic communication with one or more of the gas flow paths. Each of the discrete sensing portions comprises one of a plurality of different types of metal-organic framework (MOF). Each type of MOF is responsive to one or more chemical agents.

[0014] The gas sensor system comprises a detection assembly arranged to measure a material property of at least some of the discrete sensing portions.

[0015] The gas sensor system comprises a control system. The control system is arranged to detect one or more chemical agents in the gas flow path based at least in part on one or more values for the material property as measured by the detection assembly.

[0016] In some embodiments, the gas sensor system comprises a gas sensor comprising the at least one gas flow path, the plurality of discrete sensing portions, and the detection assembly. In some embodiments, the gas sensor is a wearable gas sensor.

[0017] The gas sensor system of the first aspect, based on MOF technology, can advantageously be made lightweight and portable while providing immediate alerts to exposed personnel (wearing or otherwise using the gas sensor system). Such a gas sensor system can be used by individual soldiers or civilians. For example, each individual soldier on operational duty can be provided with a gas sensor system (or, at least, a gas sensor of a wider gas sensor system) according to the present disclosure, without the need for trained and dedicated personnel. This provides an individualised warning system which can be quicker and more effective at identifying agents such as chemical agents.

[0018] The gas sensor system of the first aspect enables early identification, diagnosis and warning of chemical agent incidents. This could potentially save thousands of lives, both military and civilian, as the wearer is made aware of the danger at an early stage and measures can be taken to protect and evacuate personnel and civilians. Early warning to avoid mass exposure is far more effective in terms of resource use, health benefits and operational capability than later attempts at life-saving treatment, evacuation and safeguarding exposed personnel. Early warning will also enable effective evacuation of the civilian population and reduce the burden on civil preparedness and health services - thereby increasing overall defence capacity and preparedness for society as a whole.

[0019] Furthermore, the inventors have recognised that a gas sensor system based on MOF- technology can advantageously be easily adapted to detect many different types of chemical agent simply by selecting an appropriate set of MOF materials for interacting with the target molecules of interest. Such a system can be configured to be sensitive to a plurality of different agents. Such a system can also be made easily reconfigurable as will be described in more detail herein.

[0020] As used herein, the gas sensor being “wearable” means that the gas sensor is suitable for being wearable by an operator or user of the system. This may mean that the gas sensor is portable. This may mean that the gas sensor is lightweight and compact so as to be comfortable and conveniently worn. The wearable gas sensor may comprise an attachment or means for fixing the gas senor on to the body of clothing of a user of the system. Said attachment may comprise a clip or strap, for example. The wearable gas sensor may be durable and weather resistant.

[0021] As used herein, “metal-organic frameworks” or “MOFs” are a class of materials that are constructed by metal ions or clusters connected by organic ligands. MOFs are best known for their relatively very high porosity with well-defined pore sizes in the nanometre range and a very large internal surface area. The responsiveness of a MOF to one or more chemical agents can be tuned or selected based on the selection of metal ion(s) and organic ligand(s). In particular, the MOF (e.g. the internal surface area in the MOF pores) may be functionalised to selectively interact with one or more target analytes by selecting one or more combinations of metal ions and organic ligands. In the present disclosure, the target analytes are chemical agents such as CWAs or TCIs and so the MOFs of the gas sensor may be selected to be responsive to such agents. MOFs are most frequently synthesised as a powder. MOFs may comprise organic dyes, metal nanoparticles and / or carbon quantum dots.

[0022] As used herein, a type of MOF being “responsive” to one or more chemical agents may mean that the MOF is arranged to selectively interact with said chemical agent or chemical agents. Said interaction may comprise one or more physical parameters or material properties of the MOF (such as a physical or chemical property of the MOF) changing in a characteristic or deterministic manner in response to an interaction between the MOF and the or each chemical agent. The physical parameter or material property may be a quantity related to said changing property of the MOF. Thus, by measuring the material property of a MOF that is responsive to a chemical agent, the presence of said chemical agent can be detected or determined based on the material property, e.g. based on changes in the material property. The material property may include physical properties of a MOF (e.g. intrinsic physical properties of a MOF). Preferably, the material property may include one or more optical and / or electrical properties. Even more preferably, the material property may include one or more electrical properties such as conductivity or resistivity. It may be said that a MOF that is responsive to a particular chemical agent is functionalised for that agent. One element of the functionalisation may be to choose organic ligands of a particular length that creates a pore size that is large enough to allow the target molecule to diffuse into pores of the MOF. The target molecule may adsorb, chemisorb, or coordinate to any functional groups on the ligand of the MOF that are exposed in the pores or any exposed metal sites on the clusters. In some embodiments, the change in the properties of MOF in response to a target chemical agent may result in a change in the optical properties of the MOF such as a change in colour or fluorescence. The change in optical properties can then be detectable (or detected) using the detection assembly of the gas sensor system. In some embodiments, the change in the properties of the MOF in response to a chemical agent may result in a change in the electrical properties of the MOF, such as a change in conductivity, resistivity, conductance or resistance.

[0023] A single type of MOF may be responsive to a plurality of different chemical agents. This may mean that said type of MOF has a predictable, characteristic or deterministic behaviour in response to interacting with a plurality of different chemical agents. For example, a first discrete sensing portion of the gas sensor may comprise a first type of MOF. A material property may have a first value when the first type of MOF interacts with a first chemical agent. The (same) material property may have a second value (that is different to the first value) when the first type of MOF interacts with a second chemical agent (that is different to the first chemical agent). Thus, a value for the material property of the first discrete sensing portion measured using the detection assembly may be used to identify, and distinguish between, the first chemical agent and the second chemical agent (based on whether the material property is substantially equal to the first value or the second value). It may be said that the first type of MOF is responsive to the first and second chemical agents.

[0024] In some embodiments, the predictable, characteristic or deterministic behaviour of a single type of MOF in response to interacting with a plurality of different chemical agents may comprise the material property of the MOF having a value for the material property that changes over time. Thus, the first type of MOF (comprised in the first discrete sensing portion) may be arranged to have a value for the material property that changes with time. The value may change in a predictable or deterministic manner with time. In some embodiments, the first type of MOF may be arranged such that the material property has the first value when the first type of MOF interacts with a first chemical agent at a first time. The first time may be a first (predetermined) time after interaction of the first type of MOF with the first chemical agent. The first type of MOF may be arranged such that the material property has a different value to the first value at a second time (that is different to the first time, e.g. higher or lower than the first value). The second time may be a second time after interaction of the first type of MOF with the first chemical agent. The changing behaviour of the MOF may be referred to as the signature of the respective type of MOF when interacting with a particular chemical agent.

[0025] Thus, in some embodiments, the controller may be arranged to detect one or more chemical agents in the gas flow path based at least in part on detected changes in the value for the material property over time (for a particular type of MOF and / or a particular discrete sensing portion). In some embodiments, the controller may be arranged to detect one or more chemical agents in the gas flow path based at least in part on the controller being arranged to detect a signature for the chemical agent in the detected values in the material property (as those values change with time). In some embodiments, the controller may be arranged to detect the first chemical agent at least in part based on the material property of the first type of MOF (optionally, of the first discrete sensing) having the first value at a first time and the different value at a second time different to the first time.

[0026] In some embodiments, a first discrete sensing portion of the gas sensor comprises the above described first type of MOF and a second discrete sensing portion of the gas sensor comprises a second type of MOF that is different to the first. The second type of MOF may also be responsive to at least one of the first and second chemical agents. For example, the material property may have a third value when the second type of MOF interacts with the first chemical agent. The material property may have a fourth value when the second type of MOF interacts with the second chemical agent. In such embodiments, the control system is arranged to detect the presence of the first chemical agent based on both: the value of the material property measured for the first discrete sensing portion being substantially equal to the first value; and the value of the material property measured for the second discrete sensing portion being substantially equal to the third value. Similarly, the control system may be arranged to detect the presence of the second chemical agent based on both: the value of the material property measured for the first discrete sensing portion being substantially equal to the second value; and the value of the material property measured for the second discrete sensing portion being substantially equal to the fourth value. In other words, detection of a chemical agent in such embodiments may rely on the determination of a plurality of values for the material property as measured for a plurality of different discrete sensing portions comprising different types of MOF. A unique set of values for a particular material property may be associated with each chemical agent. Each value may relate to a value for the material property for a specific discrete sensing portion or type of MOF. The unique set of values may be referred to as the fingerprint for the chemical agent.

[0027] An advantage of using a plurality of different types of MOFs, and of using MOFs that are responsive to a plurality of different types of chemical agent, is that the gas sensor can accurately detect a plurality of different chemical agents. For example, the unique fingerprint approach described above may allow for accurate distinction between chemical agents.

[0028] In some embodiments, each value described above (e.g. the first, second, third and fourth values) may be a value at a first time. It has already been described that, in some embodiments, the first type of MOF may be arranged to have the first value for the material property (when interacting with a first chemical agent) at a first time and that the value for the material property of the MOF may vary with time. Similarly, the first and / or second type of MOF may be arranged such that each of the second, third and fourth values for the material property may be values at the first time. One or more of the second, third and fourth values may also change with time. For example, the first type of MOF may be arranged to have the second value for the material property at a first time after interacting with the second chemical agent. The first type of MOF may be arranged to have a different value to the second value for the material property at a second time after interacting with the second chemical agent. For example, the second type of MOF may be arranged to have the third value for the material property at a first time after interacting with the first chemical agent. The second type of MOF may be arranged to have a different value to the third value for the material property at a second time after interacting with the first chemical agent. For example, the second type of MOF may be arranged to have the fourth value for the material property at a first time after interacting with the second chemical agent. The second type of MOF may be arranged to have a different value to the fourth value for the material property at a second time after interacting with the second chemical agent. The controller may be arranged to detect the first and / or second chemical agent in the gas flow path based at least in part on detected changes in the value for the material property of the first and / or second type of MOF over time.

[0029] In some embodiments, the controller may be arranged to determine (or infer) a concentration of the detected chemical agent. This may be a concentration of the detected chemical in the gas flow path. In some embodiments, the controller may be arranged to determine the concentration of the detected chemical agent based at least in part on a signal strength received at the controller from the detection assembly. Alternatively, or additionally, the controller may be arranged to determine the concentration of the detected chemical agent based at least in part on a signal strength received at the controller from the detection assembly. The controller may be arranged to compare the detected concentration to one or more predetermined threshold values. The one or more predetermined threshold values may be predetermined threshold values for risk factor associated with the concentration of the respective chemical agent for a predetermined period. The predetermined period may be 10 minutes, 30 minutes, 1 hour, 4 hours, and 8 hours. For example, the predetermined threshold values may comprise values associated with a first level of risk, a second level risk and / or a third level of risk.

[0030] The first level of risk may be previously determined as a concentration level which, after exposure for the predetermined period, results in notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, these effects may not be disabling and / or may transient and reversible upon cessation of exposure.

[0031] The second level of risk may be previously determined as a concentration level which, after exposure for the predetermined period, results in irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.

[0032] The third level of risk may be previously determined as a concentration level which, after exposure for the predetermined period, results life-threatening health effects or death.

