Patent Publication Number: US-2012035441-A1

Title: Mount unit, sensor unit, measurement apparatus and sensor fixation method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese patent application No. 2010-176465, filed on Aug. 8, 2010, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mount unit used for fixing a sensor that can be subcutaneously embedded into a living body, a sensor unit that uses the mount unit, a measurement apparatus including the mount unit and the sensor unit, and a method for fixing the sensor. 
     2. Description of Related Art 
     For conventional blood sugar level measurements, it is necessary to prick the body of a patient with an instrument called a lancet and collect blood, each time measurement is performed. This is problematic in that a heavy physical burden is imposed on the patient and the measurement cannot be performed continuously. To solve such problems, a method called continuous glucose monitoring (CGM) has recently been proposed in which glucose concentrations in subcutaneous tissue are continuously measured. 
     In the CGM, a sensor is disposed such that a portion thereof is embedded under the skin of a patient, and a signal such as a current value depending on the glucose concentration in the interstitial fluid under the skin is continuously output by the sensor. Then, the signal is converted into a blood sugar level using a measuring device or the like. With the CGM, it is possible to continuously measure blood sugar levels (for example, see JP 2008-062072A (see  FIGS. 14 ,  17 ,  26  to  28 D, and  33 ). Although interstitial fluid is different from blood, it is considered that a glucose concentration in interstitial fluid reflects a glucose concentration in blood (blood sugar level). Therefore, the blood sugar level can be known by measuring a glucose concentration in interstitial fluid under the skin. 
     Since the CGM requires a portion of the sensor to be embedded subcutaneously into the patient, JP 2008-062072A discloses a device (embedded device) that can punch a sensor toward the skin together with a puncture needle and embed the sensor under the skin. The embedded device includes a mechanism that punches out the sensor together with the puncture needle using a spring or the like and then pulls back only the puncture needle. Here, the procedure for the sensor insertion disclosed in JP 2008-062072A will be described. 
     First, a mount unit for mounting the sensor is disposed on the skin of the patient. At this time, the mount unit is fixed to the patient&#39;s skin with a double-sided tape. Then, an embedded device on which the sensor and the puncture needle have been set is disposed in a predetermined position of the mount unit, and the sensor and the puncture needle together are punched into the skin by the embedded device. Thereafter, the puncture needle returns to its original position, but the sensor is positioned such that a portion provided with a connection terminal projects from the skin and the remaining portion is held under the skin. 
     After removal of the embedded device from the mount unit, a control unit for controlling the sensor is disposed on the mount unit. At this time, the portion of the sensor that is provided with the terminal (terminal portion) is sandwiched between the mount unit and the control unit, and the sensor is fixed to the patient with the mount unit. At the same time, the terminal of the control unit is connected to the sensor terminal projecting from the skin, completing a CGM system. 
     By subsequently operating the CGM system to perform sensing by the sensor, a signal obtained by the sensor is converted into a digital signal by the control unit, and the signal is further sent to an external measuring device by wireless or wired transmission. The measuring device calculates a specific glucose concentration based on the signal and displays the calculated value on a display screen. 
     Also, as described above, the sensor is fixed to the patient with the mount unit and the portion of the sensor that is embedded under the skin is prevented from moving accidentally. This is because if the portion of the sensor that is embedded under the skin moves and the wound formed in the skin by the embedded device is thus enlarged, the body of the patient functions so as to cover the sensor with protein in order to heal the wound, resulting in a state in which accurate measurement cannot be conducted. 
     Furthermore, since a sensor that has been covered with protein in this manner is unusable, removal of the sensor and insertion of a new sensor are necessary. However, this imposes considerable physical and financial burdens on the patient. Also, since whether a signal is output from the sensor can be known only after operation of the control unit and the measuring device, the patient may have to visit the medical institution again. Therefore, for the CGM system, the sensor that has been once embedded needs to be prevented from moving as much as possible. 
     In recent years, there is a demand for a sensor that can be embedded for a longer period of time. Accordingly, before the life of the sensor ends (before the sensor needs to be replaced), the double-sided tape used for fixing the mount unit to the patient may require replacement. 
     If double-sided tape that requires replacement in not replaced, hygiene problems such as a skin irritation and development of bacteria occur. Also, if the double-sided tape that requires replacement is not replaced, a reduction in adhesion of the double-sided tape, peeling of the double-sided tape or the like due to the turnover of the skin make the fixation of the sensor with the mount unit unstable. Consequently, the portion of the sensor that is embedded under the skin moves and the wound in the skin is thus enlarged, also causing the above-described problem of impairing accurate measurement. To solve these problems, the double-sided tape needs to be replaced regularly. 
     However, the structure of the conventional mount unit used in the CGM system disclosed in JP 2008-062072A renders it difficult to replace the double-sided tape, with the sensor being embedded under the skin. Accordingly, each time the double-sided tape is replaced, it is necessary to remove the sensor from the patient and replaced it with a new sensor, resulting in the need to perform pricking again. Also, despite applying the sensor that can be embedded for a long period of time, the sensor needs to be replaced each time the double-sided tape is replaced, and therefore sensors will be wastefully consumed. 
     SUMMARY OF THE INVENTION 
     An example of the object of the present invention is to provide a mount unit, a sensor unit, a measurement apparatus, and a sensor fixation method that can solve the above-described problems and allows for easy replacement of a fixing adhesive material layer, while preventing external force from being applied to the sensor. 
     To achieve the above-described object, a mount unit according to the present invention includes; a main body portion that holds a placement of a portion of a sensor under the skin of a living body; and two or more holding portions attached to the main body portion, wherein each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     According to the above-described feature, in the case where it is necessary to replace an adhesive material layer, the adhesive material layer of one holding portion is kept adhering to the living body, and another holding portion is moved in this state to detach the adhesive material layer of the other holding portion from the living body, and the detached adhesive material layer can be replaced with a new adhesive material layer. That is, according to the present invention, it is possible to replace an old adhesive material layer, with the sensor being fixed. The present invention allows for easy replacement of the fixing adhesive material layer, while preventing external force being applied to the sensor. 
     In a preferred mode of the above-described mount unit according to the present invention, each of the two or more holding portions is attached to the main body portion via a hinge mechanism, and mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. According to this preferred mode, it is possible to simplify the structure of the mount unit, thus realizing a reduction in manufacturing costs. 
     In another preferred mode of the above-described mount unit of the present invention, each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, and movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. According to this mode as well, it is possible to simplify the structure of the mount unit, thus realizing a reduction in manufacturing costs. 
     In another preferred mode of the above-described mount unit of the present invention, each of the two or more holding portions is attached to the main body portion so as to further be rotatable with respect to the main body portion. According to this mode as well, it is possible to simplify the structure of the mount unit, thus realizing a reduction in manufacturing costs. Further, combination of this mode with the above-described modes can further simplify the replacement work of the adhesive material layer in a more reliable manner. 
