Patent Publication Number: US-2019175018-A1

Title: System for Sensing of a Parameter of a Living Being and an Electronic Unit for Use in a System

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a non-provisional patent application claiming priority to European Patent Application No. 17205852.1 filed Dec. 7, 2017, the contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a system for sensing of a parameter of a living being. In particular, the present disclosure relates to a system comprising a unit carrying at least one sensor and associated sensor circuitry for sensing the parameter, wherein the unit may be attached to a body part. 
     BACKGROUND 
     To measure biopotentials or other parameters associated to potentials or bioimpedance on the human body, adhesive patches containing electrodes and sensor circuitry may be used. These patches may be placed at different positions where measurements are to take place. The patches may be disposable for hygienic reasons and thus might not be re-used on different persons. Also, electrodes degrade when in contact with skin which may make re-use of patches difficult. For this reason, it may be desirable to make an adhesive patch unit as simple as possible in order to minimize costs of the disposable patch unit. 
     The circuitry in the adhesive patch may be configured to transmit sensor data to a remote unit, such that the adhesive patch may need very limited processing capacity. Further, the circuitry in the adhesive patch may be configured to be powered by the remote unit such that the adhesive patch need not comprise a battery. 
     In Rose, D. P et al, “Adhesive RFID sensor patch for monitoring of sweat electrolytes,” IEEE Transactions on Biomedical Engineering, vol. 62, no. 6, June 2015, pp. 1457-1465, an adhesive radio-frequency identification (RFID) sensor patch is disclosed. The patch is battery-free, and is powered and read wirelessly by an Android smartphone and custom-app. The adhesive patch includes a Si-based chip. The system of the patch and the smartphone is relatively bulky. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides a system for sensing a parameter of a living being, wherein the system may facilitate continuous monitoring of the living being over a long time frame, while allowing use of inexpensive disposable parts. 
     According to some embodiments of the present disclosure, there is provided a system for sensing of a parameter of a living being, the system comprising a thin film transistor (TFT) unit being configured for attachment to a body part of the living being, and the TFT unit comprising at least one sensor with associated sensor circuitry for sensing the parameter of the living being, wherein the TFT unit comprises an antenna for short-range communication. The system may also comprise an electronic unit, wherein the electronic unit and the TFT unit may be configured for detachably physically connecting the electronic unit to the TFT unit, or the electronic unit may be configured for fixed arrangement on the body part of the living being in physical contact with the TFT unit, wherein the electronic unit comprises an antenna for short-range communication, wherein the TFT unit and the electronic unit form a wireless contact between the antenna of the TFT unit and the antenna of the electronic unit for powering the TFT unit by the electronic unit and communicating sensing results from the TFT unit to the electronic unit. 
     As such, in some embodiments, an electronic unit is provided which may be physically connected to the TFT unit. By physically connecting the electronic unit to the TFT unit, a firm relation between the TFT unit and the electronic unit may be defined which may thus be maintained while the living being goes on with daily life. The electronic unit and the TFT unit may be designed for defining a detachable physical connection between the electronic unit and the TFT unit so as to control the physical relationship between the electronic unit and the TFT unit when physically connected to each other. In this regard, at least one of the electronic unit and the TFT unit may comprise a physical connection interface for defining the detachable physical connection. 
     The electronic unit may be small and lightweight so as to facilitate the electronic unit being worn by a living being while being physically connected to the TFT unit while the TFT unit is attached to a body part of the living being. 
     The electronic unit may be configured for fixed arrangement on the body part to which the TFT unit is to be attached. Accordingly, the system may be designed for arrangement on a body part of the living being such that the TFT unit is attached to the body part, and the electronic unit is arranged in a fixed relation to the body part for being worn by the living being. Hence, the system may allow for the TFT unit and the electronic unit, when worn by the living being, to be arranged in physical contact, which may further allow for the TFT unit to be powered by the electronic unit and for sensing results to be received by the electronic unit. 
     A form factor of the electronic unit may be designed for a specific arrangement of the electronic unit on the living being. For instance, the TFT unit may be formed as a patch to be attached on a wrist or arm of the living being, and the electronic unit may be formed as a wristwatch or bracelet for being worn on the arm of the living being. As another example, the TFT unit may be formed as a patch to be attached to a chest of the living being, and the electronic unit may be formed as a band to be worn over the chest of the living being. As yet another example, the TFT unit may be formed as a patch to be attached to a forehead of the living being, and the electronic unit may be formed as goggles or glasses to be worn on a head of the living being. 
     The living being may be a human being. However, the living being may also be an animal, e.g., a pet or a domesticized animal, such as a dog, cat, or horse. Thus, the system may be used for monitoring a parameter of a human being or of an animal. In the following, the discussion is mainly done in relation to a human being. However, it should be understood that the system may be similarly used on an animal instead. 
     In embodiments where the TFT unit comprises an antenna and the electronic unit comprises an antenna, the TFT unit and the electronic unit may form a wireless contact through the antennas. The wireless contact may be used for powering of the TFT unit and for communicating sensing results from the TFT unit to the electronic unit. 