[0033] In some embodiments, the predetermined threshold values may be previously determined literature values. In some embodiments, the predetermined threshold values may be values determined according to the Acute Exposure Guideline Levels (AEGLs) of the United States Environmental Protection Agency. In some embodiments, the predetermined threshold values may be stored in a memory of the controller (or wider system).

[0034] The controller may be arranged to classify a risk level associated with the detected chemical agent (at the determined concentration) based on the comparison with the predetermined threshold values. For example, the controller may be arranged to classify a first level of risk based on the determined concentration level for the chemical agent being greater than a first predetermined threshold and less than or equal to a second predetermined threshold. For example, the controller may be arranged to classify a second level of risk based on the determined concentration level for the chemical agent being greater than the second predetermined threshold and less than or equal to a third predetermined threshold. For example, the controller may be arranged to classify a third level of risk based on the determined concentration being greater than the third predetermined value. The third predetermined value may be greater than the second predetermined value. The second predetermined value may be greater than the first predetermined value. The controller may be arranged to output the risk classification level.

[0035] The controller being arranged to classify risk level may be advantageous as this may allow a user of the device to take appropriate protective and / or precautionary measures for the risk level while balancing practicality and operational efficiency. For example, without this information, there may be a bias towards taking maximal protective and / or precautionary measures, particularly in a military environment, even at very low levels of concentration / risk. This may be impractical and / or hinder operational efficiency.

[0036] Above, an example comprising first and second types of MOF is described. However, it should be understood that the gas sensor may comprise further types of MOF. For example, the gas sensor may comprise n discrete sensing portions and m types of MOF. Each of the n discrete sensing portions may comprise one of the m types of MOF. n may be greater than 2, optionally greater than 10, optionally greater than 50, optionally greater than 100, optionally greater than 150. m may be greater than 2, optionally greater than 5, optionally greater than 25, optionally greater than 50, optionally greater than 100. m may be equal to n. In other words, there may be an equal number of types of MOF as there are discrete sensing portions. In such examples, each sensing portion may comprise a different type of MOF. m may be less than n. In other words, there may be more discrete sensing portions than there are types of MOF. In such example, at least some sensing portions may comprise the same type of MOF.

[0037] As used herein, a “type” of MOF refers to a specific MOF material. For example, discrete sensing portions comprising the same type of MOF may effectively comprise the same material (e.g. the same pairing of ligand(s) and metal ion and / or with the same pore size). Each type of MOF may be defined by the functionalisations it has undergone in order to be responsive to a specific chemical agent or agents.

[0038] A non-exhaustive list of MOFs that could be used for a sensing application include: UiO-66 type, CPO-27 / MOF-74, Fe-BTC, Cu-BTC, A1-MIL-101-NH2, NU-1000, MOF-808, UiO-66-N3, IRM0F-N3, and UiO-66-NO2.

[0039] In some embodiments, detecting one or more chemical agents comprises the control system being arranged to access a database. The database may be stored in a memory internal to the gas sensor system, for example a memory of the control system. In some embodiments, the memory may be external to the control system / gas sensor system. For example, the database may be stored in the cloud.

[0040] The control system may comprise a means for accessing said external memory and retrieving data therefrom.

[0041] The database may comprise a plurality of chemical agent identifiers. A chemical agent identifier may be referred to as a key, such as a primary key. Each chemical agent identifier uniquely identifies a chemical agent. Each chemical agent may be paired with one or more predetermined criteria. The one or each predetermined criterion may be specific to a material property associated with a particular discrete sensing portion or type of MOF. The or each predetermined criterion may be a criteria for the material property of a particular discrete sensing portion or type of MOF that is expected to be satisfied if the respective chemical agent (to which the criteria is paired) is interacting with said MOF or discrete sensing portion. For example, a predetermined criterion may be an expected value or range of values for the material property if the chemical agent is present. The or each predetermined criteria may be experimentally determined and / or based on literature values.

[0042] The control system may be arranged to identify the presence of a chemical agent based on the measured value or values meeting the or all predetermined criteria for a chemical agent identifier. For example, the control system may be arranged to parse the one or more values for the material property into the database and identify the chemical agent identifier whose one or more criteria are satisfied by the one or more values. The control system may be arranged to parse an array of values for the material property into the database.

[0043] In some embodiments, at least one of the chemical agent identifiers of the database is paired with a plurality of predetermined criterion. The control system may be arranged to receive a data array from the detection assembly, the data array comprising values for the material property for each type of MOF. In some embodiments, the control system is arranged such that detection of at least one of the chemical agents is based on values for the material property measured by the detection assembly for a plurality of different types of MOF. Thus, a plurality of values for the material property may be used to determine the chemical agent. The plurality of values may form a set of values or fingerprint, as described above.

[0044] In some embodiments, the gas sensor system is for detecting a plurality of chemical agents in a gas. In some embodiments, at least one of the types of MOF is responsive to a plurality of chemical agents.

[0045] In some embodiments, the detection assembly is arranged to measure (as the or each material property) at least one of: a property of light received from at least some of the discrete sensing portions and an electrical property of at least some of the discrete sensing portions. The detection assembly may preferably be arranged to detect an electrical property of at least some, optionally all, of the discrete sensing portions. The electrical property may be conductivity or resistivity.

[0046] As used herein, the property or properties of light may refer to any property of light received from a discrete sensing portion (for example, after reflection by the sensing portion) that changes in response to the MOF of the sensing portion interacting with a chemical agent for detection. Any such change may be indicative of the interactions that MOF has with a chemical agent. The combined property changes of several MOF materials in the presence of a chemical agents can be specific for that agent. The light detection assembly may be arranged to detect at least one of: polarization, brightness, intensity, illuminance, luminance, colour, wavelength and colour temperature.

[0047] The detection assembly may be arranged to measure the property or properties of light at a single wavelength. In such embodiments, the control system may be arranged to determine the presence of one or more chemical agents in a gas based at least in part on changes in the detected property of light from one or more types of MOF at the specific wavelength.

[0048] Alternatively, the detection assembly may be arranged to measure the properties of light at a plurality of wavelengths. In such embodiments, the control system may be arranged to determine the presence of one or more chemical agents in a gas based at least in part on changes in the detected property of light from one or more types of MOF at one or more of the wavelengths. In some embodiments, the control system may be arranged to perform spectral analysis on the property at the plurality of wavelengths. This may comprise the control system being arranged to determine or measure a distribution of light energy across the plurality different wavelengths and determine the presence of one or more chemical agents based on changes in that distribution.

[0049] In some embodiments, at least one of the MOFs is a luminescent metal-organic framework LMOF. In some embodiments, each MOF is an LMOF.

[0050] As used herein, an electrical property of the discrete sensing portions may refer to any electrical property of the sensing portions that changes in response to the MOF of the sensing portion interacting with a chemical agent for detection. In some embodiments, the electrical property is conductivity, resistivity, capacitance or admittance. In such examples, the discrete sensing portions having an electrical property to be measured may comprise a type of MOF arranged to have an electrical property that is responsive to the chemical agent.

[0051] In some embodiments, the detection assembly comprises pairs of electrodes electrically coupled to each discrete sensing portion and is arranged to measure (as material property ) an electrical property of each discrete sensing portion between the respective pair of electrodes.

[0052] At least one, optionally each, type of MOF comprises at least one of zinc, copper, iron, nickel, zirconium, chromium, aluminium, europium, terbium, cobolt, and a lanthanide. MOF(s) comprising zinc or copper may be preferable as such MOFs may be particularly stable. For example, the or each MOF may be a UiO-66 class MOF or a HKUST-1 MOF.

[0053] At least one, optionally each, type of MOF comprises at least one of a terphenyl- based, a bipyridine-based, a porphyrin-based, and an anthracene-based ligand. This may be the case for LMOFs.

[0054] The gas sensor may be referred to as a gas sensor device. The gas sensor device may be referred to as the primary device of the gas sensor system. The gas sensor may comprise a primary controller. The control system may comprise the primary controller.

[0055] The gas sensor system may comprise a secondary device (in addition to the primary device / gas sensor). The secondary device may comprise a secondary controller. The control system may comprise the secondary controller in addition to the primary controller. The advantage of providing the gas sensor system distributed across at least a primary and secondary device may be that the primary device can be made smaller, lighter, and more cheaply. The primary device may be the portion of the system that is designed to be wearable by individuals. Thus, size, weight and cost are important factors. For example, the primary controller may be arranged to control the detection assembly to activate at appropriate times and / or to receive signals from the detection assembly. However, the control system may be arranged such that the processing of those signals (e.g. to determine the presence or absence of a chemical agent) may be performed by the secondary controller. Said processing (performed by the secondary controller) may require greater processing power and / or memory capacity than the operations performed by the primary controller. Thus, the secondary controller may have greater processing power and / or greater memory requirements than the primary controller. By offloading the processing to the secondary controller, the primary controller may be provided as a relatively small, low-complexity, low-power, and / or low-cost controller such as a microchip for example.

[0056] The secondary controller may comprise a microcontroller unit MCU. The secondary controller or MCU may have a greater processing power than the primary controller or microchip.

[0057] In some embodiments, the primary device (gas sensor device) may comprise a first portable power source such as a first battery (for example, a rechargeable battery). A primary controller as described above has relatively low power requirements. Thus, the first battery may be a micro battery. Again, this achieves a small, lightweight, low-cost, wearable and portable gas sensor.

[0058] The secondary device may comprise a second portable power source such as a second battery. The power requirements of the secondary device may be greater than the power requirements of the primary device. Thus, the second portable power storage device may have a larger capacity for storing power or energy than first portable power storage device.

[0059] In some embodiments, the gas sensor (or primary device of the system) comprises a transmitter. The transmitter may be a transceiver. The transmitter may be arranged to transmit data wirelessly. The transmitter may be a radio transmitter, for example a wireless radio transmitter, a Bluetooth, a Wi-Fi transmitter. The transmitter may operate at other wavelengths than radio, for example infra-red.

[0060] The secondary device may comprise a receiver. The receiver may be arranged to receive signals transmitted by the transmitter of the gas sensor or primary device (when the receiver of the secondary device is in range of the transmitter primary device). Similarly, the transmitter of the primary device may be arranged to transmit signals to be received by the receiver of the secondary device (when in range). The receiver of the secondary device may be a transceiver. The primary controller (of the gas sensor) may be arranged to receive signals indicative of the detected property of light from the light detection assembly. The primary controller may be arranged to control the transmitter to transmit said signals to the receiver of the secondary device at least intermittently.

[0061] The control system may be arranged such that signals transmitted and received by the gas sensor system (e.g. transmitted and received between the primary and secondary device) are encrypted.

[0062] In some embodiments, the primary controller is arranged to be intermittently active. The primary controller may be described as being in an active mode when active. It may be said that the primary controller is arranged to control the primary device (gas sensor device) to be in an active mode when the primary controller is in the active mode. At least some of the time, the primary controller may be in a low- power or dormant. For example, the primary controller may be arranged to remain in the low-power or dormant mode when not in the active mode. This may reduce power requirements of the primary device. Again, this may allow for a smaller first portable power source (e.g. battery) to be used to power the primary device.