     In addition, in the above-described mode, it is preferable that a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation. In this case, the adhesive material layer can be replaced by simply rotating the holding portions. 
     In another preferred mode of the above-described mount unit of the present invention, the main body portion includes a mechanism that can change a contact position of at least one of the holding portions that is in contact with the living body, in a state in which the position of the sensor is held. According to this mode, it is possible to suppress a skin irritation of the living body that can be caused by a long period of contact between the skin and the adhesive material layer. 
     In order to attain the above-described object, a sensor unit of the present invention includes: a sensor of which a portion can be placed under the skin of a living body; and a mount unit for fixing the sensor to the living body, wherein the mount unit includes: a main body portion that holds a placement of the portion of the sensor under the skin of the living body; and two or more holding portions attached to the main body portion, and each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state where the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Furthermore, in order to attain the above-described object, a measurement apparatus according to the present invention is a measurement apparatus for measuring numeric information relating to a substance contained in at least one of interstitial fluid and blood that are under the skin of a living body, the apparatus including: a sensor of which a portion can be placed under the skin and that generates a signal dependent on the numeric information; a mount unit for fixing the sensor to the living body; and a control unit that receives the signal generated by the sensor and executes processing that includes digital signal processing on the signal; wherein the mount unit includes a main body portion that holds a placement of the portion of the sensor under the skin of the living body; and two or more holding portions attached to the main body portion, and each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state where the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     In a mode of the above-described measurement apparatus of the present invention, the control unit executes transmission processing for transmitting the signal that has been subjected to digital signal processing to an external measuring device. According to this mode, the signal can be converted into the numeric information by the external measuring device, and therefore the size of the control unit can be reduced. 
     Furthermore, in order to attain the above-described object, a sensor fixation method according to the present invention is a method for fixing, to a living body, a sensor of which a portion can be placed under the skin of the living body, the method including the steps of: 
     (a) using a mount unit that includes a main body portion and two or more holding portions attached to the main body portion, each of the two or more holding portions including an adhesive material layer capable of adhering to the living body and attached to the main body portion so as to allow for selection between a state in which the adhesive material layers are in contact with the living body and a state in which the adhesive material layers are separate from the living body, and holding the sensor by the main body portion of the mount unit; 
     (b) fixing the mount unit to the living body by bringing the adhesive material layer of at least one of the two or more holding portions of the mount unit into contact with the living body; and, 
     (c) in a case where any of the adhesive material layers of the two or more holding portions needs to be replaced, moving the holding portion including the adhesive material layer that needs to be replaced, in a state in which the adhesive material layer of at least one of the holding portions is in contact with the living body, and detaching the adhesive material layer that needs to be replaced from the living body. 
     In a preferred mode of the above-described sensor fixation method according to the present invention, each of the two or more holding portions is attached to the main body portion via a hinge mechanism, mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body, and, in step (c), the adhesive material layer that needs to be replaced is detached from the living body by mobilization of the holding portions with the hinge mechanism. 
     In another preferred mode of the above-described sensor fixation method of the present invention, each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body, and, in step (c), the adhesive material layer that needs to be replaced is detached from the living body by movement of the holding portions. 
     In the above mode, it is more preferable that each of the two or more holding portions is attached to the main body portion so as to be rotatable with respect to the main body portion. In this case, it is further preferable that a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation, and, in step (c), a new adhesive material layer replacing the adhesive material layer that needs to be replaced is faced toward the living body by rotation of the holding portions, and thereafter the new adhesive material layer is adhered to the living body by movement of the holding portions. 
     As described above, the mount unit, the sensor unit, the measurement apparatus, and the sensor fixation method according to the present invention allow for easy replacement of the fixing adhesive material layer, while preventing external force from being applied to the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  show the configuration of a mount unit and a sensor unit according to Embodiment 1 of the present invention:  FIG. 1A  being a perspective view;  FIG. 1B  being a plan view; and  FIG. 1C  being a bottom view. 
         FIG. 2  is a perspective view showing a tip portion of a sensor used in Embodiment 1 of the present invention. 
         FIG. 3  is a perspective view showing a measurement apparatus according to Embodiment 1 of the present invention. 
         FIGS. 4A to 4D  show a series of main steps constituting a sensor fixation method according to Embodiment 1 of the present invention. 
         FIGS. 5A to 5D  show the configuration of a mount unit and a sensor unit according to Embodiment 2 of the present invention:  FIG. 5A  being a perspective view;  FIG. 5B  being a front view;  FIG. 5C  being a side view; and  FIG. 5D  being a bottom view. 
         FIGS. 6A to 6D  show a series of main steps constituting a sensor fixation method according to Embodiment 2 of the present invention. 
         FIG. 7  is a perspective view showing a modification of the mount unit according to Embodiment 2 of the present invention. 
         FIG. 8  shows the configuration of a mount unit according to Embodiment 3 of the present invention. 
         FIGS. 9A and 9B  show a series of main steps constituting a sensor fixation method according to Embodiment 3 of the present invention. 
         FIGS. 10C and 10D  show a series of main steps constituting a sensor fixation method according to Embodiment 3 of the present invention, which are executed after execution of the step shown in  FIG. 9B . 
         FIG. 11  is a perspective view showing a mount unit according to Embodiment 4 of the present invention. 
         FIGS. 12A to 12C  show a series of main steps constituting a sensor fixation method according to Embodiment 4 of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
     Hereinafter, a mount unit, a sensor unit, a measurement apparatus, and a sensor fixation method according to Embodiment 1 of the present invention will be described with reference to  FIGS. 1 to 4 . 
     Mount Unit and Sensor Unit 
     First, the configuration of a mount unit and a sensor unit according to Embodiment 1 will be described with reference to  FIGS. 1 .  FIGS. 1A to 1C  show the configuration of a mount unit and a sensor unit according to Embodiment 1 of the present invention:  FIG. 1A  being a perspective view;  FIG. 1B  being a plan view; and  FIG. 1C  being a bottom view. 
     As shown in  FIGS. 1A to 1C , in Embodiment 1, a sensor unit  30  includes a mount unit  10  and a sensor  20  of which a portion  20   a  is placed under the skin. When the portion  20   a  is placed under the skin, the sensor  20  generates a signal according to numeric information relating to a substance contained in at least one of interstitial fluid and blood as will be described below with reference to  FIG. 2 . One example of such a substance is glucose. In this case, it is possible to identify numeric information relating to glucose, including, for example, glucose concentration, based on the signal from the sensor  20 . 
