Abstract:
An apparatus for analysing a bodily fluid sample, comprising a substrate having supported thereon: bodily fluid collecting means configured to collect a bodily fluid from the surface of a body part placed adjacent to the bodily fluid collecting means; means for analysing the collected bodily fluid sample; and means for displaying an indication of a result of the analysis.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2011/073082 filed Dec. 16, 2011, which claims priority to European Patent Application No. 10195683.7 filed Dec. 17, 2010. The entire disclosure contents of these applications are herewith incorporated by reference into the present application. 
     
    
     FIELD OF DISCLOSURE 
       [0002]    This invention relates to a bodily fluid analysis device. 
       BACKGROUND 
       [0003]    Many people are required to perform regular tests on their blood or other bodily fluid in order to monitor a disease and adjust medication appropriately. For example, diabetes sufferers may be provided with quantities of insulin, for instance by injection, sometimes a number of times daily. The quantity of insulin that is appropriate depends on the person&#39;s blood glucose level, so blood glucose level measurement can also occur a number of times daily. 
         [0004]    Blood glucose level measurement typically is a multi stage process requiring a number of separate pieces of equipment. A user may be required to carry around a bulky electronic blood glucose meter as well as a supply of test strips and lancet. After lancing the skin to elicit a blood sample, a user must transfer the blood to the test strip, activate the meter and present or insert the test strip into the meter in order to obtain a measurement. 
       SUMMARY 
       [0005]    A first aspect provides an apparatus for analysing a bodily fluid sample, comprising a substrate having supported thereon:
       bodily fluid collecting means configured to collect a bodily fluid from the surface of a body part placed adjacent to the bodily fluid collecting means;   means for analysing the collected bodily fluid sample; and   means for displaying an indication of a result of the analysis.       
 
         [0009]    The analysis of the bodily fluid sample may comprise measuring a property of the bodily fluid and the displaying of an indication of the result of the analysis may comprise displaying the result of the measuring. 
         [0010]    The means for analysing the collected bodily fluid sample may comprise a controller and at least one pair of electrodes connected to the controller. The at least one pair of electrodes may be integral with the means for collecting a bodily fluid sample. 
         [0011]    The means for analysing the collected bodily fluid sample may be configured to analyse at least one electrical signal received via a first pair of the at least one pair of electrodes. The apparatus may be configured to activate the means for analysing in response to a predetermined electrical signal received via a second pair of the at least one pair of electrodes. 
         [0012]    The apparatus may also be configured to activate the means for displaying in response to a predetermined electrical signal received via the second pair of electrodes. Alternatively, the apparatus may be configured to activate the means for displaying in response to a predetermined electrical signal received via a third pair of the at least one pair of electrodes. 
         [0013]    The second pair of electrodes may be located further from a bodily fluid collecting end of the means for collecting than the first pair of electrodes. The third pair of electrodes may be located closer to a bodily fluid collecting end of the means for collecting than the first pair of electrodes. 
         [0014]    The apparatus may further comprise an adjustable calibration resistor. The bodily fluid collecting means may comprise an absorbent material. 
         [0015]    A second aspect provides a method for analysing a bodily fluid sample, comprising:
       placing a body part adjacent to bodily fluid collecting means of a bodily fluid analysis device, wherein the bodily fluid collecting means are configured to collect a bodily fluid from the surface of the body part;   analysing the collected bodily fluid sample;   displaying an indication of a result of the analysis.       
 
         [0019]    A third aspect provides an apparatus, the apparatus comprising:
       a substrate, the substrate having supported thereon:   a collector for collecting a bodily fluid from the surface of a body part placed adjacent to the collector;   an analyser for analysing the collected bodily fluid sample; and   a display for displaying an indication of a result of the analysis.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1  shows a cutaway view of a bodily fluid analysis device; 
           [0026]      FIG. 2  shows a schematic view of the bodily fluid analysis device of  FIG. 1 ; 
           [0027]      FIGS. 3A-C  show the bodily fluid analysis device of  FIGS. 1 and 2  in an exemplary operation; 
           [0028]      FIG. 4  is a flow chart illustrating an exemplary operation of the bodily fluid analysis device of  FIGS. 1 and 2 ; 
           [0029]      FIG. 5  shows a schematic view of a second embodiment of a bodily fluid analysis device; 
           [0030]      FIGS. 6A-C  show the bodily fluid analysis device of  FIG. 5  in an exemplary operation; 
           [0031]      FIG. 7  is a flow chart illustrating an exemplary operation of the bodily fluid analysis device of  FIG. 5 ; and 
           [0032]      FIG. 8  shows a schematic view of a third embodiment of a bodily fluid analysis device. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Referring firstly to  FIGS. 1 and 2 , a cutaway view and a schematic view respectively of a bodily fluid analysis device  100  are shown. The analysis device  100  has a layered structure. The bottom layer comprises a substrate  102  in the form of a relatively thin, elongate sheet material. Formed on top of the substrate  102  at a first end of the substrate  102  is an absorbent material  104 . Formed on top of the substrate  102  at a second end, opposed to the first end, of the substrate  102  is a display  106 . Electronic components are provided on top of the substrate  102  at and around the centre of the device  100 . The electronics include a controller  108 , a printed resistor  109  and batteries  110 . The electronics are covered by a spacer glue layer  111 . 