[0063] The primary controller may be arranged to control the detection assembly. The detection assembly may be powered by the first portable power source. The primary controller may be arranged such that power is not supplied to the detection assembly in the low-power or dormant mode. This may reduce power consumption of the primary device in the low-power or dormant mode relative to the active mode.

[0064] In some embodiments, the primary controller may be arranged to switch from the low-power mode to the active mode on receipt of an interrupt signal.

[0065] The gas sensor system (e.g. the control system) may be arranged to generate the interrupt signal when movement or changes in direction or speed of the gas sensor system are detected. The gas sensor system may comprise one or more movement sensors arranged to detect said movement or said changes in direction or speed. The inventors have recognised that it may not be necessary for the gas sensor system to continuously detect for the chemical agents while a user is stationary (remaining in an area that has already been determined to be clear of harmful agents). Thus, generating the interrupt signal in this way may reduce the power requirements of the gas sensor system and, in particular, the power requirements of the primary device if present.

[0066] The gas sensor system (e.g. the control system) may be arranged to generate the interrupt signal periodically, for example after a predetermined time or in response to the end of a count-down clock. The control system may be arranged such that the interrupt signal is generated on receipt of a wake-up signal. The gas sensor system (e.g. the primary device) may be arranged to receive the wake-up signal at a receiver (e.g. the transceiver of the primary device described above). In some examples, the secondary device may be arranged to transmit the wake-up signal to the primary device.

[0067] In some embodiments, on switching to the active mode, the primary controller is arranged to determine if the material property for one or more discrete sensing portions has changed by at least a threshold amount relative to a previous measurement or a predetermined value for the material property . This may be based on signals from the detection assembly. The primary controller may be arranged to control the transmitter to transmit said signals to the receiver of the secondary device if a value for the material property has changed by at least the threshold amount. Such a change may be an initial indicator that there has been a change in the presence or absence of one or more chemical agents. The change may be a measured parameter of light at a single wavelength in some examples.

[0068] The primary controller may be arranged to not transmit said signals to the receiver of the secondary device if a material property has not changed by at least the threshold amount. The primary controller may be arranged to switch to the low- power mode if the detected property has not changed by at least the threshold amount. In this way, the primary controller may advantageously be arranged to only supply power to the transmitter of the primary device if there is an initial or early indication that the situation has changed with regard to the presence or absence of chemical agents. Substantially no power may be consumed by the transmitter of the primary device if there is no initial or early indication of such a change. This may reduce the power requirements of the primary device, and of the gas sensor system as whole.

[0069] In some embodiments, the gas sensor system comprises a MOF module. The (wearable) gas sensor (device) may comprise the MOF module. The MOF module may be referred to as a cassette or cartridge. The MOF module may comprise at least one chamber containing a MOF. The chamber may be referred to as a well or a container. In some embodiments, the MOF module defines a plurality of chambers. Each chamber may contain a discrete sensing portion. Each discrete sensing portion may contain a different type of MOF to every other chamber.

[0070] The MOF module may be removable (and / or replaceable) with respect to a housing of the gas sensor (e.g. a housing of the primary device). For example, the housing of the gas sensor may comprise or define a cavity for receiving the MOF module. The cavity and / or MOF module may be arranged such that the MOF module is receivable in the cavity (e.g. slidingly receivable). The cavity and / or MOF module may be arranged such that the MOF module is removable in the cavity (e.g. slidingly removable).

[0071] In some embodiments, the or each chamber may comprise (e.g. be formed by) a hydrophobic material such as a hydrophobic polymer material.

[0072] The MOF module being removable (and / or replaceable) with respect to a housing of the gas sensor may advantageously mean that the gas sensor system is easily adaptable for detecting different types (or different sets) of chemical agent, simply by replacing a first MOF module with a second MOF module.

[0073] The gas sensor system may comprise a first MOF module and a second MOF module. The gas sensor system may be configurable between (at least) a first detection state in which the first MOF module is removably received in the cavity of the housing and a second detection state in which the second MOF module is removably received in the cavity of the housing. The gas sensor system may be arranged to detect the presence of at least one chemical agent in the first state that the gas sensor system is not arranged to detect in the second state. For example, in the first state, the gas sensor system may be arranged to detect the presence of at least a first chemical agent contained in a gas. In the second state, the gas sensor system may be arranged to detect the presence of at least a second chemical agent contained in a gas. The gas sensor may be arranged such that the second chemical agent is not detectable when in the first state and / or such that the first chemical agent is not detectable when in the second state.

[0074] The first MOF module may comprise one or more types of MOF for detecting a first chemical agent. The second MOF module may comprise one or more types of MOF for detecting a second chemical agent that is different to the first chemical agent.

[0075] In some embodiments, more than one MOF module may be removably receivable in the housing of the gas sensor system. In other words, in any given detection state of the gas sensor system, a plurality of different MOF modules may be removably received in the housing of the gas sensor system. The or each type of MOF of each MOF module may be fluidically coupled to one or more gas flow channels of the gas sensor system in this example. An advantage of these embodiments may be the ability to “mix and match” different MOF modules. This may allow for the gas sensor system to be configured to detect different combinations of chemical agents based on a perceived risk of those chemical agents being in the local area. At least one of the plurality of chambers of the or each MOF module may be arranged to be fluidically couplable to one or more air flow paths of the gas sensor system. Optionally, a plurality or all of the chambers may be arranged to be fluidically couplable to one or more air flow paths of the gas sensor system. At least one of the plurality of chambers of the or each MOF module may be arranged to be fluidically coupled to one or more air flow paths of the gas sensor system when the MOF module is received in the cavity of housing of the gas sensor. Optionally, a plurality or all of the chambers may be arranged to be fluidically coupled to one or more air flow paths of the gas sensor system.

[0076] In some embodiments, the gas sensor system comprises an air mover or gas mover. The air mover may be arranged to move or draw gas through the at least one gas flow path, from the input port to the output port. This may ensure a flow of gas through the at least one gas flow path such that fresh or new air continuously flows past the discrete sensing portions / MOFs. This may advantageously mean that the gas or air that is being sensed by the MOFs is representative of the local air to the user rather than stagnant air representative of a previous location or time. The air mover may be a fan such as a piezo-ceramic MEMS micro-fan. If the system comprises a primary and secondary device, the primary device may comprise the air mover. The control system may be arranged such that power is supplied to the air mover in the active mode described above. The control system may be arranged such that power is not supplied to the air mover in the low power or dormant mode.

[0077] The gas sensor system may comprise one or more indicators. The control system may be arranged to trigger at least one of the indicators if a chemical agent is detected.

[0078] The one or more indictors may comprise at least one visual indicator. The visual indicator may comprise a light such as an LED. The visual indicator may comprise a plurality of lights such as a plurality of LEDs. The visual indicator may comprise a first light which may be a green light. The visual indicator may comprise a second light which may be a yellow light. The visual indicator may comprise a third light which may be a red light. The visual indicator may comprise a display such as a liquid crystal display. The control system may be arranged to trigger one or more visual indicators in response to detection of a chemical agent. This may comprise causing the visual indicator to light up. In some examples, the control system may be arranged to control the or each visual indicator differently depending on the chemical agent that has been detected. For example, the light may be controlled to flash in different sequences depending on the chemical agent or different information may be displayed on the display.

[0079] The one or more indicators may comprise an audio indicator. The audio indicator may comprise a loudspeaker, or a bell, or a buzzer. The control system may be arranged to trigger one or more audio indicators in response to detection of a chemical agent. This may comprise causing the audio indicator to make sound. In some examples, the control system may be arranged to control the or each audio indicator differently depending on the chemical agent that has been detected. For example, different sounds may be projected by the loudspeaker or different sound patterns or pulses may be sounded on the bell or buzzer.

[0080] The one or more indicators may comprise a haptic indicator. The haptic indicator may comprise a vibrator arranged to vibrate at least a portion of the gas sensor system. The vibrator may comprise a motor arranged to rotate an off-axis or eccentrically mounted mass. The control system may be arranged to trigger one or more haptic indicators in response to detection of a chemical agent. This may comprise causing the or each haptic indicator to vibrate. In some examples, the control system may be arranged to control the or each haptic indicator differently depending on the chemical agent that has been detected. For example, the haptic indicator may be controlled according to different vibration patterns.

[0081] The gas sensor system may comprise any or each of said visual, audio, or haptic indicators.

[0082] If the gas sensor system comprises a primary device and a secondary device, the primary device may comprise one or more of said indicators. The secondary device may also comprise one or more of said indicators. The gas sensor system may be arranged such that different information is provided by the indicators on the primary device to the indicators provided on the secondary device. For example, the primary device may merely provide an alert that a chemical agent has been detected. The secondary device may comprise indicators able to display greater detail of information. For example, the secondary device may present information relating to the type of chemical agent that has been detected. Further information may be given, for example the time of detection and / or the location of detection. This may enable visualisation of the information from the gas sensor system, for example based on location. In some examples, the gas sensor system may comprise a plurality of gas sensors. In such examples, the visualisation may show the information from the plurality of gas sensors.

[0083] An advantage of providing the one or more indicators is to provide immediate notification directly to potentially exposed personal. Thus, it may be particularly advantageous for the primary device (which, as above, is intended to be worn) to comprise one or more indicators as described above.

[0084] The gas sensor assembly may comprise a communication device. The communication device may be for communicating with a network comprising one or more connected devices, such as a MESH network. In some embodiments, the communication device comprises the transmitter of the primary device and / or the receiver of the secondary device. In some embodiments, the primary device is a first device of the network. The secondary device is a second device of the network.

[0085] In some embodiments, the communication device is a separate transmitter, or transceiver, not previously described. Such a communication device may be arranged to communicate with the one or more external devices. In such embodiments, the gas sensor system as a whole may be considered to be a first device of the network and the one or more external devices form further devices of the network.

[0086] The control system may be arranged to control the communication device to communicate with the network on detection of one or more chemical agents. The control device may be arranged to control the communication device to transmit a signal indicating that one or more chemical agents has been detected. The signal may comprise information indicating the type of agent or agents detected. The control system may be arranged such that the information in the signal is encrypted. The communication device may be arranged such that the signal is receivable by one or more device of the wider network. In this way, data from the gas sensor system effectively communicates warnings to the wider network and to other nearby personnel. This network will play a critical role in ensuring rapid and coordinated response, both military and civilian, in the area of operations. Based on this information, management will be able to make quick decisions about implementing protective measures, organizing evacuation, and preparing for effective and appropriate treatment as well as medical countermeasures for those affected.

[0087] In a second aspect, there is provided a method of detecting the presence of one or more chemical agents in a gas using the system of the first aspect. The method comprises contacting at least some of the plurality of discrete sensing portions with a gas to be analysed. The method comprises measuring a material property associated at least some of the discrete sensing portions. The comprises detecting one or more chemical agents in the gas flow path based at least in part on one or more measured values for the material property.

[0088] In a third aspect, there is provided a computer-implemented method of detecting the presence of one or more chemical agents using a gas sensor system as defined in the first aspect. The method comprises the steps of receiving, at the control system, signals from the detection assembly indicative of the measured material property . The method comprises determining the presence of one or more chemical agents in the gas flow path based at least in part on one or more values for the material property as measured by the detection assembly.