     The mount unit  10  is used for fixing the sensor  20  to a living body, and includes a main body portion  11  and holding portions  12   a  to  12   d . Of these, the main body portion  11  holds the placement of a portion of the sensor  20  under the skin of the living body. Specifically, in Embodiment 1, the main body portion  11  holds the sensor  20  at a portion (not shown) of the sensor  20  that is not embedded under the skin. In Embodiment 1, the main body portion  11  holds the sensor  20  such that the portion  20   a  of the sensor that is to be embedded under the skin projects from the living body side (see  FIG. 10  of the main body portion  11 . 
     At this time, in the main body portion  11 , electrical conduction is established between electrodes (see  FIG. 2  described below) of the sensor  20  and electrodes  16  (see  FIGS. 1A and 1B ) exposed on the top face of the main body portion  11 . Then, the electrodes of the sensor  20  are electrically connected to a control unit  40  (see  FIG. 3  described below) via the electrodes  16 . 
     The holding portions  12   a  to  12   d  are formed in an arm shape and attached to the main body portion  11 . Also, each of the holding portions  12   a  to  12   d  includes an adhesive material layer  13  capable of adhering to the living body, and is movable so as to allow for selection between a state in which the adhesive material layer  13  is in contact with the living body and a state in which the adhesive material layer  13  is separate from the living body. Although the number of the holding portions in the example shown in  FIGS. 1A to 1C  is four, Embodiment 1 is not limited thereto. It suffices that the number of the holding portions is two or more. 
     Specifically, in Embodiment 1, each of the holding portions  12   a  to  12   d  is attached so as to project from the side face of the main body portion  11  toward the periphery of the portion of the main body portion  11  on the living body side (see  FIG. 10 . Also, each of the holding portions  12   a  to  12   d  is attached to the main body portion  11  via a hinge mechanism  15 , and mobilization of the holding portions with the hinge mechanism  15  allows for selection between the state in which the adhesive material layer  13  is in contact with the living body and the state in which the adhesive material layer  13  is separate from the living body. 
     In the example shown  FIGS. 1A to 1C , the holding portions  12   a  and  12   c  are in the state in which the adhesive material layer  13  is in contact with the living body. 
     On the other hand, the holding portions  12   b  and  12   d  are in the state in which the adhesive material layer  13  is separate from the living body. Also, a separator film  14  is attached to the adhesive material layers  13  of the holding portions  12   b  and  12   d  in order to protect the adhesive material layers  13 . In  FIG. 1A , the separator films  14  are diagonally hatched. Note that illustration of the separator film  14  attached to the adhesive material layer  13  of the holding portion  12   d  is omitted. 
     One example of the usage of the mount unit  10  will now be described. For example, it is assumed that the mount unit  10  is adhered to the skin of a living body with the adhesive material layers  13  of the holding portions  12   a  and  12   c , but the adhesive material layers  13  of both of these holding portions have been degraded. In this case, first, the separator films  14  attached to the adhesive material layers  13  of the holding portions  12   b  and  12   d  are detached. Next, the holding portions  12   b  and  12   d  are moved so as to be lifted down such that the adhesive material layers  13  of the holding portions  12   b  and  12   d  are adhered to the living body. Thereafter, by moving the holding portions  12   a  and  12   c  so as to be lifted up, it is possible to detach the degraded adhesive material layers  13  from the living body, while keeping the sensor  20  fixed. In this manner, according to Embodiment 1, it is possible to replace the old adhesive material layers  13 , while keeping the sensor  20  fixed. 
     Furthermore, in Embodiment 1, any material having viscosity in two opposing directions may be used as the adhesive material layer  13 . For example, the adhesive material layer  13  may be a layer formed only of an adhesive material, or may be a double-sided adhesive tape. 
     Specific examples of the double-sided adhesive tape include a double-sided adhesive tape in which an adhesive material layer is provided on either side of a base material formed of non-woven fabric or the like. Examples of the adhesive material used in a layer formed only of an adhesive material and a double-sided adhesive tape include a hydrogel-based adhesive material and a silicone-based adhesive material. Of these, a silicone-based adhesive material can recover its viscosity by surface cleaning, and therefore an adhesive material layer or a double-sided adhesive tape for which a silicone-based adhesive material is used can be used repeatedly. 
     Further, an adhesive material that can be detached by application of heat or voltage (for example, see JP 2010-037354A) can be used as the adhesive material for forming the adhesive material layers  13  in Embodiment 1. By forming the adhesive material layers  13  with such an adhesive material, the adhesion between each of the holding portions and the skin can be selectively performed. Also, in this case, application of heat or voltage to the adhesive material layers  13  can be performed with a power source (not shown) of the mount unit. 
     Sensor 
     The configuration of the sensor  20  will now be described with reference to FIG.  2  as well as  FIGS. 1 .  FIG. 2  is a perspective view showing a tip portion of a sensor used in Embodiment 1 of the present invention. The following description is given based on the assumption that the substance detected by the sensor  20  is glucose and the sensor  20  is a glucose sensor. 
     As shown in  FIGS. 1 and 2 , the sensor  20  is formed in the shape of an elongated band. The sensor  20  is brought into a state in which the portion  20   a  on the tip side is placed under the skin by an embedded device (not shown). Such a state of the sensor  20  can also be referred to as a state in which the sensor  20  is implanted in the skin. 
     As shown in  FIG. 2 , the sensor  20  includes an insulating, flexible substrate  23 . There is no particular limitation with respect to the material for forming the substrate  23 . However, for example, thermoplastic resins such as polyethylene terephthalate (PET), polypropylene (PP) and polyethylene (PE) and thermosetting resins such as polyimide resin and epoxy resin can be used as the material for forming the substrate  23  because these resins have little affect on the human body. The shape of the substrate  23  may be, but is not particularly limited to, sharp-edged in order to facilitate the penetration into the skin of the living body. 
     In addition to the substrate  23 , the sensor  20  includes a pair of electrodes  21   a  and  21   b  and a portion (enzyme reagent layer)  22  on which the glucose oxidoreductase is disposed. The electrodes  21   a  and  21   b  are used for applying voltage to the enzyme reagent layer  22 . The electrodes  21   a  and  21   b  are formed on the surface of the substrate  23  in the longitudinal direction of the substrate  23 , and also function as wiring. Additionally, the electrodes  21   a  and  21   b  may be formed by evaporation, screen printing, or the like, using, for example, a conductive material such as noncorrosive metal or carbon ink. 
     In the example shown in  FIG. 2 , the enzyme reagent layer  22  is formed by immobilizing glucose oxidoreductase on the electrode  21   a . In this case, the electrode  21   a  functions as a working electrode. Glucose oxidoreductase has the function of detecting, on an electrode, a product resulting from the reaction with glucose (substrate) contained in interstitial fluid or blood, and the function of transferring electrons produced by the reaction to the electrode directly or via a mediator such as metal complex. Accordingly, upon application of voltage across the electrodes  21   a  and  21   b , electrons produced by the catalyst reaction of the enzyme can be detected on electrode  21   a  according to the amount of glucose reacted in the reaction. 