     The electronic unit and the TFT unit may together comprise components that may be useful for allowing gathering of sensing results of a parameter of the living being. By arranging some components in the electronic unit, the TFT unit may be simplified and, hence, less costly to produce. For instance, the electronic unit may comprise a battery for powering the TFT unit, such that the TFT unit might not need to have a battery. By physically connecting the electronic unit and the TFT unit or placing the electronic unit in physical contact with the TFT unit, the electronic unit may be maintained close to the TFT unit, such that continuous monitoring of the parameter may be possible. 
     The use of thin film transistor technology of the TFT unit may also reduce the costs of producing the TFT unit. The antenna of the TFT unit may be printed on a flexible substrate to provide the possibility of powering the TFT unit and communicating sensing results from the TFT unit. Thus, the antenna may be provided in a simple and inexpensive manner in the TFT unit. Further, the sensor circuitry of the TFT unit may be configured to have limited functionality in order to reduce the complexity of the sensor circuitry. 
     In combination, the reduced complexity provided by thin film transistor technology and the fact that the TFT unit does not need to have its own battery may reduce costs of producing the TFT unit. 
     Thus, the TFT unit, which might be disposable for hygienic reasons, may be less expensive. Further, in examples where the electronic unit is detachably physically connected to the TFT unit, the electronic unit may be detached from the TFT unit after the TFT unit has been used, and the electronic unit may then be re-used with another TFT unit. Thus, because the electronic unit may be re-usable, it may not be as critical that the electronic unit is very inexpensive. 
     The electronic unit may be configured to be relatively small and lightweight. For instance, even though sensing results are communicated from the TFT unit to the electronic unit, the electronic unit might not include a particularly advanced processing unit or large storage unit for processing and storing the sensing results. Rather, the electronic unit may function as an intermediate unit and further send data to a more advanced external unit. The communication between the electronic unit and the external unit may be performed using a wireless protocol with a relatively large range such that the electronic unit and the external unit need not be immediately close to each other. 
     In embodiments where the wireless contact is used for powering the TFT unit and communicating sensing results, the contact may be waterproof which may allow the system to continue working under wet conditions. Thus, a human that is being monitored may shower or engage in other activities involving water during the time of monitoring. 
     Further, by the use of a thin film transistor unit, the part of the system that is attached to a body part can be made small, thin, and lightweight and can be flexible so as to form a close, snug fit between the thin film transistor unit and the body part. This may also allow the TFT unit to be kept attached to a living being for a sufficiently long time frame. 
     In some embodiments, the TFT unit may comprise electrodes, which may form the at least one sensor. The electrodes may thus be configured to acquire a biopotential signal such that a parameter of the living being related to a biopotential measurement may be sensed. 
     In some embodiments, the TFT unit may comprise an electrode array comprising a plurality of electrodes. The TFT unit may further comprise a multiplexer, and each of the electrodes in the electrode array may be connected to the multiplexer. The TFT unit may thus enable selection of electrodes to be used in acquiring of a biopotential signal by selecting one or more outputs from the multiplexer. As such, a signal having a desired quality may be selected by selecting which electrodes are to be used for providing output from the multiplexer. Also, different measurements based on different relations between electrodes in the electrode array may be sequentially acquired by selecting which electrodes to activate by the multiplexer. 
     However, in some embodiments, the TFT unit may comprise other types of sensors or additional sensors. 
     In some embodiments, the TFT unit may comprise a photo-detector for detecting light incident on the photo-detector. The TFT unit may thus be configured to perform an optical measurement, such as detecting an absorbance or reflectance at the body part to which the TFT unit is attached, such that a parameter of the living being related to the optical measurement may be sensed. 
     In some embodiments, the TFT unit may be formed on a flexible substrate, and the sensor circuitry may be formed of thin film transistors. 
     By being formed on a flexible substrate, the TFT unit may be better suited for being attached to a living being. Thin film transistors enable use of material that is relatively flexible and can be made relatively thin, while still allowing forming of an electric circuitry. Thus, the use of thin film transistors on a flexible substrate allows the TFT unit to be made flexible and therefore suitable for being used in a TFT unit attached to a living being. 
     In some embodiments, the thin film transistors could, for instance, be formed from an organic material and/or a polymer material. As a result, the TFT unit might not be silicon-based, which may contribute to the TFT unit, which may be disposable, being less expensive. 
     In some embodiments, the TFT unit may be disposable, and the electronic unit may be re-usable with different TFT units. 
     By reducing costs of producing the TFT unit, the system may be more affordable even if the TFT unit is disposable and intended for one time use only. The TFT unit may be formed from environmentally safe materials, such that disposing of the TFT unit may have a reduced effect on the environment. As the TFT unit is to be used on living beings, the TFT unit being disposable may help reduce the transfer of diseases between living beings. 