[0089] In a fourth aspect, there is provided a data processing apparatus comprising a processor adapted to perform the steps of the method of the third aspect.

[0090] In a fifth aspect, there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method of the third aspect.

[0091] In a sixth aspect, there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of the third aspect.

[0092] Short description of the drawings

[0093] In the following description this invention will be further explained by way of exemplary embodiments shown in the drawings:

[0094] Figure 1 is a schematic showing a principal of MOF -based sensing by detecting changes in a property of light when an LMOF interacts with a gas comprising a chemical agent;

[0095] Figure 2A shows schematically the illuminance received by the light detector of Figure 1 in the absence of the chemical agent;

[0096] Figure 2B shows schematically the illuminance received by the light detector of Figure 1 in the presence of a first chemical agent;

[0097] Figure 2C shows schematically the illuminance received by the light detector of Figure 1 in the presence of a second chemical agent;

[0098] Figure 3 shows a cross-sectional schematic view of a first example of a gas sensor device according to the present invention;

[0099] Figure 4A shows schematically the illuminance received by a light detector from a plurality of different types of LMOF in the absence of a chemical agent;

[0100] Figure 4B shows schematically the illuminance received by a light detector from the plurality of different types of LMOF in the presence of first and third chemical agents; Figure 4C shows schematically the illuminance received by a light detector from the plurality of different types of LMOF in the presence of second and fourth to sixth chemical agents;

[0101] Figure 4D shows schematically the illuminance received by a light detector from the plurality of different types of LMOF in the presence of a seventh chemical agent;

[0102] Figure 4E shows schematically the illuminance received by a light detector from the plurality of different types of LMOF in the presence of an eighth chemical agent;

[0103] Figure 5 shows a schematic view of a light guide;

[0104] Figure 6 shows a schematic perspective view of a MOF module for gas sensor device of a second example of gas sensor system according to the present disclosure;

[0105] Figure 7 shows a schematic perspective view of a gas sensor device according to the present disclosure, the gas sensor device containing the MOF module;

[0106] Figure 8 shows a schematic perspective view the gas sensor device of Figure 7 in which the MOF module is removable and has been partially removed or partially inserted in a cavity of the device;

[0107] Figure 9 shows a schematic view of sensing assembly for an individual container of the MOF module of Figure 6 or 7;

[0108] Figure 10 shows a schematic of an example of the gas sensing system according to the present invention comprising a primary device and a secondary device;

[0109] Figure 11 shows a schematic of a plurality of primary devices connected to a secondary device as part of a wider network;

[0110] Figure 12 shows a schematic showing a principal of MOF-based sensing by detecting changes in an electrical property a MOF that interacts with a gas comprising a chemical agent;

[0111] Figure 13 shows a cross-sectional schematic view of an example of a gas sensor device implementing the sensing principal of Figure 12;

[0112] Figure 14 shows schematically the illuminance received by a light detector from the plurality of different types of LMOF in the presence of the eighth chemical agent at a second time after the first time, which is represented by Figure 4E above; and Figure 15 shows a schematic cross-section of an example in which MOF material is contained a well formed of a hydrophobic material.

[0113] Detailed description of the invention

[0114] The present disclosure relates to a gas sensor system employing Metal-Organic Framework (MOF) technology in a gas sensor for sensing one or more chemical agents. In general, the detection is based on deterministic and detectable changes in one or more properties of the or each MOF in response to an interaction between said MOF and the chemical agent. By measuring said property or properties, the chemical agent can be detected. Herein, two examples of sets of properties of MOF s that can be detected as part of a chemical agent sensing regime are described: namely properties of light and electrical properties.

[0115] Figure 1 is a schematic drawing representing the sensing of a target analyte 100 (in this example, a chemical agent) by detecting a property of light from a MOF. In this example, the MOF is a Luminescent Metal-Organic Framework LMOF 102. Figure 1 further comprises a light source 104 and a light detector 106. In this example, the chemical agent 100 is contained in a gas that flows past the LMOF 102. The gas is represented by arrow 108, indicating the direction of flow of the gas.

[0116] The LMOF 102 is arranged to interact with, and be responsive to, the chemical agent 100. In this example, the LMOF 102 is porous. In this example, the LMOF 102 is arranged or configured such that the chemical agent 100 can diffuse into the pores of the LMOF 102. In the schematic drawing of Figure 1, this diffusion is represented by the molecule or particle of 100a of the chemical agent 100 being contained with the LMOF 102. This process of diffusion may be referred to as gas adsorption.

[0117] In this example, the LMOF 102 being responsive to the chemical agent 100 means that the LMOF 102 is arranged to change in fluorescence in response to the chemical agent 100 / 100a being diffused in the LMOF 102. In other examples, the LMOF 102 is alternatively or additionally arranged to change colour in response to the target analyte 100 being diffused in the LMOF 102. In either case, the skilled reader will appreciate that one more optical properties of light from the LMOF 102 will change when the LMOF 102 is interacting with the chemical agent 100 versus when the LMOF 102 is not interacting with the chemical agent 100. Thus, changes in said one or more optical properties can serve as indicators of the presence of the chemical agent. In this way, the LMOF 102 can be used in a detector (such as a gas detector system according to the present invention) to sense for the presence of the target analyte 100 in the gas. In this example, the light source 104 comprises an LED arranged to emit light of substantially a first wavelength. The light source 104 is arranged to illuminate the LMOF with said light. In other examples the light source 104 may be a laser rather than an LED. In this example, the light source 104 comprises a single emitter of light (e.g. a single LED). In other examples, for example where it is advantageous for the LMOF to be illuminated with a range of wavelengths of light, the light source 104 may comprise a plurality of light emitters, e.g. a plurality of LEDs.

[0118] In this example, the light detector 106 comprises a first detector in the form of a photodetector such as a photodiode. The photodiode of this example is sensitive to visible light (e.g. between about 380 nanometres and about 700 nanometres). In other examples, the photodiode may be sensitive to non-visible wavelengths of light such as ultraviolet light (between about 10 and 400 nanometres) and infrared (between about 700 and 100 nanometres).

[0119] The skilled reader will be familiar with the operation of a photodiode for converting light energy to electrical signals. In this example, the photocurrent generated by the photodiode in response to illuminance at one or more wavelengths is known. In this example, the spectral response of the photodiode is known. In some examples, the spectral response curve of the photodiode is known. In other words, key parameters such as peak sensitivity wavelength, bandwidth, and overall shape of the response curve are known. In some examples, the photodiode is an RGB photodiode with three peak sensitivities associated respectively with a red, green and blue wavelength.

[0120] As above, in this example, the light source 104 emits light at a first wavelength. In this example, the LMOF 102 increases in fluorescence when interacting with the chemical agent 100. The wavelength of photons emitted by the LMOF 102 when interacting with chemical agent 100 will be referred to as a second wavelength. In this example, the light detector 106 is arranged to detect illuminance at the second wavelength. In other words, the detected optical property (referred to above) is illuminance in this example. The photocurrent response of the photodiode at the second wavelength is known. In this way, it is possible to convert a photocurrent generated by the photodiode into a detected illuminance at the second wavelength. Changes (e.g. an increase) of the detected illuminance at the second wavelength can be used to infer the presence of the chemical agent 100 interacting with the LMOF 102.

[0121] In some examples, a diffraction element (not shown in the drawings) such as a prism or slit or diffraction grating may be positioned between the light sensor 104 and light detector 106. As the angle of diffraction of light is dependent on wavelength (of the light), the diffraction element will disperse the light into its component wavelengths, spreading them out spatially. This spatial spread allows spectral information of the optical property to be determined. This is because the photocurrent detected by a photodiode at each spatial location can be used to determine a value for the optical property (e.g. illuminance) for a different or unique wavelength. This allows a spectral response to be determined or detected with the light detector 106. Increasing the number of measurements increases the number of data points or resolution of the spectrum.

[0122] Optionally, a lens or mirror (not shown in the drawings) may be positioned between LMOF 102 and the light detector 106. The lens or mirror is arranged to focus the light onto the surface of the light detector 106 (e.g. photodiode). In examples also comprising a diffraction element, the lens or mirror may result in each wavelength of the light being focussed at a specific position on the photodiode.

[0123] In some examples, natural light (such as sunlight) can be used to illuminate the MOF. Such example may or may not comprise a dedicated light source.

[0124] In some examples, the light detector 106 comprises a charge-coupled device CCD in addition to or instead of the photodiode.

[0125] MOFs (e.g. LMOFs) can be arranged to be responsive with all manner of target analytes including chemical agents. In this example, this could include changing colour or fluorescence when interacting with said target analytes / chemical agents. For example, the skilled reader will be able to select an LMOF comprising a metal connected to an organic ligand for detecting or sensing the respective target analyte. In some examples, the target analyte is a chemical agent. In some examples, the target agent is a chemical warfare agent such as an organophosphate. Suitable LMOFs that are functionalised for the desired target analyte to be detected or sensed can readily be selected.

[0126] Figure 2A shows schematically the spectrum 200 of light received by the light detector 106 of Figure 1 in the absence of the chemical agent 100. The x axis 204 is wavelength and the y axis 202 is illuminance (at each wavelength). There are two peaks shown in Figure 2A. A first peak 206 at a first wavelength and a second peak 208 at a second wavelength. The first wavelength is the peak wavelength of the light emitted by the light source 104. The second wavelength is the peak wavelength of the light emitted by the LMOF 102. In this example, the LMOF 102 is arranged such that the fluorescence of the LMOF 102 increases on interaction with the chemical agent 100. Thus, in the absence of the chemical agent 100 as in Figure 2A, the illuminance at the second wavelength is relatively low. In this example, the illuminance at the second wavelength is considerably lower than the illuminance at the first wavelength. In other words, the first peak 206 is larger than the second peak 208. The illuminance at the second wavelength may be referred to as resulting from residual fluorescence of the LMOF 102. In some examples, there may be no residual fluorescence effect in the absence of the target analyte. Thus, there may be no second peak 208 in such examples.

[0127] Figure 2B shows schematically the spectrum 250 of light received by the light detector 106 of Figure 1 in the presence of the chemical agent 100. The x axis 254 is wavelength and the y axis 252 is illuminance (at each wavelength). There are two peaks shown in Figure 2B. A first peak 256 is at the first wavelength and so corresponds to the first peak 206 in Figure 2A. A second peak 258 is at the second wavelength and so corresponds to the second peak 208. In the presence of the chemical agent 100 as in Figure 2B, the illuminance at the second wavelength has increased relative to the illuminance at the second wavelength in Figure 2A. In other words, the second peak 258 is larger than the second peak 208. This is because the LMOF 102 is arranged such that the fluorescence of the LMOF 102 increases in the presence of the chemical agent. The illuminance at the second wavelength increases as the fluorescence of the LMOF 102 increases. In this example, the light of the first peak 256 corresponds to photons of light that have been received at the light detector 106 from the light source 104 (e.g. without conversion by the LMOF 102). When the LMOF 102 increases in fluorescence, more of the photons from the light source will be converted into photons of the second wavelength. Thus, as the LMOF 102 increases in fluorescence and the second peak 258 increases in size, the first peak 256 decreases in size in this example. This is why the first peak 256 is smaller than the first peak 206.