     Examples of glucose oxidoreductase that can be used in Embodiment 1 include glucose oxidase (GOD) and glucose dehydrogenase (GDH). Examples of the method for immobilizing glucose oxidoreductase include various known methods, including, for example, cross-linking using glutaraldehyde. 
     With this configuration, the value of the electric current flowing through the electrodes  21   a  and  21   b  changes according to the glucose concentration, and therefore the glucose concentration can be identified by measuring the current. In Embodiment 1, the current flowing through the electrodes  21   a  and  21   b  corresponds to “signal dependent on numeric information relating to a substance”. 
     Measurement Apparatus 
     Next, the configuration of a measurement apparatus according to Embodiment 1 will be described with reference to  FIG. 3 .  FIG. 3  is a perspective view showing a measurement apparatus according to Embodiment 1 of the present invention. A measurement apparatus  50  shown in  FIG. 3  is an apparatus that measures numeric information relating to a substance contained in at least one of interstitial fluid and blood that are under the skin of a living body. As previously mentioned in the description in relation to  FIGS. 1 and 2 , one example of such a substance is glucose. In this case, one example of the numeric information is glucose concentration. 
     As shown in  FIG. 3 , the measurement apparatus  50  includes the sensor unit  30  shown in  FIGS. 1A to 1C  and a control unit  40 . In the example shown in  FIG. 3 , the sensor unit  30  is disposed on the skin of a living body  60 , and the tip portion  20   a  of the sensor  20  is placed under the skin of the living body  60 . 
     The control unit  40  includes a recess  42  for housing the sensor unit  30  and electrodes  41 . When the control unit  40  is disposed on the sensor unit  30  to house the sensor unit  30  in the recess  42 , the electrodes  41  are connected to the electrodes  16  of the mount unit  10  and are consequently also connected to the electrodes  21   a  and  21   b  (see  FIG. 2 ) of the sensor  20 . 
     Further, the control unit  40  has the function of receiving a signal generated by the sensor  20  and executing the processing including digital signal processing on the received signal. Examples of the processing as mentioned herein include digital signal processing such as signal amplification processing and A/D conversion processing, and transmission processing. Specifically, the control unit  40  applies voltage to the electrodes  21   a  and  21   b  (see  FIG. 2 ) of the sensor via the electrodes  16  of the mount unit  10 . At the same time, the control unit  40  monitors the value of the current flowing through the electrodes  21   a  and  21   b . Then, the control unit  40  generates, by digital processing, a digital signal identifying the level of the current value. 
     Thereafter, the control unit  40  can transmit the generated digital signal to an external measuring device via wired or wireless transmission. As with a conventional measuring device, this measuring device calculates a specific glucose concentration based on the received digital signal and displays the calculated value on a display screen or the like. Note that the control unit  40  itself may perform the glucose concentration calculation and the like in this embodiment. 
     Sensor Fixation Method 
     Next, a sensor fixation method according to Embodiment 1 of the present invention will be described with reference to  FIGS. 4A to 4D .  FIGS. 4A to 4D  show a series of main steps constituting a sensor fixation method according to Embodiment 1 of the present invention. 
     In the example shown in  FIGS. 4A and 4B , the sensor unit  30  is disposed on the skin of the living body  60 , and the tip portion  20   a  of the sensor  20  is placed under the skin of the living body  60 . Also, the mount unit  10  constituting the sensor unit  30  is adhered to the skin of the living body  60  with the adhesive material layers  13  of the holding portions  12   a  and  12   c , but the adhesive material layers  13  of both of these holding portions have been degraded. 
     The following is a description of a method for fixing the sensor  20  to the living body  60  in the above-mentioned case, while replacing a degraded adhesive material layer  13  with a new adhesive material layer  13 . In the following description, reference is made to  FIGS. 1 to 3  as needed. 
     As shown in  FIG. 4A , the adhesive material layers  13  of the holding portions  12   b  and  12   d  are unused, and therefore the separator films  14  are attached to the adhesive material layers  13 . The separator films  14  are diagonally hatched in  FIG. 4A  as well. However, illustration of the separator film  14  attached to the adhesive material layer  13  of the holding portion  12   d  is omitted. 
     Next, after the separator films  14  are detached from the adhesive material layers  13 , the holding portions  12   b  and  12   d  are lifted down such that the adhesive materials layers  13  of the holding portions  12   b  and  12   d  are adhered to the living body  60  as shown in  FIG. 4B . Thereafter, as shown in  FIG. 4C , the holding portions  12   a  and  12   c  are lifted up, and the degraded adhesive material layers  13  are detached from the living body  60 . 
     Next, as shown in  FIG. 4D , the degraded adhesive material layers  13  are removed from the holding portions  12   a  and  12   c . Then, new adhesive material layers  13  are applied to the holding portions  12   a  and  12   c . The new adhesive material layers  13  are used when the adhesive material layers  13  of the holding portions  12   b  and  12   d  have been degraded. 
     In this manner, according to Embodiment 1, it is possible to detach a degraded adhesive material layer  13  from the living body  60 , while keeping the sensor  20  fixed. Furthermore, it is possible to replace a degraded adhesive material layer  13  with a new adhesive material layer, while keeping the sensor  20  fixed. 
     Although the mount unit  10  is fixed using only two of the four holding portions in the example shown in  FIGS. 4A to 4D , Embodiment 1 is not limited thereto. In Embodiment 1, the mount unit  10  may be fixed using all of the holding portions  12   a  to  12   d . In this case, with at least only one holding portion lifted down, the lifting-up of other holding portions and the replacement of the adhesive material layers  13  may be performed. Thereafter, the holding portions whose adhesive material layers  13  have been replaced may be lifted down, and the lifting-up of the remaining holding portions and the replacement of the adhesive material layers  13  may be performed. Accordingly, it is possible to replace all of the degraded adhesive material layer  13  with new adhesive material layers  13 , while keeping the sensor  20  fixed. 
     Embodiment 2 
     Next, a mount unit, a sensor unit, a measurement apparatus, and a sensor fixation method according to Embodiment 2 of the present invention will be described with reference to  FIGS. 5 to 7 . 
     Mount Unit, Sensor Unit, and Measurement Apparatus 
     First, the configuration of a mount unit, a sensor unit, and a measurement apparatus according to Embodiment 2 will be described with reference to  FIGS. 5 .  FIGS. 5A to 5D  show the configuration of a mount unit and a sensor unit according to Embodiment 2 of the present invention:  FIG. 5A  being a perspective view;  FIG. 5B  being a front view;  FIG. 5C  being a side view; and  FIG. 5D  being a bottom view. 