         [0034]    The controller  108  is connected to at least one pair of electrodes  112 ,  114 , which are also formed on top of the substrate  102 . The device  100  has measurement electrodes  112  and activation electrodes  114 . Both the measurement electrodes  112  and the activation electrodes  114  overlap with the absorbent material  104 . The absorbent material  104  has an exposed end located at an extremity of the device  100 . The measurement electrodes  112  are located closer to this exposed end of the absorbent material  104  than the activation electrodes  114 . 
         [0035]    The top layer of the device  100  (visible only in  FIG. 1 ) comprises at least one cover which protects the components formed on top of the substrate  102 . A first cover plate  116  overlies the absorbent material  104  and a second cover plate  118  overlies the electronics and spacer glue  111 . The display  106  may be a Liquid Crystal Display (LCD), comprising an LCD fill  120  and a LCD cover plate  122 . A capillary vent  124  is defined at the point where the first cover plate  116  and the second cover plate  118  meet. 
         [0036]    The controller  108  is connected to the LCD fill  120  of the display  106  and to the measurement electrodes  112  and the activation electrodes  114 . These connections may be made via conductive paths formed on the substrate  102 . The controller  108  is configured to receive signals from the measurement electrodes  112  and the activation electrodes  114  and to send control signals to the display  106 . The measurement electrodes  112  and the activation electrodes  114  may be made of any conductive material, for example carbon or a metal. 
         [0037]    The absorbent material  104  may be located at a first end of the substrate  102  such that one end of the absorbent material  104  is exposed. The end of the absorbent material  104  which is exposed may be made more noticeable to a user of the device  100  by the addition of colour, texture or other markings, a notch or indentation or by protruding a short distance beyond the substrate  102  and first cover plate  116 . The absorbent material  104  may be a wicking material having a capillary structure. Fluid applied to the exposed end of the absorbent material  104  is drawn into the body of the absorbent material  104  by capillary action. The capillary vent  124  may facilitate the capillary action by allowing air within the absorbent material  104  to be displaced by the fluid. 
         [0038]    The absorbent material  104  may contain a chemical substance such as an enzyme. The absorbent material  104  may be doped with the chemical substance during manufacture. When bodily fluid is absorbed into the material  104 , it reacts with the chemical substance to create an electrical signal. The chemical substance present in the absorbent material  104  may be selected to react with specific target substance in the bodily fluid or to catalyze a reaction involving a target substance in the bodily fluid. For example, the target substance may be blood glucose. The blood glucose may react with an enzyme in the absorbent material  104  which is subsequently reoxidised to produce electrical charge. A mediator may be in involved in the reoxidation of the enzyme. The electrical charge produced may then flow as a current through attached electrodes. The target substance may be another component of blood, for example glycated haemoglobin (HbA1c) or a ketone. 
         [0039]    The chemical substance may be present throughout the absorbent material  104  or it may only be present in a portion of the absorbent material  104 . The absorbent material  104  may occupy the entire width of the substrate  102  or it may occupy only a portion of the width of the substrate  102 . In the embodiment of  FIG. 2 , the absorbent material  104  occupies only a portion of the whole width of the substrate  102  and is centrally located as is indicated by the dashed line. The remaining material at this first end of the device  100  is a non absorbent material, such as a plastic. Alternatively the substrate  102  may be of greater thickness so as to form a recess for the absorbent material  104 . The substrate  102  may be a plastic material or any other suitable material such as silicon. 
