Patent Publication Number: US-2015059471-A1

Title: Sensing

Description:
TECHNOLOGICAL FIELD 
     Embodiments of the present invention relate to an apparatus and a method. In particular, they relate to sensing using the apparatus and method. 
     BACKGROUND 
     In order to process data representing a real-world parameter, it is necessary to sense that parameter and covert the sensed value to data. 
     There is therefore a need for improved sensors. 
     BRIEF SUMMARY 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: a first sensor comprising a sensing material that is sensitive to a first parameter and a second parameter, wherein sensitivity to the first parameter changes sensitivity to the second parameter, wherein the first parameter is deformation and the second parameter is concentration of a gaseous analyte; and a second sensor sensitive to at least one of the first parameter and the second parameter. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: processing an output from a first sensor comprising a sensing material that is sensitive to a first parameter and a second parameter, wherein sensitivity to the first parameter changes sensitivity to the second parameter, wherein the first parameter is deformation and the second parameter is concentration of a gaseous analyte; and processing an output from a second sensor sensitive to at least one of the first parameter and the second parameter. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: 
     processing an output from a first sensor comprising a sensing material that is sensitive to a first parameter and a second parameter, wherein sensitivity to the first parameter changes sensitivity to the second parameter, wherein the first parameter is deformation and the second parameter is concentration of a gaseous analyte; and 
     processing an output from a second sensor sensitive to at least one of the first parameter and the second parameter. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: a first sensor comprising a sensing material that is sensitive to a first parameter and a second parameter, wherein sensitivity to the first parameter changes sensitivity to the second parameter; and wherein a sensitivity of the first sensor to one of the first and the second parameter is controlled by maintaining, as a constant, the other of the first and the second parameters. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: processing an output from a first sensor comprising a sensing material that is sensitive to a first parameter and a second parameter, wherein sensitivity to the first parameter changes sensitivity to the second parameter; wherein a sensitivity of the first sensor to one of the first and the second parameter is controlled by maintaining, as a constant, the other of the first and the second parameters. 
    
    
     
       BRIEF DESCRIPTION 
       For a better understanding of various examples that are useful for understanding the brief description, reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  illustrates an example of an apparatus configured to detect a first parameter p1 and/or a second parameter p2; 
         FIGS. 2A to 2D  illustrate examples of different outputs from the apparatus to processing circuitry; 
         FIG. 3  illustrates an example of an apparatus comprising one or more sensors; 
         FIG. 4  illustrates a cross-section of an example of the sensing material in the apparatus; 
         FIGS. 5A and 5B  illustrate examples where a sensitivity of the first sensor to one of the first and the second parameters is controlled by maintaining, as a constant, the other of the first and the second parameters; 
         FIG. 6  plots variation of output from the apparatus with deformation and with concentration of gaseous. analyte; 
         FIG. 7  illustrates an example of processing circuitry comprising a processor and a memory; and 
         FIG. 8  illustrates an apparatus comprising temperature compensation circuitry. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example of an apparatus  10 . The apparatus  10  is configured to detect a first parameter p1 and/or a second parameter p2, and, may be referred to as a sensor apparatus  10  (when not is use) and a sensing apparatus  10  (when in use). 
     The apparatus  10  may be part of a larger apparatus comprising processing circuitry  2 . 
     The apparatus  10  comprises a first sensor  20  and a second sensor  30 . 
     The first sensor  20  comprises a sensing material  22  that is sensitive to the first parameter p1 and the second parameter (p2). The sensitivity of the sensing material  22  to the first parameter p1 changes a sensitivity of the sensing material  22  to the second parameter. 
     The second sensor  30  is sensitive to at least one of the first parameter p1 and the second parameter p2. 
     The sensitivity of the first sensor  20  to the first parameter p1 is different to a sensitivity of the second sensor  30  to the first parameter p1 and/or the sensitivity of the first sensor  20  to the second parameter p2 is different to a sensitivity of the second sensor  30  to the second parameter p2. 