     As shown in  FIGS. 5A to 5D , a sensor unit  80  includes a mount unit  70  and a sensor  20  in Embodiment 2. The sensor  20  is the same as the sensor described in Embodiment 1 with reference to  FIG. 2 . The mount unit  70  includes a main body portion  71 . The main body portion  71  holds a portion (not shown) of the sensor  20  that is not embedded under the skin, as with the main body portion  11  of the mount unit  10  shown in  FIGS. 1 . 
     Although the mount unit  70  includes holding portions as with the mount unit  10  shown in  FIGS. 1 , the holding portions of the mount unit  70  in Embodiment 2 are different in configuration from those in Embodiment 1. The following description is focused on the difference between Embodiment 2 and Embodiment 1. 
     As shown in  FIGS. 5A to 5D , the sensor unit  70  includes holding portions  72   a  and  72   b  unlike the mount unit  10  shown in  FIGS. 1 . Each of the holding portions  72   a  and  72   b  is attached to the main body portion  71  so as to be movable in a direction toward the living body and a direction away from the living body in the projecting state (see  FIGS. 5B and 5C ). 
     In other words, each of the holding portions  72   a  and  72   b  is capable of moving vertically in the thickness direction of the main body portion  71 . Then, movement of each of the holding portions  72   a  and  72   b  allows for selection between a state in which the adhesive material layer  73  is in contact with the living body and a state in which the adhesive material layer  73  is separate from the living body. 
     Each of the holding portions  72   a  and  72   b  has the shape of a roller and is attached rotatably to the main body portion  71 . Specifically, each of the holding portions  72   a  and  72   b  can also rotate about its axis in the projecting direction, that is, its axis extending from the portion attached to the main body portion  71  toward the tip end portion as the rotation axis (see  FIGS. 5A and 5C ). 
     Further, a plurality of adhesive material layers  73  are provided on the outer face of each of the holding portions  72   a  and  72   b  in the direction of rotation. With this configuration, in Embodiment 2, it is possible to replace a degraded adhesive material layer with a new adhesive material layer  73  by simply rotating the holding portion  72   a  or  72   b  as will be described below. 
     Note that a separator film  74  is attached to unused adhesive material layers  73  for protecting the adhesive material layers  73 . In  FIGS. 5A ,  5 B and  5 D, the separator films  74  are diagonally hatched. 
     Although only two holding portions are shown in the example shown in  FIGS. 5A to 5D , it suffices that the number of the holding portions is two or more in Embodiment 2 as well. For example, the number of the holding portions may be three or more. Further, in the case where the number of holding portions are three or more in Embodiment 2, the mount unit  70  may be fixed using only some of the holding portions (for example, two holding portions), or may be fixed using all of the holding portions. 
     In Embodiment 2 as well, the measurement apparatus includes a sensor unit  80  and a control unit as with Embodiment 1. The control unit may be the same as the control unit  40  shown in  FIG. 3  in Embodiment 1. In this case, the measurement apparatus according to Embodiment 2 can be configured by attaching the control unit to the sensor unit  80 . 
     Sensor Fixation Method 
     Next, a sensor fixation method according to Embodiment 2 of the present invention will be described with reference to  FIGS. 6A to 6D .  FIGS. 6A to 6D  show a series of main steps constituting a sensor fixation method according to Embodiment 2 of the present invention. 
     In the example shown in  FIGS. 6A to 6D , the sensor unit  80  is disposed on the skin of the living body  60 , and the tip portion  20   a  of the sensor  20  is placed under the skin of the living body  60 . Also, the mount unit  70  constituting the sensor unit  80  is adhered to the skin of the living body  60  with one of the adhesive material layers  73  of each of the holding portions  72   a  and  72   b , but the adhesive material layers  73  in use have been degraded. 
     The following is a description of a method for fixing the sensor  20  to the living body  60  in the above-mentioned case, while replacing a degraded adhesive material layer  73   a  (see  FIGS. 6B  and (c)) with a new adhesive material layer  73 . In the following description, reference is made to  FIG. 5  as needed. 
     As shown in  FIG. 6A , separator films  74  are attached to unused adhesive material layers  73  in the holding portions  72   a  and  72   b . The separator films  74  are diagonally hatched in  FIGS. 6A to 6D  as well. 
     Next, as shown in  FIG. 6B , only the holding portion  72   a  is moved in the direction away from the living body  60 , and the degraded adhesive material layer  73   a  of the holding portion  72   a  is detached from the living body. At this time, the holding portion  72   b  is left as is, and therefore, the mount unit  70  is kept fixed to the living body  60  with the adhesive material layer  73  of the holding portion  72   b.    
     Next, as shown in  FIG. 6C , the holding portion  72   a  is rotated, and the separator film  74  of an unused adhesive material layer  73  is detached. Thereafter, the holding portion  72   a  is further rotated, and thereby the adhesive material layer  73  from which the separator film  74  has been detached is faced toward the living body  60  instead of the degraded adhesive material layer  73   a.    
     Next, as shown in  FIG. 6D , the holding portion  72   a  is moved in the direction toward the living body  60 , and thereby the adhesive material layer  73  from which the separator film  74  has been detached in the step shown in  FIG. 6C  is adhered to the living body  60 . By the steps shown in  FIGS. 6A to 6D , adhesion to the living body  60  is achieved by the new adhesive material layer  73  replacing the degraded adhesive material layer  73   a  in the holding portion  72   a.    
     After performing the steps shown in  FIGS. 6A to 6D  for the holding portion  72   b , adhesion to the living body  60  is achieved with the new adhesive material layer  73  replacing the degraded adhesive material layer in the holding portion  72   b  as well. 
     In this manner, according to Embodiment 2 as well, it is possible to detach the degraded adhesive material layer  73   a  (see  FIGS. 6B and 6C ) from the living body  60 , while keeping the sensor  20  fixed, as with Embodiment 1. Furthermore, it is possible to replace the degraded adhesive material layer  73   a  with a new adhesive material layer  73 , while keeping the sensor  20  fixed. Furthermore, according to Embodiment 2, it is possible to replace the degraded adhesive material layer  73   a  with a new adhesive material layer  73  by simply rotating the holding portion  72   a  or  72   b.    
     Modification 
     Here, a modification of the mount unit according to Embodiment 2 will be described with reference to  FIG. 7 .  FIG. 7  is a perspective view showing a modification of the mount unit according to Embodiment 2 of the present invention. 
     As shown in  FIG. 7 , in this modification, grooves  75  that permit the horizontal movement of the holding portions are provided on the side face of the main body portion  71 . In  FIG. 7 , only the groove  75  corresponding to the holding portion  72   a  is shown. 