         [0040]    In some embodiments, the absorbent material  104  is configured to absorb a predetermined amount of fluid. Depending on the bodily fluid which is being absorbed, the property of the fluid which is to be measured and the method by which the measurement is to be taken, the volume of fluid present in the absorbent material  104  may affect the measurement. Configuration of the absorbent material  104  to absorb a predetermined amount of fluid helps to improve measurement accuracy. 
         [0041]    The controller  108  may be a microcontroller or integrated circuit of any suitable type. The controller  108  may store software or algorithms in flash memory (not shown) and may have volatile memory such as RAM (not shown) for executing the software. The spacer glue layer  111  covering the controller  108  and other electronics ensures that no circuit crossing or shorting occurs and prevents the electronics from becoming dislodged or disconnected. The controller  108  is connected to each of the measurement electrodes  112  in order to measure a property of the bodily fluid sample absorbed in the absorbent material  104 . 
         [0042]    The batteries  110  are configured to provide power to the controller  108  and the display  106 . In some embodiments, the batteries have a energy storage capacity which is sufficient only to power the controller  108  to compute a single measurement and to power the display  106  for a reasonable time, e.g. a few minutes. As the device  100  requires only a small amount of energy, the batteries  110  may be replaced with another source of power such as a capacitor able to collect energy from radio frequency signals emitted by a mobile transmitting device such as a mobile phone. Thus a user of the device  100  may be able to power or charge the device  100  using an application on their mobile phone or the device  100  may charge by being in close proximity to the user&#39;s mobile phone for a short time. The device  100  may also be able to collect energy from ambient electromagnetic radiation. In some embodiments, the batteries  110  are replaced with means for collecting energy from a user of the device  100 . For example the device  100  may have an area which the user compresses between their fingers to impart energy to the device  100 . Alternatively the device  100  may contain both batteries  110  and other means for collecting energy. 
         [0043]    The measurement electrodes  112  and the activation electrodes  114  are disposed on the substrate  102  and overlap with at least a portion of the absorbent material  104 . Each of the measurement electrodes  112  and the activation electrodes  114  may comprise a pair of electrodes spaced apart. The space between the electrodes is at least partially occupied by absorbent material  104 . The measurement electrodes  112  are configured to transmit electrical signals generated by the reaction of bodily fluid with a chemical substance present in the absorbent material  104  to the controller  108  so that a property of the bodily fluid can be measured. This property may be a concentration of a specific substance present in the bodily fluid. The activation electrodes  114  are also configured to pass electrical signals generated in the absorbent material  104  to the controller  108 . These signals are used as a trigger for activation of the controller  108  and the display  106 . For example, the controller  108  may be configured to detect only signals above a certain threshold which are received from the activation electrodes  114 . When a signal above the threshold is detected, the controller  108  and display  106  are activated. 
         [0044]    The resistor  109  is disposed on a conductive path linking the controller  108  to one of the measurement electrodes  112 . This allows the electrical resistance of the circuit path formed by the controller  108 , measurement electrodes  112  and absorbent material  104  to be predetermined. The controller  108  may rely on having an accurate value for the resistance of this circuit path in order to produce an accurate measurement. The resistor  109  may be a printed circuit resistor. 
         [0045]    In alternative embodiments, the resistor  109  is disposed on a conductive path that begins and ends at the controller  108  and does not incorporate any of the electrodes  112 ,  114 . The resistor may be used for calibration, for example to adjust a lot to lot manufacturing accuracy of the device  100 . For example, after determining a calibration value of a lot of test strips during production, the resistance of the resistor  109  may be adjusted by laser cutting. 
         [0046]    The resistor  109  may be printed on the substrate  102  with a carbon containing ink, for example. After determining a calibration value of the lot of test strips during production, the resistance of the resistor  109  may be adjusted by modifying the printing process of resistor  109 . The resistance of resistor  109  may be used during use of device  100  as a calibration value to adjust a measurement result. 
         [0047]    In further example embodiments, a capacitor is used for storing a calibration value on the device  100  instead of a resistor. Modifying the capacitor may be done by laser cutting or the printing process during production. 
         [0048]    In further example embodiments, a calibration value may be stored in a non-volatile memory of the device during production, for example in the flash memory. Thus, no dedicated resistor or capacitor may be needed for calibration. 
         [0049]    The batteries  110  are disposed on a conductive path which begins and ends at the controller  108 . 