     In some examples but not necessarily all examples, the first parameter p1 may be deformation (D) of the apparatus  10  and the second parameter p2 may be a concentration of a gaseous analyte at the apparatus  10 . 
     The gaseous analyte may be water. The second parameter p2 may then be relative humidity (RH). 
     The apparatus  10  may be used with other gaseous analytes such, for example, NH 3 , NO 2 , Cl 2  as well as organic solvents including methanol and ethanol. 
     The deformation (D) may, for example, be a stretching deformation and/or a bending deformation and/or a twisting deformation. 
     In some examples but not necessarily all examples, the second sensor  30  may comprise the sensing material  22  that is sensitive to the first parameter p1 and the second parameter p2. 
       FIG. 6  illustrates an example of how a sensitivity of the sensing material  22  may vary with deformation and/or concentration of a gaseous analyte (relative humidity in this example). The y-axis represents sensor output value and the x-axis represents concentration of the gaseous analyte (relative humidity). A first series of plots is made in the figure mapping measured output against variable relative humidity, when the sensing material  22  is flat. A second series of plots is made in the figure mapping measured output against variable relative humidity, when the sensing material  22  is deformed (bent). 
     It is apparent that the output response of sensing material  22  is dependent upon both the relative humidity at the sensing material  22  and the deformation of the sensing material  22 . The variation of the output to humidity (sensitivity to humidity) changes when the sensing material  22  is deformed. The variation of the output to deformation (sensitivity to deformation) changes when the sensing material  22  is exposed to different relative humidity. 
     Similar plots may be obtained for other gaseous analytes, such as those described previously. 
       FIG. 1  also illustrates processing circuitry  2 . The processing circuitry  2  is configured to process an output  21  from the first sensor  20  and process an output  31  from the second sensor  30  and determine a value for the first parameter p1 and/or a value for the second parameter p2. 
     The processing circuitry  22  may use the output  21  from the first sensor  20  and the output  31  from the second sensor  30  to look-up values for the first parameter p1 and the second parameter p2 from a database. 
       FIG. 7  illustrates one example of processing circuitry  2  comprising a processor  4  and a memory  6 . 
     The processor  4  is configured to read from and write to the memory  6 . The processor  4  may also comprise an output interface via which data and/or commands are output by the processor  4  and an input interface via which data and/or commands are input to the processor  4 . 
     The memory  6  stores a computer program  5  comprising computer program instructions (computer program code) that controls the operation of the processing circuitry  2  when loaded into the processor  4 . The computer program instructions, of the computer program  5 , provide the logic and routines that enables the apparatus to perform the one or more of the methods illustrated in  FIGS. 2A to 2D . The processor  4  by reading the memory  6  is able to load and execute the computer program  5 . 
     The apparatus therefore comprises: at least one processor  4 ; and at least one memory  5  including computer program code  5  the at least one memory  6  and the computer program code  5  configured to, with the at least one processor  4 , cause the apparatus  10  at least to perform: 
     processing an output  21  from a first sensor  20  comprising a sensing material  22  that is sensitive to a first parameter p1 and a second parameter p2, wherein sensitivity to the first parameter p1 changes sensitivity to the second parameter p2; and 
     processing an output  22  from a second sensor  30  sensitive to at least one of the first parameter p1 and the second parameter p2. 
     This processing determines a value for the first parameter p1 and/or a value for the second parameter p2. 
     The processing may use the output  21  from the first sensor  20  and the output  31  from the second sensor  30  to look-up values for the first parameter p1 and/or the second parameter p2 from a database  7  stored in the memory  6  or elsewhere 
     In some examples but not necessarily all examples, a sensitivity of the first sensor  20  to the first parameter p1 is different to a sensitivity of the second sensor  30  to the first parameter p1. 
     In some examples but not necessarily all examples, the first parameter p1 is deformation and the second parameter p2 is concentration of a gaseous analyte. 