[0128] In this example, the light detector 106 is arranged to detect illuminance at the second wavelength. The peak sensitivity of the light detector 106 is represented by the dotted line 210 in Figure 2A and by the dotted line 260 in Figure 2B. Thus, the light detector 106 will detect a greater illuminance in the presence of the chemical agent 100 compared to in the absence of the chemical agent 100. In the case of the light detector 106 being a photodiode, this will mean that the photocurrent generated by the photodiode in the presence of the chemical agent 100 will be greater than in the absence of the chemical agent 100. Thus, the magnitude of the photocurrent can be used to detect the presence of the chemical agent 100. In some examples, if the photocurrent (or detected illuminance at the second wavelength) is above a threshold, it may be determined that the respective target analyte is present.

[0129] In some examples, the light detector 106 may be arranged to detect illuminance at the first wavelength instead of (or as well as) the second wavelength. In such examples, a drop in detected illuminance may be used to determine the presence of the target analyte instead of an increase. As described above, in some examples, the light detector 106 may be sensitive to a range of wavelengths. In such examples, the full spectra shown in Figures 2A and 2B may be detected by the light detector rather than a single wavelength (at 210, 260). This may allow for other detection schemes. For example, a ratio of the magnitude first and second peaks at the first and second wavelength could be detected and changes in that ratio could be used to determine the presence (or absence) of the respective chemical agent. This may also be useful when detecting the light received from the plurality of different LMOFs at the light detector 106 as will be described in more detail herein.

[0130] Figures 2A and 2B are schematic and so are not drawn accurately or to scale. The purpose of Figures 2A and 2B is primarily to demonstrate that the second peak will change in the presence of the chemical agent 100 vs in the absence of the ta chemical agent. In this example, the second peak increases in size because the fluorescence of the LMOF increases in response to interacting with the chemical agent 100. In some examples, the second peak 208 may be negligible or nonexistent in the absence of the chemical agent 100. In some examples, light directly from the light source 104 may not be received at the light detector 106 and so the first peaks 206, 256 may be negligible.

[0131] In some examples, the LMOF is responsive to a plurality of different chemical agents and may respond differently to the different chemical agents. For example, the spectrum of Figure 2B may correspond to the spectrum 250 of light received by the light detector 106 in the present of a first chemical agent. The LMOF may also be responsive to a second chemical agent. Figure 2C shows schematically a spectrum 251 of light received by the light detector 106 of Figure 1 in the presence of the second chemical agent. The spectrum 251 is similar to that of Figure 2A and 2B in that it comprises a first peak 266 at the first wavelength and a second peak 268 at the second wavelength. However, Figure 2C differs from Figure 2B in that the second peak 268 of Figure 2C is lower than the second peak 258 of Figure 2B. This is because, although the LMOF 102 is arranged such that the fluorescence of the LMOF 102 increases in the presence of the second chemical agent, it is not arranged to increase as much as it does in the presence of the first chemical agent. Therefore, a different photocurrent will be generated at the second wavelength when the first chemical agent interacts with the LMOF 102 than when the second chemical agent interacts with the LMOF 102. Knowing the expected photocurrents for the different chemical agents allows the detected photocurrent to be used to distinguish between a plurality of different chemical agents.

[0132] Figure 3 shows a cross-sectional schematic view of a first example of a gas sensor system according to the present invention. In this example, the gas sensor system comprises a gas sensor device 300. The gas sensor device 300 comprises a housing 302. The housing defines a gas (or air) input port 304 and a gas (or air) output port 306. A gas flow path or channel 308 is defined through the gas sensor device 300, from the gas input port 304 to the gas output port 306. The gas flow path 308 is arranged such that gas to be analysed can flow from the gas input port 304 to the gas output port 306.

[0133] The gas sensor device 300 of Figure 3 is arranged to detect the presence of one or more chemical agents 350 based on a MOF sensing scheme for detecting optical properties associated with the MOF(s) similar to what has been described in relation to Figures 1, 2A and 2B. Thus, in this example, a detection assembly 309 comprising a light source 310 and a light detector is provided. The light source 310 is arranged to emit light of at least a first wavelength. The detection assembly 309 comprises a lens 312 optically coupled to the light source 310 and a light trap 314. The gas sensor device 300 comprises an LMOF 316 which is fluidically coupled to the gas flow path 308. The LMOF 316 is optically coupled to a light detector that is positioned below the LMOF 316 (such that the light detector is not visible in Figure 3 but may be one or more photodiodes or CCDs arranged to measure illuminance at least the second wavelength of light, as described previously). In this example, the LMOF 316 is contained in a container defined by the housing 302 of the device 300.

[0134] In this example, the light source 310 is a light emitting diode. The lens 312 is arranged to ensure that the light emitted by the light source 310 is collimated. While Figure 3 shows a single lens, there may be a plurality of optical components downstream of the light source 310. For example, beam expansion optics comprising a pair of lenses may be located downstream of the light source 310 to expand and collimate the light emitted from the light source 310. Two light rays emitted by the light source 310 are represented by the dashed lines extending from the light source 310 towards the gas flow path 308 and on to the light trap 314.

[0135] The light trap 314 is a component of the gas sensor system 300 that is designed to absorb or block the light emitted from the light source 310 from propagating beyond the light trap. In examples, the light trap 314 may comprise at least one of a baffle, a blackened surface of a portion of the gas flow channel 308, and a light-absorbing material. The light trap 314 prevents stray light from being received at the light detector. For example, the light trap 314 may be arranged to absorb substantially all of the light incident thereon and so prevent back-reflection of light from the light source 310 being incident on the light detector. Said stray light might otherwise affect the accuracy of measurements made by the light detector.

[0136] The gas sensor device 300 also comprises a (first) battery 318 and a (first) controller 320. In this example, the gas sensor device 300 also comprises an air mover 322 in the form of a piezo-ceramic MEMS micro-fan. The first battery 318 is electrically coupled or couplable to the first controller 320. The first controller 320 is arranged to control the light source 310, the light detector and the air mover 322.

[0137] In response to an activation signal, the first controller 320 is arranged to activate the light source 310 such that light is emitted by the light source. The first controller 320 is further arranged to activate the air mover 322 such that the air mover moves or draws gas to be analysed through the gas flow path 308. In particular, the air mover 322 is arranged such that, when activated, gas to be analysed is drawn from the gas inlet 304, through the gas flow path 308 passed the LMOF 316, and on to the gas outlet 306. The flow of gas is represented by the arrows in Figure 3.

[0138] As the LMOF 316 is fluidically coupled to the gas flow path 308, the gas to be analysed flows over, around and / or interacts with the LMOF 316. If the gas to be analysed comprises a chemical agent 350 (represented by the small black circles in Figure 3), then that chemical agent 350 will interact with the LMOF 316 as the chemical agent is drawn through the gas flow path 308 by the air mover 322.

[0139] The LMOF 316 is arranged to increase in fluorescence in the presence of the chemical agent 350. Thus, as described in relation to Figures 1, 2A and 2B, the illuminance at the second wavelength will increase when the chemical agent 350 is present in the gas to be analysed - as is the case in Figure 3.

[0140] In this example, the first controller 320 is arranged to receive signals from the light detector. Said signals may correspond to a photocurrent generated by the light detector. In this example, the first controller 320 is arranged to determine detected illuminance, for example at the second wavelength. For example, the first controller 320 is arranged to convert the photocurrent into a value of illuminance based on a known response profile of the light detector. In this example, the first controller 320 is arranged to determine the presence or absence of the chemical agent 350 from the gas to be analysed based on the value of illuminance. This was described in relation to Figure I, 2A and 2B already. For example, the first controller 320 may be arranged to determine presence of the chemical agent 350 based on the absolute value of illuminance. This may involve comparing the absolute value of illuminance to a threshold. This may alternatively or additionally involve parsing the threshold to a database comprising chemical agent identifiers paired with threshold criteria. A chemical agent may be identified by the value of illuminance meeting a threshold criteria for a chemical agent identifier.

[0141] In some examples, the first controller 320 can be arranged to determine the presence of the chemical agent 350 if the absolute value of illuminance is greater than the threshold. In some examples, the first controller 320 can be arranged to determine the presence of chemical agent 350 based on a change in the value of illuminance from an initial or threshold value stored in a memory of the first controller 320. Again, the first controller 320 can be arranged to detect the presence of the chemical agent 350 based on the change being equal to or greater than the initial or threshold value.

[0142] In this example, the chemical agent is indicative of the presence of a chemical agent. Thus, by determining the presence of the chemical agent 350, the first controller 320 may also be arranged to determine the presence of such an agent contained in the gas to be analysed and so contained in the local area. The first controller 320 may be arranged to trigger an alert procedure based on this. For example, the first controller 320 may be arranged to control one or more indicators (such as one or more visual, audio, and / or haptic indicators) of the gas sensor system and / or the first controller 320 may be arranged to send an alert one or more other controllers of the gas sensor system. This will be described in more detail in relation to later examples.

[0143] In some examples, the gas sensor device 300 can alternatively or additionally be made sensitive to a plurality of different chemical agents. This could be achieved by providing a plurality of different types of MOF with each type MOF being arranged for detecting a different chemical agent and / or by providing a type of MOF that is responsive to a plurality of different chemical agents (as described above, in particular with reference to Figure 2C).

[0144] So, in some examples, the gas sensor device 300 comprises a plurality of different types of MOF. In some examples, each type of MOF is contained in the same container. In some examples, each type of LMOF may be arranged such that the change in optical property (e.g. change in fluorescence) occurs at a different or unique peak wavelength and / or such that the properties of the peak (e.g. full-width half maximum and / or maximum illuminance) is different or unique for that particular LMOF. Thus, the first controller 320 may be arranged to perform spectral analysis of the light received by the light detector (or light detectors) to determine the or each target analyte that is present in the gas flow. This is described in more detail in relation to Figures 4A to 4C.

[0145] Figure 4A is a schematic of the spectrum 400 of light emitted by six types of LMOF for detecting eight different chemical agents. In this example, each LMOF is arranged to change in fluorescence in response to interacting with one or more chemical agents. The x axis 404 is wavelength and the y axis 402 is illuminance (at each wavelength).

[0146] The spectrum 400 of Figure 4A represents the situation in which no chemical agents are present / interacting with the LMOFs. First to sixth types of LMOF contribute, respectively, to peaks 410A to 410E. However, in this example, each type of LMOF has a residual fluorescence even in the absence of the respective target analyte. Thus, the six types of LMOF results in six different peaks. In this example, each peak is centred on a different wavelength. In this example, each peak has the same maximum illuminance. In other examples, the residual fluorescence of the different LMOFs may be different resulting in different peaks having different maximum illuminance. Of course, in some examples, the residual fluorescence of one or more of the LMOFs is substantially zero (i.e. negligible) and so no peaks may be apparent. However, it is helpful in the schematic that is Figure 4A to illustrate six peaks.