         [0050]    The display  106  may be a numerical display configured to display three digits. In some other embodiments the display  106  may be configured to display more than three digits. The best choice of display depends on the range and accuracy of the measured property required. In some embodiments, the display  106  may be configured to display a decimal point before or after the first or second digit. Alternatively the decimal point may be in a fixed location, for example after the second digit. Each digit of the display  106  may comprise a seven-segment display capable of displaying the numbers 0 to 9. Only a single connection between the controller  108  and the display  106  is shown, however there may be several individual connections. There may be a connection between the controller  108  and the display  106  for each digit, or for each segment of each digit, or there may be a multiplexed connection. 
         [0051]    The LCD cover plate  122  of the display is transparent. This allows illuminations in the LCD fill  120  to be seen by a user of the device  100 . The LCD cover plate  122  may for example be made of a glass material. The display  106  may permanently display a unit in which the measurement is expressed, for example mg/dl, mmol/l or mol/l as shown in  FIG. 2 . This unit indication may be printed or otherwise adhered to the LCD cover plate  122 . 
         [0052]    The device  100  is preferably small in size, for example about 10-20 mm wide, 40-80 mm long and less than 10 mm thick. This makes the device  100  easily portable for a user. A user may easily carry a number of these devices  100  around with them. Because the functions of a test strip and analysis device are combined in a single device of small size, a user does not need to carry a separate meter, which may be a relatively bulky item. Multiple devices may be provided to a potential user in individual blister packaging or in a resealable vial. Such packaging keeps the devices  100  and in particular the absorbent material  104  dry and free from contaminants allowing a “shelf life” to be attributed to each device  100 . 
         [0053]    In operation, a user of the device  100  presents bodily fluid to the exposed end of the absorbent material  104 . The bodily fluid is absorbed into the absorbent material  104 . The analyte in the bodily fluid undergoes a reaction with a chemical substance present in the absorbent material  104  or undergoes a reaction which is catalyzed by an enzyme present in the absorbent material  104 . This reaction produces an electrical charge which may pass as a current through the electrodes  112 ,  114  and via the conductive paths to the controller  108 . The amount of analyte contained in the bodily fluid determines the magnitude of the electrical signal that reaches the controller  108 . The property of the electrical signal measured at the controller  108  may be a current and/or voltage of the signal and may involve a time element, for instance by integrating an electrical parameter over time. 
         [0054]    As previously described, in some embodiments the controller  108  and display  106  are not activated until an electrical signal above a certain threshold is received via the activation electrodes  114 . As more bodily fluid is absorbed, more individual chemical reaction takes place, which increases the amount of electrical charge produced. The activation electrodes  114  are located further from the exposed end of the absorbent material  104  than the measurement electrodes. This ensures that when the threshold signal value is exceeded, there is sufficient quantity of bodily fluid in the volume between the measurement electrodes  112 . By activating the controller  108  and display  106  only when a threshold signal level is exceeded, it can be ensured that a sufficient volume of fluid is present in the absorbent material  104  for an accurate measurement to be made. 
         [0055]    Once the controller  108  has been activated, it executes software and/or algorithms with which it has been programmed. The controller  108  is programmed to interpret signals received via the measurement electrodes  112  so as to make a measurement of a property of the bodily fluid. The controller  108  may produce a measurement based on a single signal sample received via the measurement electrodes  112 . Alternatively the controller  108  may record a series of signals received via the measurement electrodes  112 . The controller  108  may compute a measurement based on an analysis of the series of received signals. 
         [0056]    Once the controller  108  has computed a measurement of a property of the bodily fluid, it sends signals to the display  106  to cause it to display the result of the measurement. The display may show the measurement for a predetermined time or for as long the capacity of the batteries  110  allow. 
         [0057]    In some embodiments, the bodily fluid which is collected by the device  100  is blood and the property of the blood which is measured is the blood glucose level. The process of making a blood glucose level measurement with the device  100  will now be described with reference to  FIGS. 3A-C  and the flow chart of  FIG. 4 . 
         [0058]    Referring firstly to  FIG. 3A , the device  100  is shown in an idle state. The controller  108  and display  106  are inactive. A user of the device  100  has used a lancet or similar to elicit blood from their finger and is about to present the blood to the exposed end of the absorbent material  104 . 