     In some examples but not necessarily all examples, the second sensor  20  may comprise the sensing material  22  that is sensitive to the first parameter p1 and the second parameter p2. 
       FIGS. 2A to 2D  illustrates examples of different outputs  21 ,  31  from the apparatus  10  to the processing circuitry  2 . 
     In each of these examples, for a range of values of the second parameter p2, a sensitivity of the first sensor  20  to the first parameter p1 is different to a sensitivity of the second sensor  30  to the first parameter p1 and/or, for a range of values of the first parameter, a sensitivity of the first sensor  20  to the second parameter p2 is different to a sensitivity of the second sensor  30  to the second parameter p2. 
     This difference in sensitivity produces a differential input to the processing circuitry  22 , comprised of the pair of outputs  21 ,  31  from the first and second sensors  20 ,  30 . The differential input is in respect of the first parameter p1 and/or the second parameter p2. 
     In  FIG. 2A , the first sensor  20  is configured to be sensitive to one of the first and second parameters but not the other one of the first and second parameters. The second sensor  30  is configured to be sensitive to the other of the first and second parameters but not the one of the first and second parameters. 
     The output s1 from the first sensor  20  is therefore, in this example, dependent upon only the first parameter p1. The output s2 from the second sensor  30  is therefore, in this example, dependent upon only the second parameter p2. 
     In  FIG. 2B  and  FIG. 2C , the first sensor  20  is configured to be sensitive to both of the first and second parameters p1, p2 and the second sensor  30  is configured to be sensitive to only one of the first and second parameters p1, p2. 
     In the example of  FIG. 2B , the output s1 from the first sensor  20  is dependent upon the first parameter p1 and the second parameter p2. The output s2 from the second sensor  30  is dependent upon only the second parameter p2. 
     In the example of  FIG. 2C , the output s1 from the first sensor  20  is dependent upon the first parameter p1 and the second parameter p2. The output s2 from the second sensor  30  is dependent upon only the first parameter p1. 
     In  FIG. 2D , the first sensor  20  is configured to be sensitive to both of the first and second parameters p1, p2 and the second sensor  30  is configured to be sensitive to both the first and second parameters p1, p2 but in a manner different to the first sensor  20 . 
       FIG. 3  illustrates an example of an apparatus  10  comprising one or more sensors  62 . For clarity, only a single sensor  62  is illustrated. This may be the first sensor  20  or the second sensor  30 . 
     The sensor  62  comprises sensing material  22  supported by a flexible substrate  50 . A pair of electrodes  52  are electrically connected to the sensing material  22 . 
     The flexible substrate  50  may be formed from polyethylene polymer such as for example polyethylene napthalate (PEN) or polyethylene terephthalate (PET) or flexible glass. 
     The sensing material  22 , may be formed by drop cast, spraying, spin coating, ink jet printing or screen printing. 
     The electrodes  52  may be positioned on an upper surface of the sensing material  22  such that the sensing material  22  is positioned between the electrodes  52  and the flexible substrate  50 . 
     Alternatively, electrodes  52  may be positioned on an upper surface of the flexible substrate such that the electrodes  52  are positioned between the sensing material  22  and the flexible substrate  50 . The electrodes  52  may be deposited on the substrate  50  (e.g. by screen printing or inkjet printing), followed by deposition of the sensing material  22  on top. 
     The electrodes  52  may be silver (Ag) printed electrodes. 
     The sensing material  22  is sensitive to the first parameter p1 and the second parameter (p2). The sensitivity of the sensing material  22  to the first parameter p1 changes a sensitivity of the sensing material  22  to the second parameter. 
     In this example the first parameter p1 is deformation (D) of the apparatus  10  and the second parameter is concentration of a gaseous analyte at the apparatus  10 . 