     By being re-usable with different TFT units, the electronic unit can be used a large number of times, even if the TFT unit is disposed of. Thus, the costs of the system can be kept down. The physical connection between the electronic unit and the TFT unit may be reusable, such that detaching of the electronic unit from the TFT unit enables re-use of the electronic unit. 
     In some embodiments, the TFT unit may be configured to form a waterproof enclosure of the sensor circuitry. 
     By forming a waterproof enclosure, the TFT unit may be better suited for use in wet conditions. This may facilitate using the system for monitoring over a significantly long time as a human being may go on with daily life while wearing the TFT unit. The at least one sensor of the TFT unit, such as electrodes, may protrude from the enclosure so as to allow the at least one sensor to make contact with the body part or receive a signal that is to be measured. 
     In some embodiments, the TFT unit may be a patch comprising an adhesive for attachment to skin of the living being. 
     The patch of the TFT unit may cause the TFT unit to be better suited for being attached to a living being. The patch may further be provided with a removable film or any other type of protection for covering the adhesive before use of the patch. 
     In some embodiments, the sensor circuitry may be configured to perform modulation of an analog or digital signal for communicating sensing results to the electronic unit. 
     The sensing results may be overlaid as modulations on a carrier signal that may be communicated to the electronic unit. Thus, the communication of sensing results may be performed with reduced complexity or in a simplified manner, allowing the TFT unit to be based on simplified or less complex circuitry. 
     In some embodiments, the TFT unit may be configured to pre-process sensing results before communicating the sensing results to the electronic unit. Thus, some pre-processing may be performed in the TFT unit while still allowing the TFT unit to be relatively simple and inexpensive. For instance, the sensor circuitry of the TFT unit may comprise circuitry for converting an acquired analog signal into time domain or into a digital signal and also performing further pre-processing of the acquired signal (e.g., some filtering of the signal). 
     In some embodiments, the electronic unit may comprise a processor unit for processing received sensing results. 
     By including a processor unit in the electronic unit, the sensing results may be processed by the electronic unit. As such, the electronic unit may analyze the sensing results, e.g., to extract features relating to the parameter of the living being. Thus, the electronic unit may store and/or forward only processed sensing results, thereby reducing the amount of data may be stored and/or transmitted. 
     The processor unit may be configured to perform basic analysis of the sensing results, e.g., in order to provide sensing results in a manner that may be better understood or reviewed by a doctor or a user of the system. However, the processor unit may not necessarily be configured to perform deeper analysis of the sensing results. Rather, advanced analysis which may require relatively large processing resources may be performed by an external unit that may eventually receive the sensing results. 
     In some embodiments, the electronic unit may comprise a memory for storing sensing results. 
     Storing sensing results allows for retrieval and further processing of the sensing results. The sensing results may be stored as such in the memory, e.g., as raw data. Alternatively or additionally, sensing results that have been processed by the processing unit may be stored in the memory. 
     The memory may function as a buffer memory in order to temporarily store sensing results that are to be transmitted to an external unit. Thus, the electronic unit may be set up to simply forward any sensing results to an external unit, e.g., through wireless communication with the external unit. The memory may then be used as a buffer memory for storing recent sensing results. Thus, sensing results may not be lost if a connection to the external unit is temporarily lost or data transfer is too slow. 
     Alternatively or additionally, the memory may function as a relatively long-term memory, wherein some or all sensing results acquired during a session of use of the system may be stored in the memory. Thus, the electronic unit may not necessarily need to communicate with an external unit during the session of acquiring sensing results. 
     In some embodiments, the electronic unit may comprise a communication unit for communication with an external unit. 
     The communication unite may allow for transfer of sensing data and/or results to an external unit which can have increased storage and/or processing power compared to the electronic unit, allowing further processing of the sensing results and/or data. The external unit may be remote from the electronic unit and may thus not even be worn by the living being that is monitored. 
     In examples where the electronic unit comprises a communication unit, the electronic unit may not even include a processing unit. The electronic unit having a communication unit may be set up to continuously transfer sensing results through the communication unit to an external unit, such that no processing of sensing results is performed in the electronic unit. 
     However, in some embodiments, the communication unit may not be configured for wireless communication to the external unit. Instead, the communication unit may comprise an output port for physically connecting the external unit to the electronic unit. Thus, the sensing results may, for instance, be communicated to the external unit after a session of acquiring sensing results, e.g., by plugging a universal serial bus (USB) stick in the output port. The electronic unit may be provided with a cover or cap for protecting the output port and the electronic unit during acquiring of sensing results, e.g., so as to prevent water from entering the electronic unit. 
     In some embodiments, the electronic unit may comprise a battery. 
     The battery may be used for powering the system. The battery may allow storing of energy in the electronic unit, such that the electronic unit may provide power to the system during an entire session of acquiring sensing results, such as for an entire day or even longer. 
     In some embodiments, the battery may be rechargeable, and the electronic unit may be configured for wireless charging of the battery. 