         [0059]    In  FIG. 3B , the user has presented the blood to the absorbent material  104  by pressing their finger against the exposed end of the absorbent material  104 . The blood is absorbed into the absorbent material  104  by capillary action. The absorbent material  104  becomes saturated with the blood as indicated by the cross hatching. The blood reacts with an enzyme present in the absorbent material  104  to produce an electrical current in the absorbent material  104 . When an electrical current above a threshold level passes through the activation electrodes  114 , the controller  108  and display  106  are activated. The controller  108  begins measuring signals received from the measurement electrodes  112 . The display  106  may show a standby state, for example by illuminating the bottom segment of each digit of the display  106 . 
         [0060]    In  FIG. 3C , the controller  108  has finished making its measurement of the blood glucose level of the absorbed blood sample. The controller  108  controls the display  106  to display the result of the measurement to the user. The display  106  continues to display the result of the measurement until the available power supply is exhausted. 
         [0061]      FIG. 4  is a flow chart illustrating the process of measuring a blood glucose level using the device  100 . 
         [0062]    The process begins at step  400 . At step  402  the user presents blood to the device  100  at the exposed end of the absorbent material  104 . This step of the process is shown in  FIG. 3A . At step  404  the blood is absorbed into the device  100  by capillary action. The capillary action causes the blood to fill all of the absorbent material  104  such that it becomes saturated. At step  406  the blood reacts with a chemical substance embedded in the absorbent material  104 . Specifically, the glucose in the blood reacts with an enzyme, for example glucose oxidase or glucose dehydrogenase. The reaction produces electrical charge which flows as a current through the saturated absorbent material  104  to the electrodes  112 ,  114 . 
         [0063]    At step  408  it is determined if an electrical signal received at the controller  108  via the activation electrodes  114  is above a threshold level. This step may be performed in hardware at the controller  108  such that the controller  108  may remain inactive during the determination. If the signals being received are below the threshold level, the process returns to step  404 . This may indicate that not enough blood has been absorbed or that the reaction rate is too low. The device  100  may be configured such that when the absorbent material  104  is saturated with a blood sample of a sufficient quality, the threshold signal value is exceeded. When it is determined that the threshold value is exceeded, the process moves to step  410 . 
         [0064]    At step  410 , the controller  108  begins measuring the blood glucose level in the absorbed blood sample. The controller  108  is configured to receive electrical signals produced by the reaction of the blood glucose with the enzyme in the absorbent material  104  via the measurement electrodes  112 . The controller  108  may receive multiple signals in order to make the measurement. The signals may for example be multiple consecutive values of a voltage or a current separated over time. The measurement may involve a time element, for instance integrating the values over time. 
         [0065]    At step  412  the display  106  is activated. When initially activated the display  106  may be in a standby mode. This standby mode may consist of illuminating at least some of the pixels of the display. This has the added advantage of signalling to a user of the device  100  that the blood sample they have provided is of a sufficient volume and quality and that a measurement is underway. Step  412  is performed in response to a positive determination at step  408 . Step  412  may therefore begin simultaneously with step  410 . Step  412  of the process is shown in  FIG. 3B . 
         [0066]    At step  414  it is determined if the measurement of the blood glucose level is complete. In some embodiments, the controller  108  may perform the measurement relatively quickly based on a single or a few signals from the measurement electrodes  112 . In some other embodiments the controller  108  may record signals over a short period of time in order to produce a more accurate measurement of the blood glucose level. If the measurement is not complete, the display continues to operate in standby mode at step  412 . Once it is determined that the measurement is complete the process continues at step  416 . 
         [0067]    At step  416  the display  106  is caused by the controller  108  to display a result of the measurement. The display  106  may continue to display the result of the measurement until the power supply of the device  100  is exhausted. This step is shown in  FIG. 3C . In some embodiments, the device  100  is a single use blood glucose meter for taking a single blood glucose level reading. Therefore, after the user has noted the reading from the display  106 , the device  100  may be discarded. The process ends at step  418 . 
         [0068]    Referring now to  FIG. 5 , a second embodiment is shown. The device  500  of  FIG. 5  differs from the device  100  in that it has three pairs of electrodes. The device  500  has controller activation electrodes  502 , measurement electrodes  504  and display activation electrodes  506 . Each pair of electrodes  502 ,  504 ,  506  is formed on the substrate  102  and overlaps with the absorbent material  104 . As shown the controller activation electrodes  502  are located closest to the exposed end of the absorbent material  104 . The measurement electrodes  504  are located behind the controller activation electrodes  502 ; further from the exposed end of the absorbent material  104 . The display activation electrodes  506  are located behind the measurement electrodes  504 ; furthest from the exposed end of the absorbent material  104 . All three pairs of electrodes  502 ,  504 ,  506  are connected to the controller  108  via conductive paths formed on the substrate  102 . The display  106 , batteries  110  and resistor  109  of the device  500  are substantially the same as those of the device  100  of the first embodiment and are therefore not described in detail again here. 