     As illustrated in  FIG. 4 , in some but not necessarily all examples, the sensing material  22  may comprise a stack  40  of two-dimensional layers  42  of the same material. Each two-dimensional layer  42  has a thickness less than 100 nm or 1000 nm. The separation between stacked 2D layers  42  is sufficient to enable the diffusion of the gaseous analyte between the 2D layers  42 . 
     Examples of suitable sensing material  22  include graphene, graphene oxide, reduced graphene oxide, functionalised graphene, boron nitride and transition metal dichalogenides such as, for example, disulphides such as, for example, molybdenum disulfide (MoS 2 ). 
     Each sensing material  22  is optimal for different gaseous analytes. 
     Molybdenum disulfide (MoS 2 ) may be used to sense triethylamine. 
     Graphene may be used to sense nitrogen dioxide (NO 2 ), ammonia (NH 3 ) or carbon dioxide (CO 2 ). 
     Graphene oxide may be used to sense humidity. 
     the sensing material  22  is graphene oxide. 
     In some but not necessarily all examples the sensing material  22  comprises functional groups—such as hydroxyl, epoxy, carboxyl groups—that can provide hydrogen ions (protons) in the presence of water or other gaseous analytes. This decreases an electrical resistance of the sensing material  22  in the presence of water vapour (humidity) or other gaseous analytes. 
     The sensing material  22  may be strongly electropositive or strongly electronegative with respect to the gaseous analyte. The gaseous analyte will then either donate electrons (sensing material  22  is electronegative) or withdraw electrons (sensing material  22  is electronegative), causing a change in electronic properties such as, for example, electrical conductivity. 
     In some but not necessarily all examples, the sensitivity of the sensing material  22  to the gaseous analyte may be selectively controlled by controlling the number of layers  42  in the stack  40 . For example, a thin film of sensing material  22  may be less than 1000 nm and sensitive to humidity, whereas a thick film of sensing material  22  may be greater than 2000 nm and more sensitive to humidity. 
     In some but not necessarily all examples, the sensitivity of the sensing material  22  to the gaseous analyte and/or deformation may be selectively controlled by using different sensing material  22 . For example, the first sensor  20  may use graphene oxide as the sensing material  22  and the second sensor  30  may use graphene oxide as the sensing material  22 , however the sensitivity of the first and/or second sensor may be differentially controlled by using different species of sensing material  22  or different variants of the same species of sensing material  22  in the first and second sensors. For example, the sensing material  22  of one of the first and second sensors may comprise one or more functional groups absent from the sensing material  22  of the other one of the first and second sensors. 
       FIGS. 5A and 5B  illustrate examples where a sensitivity of a sensor  62  to one of the first and the second parameters p1, p2 is controlled by maintaining, as a constant, the other of the first and the second parameters. Additional structure  60  is provided at the sensor  62  to maintain, as a constant, one of the first and second parameters. The additional structure  60  blocks changes associated with that parameter. For clarity, only a single sensor  62  is illustrated. This may be the first sensor  20  or the second sensor  30 . 
     In the example of  FIG. 5A , a sensitivity of a sensor  62  to the first parameter (Deformation of the sensor  62 ) is selectively controlled whereas a sensitivity of the sensor  62  to the second parameter (Concentration of gaseous analyte at the sensor  62 ) is not selectively controlled. This is achieved by maintaining, as a constant, the deformation of the sensor  62  by physically attaching a non-flexible coating  64  that provides a physical structure that restrains movement of the sensing material  22  at a fixed deformation or at no deformation. The deformation (or no deformation) is therefore constant and locked-in by the stiff coating  64 . 
     In some but not necessarily all embodiments, the coating  64  may be permeable to allow the gaseous analyte (e.g. water vapour) to ingress and reach the sensing material  22 . 