[0147] The spectrum 420 of Figure 4B represents the situation in which the first and third chemical agent is present in the gas to be detected by the gas sensor device. In this example, the first and third types of LMOF are responsive, respectively, to the first and third chemical agents. The fluorescence of the first and third types of LMOF therefore changes (and, in this example, increases). This results in the illuminance maximum of peaks 410A and 410C increasing while the other peaks remain as per the spectrum 400 of Figure 4A.

[0148] The spectrum 430 of Figure 4C represents the situation in which the second and fourth to sixth chemical agents are present in the gas to be detected by the gas sensor device but not the first or third agents. In this example, the second and fourth to sixth types of LMOF are responsive, respectively, to the second and fourth to sixth chemical agents. The fluorescence of the second and fourth to sixth types of LMOF therefore changes (and, in this example, increases). This results in the illuminance maximum of peaks 410B, 410D, 410E and 41 OF increasing while the other peaks remain as per the spectrum 400 of Figure 4A.

[0149] As described above, a type of MOF may be arranged to be responsive to a plurality of different chemical agents. In this example, the first to fourth and sixth types of LMOF are each additionally responsive to a seventh chemical agent. Furthermore, the first to fifth types of LMOF are each additionally responsive to an eighth chemical agent.

[0150] The spectrum 440 of Figure 4D represents the situation in which only the seventh chemical agent is present in the gas to be detected by the gas sensor device. The fluorescence of the first to fourth and sixth types of LMOF therefore changes (and, in this example, increases from the baseline shown in Figure 4A). This results in the illuminance maximum of peaks 410A to 410D and 41 OF increasing while the peak 410E remains as per the spectrum 400 of Figure 4 A. Multiple peaks increase because multiple types of MOF are responsive to the seventh chemical agent. However, each of these increasing peaks is different to the respective peaks shown in Figures 4B or 4C because the MOFs are interacting with the seventh chemical agent rather than the first to sixth chemical agent (nor the eighth chemical agent).

[0151] The spectrum 450 of Figure 4E represents the situation in which only the eighth chemical agent is present in the gas to be detected by the gas sensor device. The fluorescence of the first to fifth types of LMOF therefore changes (and, in this example, increases from the baseline shown in Figure 4A). This results in the illuminance maximum of peaks 410A to 410E increasing while peak 41 OF remains as per the spectrum 400 of Figure 4A. Again, multiple peaks increase because multiple types of MOF are responsive to the eighth chemical agent. However, each of these increasing peaks is different to the respective peaks shown in Figures 4B, 4C or 4D because the MOFs are interacting with the eighth chemical agent rather than the first to seventh chemical agent.

[0152] Figures 4 A to 4E show how the overall response of the plurality of types of MOF to chemical agents may be unique depending on the chemical agents that are present. Multiple different chemical agents can be detected using a plurality of different types of MOF. The unique response from the plurality (or array) of MOFs can be referred to as the “fingerprint” associated with that type of MOF. The fingerprint can be used to accurately distinguish between the different chemical agents. For example, the gas sensor system may be arranged to compare the fingerprint to a database comprising chemical agent identifiers paired with threshold criteria for the fingerprints. One or more chemical agents may be identified based on the measured fingerprint matching the threshold criteria in the database for one or more chemical agent identifiers.

[0153] In some examples, the plurality of types of MOF have a response that varies with time. For example, Figure 4E may represent the situation in which only the eighth chemical agent is present in the gas to be detected by the gas sensor device and at a first time. In other words, the illuminance maximum of peaks 410A to 410E represent the peaks at a first time. Figure 14 shows how the peaks have changed at a second time, after the first time. Figure 14 shows the peaks of Figure 4E (at the first time) with broken lines. Figure 14 additionally comprises peaks 1410A to 1410E which represent how the peaks have changed between the first and second time. Specifically, the peaks 1410A, 1410B, 1410D and 1410E have decreased in intensity at the second time relative the respective peaks at the first time 410A, 410B, 410D, 410E. Peak 1410C has increased relative to peak 410C. This change over time is a characteristic behaviour for the plurality of types of MOFs over time when in the presence of the eighth chemical agent. In such example, the controller can be arranged to detect this characteristic behaviour to identify / detect the presence of the chemical agent. In examples comprising a plurality of different types of LMOF (as described above) the light detector may be arranged to detect illuminance across a range of spectrums rather than a single wavelength (e.g. to analyse the spectra shown in Figures 4A and 4E). This may be achieved by providing a diffractive element between the LMOF container and the light detector to achieve a spatial distribution of wavelengths at the light detector, as described previously. The skilled reader will appreciate that the first controller 230 can be arranged to receive signals (e.g. a photocurrent) from the photodiode that includes spatial information. The first controller 230 may be further arranged to determine an illuminance spectrum based on said signals. The first controller 230 may be arranged to automatically detect individual peaks of said spectrum and to determine the presence of certain target analytes (and therefore agents) based on said peaks.

[0154] The illustrative drawings of Figures 4 A to 4E show the peaks as being substantially uniformly spaced and separated. This means that it is straightforward to identify individual peaks. However, it should be understood that in reality the maximum wavelength of the peaks will depend on the properties of the individual LMOF. LMOFs may be chosen that have substantially non-overlapping peaks such that the peaks are distinguishable from one another. However, in some examples, this may not be possible. In such cases, the first controller can be arranged to measure properties of the peaks, for example the FWHM of the peak. In the example of Figure 4 A to 4E, the FWHM of peak 414 A is greater than the FWHM of all the other peaks. Thus, the first controller is able to distinguish peak 414A from adjacent peaks (e.g. 412C) based on the FWHM measurement.

[0155] In some examples, the light source 310 is optically coupled to the LMOF 316 via a light guide or light guide extending along at least a portion of the optical axis from the light source 310 to the LMOF 316. Alternatively, or additionally, the LMOF 316 is optically coupled to the light detector via a light guide or light guide extending along at least a portion of the optical axis from the LMOF 316 to the light detector.

[0156] Figure 5 shows a schematic view of a light guide 506. The light guide 506 comprises an input 508 and an output 510. In the example of Figure 5, the input 508 is arranged to receive light from a light source 502 coupled to a substrate 504 such as a printed circuit board (PCB). The light guide 506 comprises a transparent body which, in this example, is formed of an acrylic material. The light guide 506 is arranged to confine in-coupled light at the input 508 (from the light source) within the body of the light guide 506 as a result of total internal reflection of the incoupled light within the light guide 506. In this way, substantially all of the light that is in-coupled at the input 508 is propagated to the output 510. The output 510 is arranged such that the light is out-coupled at the output 510. In this example, the light guide 506 comprises a turn 514 or bend which in this example is a 90 degree bend. Because the in-coupled light is confined within the light guide 506, said light is confined to make the turn 514. In this way, a light guide 506 can be arranged to propagate light round the corners. While Figure 5 shows a single right angle turn 514, it should be understood that the light guide 506 can comprise a plurality of turns in some examples. In some examples, one or more of the turns of the light guide 506 are greater than or less than 90 degrees. In some examples, the minimum bend radius of the turn 506 is substantially equal to double the diameter or thickness of the light guide 506, as represented between the arrows at 512 in Figure 5.

[0157] Above, it was described how the gas sensor system of Figure 3 could comprise a plurality of different types of MOF and how this plurality of different types of MOF could be contained in the same container. Figures 6 and 7 show features of a second example of a gas sensor system according to the present disclosure comprising a plurality of MOF-containing containers instead of a single MOF-containing container. In particular, Figure 6 shows a MOF module 600 for the gas sensor system and Figure 7 shows a gas sensor device 700 of the gas sensor system in which the MOF module 600 is received by a housing 702 of the device 700.

[0158] The MOF module 600 may be referred to as a MOF cartridge. The MOF module 600 comprises a plurality of individual cavities or containers 602. In this example, the containers 602 are arranged in a two-dimensional array. A first dimension of the array extends from 1 to 12 of Figure 6 and a second dimension of the array extends from A to H of Figure 6 such that, in this example, the array is a 12 by 8 array. However, it should be understood that the MOF module 600 may comprise any number of containers 602 and that these cavities may or may not be arranged as an array.

[0159] Each container 602 comprises one or more MOFs. The MOF(s) contained in each container may be referred to a discrete sensing portion. In this example, each container 602 comprises a different type of LMOF where each type of LMOF is responsive to one or more chemical agents, as described previously.

[0160] Figure 7 shows a schematic of a gas sensor device 700. The gas sensor device 700 comprises a housing 702 which defines a cavity 705 in which the MOF module 600 of Figure 6 is received. In this example, a top portion of the gas sensor device 700 is formed of a transparent material such as glass or plastic. Therefore, the MOF module 600 and the individual containers 602 are visible in Figure 7. However, it should be understood that the MOF module 600 is encased / surrounded by the housing 702 and the transparent material.

[0161] The gas sensor device 700 comprises a gas input port 704 and a gas output port 706.

[0162] The gas input port 704 is arranged such that gas to be sensed / analysed from outside of the gas sensor device 700 can be drawn or flow into the gas sensor device 700. The gas sensor device 700 is arranged such that one or more gas flow path fluidically connects the gas input port 704 to the gas output port 706. The one or more gas flow paths are in fluidic communication with the plurality of containers 602 of the MOF module 600 such that the one or more gas flow paths are in fluidic communication with the LMOFs contained in said containers. As described previously, this means that target analytes contained in the gas interact with the LMOFs.

[0163] In some examples, a hollow space is defined between MOF module 600 and the transparent top portion of the gas sensor device 700. In such examples, gas to be sensed that flows from the gas input port 704 to the gas output port 706 may flow through said hollow space. This flow may be in the general direction shown by the arrow in Figure 7. Each container 602 of the MOF module 600 may take the form of a blind chamber. An upper or top portion of each container 602 may be open and may in fluidic communication with said hollow space. Thus, as gas to be sensed flows through the hollow space, said gas may interact with the LMOFs contained in each of the containers 602.

[0164] In some examples, a plurality of gas flow channels may be defined through the MOF module 600 itself. These are not illustrated in the drawings. Each gas flow channel may connect a plurality of containers 602 in series. For example, a first gas flow channel may connect each container 602 in the “A” channel together in series. Thus, gas flowing through the first gas flow channel may pass through container 1 through to container 12 in the “A” channel in turn. Each gas flow channel may extend substantially in the direction shown by the arrow in Figure 7 through the MOF module 600. In such examples, each gas flow channel may be fluidically coupled to the gas input port 704 at one end and the gas output port 706 at the other end.

[0165] In the example shown in Figure 7, the MOF module 600 is removable from the cavity 705. In this example, the housing 702 of the gas sensor device 700 comprises a closable opening 708. In Figure 7, the closable opening 708 is closed. In some examples, the closable opening 708 comprises a slidable or hinged portion of the housing that is openable and closable with respect to the rest of the housing 702. Figure 8 the MOF module 600 mid-way between being removed (or inserted) through the closable opening 708.