     Wireless charging allows for charging of the battery without any physical connections. Thus, the electronic unit may not comprise a connection for plugging an external power source into the electronic unit, which may reduce the risk that the electronic unit is damaged by water entering the connection during use. 
     In some embodiments, the electronic unit may be configured for charging the battery through a physical connection to a power source. An output port in which the physical connection is formed may be covered during acquiring of sensing results, so as to protect the electronic unit. For instance, the battery may be charged while connecting an external unit to the electronic unit for transferring sensing results to the external unit. In some examples, the battery may be charged by a USB stick. 
     In some embodiments, the electronic unit may comprise a housing providing a waterproof enclosure of components of the electronic unit. 
     The waterproof enclosure may allow the electronic unit to continue to function in wet environments. The waterproof enclosure may partially or completely seal the electronic unit and may protect the components of the electronic unit from outside conditions. Since the electronic unit may be configured to power the TFT unit and receive the sensing results through a wireless contact and the electronic unit may further be configured for wireless charging of the battery and wireless communication with an external unit, the waterproof enclosure may be provided without any openings or connections through the housing, while still allowing the electronic unit to function as described herein. 
     In some embodiments, the wireless contact between the TFT unit and the electronic unit may be formed through an inductive or capacitive coupling between the antenna of the TFT unit and the antenna of the electronic unit. 
     An inductive or capacitive coupling may allow the TFT unit and the electronic unit to form a wireless connection for transferring power to the TFT unit and sensing results to the electronic unit. This may allow the TFT unit and electronic unit to be in contact without any openings of the TFT unit or electronic unit. The units can thus be made waterproof and more robust while still allowing them to be in contact. 
     Further, having a wireless contact based on inductive or capacitive coupling may allow for the antennas in the TFT unit and the electronic unit to have a reduced complexity and to be relatively simple. 
     In some embodiments, communication between the TFT unit and the electronic unit may be performed using radio frequency identification (RFID) communication or near field communication (NFC). 
     RFID communication or NFC are suitable protocols for providing a wireless, short-range connection. Thus, these types of communication may be well suited for use by the TFT unit and the electronic unit, which may be configured to be in close relation to each other. 
     In some embodiments, the electronic unit and the TFT unit may be configured for detachably physically connecting the electronic unit to the TFT unit by using at least one of: an adhesive, a magnetic coupling, or one or more interlocking elements, such as hook and loop fasteners. 
     A user may thus connect the electronic unit to the TFT unit using various connecting mechanisms. The physical connection may provide a firm relation between the TFT unit and the electronic unit, such that the connection may be maintained even when the living being wearing the TFT unit is moving around. Any other type of detachable physical connections for providing a physical connection that is attachable and detachable without damaging the TFT unit and/or the electronic unit may be used as well. 
     According to some embodiments of the present disclosure, there is provided an electronic unit for use in a system for sensing of a parameter of a living being, the electronic unit comprising: a physical connection interface configured for detachably physically connecting the electronic unit to a thin film transistor (TFT) unit; and a wireless communication unit for forming an inductive or capacitive coupling to the TFT unit for powering the TFT unit and receiving sensing results from the TFT unit. 
     The electronic unit may allow for a simple TFT unit to be used. The electronic unit may be re-usable and may therefore allow for a disposable part of the system to be maintained as inexpensive as possible. 
     The electronic unit may function as an intermediate unit between the TFT unit and an external unit having more extensive processing resources. Thus, the electronic unit may also be relatively simple and may provide limited functionalities so as to ensure that the electronic unit is small and lightweight, thereby allowing the electronic unit to be physically connected to the TFT unit while the TFT unit is used for sensing a parameter of a living being. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified drawing of a system, according to an example embodiment. 
         FIG. 2  is a simplified drawing illustrating a physical connection of a thin film transistor unit and an electronic unit of the system depicted in  FIG. 1 , according to an example embodiment. 
         FIG. 3  is a schematic view of internal components of the thin film transistor unit and the electronic unit depicted in  FIG. 2 , according to an example embodiment. 
         FIG. 4  is a simplified drawing of a system, according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a system  100  according to an example embodiment for sensing a parameter of a living being. The system  100  includes a thin film transistor (TFT) unit  110  and an electronic unit  120 . An external unit  200  is also shown in  FIG. 1 . The external unit  200  may be part of the system  100  and may, in some examples, be a specially adapted unit for cooperating with the other parts of the system  100 . However, in other examples, the external unit  200  may be any conventional external unit  200  having data processing capability, possibly provided with a specific software application relating to the system  100  for sensing a parameter of a living being. 
     The TFT unit  110  is configured for being attached to a living being, e.g., a human being. The electronic unit  120  and the TFT unit  110  are detachably physically connected to each other. The TFT unit  110  and the electronic unit  120  are together configured to monitor a living being and gather sensing results of a parameter of the living being. Some of the components for monitoring and gathering may be situated in the TFT unit  110 , and some may be situated in the electronic unit  120 . In order to reduce costs of the TFT unit  110 , the number and/or complexity of components in the TFT unit  110  may be reduced. 