     In this manner, this modification includes a mechanism that can change the contact position of at least one holding portion that is in contact with the living body, in a state where the position of the sensor  20  is held. This makes it possible to change the portion of the skin that is in contact with the adhesive material layer  73 , without changing the position of the sensor  20 . Accordingly, it is possible to suppress a skin irritation resulting from a long period of contact between the skin and the adhesive material layer  73 . 
     Embodiment 3 
     Next, a mount unit, a sensor unit, a measurement apparatus, and a sensor fixation method according to Embodiment 3 of the present invention will be described with reference to  FIGS. 8 to 10 . 
     Mount Unit, Sensor Unit, and Measurement Apparatus 
     First, the configuration of a mount unit, a sensor unit, and a measurement apparatus according to Embodiment 3 will be described with reference to  FIG. 8 .  FIG. 8  shows the configuration of a mount unit according to Embodiment 3 of the present invention. 
     As shown in  FIG. 8 , in Embodiment 3, a sensor unit  100  includes a mount unit  90  and a sensor  20 . The sensor  20  is the same as the sensor described in Embodiment 1 with reference to  FIG. 2 . 
     Also, the mount unit  90  includes a main body portion  91  to which holding portions  92   a  and  92   b  are attached. Further, as with the holding portions  72   a  and  72   b  shown in  FIGS. 5A to 5D  in Embodiment 2, the holding portions  92   a  and  92   b  have the shape of a roller and are attached rotatably to the main body portion  91 . 
     Further, in Embodiment 3 as well, a plurality of adhesive material layers  93  are provided on the outer face of each of the holding portions  92   a  and  92   b  in the direction of rotation as with Embodiment 2. Accordingly, it is possible to replace a degraded adhesive material layer with a new adhesive material layer  93  by simply rotating the holding portion  92   a  or  92   b . Note that a separator film  94  is attached to unused adhesive material layers  93  for protecting the adhesive material layer  93 . In  FIG. 8 , the separator films  94  are diagonally hatched. 
     However, unlike in Embodiment 2, the holding portions  92   a  and  92   b  are attached inside the main body portion  91  in Embodiment 3. Note that, for the sake of illustration, the part of the holding portions  92   a  and  92   b  that is actually hidden behind the main body portion  91  and thus cannot be visually observed is also shown in  FIG. 8 . 
     Specifically, as shown in  FIG. 8 , the main body portion  91  includes, on opposing side faces thereof, two sets of pairs of grooves  95   a  and  95   b . Each of the holding portions  92   a  and  92   b  is held between a groove  95   a  and a groove  95   b  in a state in which it is sandwiched between the groove  95   a  and the groove  95   b.    
     Sandwiching between the grooves  95   a  and  95   b  is achieved by catching, on the respective grooves, both ends of a shaft  98  passing through the center of each of the holding portions. Additionally, each of the grooves is formed in a rectangular shape in the horizontal direction of the main body portion  91 , and the width of the grooves is set to be greater than the diameter of the shaft  98 . 
     This enables the holding portions  92   a  and  92   b  to move vertically (in the thickness direction of the main body portion) and horizontally. Further, the main body portion  91  is provided with an opening  97  for each holding portion for allowing the operator to manually move the holding portions  92   a  and  92   b . That is, the mount unit  90  includes a mechanism that can change the contact position of at least one holding portion that is in contact with the living body, in a state in which the position of the sensor  20  is held. 
     Although only two holding portions are shown in the example shown in  FIG. 8 , it suffices that the number of the holding portions is two or more in Embodiment 3 as well. For example, the number of the holding portions may be three or more. Further, in the case where the number of holding portions are three or more in Embodiment 3, the mount unit  90  may be fixed using only some of the holding portions (for example, two holding portions), or may be fixed using all of the holding portions. 
     In Embodiment 3 as well, the measurement apparatus includes a sensor unit  90  and a control unit as with Embodiment 1. The control unit may be the same as the control unit  40  shown in  FIG. 3  in Embodiment 1. In this case, the measurement apparatus according to Embodiment 3 can be configured by attaching the control unit to the sensor unit  90 . 
     Sensor Fixation Method 
     Next, a sensor fixation method according to Embodiment 3 of the present invention will be described with reference to  FIGS. 9A to 10D .  FIGS. 9A and 9B  show a series of main steps constituting a sensor fixation method according to Embodiment 3 of the present invention.  FIGS. 10C and 10D  show a series of main steps constituting a sensor fixation method according to Embodiment 3 of the present invention, which are executed after execution of the step shown in  FIG. 9B . 
     In the example shown in  FIGS. 9A to 10D , a sensor unit  100  is disposed on the skin of a living body  60 , and the tip portion of the sensor  20  is placed under the skin of the living body  60 . 
     As shown in  FIG. 9A , the mount unit  90  constituting the sensor unit  100  is adhered to the skin of the living body  60  with one of the adhesive material layers  93  of each of the holding portions  92   a  and  92   b . However, the adhesive material layers  93   a  in use have been degraded and needs to be replaced. On the other hand, a separator film  94  is attached to unused adhesive material layers  93  of the holding portions  92   a  and  92   b.    
     Next, as shown in  FIG. 9B , only the holding portion  92   a  is moved in the direction away from the living body  60 , i.e., moved upward, and the degraded adhesive material layer  93   a  of the holding portion  92   a  is detached from the living body. At this time, the holding portion  92   b  is left as is, and therefore, the mount unit  90  is kept fixed to the living body  60  with the adhesive material layer  93   a  of the holding portion  92   b.    
     Next, as shown in  FIG. 10C , the holding portion  92   a  is rotated, and the separator film  94  of an unused adhesive material layer  93  is detached. Thereafter, the holding portion  92   a  is further rotated, and thereby the adhesive material layer  93  from which the separator film  94  has been detached is faced toward the living body  60  instead of the degraded adhesive material layer  93   a.    
     Next, as shown in  FIG. 10D , the holding portion  92   a  is moved horizontally. Thereafter, the holding portion  92   a  is moved in the direction toward the living body  60 , i.e., downward, before the adhesive material layer  93  from which the separator film  94  has been detached in the step shown in  FIG. 10C  is adhered to the living body  60 . Thereafter, the above-described upward movement, detachment of the separator film, rotation, horizontal movement, and adhesion by the new adhesive material layer are similarly performed for the holding portion  92   b  as well. 
     Consequently, according to Embodiment 3 as well, it is possible to detach the degraded adhesive material layer  93   a  (see  FIG. 9A ) from the living body  60  and replace the degraded adhesive material layer  93   a  with a new adhesive material layer  93 , while keeping the sensor  20  fixed, as with Embodiment 1. 