     In the example of  FIG. 5B , a sensitivity of a sensor  62  to the second parameter (concentration of gaseous analyte at the sensor  62 ) is selectively controlled whereas a sensitivity of the sensor  62  to the second parameter (Deformation of the sensor  62 ) is not selectively controlled. This is achieved by maintaining, as a constant, the concentration of the gaseous analyte at the sensor  62  by sealing the sensor  62  using a coating  66  that provides a physical structure that seals the sensing material  22  at a fixed concentration of the gaseous analyte (e.g. fixed humidity) and prevents ingress or egress of the gaseous analyte. The concentration of the gaseous analyte is therefore constant and locked-in by the impermeable coating  66 . 
     In some but not necessarily all embodiments, the coating  64  may be flexible and unattached to the sensing material  22  so that there is a gap or void  68  between the impermeable coating  66  and the sensing material  22 . This allows deformation of the sensing material  22 . 
       FIG. 8  illustrates an apparatus  10  comprising temperature compensation circuitry  70 . The temperature compensation circuitry  70  comprises a Wheatstone bridge arrangement. In a Wheatstone bridge a first series combination of resistors R 1 , R 3  is connected between a first node  71  and a second node  72  and a second series combination of resistors R 2 , R 4  is connected between the first node  71  and the second node  72  in electrical parallel to the first series combination of resistors. 
     The resistor R 1  in the first series combination of resistors is connected between the first node  71  and a third node  73 . The resistor R 3  in the first series combination of resistors is connected between the third node  73  and the second node  72 . 
     The resistor R 2  in the second series combination of resistors is connected between the first node  71  and a fourth node  74 . The resistor R 4  in the second series combination of resistors is connected between the fourth node  74  and the second node  72 . 
     An input voltage Vin is applied between the first node  71  and the second node. 
     An output voltage Vout is taken between the third node  73  and the fourth node  74 . 
     When the bridge is balanced, R 1 /R 3 =R 2 /R 4 . 
     One or more of the resistor R 1 , R 2 , R 3 , R 4  may be provided by a first sensor  20 . 
     In some examples but not necessarily all examples, none, one or more of the remaining resistor R 1 , R 2 , R 3 , R 4  may be provided by a second sensor  30 . 
     The presence of the first and/or second parameter results in a change in a resistance and an unbalancing of the bridge. 
     The use of a first sensor  20  as resistor R 1  and the use of the second sensor  30  as the resistor R 2  may provide temperature compensation. 
     The configuration of the Wheatstone bridges (half or full bridge) could be implemented for one sensor for temperature compensation or separately (individually) for sensor elements where the sensors have a different (permeable, non-permeable) sensor configuration. The compensation of temperature is applicable while the devices are deformed. 
     A sensor when deformed may require temperature compensation. In one particular configuration when the material, for example graphene oxide, is coated with a permeable coating and a similar device has an impermeable coating then both sensors may require temperature compensation Wheatstone bridge configuration. 
     If one device is used on its own (that is individually/separately) then temperature compensation Wheatstone bridge configuration may also be required. 
     For temperature compensation a sensor may require half or full bridge circuit compensation. 
     Referring back to  FIG. 7 , the computer program  5  may arrive at the processing circuitry  2  via any suitable delivery mechanism. The delivery mechanism may be, for example, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), an article of manufacture that tangibly embodies the computer program  5 . The delivery mechanism may be a signal configured to reliably transfer the computer program  5 . In some examples, the processing circuitry  2  may propagate or transmit the computer program  5  as a computer data signal. 
     Although the memory  6  is illustrated as a single component it may be implemented as one or more separate components some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage. 
     Although the processor  4  is illustrated as a single component it may be implemented as one or more separate components some or all of which may be integrated/removable. 
     References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single /multi-processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. 
     As used in this application, the term ‘circuitry’ refers to all of the following: 
     (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and 
     (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and 
     (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. 
     This definition of ‘circuitry’ applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or other network device.” 
     As used here ‘module’ refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user. The apparatus  10  may be a module for incorporation into another apparatus. 
     The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one . . . ” or by using “consisting”. 
     In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.