     The system  100  may be designed such that the TFT unit  110  is disposable and the electronic unit  120  is re-usable. When the TFT unit  110  is disposed of, the TFT unit  110  and the electronic unit  120  are detached from each other, and the electronic unit  120  can be detachably physically connected to a new TFT unit  110 . The new TFT unit  110  can be attached to the same human being, as the TFT unit  110  which was disposed was attached to, or to another human being. Thus, the electronic unit  120  may be re-used for different sessions of sensing a parameter of a human being, either for the same person or for different persons. 
     The electronic unit  120  can be connected to an external unit  200 , either by a wire or wirelessly. The electronic unit  120  may thus transfer sensing results to the external unit  200 , which may have larger processing resources for processing and/or analyzing the sensing results. Thus, the electronic unit  120  may be relatively simple and might not be configured to perform complex processing of sensing results. 
     Transfer of sensing results to the external unit  200  may be performed in real-time. In such an embodiment, the electronic unit  120  may be connected to the external unit  200  using a wireless connection. As such, the external unit  200 , in some examples, might not be connected through a physical wire to the electronic unit  120  during gathering of sensing results. 
     Alternatively, transfer of sensing results to the external unit  200  may be performed after a session of gathering sensing results has been completed. The electronic unit  120  may then be detached from the TFT unit  110 , before being connected, through a wired or wireless connection, to the external unit  120  for transferring sensing results. 
     The TFT unit  110  includes at least one sensor  112  and associated sensor circuitry  114  for sensing a parameter of a human being. According to an embodiment, the at least one sensor  112  may comprise electrodes adapted for sensing a biopotential or bioimpedance signal of the human being. According to another embodiment, the at least one sensor  112  may comprise a photo-detector for detecting incident light on the photo-detector. The photo-detector may thus be configured to make an optical measurement, e.g., for determining a reflectance or absorbance of a body part, such as tissue, of the human being to which the TFT unit  110  is attached. 
     The TFT unit  110  and the electronic unit  120  may form a wireless contact when the electronic unit  120  is physically connected to the TFT unit  110 . The electronic unit  120  may power the TFT unit  110  through this wireless contact. Sensing results may also be communicated from the TFT unit  110  to the electronic unit  120  through this wireless contact. As mentioned above, the electronic unit  120  may communicate sensing results to the external unit  200 . 
     As a result of the wireless contact being formed between the TFT unit  110  and the electronic unit  120 , the TFT unit  110  may comprise a watertight housing  116  enclosing and protecting the sensor circuitry  114  while allowing the TFT unit  110  to be powered and to communicate with the electronic unit  120 . Likewise, the electronic unit  120  may also comprise a watertight housing  122  enclosing and protecting components of the electronic unit  120 . Accordingly, in some examples, both the TFT unit  110  and the electronic unit  120  may be used in wet environments, such that the TFT unit  110  and the electronic unit  120  may, e.g., be worn by a human being while showering. 
     The electronic unit  120  may further comprise a battery  124 . The electronic unit  120  may thus be configured to power the TFT unit  110  using energy stored in the battery  124 . In order for the electronic unit  120  to be re-usable a number of times, the battery  124  may be rechargeable. The electronic unit  120  may be configured for allowing the battery  124  to be wirelessly recharged. Accordingly, in some examples, the electronic unit  120  might not comprise a battery lid for allowing changing batteries or a port for allowing the electronic unit  120  to be plugged into an external power source for charging the battery  124 . Hence, the battery  124  may be arranged inside a watertight housing, which may further facilitate use of the electronic unit  120  in a wet environment. 
     The system  100  may enable monitoring, such as continuous monitoring, of a parameter of a human being using an inexpensive disposable TFT unit  110  and a re-usable electronic unit  120 , where the electronic unit  120  may provide further functionalities that are not provided by the TFT unit  110 . 
     The TFT unit  110  and the electronic unit  120  may be configured to be worn by a human being in a manner such that the TFT unit  110  and the electronic unit  120  may not significantly adversely affect the human being in daily life while the sensing results are gathered. For instance, no wired connection to an external unit  200  may be used during gathering of sensing results, or an external unit  200  need not be in close proximity to the TFT unit  110  or the electronic unit  120  during gathering of sensing results. 
     Further, the TFT unit  110  and the electronic unit  120  may comprise watertight enclosures such that the TFT unit  110  and/or the electronic unit  120  may avoid being damaged even if they come in contact with water, such as if the human being is taking a shower while wearing the TFT unit  110  and the electronic unit  120 . 
       FIG. 2  illustrates a TFT unit  110  and an electronic unit  120 . The TFT unit  110  and the electronic unit  120  may be detachably physically connectable to each other. 
     The TFT unit  110  may be made sufficiently small, thin, and lightweight, such that it may be attached to and carried by a human being while the human being goes on with daily life. 