     Furthermore, according to Embodiment 3, it is possible to change the portion of the skin that is in contact with the adhesive material layer  93  by horizontal movement of the holding portions  92   a  and  92   b , and therefore it is possible to suppress a skin irritation resulting from a long period of contact between the skin and the adhesive material layer  93 , as with the modification of Embodiment 2. In addition, according to Embodiment 3, the holding portions  92   a  and  92   b  are housed inside the main body portion  91 , and therefore the detachment of the adhesive material layer  93  from the living body  60  due to external force applied to the holding portions  92   a  and  92   b  is also suppressed. 
     Embodiment 4 
     Next, a mount unit, a sensor unit, a measurement apparatus, and a sensor fixation method according to Embodiment 4 of the present invention will be described with reference to  FIGS. 11 and 12 . 
     Mount Unit, Sensor Unit, and Measurement Apparatus First, the configuration of a mount unit, a sensor unit, and a measurement apparatus according to Embodiment 4 will be described with reference to  FIG. 11 . 
       FIG. 11  is a perspective view showing a mount unit according to Embodiment 4 of the present invention. 
     As shown in  FIG. 11 , a sensor unit  120  includes a mount unit  110  and a sensor  20  in Embodiment 4. The sensor  20  is the same as the sensor described in Embodiment 1 with reference to  FIG. 2 . 
     The mount unit  110  includes a main body portion  111  to which holding portions  112   a  to  112   e  are attached. As with the holding portions  12   a  to  12   d  shown in  FIG. 1  in Embodiment 1, the holding portions  112   a  to  112   e  are formed in an arm shape and attached to the side face of the main body portion  111  via a hinge mechanism (not shown in  FIG. 11 ). 
     For each of the holding portions  112   a  to  112   e  as well, mobilization of the holding portions with the hinge mechanism  15  allows for selection between the state in which the adhesive material layer  113  is in contact with the living body and the state in which the adhesive material layer  113  is separate from the living body. Further, an adhesive material layer  113  capable of adhering to the living body is provided on the face of each holding portion on the living body side. 
     In this manner, the mount unit  110  includes movable holding portions in Embodiment 4 as with the mount unit  10  shown in  FIG. 1  in Embodiment 1. However the mount unit  110  is different from the mount unit  10  in the following aspects. 
     In Embodiment 4, the mount unit  110  includes a mechanism that can change the contact position of at least one holding portion that is in contact with the living body, in a state in which the position of the sensor  20  is held. Specifically, in Embodiment 4, the main body portion  111  includes an upper portion  111   a , a middle portion  111   b , and a lower portion  111   c . Of these, the upper portion  111   a  and the lower portion  111   c  are each attached to the middle portion  111   b  such that they are independently rotatable in the direction indicated by the arrows in  FIG. 11 . The sensor  20  and electrodes  115  are attached to the middle portion  111   b  and remain stationary even if the upper portion  111   a  and the lower portion  111   c  are rotated. 
     Of the holding portions, the holding portions  112   a ,  112   c , and  112   e  are attached to the lower portion  111   c . Also, the holding portions  112   a ,  112   c , and  112   e  are formed so as not to prevent rotation of the upper portion  111   a  when they are separated from the living body (when they are lifted up). 
     On the other hand, the holding portions  112   b  and  112   d  are attached to the upper portion  111   a . The holding portions  112   b  and  112   d  are formed so as not to prevent rotation of the lower portion  111   c  when they are brought into contact with the living body (when they are lifted down). In other words, the holding portions  112   b  and  112   d  are formed so as to come into contact with the living body when they are lifted down, at positions further removed than the holding portion  112   a ,  112   c , an  112   e , so as not to come into contact with the lower portion  111   c.    
     In the example show in  FIG. 11 , the holding portions  112   a ,  112   c , and  112   e  are in the state in which the adhesive material layers  113  are in contact with the living body. On the other hand, the holding portions  112   b  and  112   d  are in the state in which the adhesive material layers  113  are separate from the living body. Also, a separator film  114  is attached to the adhesive material layers  113  of the holding portions  112   b  and  112   d  for protecting the adhesive material layers  113 . In  FIG. 11 , the separator films  114  are diagonally hatched. Note that illustration of the separator film  114  attached to the adhesive material layer  13  of the holding portion  112   d  is omitted. 
     Sensor Fixation Method 
     Next, a sensor fixation method according to Embodiment 4 of the present invention will be described with reference to  FIG. 12 .  FIGS. 12A to 12C  show a series of main steps constituting a sensor fixation method according to Embodiment 4 of the present invention. 
     In the example shown in  FIGS. 12A to 12C , the sensor unit  120  is disposed on the skin of a living body  60 , and the tip portion of the sensor  20  is placed under the skin of the living body  60 . 
     As shown in  FIG. 12A  the mount unit  110  constituting the sensor unit  120  is adhered to the skin of the living body  60  with the adhesive material layers  113  of the holding portions  112   a ,  112   c , and  112   e . However, the adhesive material layers  113  of at least one of the holding portions  112   a ,  112   c , and  112   e  has been degraded and needs to be replaced. On the other hand, the adhesive material layers  113  of the holding portions  112   b  and  112   d  are unused, and therefore a separator film  114  is attached thereto. 
     Next, after the separator films  114  are detached from the adhesive material layers  113 , the holding portions  112   b  and  112   d  are lifted down and the adhesive material layers  113  thereof are adhered to the living body  60  as shown in  FIG. 12B . At this time, the position of contact between each of the holding portions  112   b  and  112   d  and the living body  60  can be selected by rotating the upper portion  111   a.    
     Next, as shown in  FIG. 12C , the holding portions  112   a ,  112   c , and  112   e  are brought into the lifted state (the state in which they are separate from the living body  60 ). Then, in this state, the degraded adhesive material layer  113  is replaced. 
     Thereafter, in the case where the adhesive material layers  113  of the holding portions  112   b  and  112   d  have been degraded, the position of the contact between each of the holding portions  112   a ,  112   c , and  112   e  and the living body  60  is selected by rotating the lower portion  111   c , and then the holding portions  112   a ,  112   c , and  112   e  are brought into contact with the living body  60  again. Then, the holding portions  112   b  and  112   d  are brought into the lifted state. 
     In this manner, according to Embodiment 4, it is possible to detach a degraded adhesive material layer  113  from the living body  60 , while keeping the sensor  20  fixed, as with Embodiment 1. Furthermore, it is also possible to replace a degraded adhesive material layer  113  with a new adhesive material layer, while keeping the sensor  20  fixed. 