[0166] Providing a removable MOF module 600 allows for a first MOF module 600 to be removed and replaced with a second MOF module 600. The first MOF module 600 may have different types LMOF types to the second MOF module 600. Thus, an advantage of providing a removable MOF module 600 is that the chemical agents that can be detected by the gas sensor device 700 can be changed or modified by changing the MOF module 600.

[0167] Figure 9 shows a schematic view of an example of a detection arrangement 900 for sensing changes in an optical property of the LMOF 902 contained in an individual container 602 of the MOF module 600 in response to interacting with a target analyte for which the LMOF 902 is functionalised for. In this example, the detection arrangement 900 comprises a light source 906 and a light detector 912 on a printed circuit board PCB 904. In this example, the light source 906 is a light emitting diode LED and the light detector 912 is a photodiode. The light source 906 is optically coupled to a first light guide 908 that extends between the light source 906 and the container 602. The first light guide 908 is arranged such that light from the light source 906 is in-coupled into the first light guide 908 at a first end of the first light guide 908 and said light is constrained and / or guided to a second end of the first light guide 908. The second end of the first light guide 908 is optically coupled to the container 902 such that the light is out-coupled at the second end to illuminate the LMOF 902 contained in the container 902. The detection arrangement 900 further comprises a second light guide 910 arranged such that light from the LMOF 902 received at a first end of the second light guide 910 is in-coupled into the second light guide 10. The second light guide 910 is arranged such that said light is constrained and / or guided to a second end. The second end of the second light guide 910 is optically coupled to the light detector 912 such that the light is out-coupled at the second end to illuminate the light detector 912. In this way, changes in a property of light received from the light detector 912 can be determined by the detector and target analytes and agents can be determined similarly to what was described in relation to Figures 1 to 4E.

[0168] As above, the light guides 908, 910 constrain and / or guide in-coupled light. This may advantageously mean that the amount of stray light that reaches the light detector 912 is substantially reduced. For example, this may mean that the light detector 912 can be provided substantially adjacent to the light source 906 (as shown in Figure 9) with a minimal amount of stray light reaching the light detector 912 from the light source 906.

[0169] In some examples, ambient light may be used to illuminate the LMOFs contained in the MOF module 600. For example, ambient light (such as sunlight) may be received by the LMOFs through the transparent material forming the top surface of the gas sensor device 700. In such examples, there may be no need to provide a light source 906. Of course, it may be advantageous to provide a light source 906 arranged to illuminate the LMOF as well as ambient light such that, in cases where there is no ambient light, sensing can continue. In some examples, an individual sensing arrangement 900 may be provided for each container 602. For example, each container 602 may be optically coupled to an individual light source 906 and an individual light detector 912, as shown in Figure 9. However, in some examples, one or more light sources 906 may be optically coupled to a plurality of containers 602. Alternatively, or additionally, one or more light detectors 912 may be optically coupled to a plurality of containers 602.

[0170] In some examples, the or each sensing arrangement 900 is provided as part of the MOF module 600. In such examples, the MOF module 600 may comprise an electrical connector that is couplable to an electrical connector of the gas sensor device 700 when the MOF module 600 is received in the cavity 705. Suitable electrical connections and / or wires may be provided to provide power to the sensing arrangement(s) 900 of the MOF module 600 from a power source of the gas sensor device 700 and for electrical signals to be received at the gas sensor device 700 from the MOF module 600. Thus, removable of the MOF module 600 also results each of the sensing arrangements 900 being removable in such examples. Furthermore, replacement of the MOF module 600 results in replacement of each of the sensing arrangements 900. The advantage of this arrangement is that each light source 906 and / or light detector 912 may be arranged to be tuned for the particular type of LMOF or LMOFs that are used in the sensing process. However, the disadvantage of this arrangement is that the complexity and cost of the MOF module 600 is significantly increased.

[0171] In some examples, at least a portion of the or each sensing arrangement is provided as a non-removable part of the MOF module 600. Said portion may remain fixed in place relative to the (removable) MOF module. When the MOF module is received in the cavity 705, the or each sensing arrangement may be optically coupled to the containers 602 as described above. For example, said portion may comprise the light source 906, light detector 912, and the first and second light guides 908, 910. When the MOF module 600 is received in the cavity 705, the second end of each first light guide 908 and the first end of each second light guide 910 may be optically coupled to the or each respective container 602 / LMOF 902.

[0172] Thus far, several examples of a gas sensor device 300, 700 of a gas sensor system have been described. In some examples, that gas sensor device 300, 700 is a primary device of the gas sensor system and the gas sensor system further comprises one or more further devices such as a secondary device. Figure 10 schematically illustrates such a gas sensor system.

[0173] The gas sensor system 1000 of Figure 10 comprises a primary device 1002 and a secondary device 1052. The primary and secondary devices 1002, 1052 are shown schematically in Figure 10 with electrical components shown as blocks. The primary device 1002 comprises a primary or first controller 1004, a portable power source 1006, light source electronics 1008, light detection electronics 1010, a transceiver 1012 and an indicator 1014. In this example, the first controller 1004 is a low-power microchip, the portable power source 1006 is a micro-battery, the transmitter is a radio transceiver for communicating with a receiver (e.g. transceiver) of the secondary device 1052 and the indicator 1014 is a visual indicator in the form of an LED. In this example, the light source electronics 1008 and the light detection electronics 1010 represent the electronics associated with one or more of the sensing arrangements described previously. For example, the light source electronics may comprise one or more light sources such as one or more lasers or LEDs and the light detection electronics may comprise one or more light detectors such as one or more photodiodes or one or more CCDs. The primary device 1002 further comprises suitable electrical components and connections to connect the first controller 1004 to the portable power source 1006, the light source electronics 1008 and the light detection electronics 1010, as well as the transceiver 1012 and the indicator 1014.

[0174] Not shown in Figure 10, the primary device comprises one or more containers, each container containing one or more types of LMOF as described in relation to Figures 3 and 7. The primary device may also comprise a MOF module as described in relation to Figure 7. The primary device may also comprise the gas input and output ports and the one or more gas flow paths.

[0175] The secondary device 1052 comprises a second or secondary controller 1054, a second portable power source 1056, a transceiver 1062 and an indicator 1064. In this example, the second controller 1054 is a microcontroller unit MCU, the second portable power source 1056 is a rechargeable battery, the transceiver 1062 is a radio transceiver for communicating with the transceiver of the primary device 1002 and the indicator 1064 is a visual indicator in the form of an liquid crystal display LCD. The second portable power source 1056 has a larger capacity for energy storage than portable power source 1006 of the primary device 1002. Furthermore, the second controller 1054 has a greater processing power and / or memory that the first controller 1004.

[0176] An advantage of providing the gas sensor system 1000 distributed across at least a primary and secondary device 1002, 1052 is that the primary device can be made smaller, lighter, and more cheaply. This may be achieved in particular because the power source and the processing electronics of the primary device 1002 are smaller, lighter, and cheaper. Because the primary device 1002 is lightweight it can be made wearable by personnel and unobtrusive while the secondary device 1052 (which can communicate with the primary device 1002 remotely) may remain in a more convenient or central location. The secondary device 1052 may be carried and / or portable. The secondary device 1052 may remain e.g. in a vehicle while the personnel (wearing the primary device 1002) enter an area containing a risk of agents. The secondary device 1052 may be carried by one of the personnel. In some examples, the secondary device 1052 may remain at base.

[0177] The first controller 1004 is arranged to be intermittently active. The first controller 1004 could be described as being in an active mode when active. The first controller 1004 is arranged to remain in a low-power or dormant mode when not in the activemode. This reduces power requirements of the primary device 1002. The first controller is arranged such that power is not supplied to the light detection electronics in the low-power or dormant mode. The first controller 1004 is arranged such that power is not supplied to the light source electrics in the low-power or dormant mode.

[0178] The first controller 1004 is arranged to switch from the low-power mode to the active mode on receipt of an interrupt signal. The gas sensor system 1000 (e.g. the primary device 1002) comprises a movement sensor in some examples (not shown in the drawings). The gas sensor system 1000 is arranged to generate the interrupt signal when movement or changes in direction or speed of the gas sensor system are detected.

[0179] In other examples, the gas sensor system 1000 is arranged to generate the interrupt signal periodically, for example after a predetermined time or in response to the end of a count-down clock.

[0180] On switching to the active mode, the first controller 1004 is arranged to determine if the detected property of light has changed by at least a threshold amount relative to a previous measurement or a predetermined value for the detected property based on signals from the detection electronics 1010. The first controller 1004 is arranged to control the receiver 1012 to transmit said signals to the transceiver 1062 of the secondary device 1052 if a detected property of light from at least one of the types of MOF has changed by at least the threshold amount. The threshold amount is stored in a memory of the first controller 1004. This comparison is a simple calculation that can be performed by the low-power first controller.

[0181] The first controller 1002 is arranged to not transmit said signals to the secondary device 1052 if a detected property has not changed by at least the threshold amount. The first controller 1002 is arranged to switch to the low-power mode if the detected property has not changed by at least the threshold amount. In this way, the first controller 1002 arranged to only supply power to the transceiver of the primary device 1002 if the there is an initial or early indication that the situation has changed with regard to the presence or absence of target analytes. Substantially no power is consumed by the transceiver of the primary device 1002 if there is no initial or early indication of such a change. This may reduce the power requirements of the primary device, and of the gas sensor system as whole.

[0182] The first controller 1002 is arranged to transit said signals to the secondary device 1052 if a detected property has changed by at least the threshold amount. Said signals are encrypted and received at the second transceiver 1062 of the secondary device. The secondary device 1052 (in particular the second controller) is then arranged to process the received signals. This processing has been described previously and may include the spectral analysis described above.

[0183] The first and secondary devices 1002, 1052 comprise visual indicators. The gas sensing system 1000 is arranged to trigger or activate these indicators if an agent is detected by the second controller 1054. For example, the second controller 1054 may be arranged to control the second transceiver 1062 to transmit a signal to the first transceiver 1012 instructing the first controller 1004 to activate the LED 1014 to flash. The second controller 1054 may also be arranged to control the LCD 1064 of the secondary device 1052 to display a warning that an agent has been detected. In some examples, different information is provided by the different indicators. For example, the LED 1014 of the primary device 1002 may merely provide an alert that a target analyte has been detected. The LCD 1064 of the secondary device 1052 may be able to display greater detail of information. For example, the LCD 1064 may present information relating to the type of target analyte that has been detected. Further information may be given, for example the time of detection and / or the location of detection

[0184] In some examples, the primary and secondary devices 1002, 1052 comprise further indicators and / or different indicators. For examples, the first and / or the secondary device 1002, 1052 comprise audio and haptic indicators in addition to or instead of visual indicators.

[0185] Figure 10 shows a gas sensor system 1000 comprising a single primary device 1002 and a single secondary device 1052. However, it should be understood that the system may be provided as a network with a plurality of primary devices 1002 communicating with a single secondary device 1052. This is shown in Figure 11. Figure 11 shows four individuals 1102. Each individual 1102 is wearing a wearable primary device. Each wearable primary device is in communication with a single secondary device 1052. The single secondary device 1052 is arranged to perform the “heavy lifting” of the signal processing for each of the primary devices 1002 (e.g. to perform spectral analysis and / or to detect the presence of one or more target analyte and / or one or more agents in the signals received from each primary device). If an agent is detected based on data received from one (or more) of the primary devices 1002, the secondary device 1052 may send a signal to all primary devices to trigger the respective indicators to warn all personnel / individuals 1102 of a possible agent event.