     The TFT unit  110  may include or take the form of a patch. The TFT unit  110  may have a first side and a second side. The first side may be configured to be attached to a human being. If so, it may be attached such that the attachment can withstand water, moisture, and/or damp environments. The first side may be attachable by an adhesive. The TFT unit  110  may be suitable to be attached to a human being. The first side may be attachable to a human being such that it can be detached and reattached. 
     The TFT unit  110  may comprise a flexible substrate. The flexible substrate may be an organic material. The flexible substrate may alternatively be a polymer material. The substrate may be flexible in a sense that the substrate may adapt to and take a shape so as to follow a contour of a human being, such as a portion of skin of the human being, e.g., on an arm of the human being. The substrate may further be flexible in that the substrate may change shape so as to adapt to changes in the shape of the portion of skin while the human being moves around and goes on with daily life. 
     The TFT unit  110  may be waterproof. The TFT unit  110  may provide a watertight enclosure of components within the TFT unit  110  in various ways. For instance, the flexible substrate may provide a water barrier to components, such as the sensor circuitry  114  which may be printed on the flexible substrate. Another layer of flexible water repellent material may be added on top of the components such that components within the TFT unit  110  are surrounded by watertight material. In some examples, a separate outer housing  116  of the TFT unit  110  may be watertight so that water or moisture is inhibited from passing through the outer housing  116 . For instance, the outer housing  116  may be a single part and thus have no joints between parts. 
     The at least one sensor  112  of the TFT unit  110  may extend through the enclosure. For instance, if the at least one sensor  112  comprises electrodes, the electrodes may extend through the enclosure so as to allow the electrodes  112  to be in direct contact with the human being, e.g., with skin of the human being. 
     If the at least one sensor  112  need not be in direct contact with the human being, the at least one sensor  112  may be arranged within the enclosure. For instance, if the enclosure is transparent, a photo-detector may be arranged inside the enclosure while enabling the photo-detector to receive light. 
     The second side of the TFT unit  110  may be configured such that the TFT unit  110  may form a detachable physical connection with the electronic unit  120 . For instance, the TFT unit  110  may comprise a physical connector interface for providing an interface for connecting to the electronic unit  120 . The physical connector interface may include an element on an outer surface, wherein the element is configured for interacting with a corresponding element on the electronic unit  120 . Similarly, the electronic unit  120  may comprise a physical connector interface for providing an interface for connecting to the TFT unit  110 . 
     The TFT unit  110  and the electronic unit  120  may be detachably physically connected to each other by an adhesive, a magnetic coupling, a hook and loop fastening, or one or more interlocking elements. The detachable physical connection may be achieved based on an element arranged on just one of the two units. Alternatively, the detachable physical connection may be achieved based on cooperating elements which are arranged on each of the units. The detachable physical connection may, for instance, include or take the form of a snap fastener, as illustrated in  FIG. 2 . As another example, the TFT unit  110  and the electronic unit  120  may comprise a threaded part such that the detachable physical connection may be formed by screwing the electronic unit  120  into or onto the TFT unit  110 . As another example, the detachable physical connection may be formed between a protrusion formed on one of the TFT unit  110  and electronic unit  120  and a matching indentation formed on the other one of the TFT unit  110  and electronic unit  120 . As yet another example, the detachable physical connection may be formed by a clip connection, the clip situated on one of the TFT unit  110  and the electronic unit  120 . The detachable physical connection may be strong and robust enough that the TFT unit  110  and the electronic unit  120  remains connected while the system is attached to a human being. 
     The electronic unit  120  may be made sufficiently small and lightweight such that it may be carried by a human. Thus, the electronic unit  120 , when physically connected to the TFT unit  110  that is attached to the human being, does not significantly obstruct the human being in daily life. 
     The electronic unit  120  may be waterproof, such that the electronic unit  120  may comprise outer layers of water repellent material enclosing components of the electronic unit  120 . For instance, the electronic unit  120  may comprise an outer housing  122  being watertight so that water or moisture is not allowed to pass through the outer housing  122 . For instance, the outer housing  122  may be a single part and thus have no joints between parts. All components of the electronic unit  120  may be arranged inside the housing  122  so as to ensure that the housing  122  is waterproof. However, some components may partly extend through the housing  122 , e.g., a light guide for providing a user interface, such as by allowing a status of the electronic unit  120  to be indicated. 
     The detachable physical connection may also be waterproof, in that the detachable physical connection itself is not adversely affected by water, moisture, or damp environments. However, because the physical connection between the TFT unit  110  and the electronic unit  120  might not include any electrical components, in some examples, the detachable physical connection might not be waterproof. 
     Both the TFT unit  110  and the electronic unit  120  may be robust enough that they withstand the wear and tear that comes with being attached to a human being while the human being goes on with daily life. As the electronic unit  120  may be re-used, the electronic unit  120  may be especially robust to withstand the wear and tear from long-time use while being attached to a human being. 