     Furthermore, according to Embodiment 4, the upper portion  111   a  and the lower portion  111   c  can be rotated independently, thus making it possible to change the portion of the living body that is in contact with the adhesive material layer  113 , while keeping the sensor  20  fixed. Therefore, according to Embodiment 4 as well, it is possible to suppress a skin irritation resulting from a long period of contact between the skin and the adhesive material layer  113 , as with the modification of Embodiment 2 and Embodiment 3. 
     The whole or part of the exemplary embodiments disclosed above can be described as, but not limited to, the following Supplementary note s. 
     Supplementary Note 1 
     A mount unit including: 
     a main body portion that holds a placement of a portion of a sensor under the skin of a living body; and 
     two or more holding portions attached to the main body portion, 
     wherein each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 2 
     The mount unit according to supplementary note 1, 
     wherein each of the two or more holding portions is attached to the main body portion via a hinge mechanism, and 
     mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 3 
     The mount unit according to supplementary note 1, 
     wherein each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, and 
     movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 4 
     The mount unit according to supplementary note 3, wherein each of the two or more holding portions is attached to the main body portion so as to further be rotatable with respect to the main body portion. 
     Supplementary Note 5 
     The mount unit according to supplementary note 4, wherein a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation. 
     Supplementary Note 6 
     The mount unit according to supplementary note 1, wherein the main body portion includes a mechanism that can change a contact position of at least one of the holding portions that is in contact with the living body, in a state in which the position of the sensor is held. 
     Supplementary Note 7 
     A sensor unit including: a sensor of which a portion can be placed under the skin of a living body; and a mount unit for fixing the sensor to the living body, 
     wherein the mount unit includes: 
     a main body portion that holds a placement of the portion of the sensor under the skin of the living body; and 
     two or more holding portions attached to the main body portion, and 
     each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state where the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 8 
     The sensor unit according to supplementary note 7, wherein each of the two or more holding portions is attached to the main body portion via a hinge mechanism, and 
     mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 9 
     The sensor unit according to supplementary note 7, 
     wherein each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, and 
     movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 10 
     The sensor unit according to supplementary note 9, wherein each of the two or more holding portions is attached to the main body portion so as to further be rotatable with respect to the main body portion. 
     Supplementary Note 11 
     The sensor unit according to supplementary note 10, wherein a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation. 
     Supplementary Note 12 
     The sensor unit according to supplementary note 7, wherein the main body portion includes a mechanism that can change a contact position of at least one of the holding portions that is in contact with the living body, in a state in which the position of the sensor is held. 
     Supplementary Note 13 
     A measurement apparatus for measuring numeric information relating to a substance contained in at least one of interstitial fluid and blood that are under the skin of a living body, the apparatus including; 
     a sensor of which a portion can be placed under the skin and that generates a signal dependent on the numeric information; 
     a mount unit for fixing the sensor to the living body; and 
     a control unit that receives the signal generated by the sensor and executes processing that includes digital signal processing on the signal; 
     wherein the mount unit includes a main body portion that holds a placement of the portion of the sensor under the skin of the living body; and
         two or more holding portions attached to the main body portion, and   each of the two or more holding portions includes an adhesive material layer capable of adhering to the living body and is movable so as to allow for selection between a state where the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body.       

     Supplementary Note 14 
     The measurement apparatus according to supplementary note 13, wherein the control unit executes transmission processing for transmitting the signal that has been subjected to digital signal processing to an external measuring device. 
     Supplementary Note 15 
     The measurement apparatus according to supplementary note 13, 
     wherein each of the two or more holding portions is attached to the main body portion via a hinge mechanism, and 
     mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 16 
     The measurement apparatus according to supplementary note 13, wherein each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, and 
     movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body. 
     Supplementary Note 17 
     The measurement apparatus according to supplementary note 16, wherein each of the two or more holding portions is attached to the main body portion so as to further be rotatable with respect to the main body portion. 
     Supplementary Note 18 
     The measurement apparatus according to supplementary note 17, wherein a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation. 
     Supplementary note 19 
     The measurement apparatus according to supplementary note 13, wherein the main body portion includes a mechanism that can change a contact position of at least one of the holding portions that is in contact with the living body, in a state in which the position of the sensor is held. 
     Supplementary Note 20 
     A sensor fixation method for fixing, to a living body, a sensor of which a portion can be placed under the skin of the living body, the method including the steps of: 
     (a) using a mount unit that includes a main body portion and two or more holding portions attached to the main body portion, each of the two or more holding portions including an adhesive material layer capable of adhering to the living body and attached to the main body portion so as to allow for selection between a state in which the adhesive material layers are in contact with the living body and a state in which the adhesive material layers are separate from the living body, and holding the sensor by the main body portion of the mount unit; 
     (b) fixing the mount unit to the living body by bringing the adhesive material layer of at least one of the two or more holding portions of the mount unit into contact with the living body; and, 
     (c) in a case where any of the adhesive material layers of the two or more holding portions needs to be replaced, moving the holding portion including the adhesive material layer that needs to be replaced, in a state in which the adhesive material layer of at least one of the holding portions is in contact with the living body, and detaching the adhesive material layer that needs to be replaced from the living body. 
     Supplementary Note 21 
     The sensor fixation method according to supplementary note 20, 
     wherein each of the two or more holding portions is attached to the main body portion via a hinge mechanism, 
     mobilization of the holding portions with the hinge mechanism allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body, and,
         in step (c), the adhesive material layer that needs to be replaced is detached from the living body by mobilization of the holding portions with the hinge mechanism.       

     Supplementary Note 22 
     The sensor fixation method according to supplementary note 20, 
     wherein each of the two or more holding portions is attached to the main body portion so as to be movable in a direction toward the living body and a direction away from the living body, 
     movement of the holding portions allows for selection between a state in which the adhesive material layer is in contact with the living body and a state in which the adhesive material layer is separate from the living body, and, 
     in step (c), the adhesive material layer that needs to be replaced is detached from the living body by movement of the holding portions. 
     Supplementary Note 23 
     The sensor fixation method according to supplementary note 22, wherein each of the two or more holding portions is attached to the main body portion so as to be rotatable with respect to the main body portion. 
     Supplementary Note 24 
     The sensor fixation method according to supplementary note 23, 
     wherein a plurality of the adhesive material layers are provided on an outer face of each of the two or more holding portions in the direction of rotation, and, 
     in step (c), a new adhesive material layer replacing the adhesive material layer that needs to be replaced is faced toward the living body by rotation of the holding portions, and thereafter the new adhesive material layer is adhered to the living body by movement of the holding portions. 
     As described above, according to the present invention, in the case where adhesive tape or the like is used for fixing a mount of an embedded sensor to a living body, it is possible to easily replace the adhesive tape while preventing external force from being applied to the sensor. The present invention is particularly useful in the filed of CGM, in which such a demand exists. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.