         [0069]    The controller  108  is configured to receive signals from the controller activation electrodes  502 , measurement electrodes  504  and display activation electrodes  506 . These signals are produced by the reaction of a bodily fluid sample with a chemical substance or enzyme embedded in the absorbent material  104  as described above in relation to device  100 . 
         [0070]    The controller  108  of the device  500  may be configured to detect only signals above a certain threshold which are received from the controller activation electrodes  502  and display activation electrodes  506 . When a signal above a threshold value is detected via the controller activation electrodes  502 , the controller  108  is activated. The controller  108  may then begin recording signals received via the measurement electrodes  504 . When a signal above a threshold value is detected via the display activation electrodes  506 , the display  106  is activated. The display  106  may be activated in a standby mode. Since the display activation electrodes  506  are located further from the exposed end of the absorbent material  104  than the controller activation electrodes  502 , the controller  108  is activated before the display  106 . This results in the display  106  being activated for the shortest possible time before a reading is displayed. This reduces the total amount of power required to make a measurement of a property of a bodily fluid and to display the result of the measurement to a user of the device  500  for a given period of time. 
         [0071]    The controller  108  and display  106  only draw power from the batteries  110  when active. When inactive, the current discharge from the batteries  110  is zero or close to zero such that the shelf life of the device  100 ,  500  is not affected. 
         [0072]    The signal from display activation electrodes  506  may also be used in the measurement of an analyte in the bodily fluid. For example, by measuring the time when the bodily fluid reaches the display activation electrodes  506 , a measurement of the viscosity or the amount of bodily fluid can be made. 
         [0073]    The process of making a blood glucose level measurement with the device  500  will now be described with reference to  FIGS. 6A-C  and the flow chart of  FIG. 7 . 
         [0074]    In  FIG. 6A , the user has presented a blood sample to the absorbent material  104  by pressing their finger against the exposed end of the absorbent material  104 . The blood then begins to be absorbed into the absorbent material  104  by capillary action. The controller  108  and display  106  are in an inactive state. 
         [0075]    In  FIG. 6B , blood is absorbed into the absorbent material  104 . The blood reacts with an enzyme present in the absorbent material  104  to produce an electrical current in the absorbent material  104 . When an electrical current above a threshold level passes through the controller activation electrodes  502 , the controller  108  is activated. The controller  108  then begins measuring signals received from the measurement electrodes  504  in order to compute a blood glucose level of the absorbed blood. The threshold level may be set such that there is a high probability of blood being present between the measurement electrodes  504 . At this stage the display  106  remains inactive. Alternatively, only a single segment or symbol of the display  106  is activated to indicate that the device  500  performs a measurement, while all other segments and/or symbols of the display  106  remain inactive. 
         [0076]    In  FIG. 6C , blood has been absorbed substantially throughout the absorbent material  104 . At this stage a threshold signal level passing through the display activation electrodes  506  is exceeded, causing the display  106  to be activated. Once the controller  108  has finished computing the measurement of the blood glucose level, it controls the display  106  to display the result of the measurement. The display  106  continues to display the result of the measurement until the available power supply is exhausted. 
         [0077]      FIG. 7  is a flow chart illustrating the process of measuring a blood glucose level using the device  500 . 
         [0078]    The process begins at step  700 . At step  702  the user presents blood to the device  500  at the exposed end of the absorbent material  104 . At step  704  the blood is absorbed into the device  500  by capillary action. Step  704  of the process is shown in  FIG. 6A . 
         [0079]    At step  706  the blood reacts with a chemical substance embedded in the absorbent material  104 . Specifically, the glucose in the blood reacts with an enzyme. The reaction produces electrical charge which flows as a current through the saturated absorbent material  104  and out via one of the pairs of electrodes  502 ,  504 ,  506  to the controller  108 . The amount of glucose in the blood determines the amount of electrical charge created by this reaction. 