       FIG. 3  illustrates a TFT unit  110  and an electronic unit  120  with their respective components according to an example embodiment where the at least one sensor  112  comprises electrodes. 
     The TFT unit  110  may include electrodes  112  and associated sensor circuitry  114 . The sensor circuitry  114  may include thin film transistors forming the circuitry  114 . 
     The sensor circuitry  114  may include a modulator  114   a  for modulating an analog or digital signal, such as for generating a signal carrying sensing results that may be transmitted to the electronic unit  120 . The TFT unit  110  may further include circuitry  114   b  for extracting power from a signal from the electronic unit  120 . The circuitry  114   b  may, for instance, comprise a rectifier and regulator circuit. 
     The electrodes  112  and associated sensor circuitry  114  may sense a biopotential of a human being. The electrodes  112  and associated circuitry  114  may be configured such that they sense a biopotential of a human being when the electrodes  112  are in contact with skin of a human being. 
     The TFT unit  110  may include a processor for pre-processing sensing results received from electrodes  112 . The processor may, for example, also convert a signal carrying sensing results into a digital signal. The processor may, for example, also perform filtering of a signal carrying sensing results. The processor of the TFT unit  110  may be a specific piece of circuitry configured for a specific process. 
     In some embodiments, the TFT unit  110  may comprise an electrode array comprising a plurality of electrodes  112 . The associated sensor circuitry  114  may further comprise a multiplexer, to which the electrodes  112  may be connected. The lines for connecting each of the electrodes to the multiplexer may be formed in thin film transistor electronics of the TFT unit  110 . The multiplexer may be configured to output a signal to the modulator  114   a  for generating a signal carrying sensing results that may be transmitted to the electronic unit  120 . The multiplexer may thus selectively provide output based on signals detected by electrodes  112  in the array. 
     The TFT unit  110  and the electronic unit  120  may each include elements for forming a wireless coupling between the TFT unit  110  and the electronic unit  120 . The wireless coupling between the TFT unit  110  and the electronic unit  120  may be an inductive coupling or a capacitive coupling. As illustrated in  FIG. 3 , the TFT unit  110  may thus comprise an antenna  118 , here illustrated in the form of an inductor  118 , and the electronic unit  120  may comprise an antenna  126 , here illustrated in the form of a corresponding inductor  126 . The inductors  118 ,  126  may be arranged in the TFT unit  110  and the electronic unit  120 , respectively, such that the inductors  118 ,  126  may be arranged in close proximity to each other when the electronic unit  120  is physically connected to the TFT unit  110 . The TFT unit  110  and the electronic unit  120  may communicate sensing data through the wireless coupling. The TFT unit  110  may be powered by the electronic unit  120  through the wireless coupling. 
     The TFT unit  110  and the electronic unit  120  may communicate using radio frequency signals that are transferred between the inductors  118 ,  126  of the TFT unit  110  and the electronic unit  120 , respectively. The communication may be implemented, e.g., using radio frequency identification (RFID) or using near field communication (NFC). 
     The electronic unit  120  may include a battery  124 . The battery  124  may be chargeable wirelessly or through a physical connection. The battery  124  may provide power to the electronic unit  120  and may also be used for powering the TFT unit  110  through the wireless coupling. 
     The electronic unit  120  may include a receiver  128  which may demodulate a received signal. The receiver  128  may thus demodulate a signal received from the TFT unit  110  so as to extract sensing results communicated from the TFT unit  110 . 
     The electronic unit  120  may include a processor  130  for processing sensing results. The processor  130  of the electronic unit  120  may be a general-purpose processing unit, such as a central processing unit (CPU), which may be loaded, or otherwise provided, with computer program instructions that, when executed by the processor  130 , cause the processor  130  to perform some or all of the operations described herein. The processor  130  may alternatively be a special-purpose circuitry for providing only specific logical operations. Thus, the processor  130  may, e.g., include or take the form of an application-specific integrated circuit (ASIC), an application-specific instruction-set processor (ASIP), a field-programmable gate array (FPGA), or a digital signal processor (DSP). 
     The electronic unit  120  may include a communication unit  132  which may communicate sensing results to the external unit  200 , e.g., through wired communication or through a wireless communication such as radio communication. 
     The electronic unit  120  may include a memory  134  for storing sensing results. Thus, sensing results may be stored in the electronic unit  120  such that sensing results need not continuously be transmitted to the external unit  200 . The memory  134  may be used to store some or all sensing results that are gathered during a session of using the system  100 . The memory  134  may alternatively be used as a buffer memory  134  for temporarily storing sensing results so that sensing results might not be lost if a connection to the external unit  200  is temporarily lost. 
     The electronic unit  120  may include circuitry  136  for generating a signal for powering the TFT unit  110  through the wireless coupling. The circuitry  136  may generate a radio frequency signal and may comprise a power amplifier for amplifying the signal. 