[0186] In some examples, the or each primary and secondary device of the gas sensor system may be connected or connectable to a wider network of connected or loT devices. For example, the or each primary and secondary devices may be part of a MESH network.

[0187] Above, examples of a gas sensor system employing sensing based on detecting properties of light of MOFs has been described. In some examples, this is replaced with a sensing regime based on detecting electrical properties of MOFs instead of optical properties of MOF. Such a sensing regime will now be described herein. It should be understood that other features of the system describe above (such as, but not exclusively, the MESH network, the removable MOF cartridge, detecting a plurality of chemical agents etc) are equally applicable to a MOF -based gas sensor regardless of the specific sensing regime used.

[0188] Figure 12 is a schematic drawing representing the sensing of a chemical agent 1200 using a Metal-Organic Framework MOF 1202. Figure 12 comprises a substrate 1201 on which the MOF 1202 is provided. Embedded in the substrate 1201 is a first electrode 1204 and a second electrode 1206 electrically connected to the MOF 1202. A voltmeter 1208 is connected to the first and second electrodes 1204, 1206 arranged to measured voltage drop across the MOF 1202. The conductivity of the MOF 1202 can be determined based on the measured voltage drop. In this example, the target analyte 1200 is contained in a gas that flows passed the LMOF 1202. The gas is represented by arrow 1210, indicating the direction of flow of the gas.

[0189] The LMOF 1202 is arranged to interact with, and be responsive to, the chemical agent 1200. In this example, the LMOF 1202 being responsive to the chemical agent 1200 means that the LMOF 1202 is arranged to change in electrical conductivity in response to the chemical agent 1200 interacting with the LMOF 1202. Thus, changes in electrical conductivity can serve as an indicator of the presence of the target analyte. In this way, the LMOF 1202 can be used in a detector (such as a gas detector system according to the present invention) to sense the presence of the chemical agent 1200 in the gas. Knowing the expected electrical conductivity for the different chemical agents allows the detected photocurrent to be used to distinguish between a plurality of different chemical agents. Figure 13 shows a cross-sectional schematic view of an example of a gas sensor system according to the present invention employing a conductivity sensing regime. In this example, the gas sensor system comprises a gas sensor device 1300. The gas sensor device 1300 comprises a housing 1302. The housing defines a gas (or air) input port 1304 and a gas (or air) output port 1306. A gas flow path or channel 1308 is defined through the gas sensor device 1300, from the gas input port 1304 to the gas output port 1306. The gas flow path 1308 is arranged such that gas to be analysed can flow from the gas input port 1304 to the gas output port 1306. The gas sensor device 1300 of Figure 13 is arranged to detect the presence of one or more chemical agents 1350 based on a MOF sensing scheme as described in relation to Figures 12. Thus, in this example, the device comprises a detection assembly 1309 comprising first and second electrodes 1351, 1352 that are electrically coupled to a MOF 1316 of the gas sensor device 1300. The MOF 1316 is fluidically coupled to the gas flow path 1308. In this example, the MOF 1316 is contained in a container defined by the housing 1302 of the device 1300.

[0190] The gas sensor device 1300 is arranged to use the first and second electrodes 1351, 1352 to repeatedly measure the voltage drop across the MOF 1316 and so determine conductivity repeatedly. The behaviour (i.e. the conductivity) of the MOF 1316 in response to interacting with different chemical agents is known. Therefore, by measuring the conductivity, the gas sensor device 1300 may determine the presence of a particular chemical agent.

[0191] The gas sensor device 1300 also comprises a (first) battery 1318 and a (first) controller 1320. In this example, the gas sensor device 1300 also comprises an air mover 1322 in the form of a piezo-ceramic MEMS micro-fan. The first battery 1318 is electrically coupled or couplable to the first controller 1320. The first controller 1320 is arranged to control the supply of electrical current to the first and second electrodes 1351, 1352. The first controller 1320 is also arranged to measure conductivity based on the voltage drop across the MOF 1316.

[0192] Similarly to what was described in relation to Figure 10, the gas sensor device 1300 may be referred to as a primary device. A gas sensor system comprising the gas sensor device 1300 may additionally a secondary device comprising a secondary battery and a secondary controller. The secondary battery may have a large capacity than the primary battery 1318 and the secondary controller may have more processing power and / or more memory that the primary controller. The primary device may be light weight, compact, portable and / or wearable. The “heavy lifting” of the data processing may be performed by the secondary device.

[0193] Other features described in relation to the optical examples above apply to the electrical conductive examples. For example, the electrical conductivity example may comprise a removable cartridge. The electrical conductivity example may comprise an array of MOFs. The electrical conductivity example may comprise a plurality of different types of MOF and / or each type of MOF may be responsive to a plurality of different chemical agents. For example, a particular type of MOF may have a first conductivity when interacting with a first chemical agent and a second conductivity when interacting with a second chemical agent. Thus, a fingerprint principal may be used, as described above.

[0194] Figure 15 is a schematic cross-sectional view of another detection regime for detection the presence of a chemical agent using a MOF. Like features to previous examples are numbered accordingly. In this example, the main difference is that the

[0195] MOF 1202 is contained in a well 1502 formed of a hydrophobic polymer material.

[0196] This has the advantage that moisture in the gas 1210 is directed to the MOF material 1202 to improve detection. The well 1502, in this example, has been printed.

Claims

42CLAIMS1. A gas sensor system for detecting the presence of one or more chemical agents in a gas, the gas sensor system comprising: a wearable gas sensor (300, 1300) comprising: at least one gas flow path (308, 1308) arranged such that gas to be analysed can flow from an input port (304, 1304) to an output port (306, 1306) via the or each gas flow path; a plurality of discrete sensing portions each in fluidic communication with one or more of the gas flow paths (308, 1308) and comprising at least one of a plurality of different types of metal-organic frameworks MOFs (316, 1316), each type of MOF being responsive to one or more chemical agents; and a detection assembly (309, 1309) arranged to measure a material property of at least some of the discrete sensing portions; wherein the gas sensor system comprises a control system (320, 1320) arranged to detect one or more chemical agents in the gas flow path (308, 1308) based at least in part on one or more values for the material property.

2. A gas sensor as defined in claim 1, wherein the detection assembly (309 , 1309) is arranged to measure an electrical property of the discrete sensing portions such as conductivity.

3. A gas sensor as defined in claim 2, wherein the detection assembly comprises pairs of electrodes (1351, 1352) electrically coupled to each discrete sensing portion and is arranged to measure an electrical property of each discrete sensing portion between the respective pair of electrodes.

4. A gas sensor as defined in any one of the preceding claims, wherein detecting one or more chemical agents comprises the control system (320, 1320) being arranged to: access a database, the database comprising a plurality of chemical agent identifiers paired with one or more predetermined criteria for the material property of one or more types of MOF; and identify the presence of a chemical agent based on the measured value or values meeting the or all predetermined criteria for a chemical agent identifier.

435. A gas sensor as defined in claim 4, wherein at least one of the chemical agent identifiers of the database is paired with a plurality of predetermined criterion.

6. A gas sensor as defined in any one of the preceding claims, wherein the control system is arranged such that detection of at least one of the chemical agents is based on values for the material property measured for a plurality of different types of MOF.

7. A gas sensor as defined in any one of the preceding claims, wherein the gas sensor system is for detecting a plurality of chemical agents in a gas.

8. A gas sensor as defined in any one of the preceding claims, wherein at least one of the types of MOF is responsive to a plurality of chemical agents.

9. A gas sensor system as defined in any one of the preceding claims, wherein the gas sensor (1002) comprises a primary controller (1004); and wherein the gas sensor system comprises a secondary device (1052) comprising a secondary controller (1054).

10. A gas sensor system as defined in claim 9, wherein the gas sensor (1002) comprises a transmitter (1012) and the secondary device (1052) comprises a receiver (1062), and wherein the primary controller (1004) is arranged to receive signals indicative of the values for the material property from the detection assembly and the primary controller (1004) is arranged to control the transmitter of the primary device (1012) to transmit said signals to the receiver (1062) of the secondary device (1052) at least intermittently.

11. A gas sensor system as defined in claim 9 or 10, wherein the primary controller (1002) is arranged such that the gas sensor is intermittently in an active mode and otherwise remains in a low-power mode.

12. A gas sensor system as defined in any claim 11, wherein the primary controller (1002) is arranged to switch from the low-power mode to an active mode on receipt of an interrupt signal, wherein the gas sensor system is arranged to generate the interrupt signal:• based on a detected movement of the system;• based on detected changes in direction or speed of the system;• on receipt of a wake-up radio signal; and / or• after a predetermined time.4413. A gas sensor system as defined in claim 11 and 12 wherein, on switching to the active mode, the primary controller (1002) is arranged to determine if the material property has changed by at least a threshold amount relative to a previous measurement or a predetermined value for the material property; wherein the primary controller is arranged to control the transmitter of the gas sensor to transmit said signals to the receiver of the secondary device if the material property has changed by at least the threshold amount; and wherein the primary controller is arranged to switch to the low-power mode if the material property has not changed by at least the threshold amount.

14. A gas sensor system as defined in any one of the preceding claims, wherein the gas sensor comprises a MOF module (600) comprising a plurality of chambers (602), each chamber being for containing a respective discrete sensing portion.

15. A gas sensor system as defined in claim 14, wherein the MOF module (600) is removable with respect to a housing (702) of the gas sensor.

16. A gas sensor system as defined in claim 15, wherein gas sensor system comprises a first MOF module and a second MOF module, the gas sensor system being configurable between a first detection state in which the first MOF module is removably received in said housing and a second detection state in which the second MOF module is removably received in said housing.

17. A gas sensor system as defined in claim 16, wherein the gas sensor system is arranged to detect the presence of at least one target analyte in the first state that the gas sensor system is not arranged to detect in the second state.

18. A gas sensor system as defined in any one of the preceding claims, further comprising an air or gas mover (322, 1322) arranged to draw gas through the at least one gas flow path (308, 1308), from the input port (304, 1304) to the output port (306, 1306).

19. A method of detecting the presence of one or more chemical agents in a gas using the system of any one of the preceding claims, the method comprising: contacting at least some of the plurality of discrete sensing portions with a gas to be analysed; measuring a material property of at least some of the discrete sensing portions; and detecting one or more chemical agents in the gas flow path based at least in part on one or more measured values for the material property.

20. A computer-implemented method of detecting the presence of one or more chemical agents using a gas sensor system as defined in any one of claims 1 to 18, the method comprising the steps of: receiving, at the control system, signals from the detection assembly indicative of the measured material property; and determining the presence of one or more chemical agents in the gas flow path based at least in part on one or more values for the material property as measured by the detection assembly.

21. A data processing apparatus comprising a processor adapted to perform the steps of the method of claim 20.

22. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method of claim 20.

23. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of claim 20.

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