         [0080]    At step  708  it is determined if an electrical signal received at the controller  108  via the controller activation electrodes  502  is above a threshold level. This step may be performed in hardware at the controller  108  such that the controller  108  may remain inactive during the determination. If the signals being received are below the threshold level, the controller  108  remains inactive and the process returns to step  704 , i.e. not enough blood has yet been absorbed or not enough charge has yet been produced by the reaction. When it is determined that the threshold value is exceeded, the process moves to step  710 . At this stage it can be assumed that very little charge is flowing via the display activation electrodes  506 . 
         [0081]    At step  710 , the controller  108  begins measuring the blood glucose level in the absorbed blood sample. The controller  108  is configured to receive electrical signals produced by the reaction of the blood glucose with the enzyme in the absorbent material  104  via the measurement electrodes  504 . The controller  108  may receive multiple signals in order to make the measurement. Step  710  of the process is shown in  FIG. 6B . 
         [0082]    At step  712  it is determined if an electrical signal received at the controller  108  via the display activation electrodes  506  is above a threshold level. This step may be performed in hardware or software at the controller  108 . If the signals being received are below the threshold level, the display  106  remains inactive. When it is determined that the threshold value is exceeded, the process moves to step  714 . The device  500  is configured such that when the absorbent material  104  is saturated with blood, the signal received at the controller  108  via the display activation electrodes  506  exceeds the threshold value. 
         [0083]    At step  714  the display  106  is activated. When initially activated the display  106  may be in a standby mode. This standby mode may consist of illuminating at least some of the pixels of the display. This has the added advantage of signalling to a user of the device  500  that the blood sample they have provided is of sufficient volume and quality and that a measurement is underway. 
         [0084]    At step  716  it is determined if the measurement of the blood glucose level is complete. If the measurement is not complete, the display  106  continues to operate in standby mode at step  714 . Once it is determined that the measurement is complete the process continues at step  718 . At some time before it is determined that the signal received via the display activation electrodes  506  exceeds the threshold value, the controller  108  may complete its calculation of the blood glucose level. The controller  108  may then be configured to store the result of the measurement until the display  106  is active or the controller  108  may begin sending control signals to the display  106  immediately on completion of the measurement. 
         [0085]    At step  718  the display  106  is caused by the controller  108  to display a result of the measurement. In the situations where the controller  108  has completed its calculation of the blood glucose level before the display is activated, when a positive determination is made at step  712 , steps  714  and  716  may occur very quickly such that the display  106  spends only a very brief time in standby mode. This further reduces the power consumption of the device  500 . The display  106  may continue to display the result of the measurement until the power supply of the device  500  is exhausted. Step  718  is shown in  FIG. 6C . In some embodiments, the device  500  is a single use blood glucose meter for taking a single blood glucose level reading. Therefore, after the user has noted the reading from the display  106 , the device  500  may be discarded. The process ends at step  720 . 
         [0086]    As previously mentioned, the volume of bodily fluid absorbed by the absorbent material  104  may, in some measurement techniques and for some target substances, affect the measurement of that target substance. The absorbent material  104  may therefore be manufactured to absorb a predetermined amount of fluid. This amount may depend on the structure and number of capillaries which form the absorbent material  104 . The concentration of chemical substance embedded in the absorbent material  104  and which reacts with the target substance in the bodily fluid may also affect the measurement of the target substance. Although efforts may be made to ensure that each device  100 ,  500  is identical and each piece of absorbent material  104  used in these devices  100 ,  500  is identical, there may be some batch variation in the absorptive capacity and chemical substance concentration within the absorbent material  104 , particularly when the devices are mass produced. Further, variation in the geometry due to manufacturing tolerances may effect the measurement. 
         [0087]      FIG. 8  shows an embodiment of the device  100  in which some batch variation of the absorbent material  104  has occurred during manufacture. For example, one device  100  of each batch may be tested after it has been manufactured in order to determine a calibration value for the devices produced in that batch. In order for the device  100  to be able to produce an accurate measurement of a property of absorbed bodily fluid, the electrical resistance of the measurement circuit path may need to be accurate within a small tolerance. This may be achieved by measuring a control solution with an accurate concentration of analyte, such as glucose. 
         [0088]    In the embodiment of the device  100  shown in  FIG. 8 , the resistor  109  is a printed resistor. Printed resistors can be trimmed with a laser such that their resistance is decreased. After the laser trimming a detached part  800  of resistor  109  no longer forms a part of the measurement circuit path. In this manner, batch variation in the properties of the absorbent material  104  can be corrected. 
         [0089]    It will be appreciated that the above described embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present application. Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and/or combination of such features.