     The system  100  may be configured such that the TFT unit  110  senses a biopotential of a human being. The TFT unit  110  may then communicate a signal carrying a sensing result to the electronic unit  120 . The TFT unit  110  may pre-process the sensing result before communication. The electronic unit  120  may receive the signal. The electronic unit  120  may perform processing of the sensing results. The electronic unit  120  may store the sensing results, unprocessed or not, in a memory. The electronic unit  120  may also communicate the sensing results, unprocessed or not, to the external unit  200 . The electronic unit  120  may store the sensing results prior to communication with the external unit  200 , or it may communicate the sensing results without storing. 
     The external unit  200  may be used for storing sensing results. The external unit  200  may further be used for processing the sensing results, e.g., for extracting information relevant for presentation to a user. The external unit  200  may also be used for further transmitting sensing results to other units, e.g., communicating sensing results over a computer network. 
     The external unit  200  may further be used for powering the electronic unit  120 . The external unit  200  may thus be connected to the electronic unit  120  or arranged in close proximity to the electronic unit  120  for recharging the battery  124 , e.g., between sessions of gathering sensing results. 
     It should also be understood that the external unit  200  may be used for any combination of these functions. 
     The system  100  may be configured such that the electrodes  112  of the TFT unit  110  senses a biopotential of a human being. The TFT unit  110  may then condition an analog signal from the electrodes  112 . The TFT unit  110  may modulate the signal from the electrodes  112  to form a modulated signal carrying the sensing results and to make the signal suitable for transmission over the wireless coupling. The TFT unit  110  may convert the analog signal into a digital signal before modulating the signal. The TFT unit  110  may pre-process the signal to extract information deemed useful and leave out information deemed unwanted. 
     The TFT unit  110  may then communicate the signal carrying the sensing results to the electronic unit  120  through the wireless coupling between them. 
     The electronic unit  120  may, after receiving the signal over the wireless coupling, process the received signal. For example, the signal may be analyzed, and useful data may be extracted from the signal, leaving out unwanted data. The extracted data may be compressed by the electronic unit  120  for easier transfer and/or storage. The electronic unit  120  may temporarily store the processed data in the memory  134 . 
     After receiving the signal from the TFT unit  110 , the electronic unit  120  may communicate sensing results to the external unit  200 . The communication of the sensing results may or may not be performed after processing of the received signal by the electronic unit  120 . The communication of the signal from the electronic unit  120  to the external unit  200  may be performed wirelessly, for example, using a radio communication. However, the communication may also or alternatively be achieved through a wired contact. 
     After receiving the signal from the TFT unit  110 , the electronic unit  120  may store the sensing results in the memory  134 . The storage may be done after processing the sensing results. The stored sensing results may be communicated to the external unit  200 , wherein the communication may be performed at any chosen point of time. 
     In some embodiments, the TFT unit  110  may comprise one or more photo-detectors instead of, or in addition to, the electrodes. The one or more photo-detectors may be configured to detect an intensity of light incident on the photo-detector. The photo-detector may thus be configured, e.g., to detect absorbance or reflectance of light relating the detected light to light intensity from a light source illuminating the body part to which the TFT unit  110  is attached. The detected light from a plurality of photo-detectors may be compared, which may be used for, e.g., determining an amount of a substance in the body part based on relation of detected amounts of light for different wavelengths. 
     The associated sensor circuitry  114  may control an exposure period for the one or more photo-detectors and control when a signal from the one or more photo-detectors is to be output. The sensor circuitry  114  may further include the modulator  114   a  for modulating analog or digital signals from the one or more photo-detectors, such as for generating a signal carrying sensing results that may be transmitted to the electronic unit  120 . 
       FIG. 4  illustrates a system  300 , according to an example embodiment, for sensing a parameter of a living being. The system  300  includes a thin film transistor (TFT) unit  310  and an electronic unit  320 . The system  300  may further include an external unit  200 , which may be similar to or the same as the external unit  200  depicted in  FIG. 1 . 
     The system  300  depicted in  FIG. 4  is similar to the system  100  described above in connection with  FIGS. 1-3 , but with some differences described below. It should be realized that, apart from the below described differences, any features of system  100  may also apply or be used in system  300 . 
     The TFT unit  310  and the electronic unit  320  are not configured for being physically connected. Instead, the TFT unit  310  is configured for being attached to a body part of a living being, and the electronic unit  320  is configured for fixed arrangement on the body part. Thus, when the TFT unit  310  is attached to the living being, the electronic unit  320  may be arranged on the same body part to which the TFT unit  310  is attached, such that the TFT unit  310  and the electronic unit  320  are arranged in close relation to each other. 
     The TFT unit  310  and the electronic unit  320  may thus be arranged such that the electronic unit  320  wholly or partially overlaps the TFT unit  310  on the body part. The arrangement of the TFT unit  310  and the electronic unit  320  may facilitate a wireless contact between the TFT unit  310  and the electronic unit  320  due to the antennas of the TFT unit  310  and the electronic unit  320  being arranged in close relation to each other. 
     TFT unit  310  may be similar to TFT unit  110 , except TFT unit  310  need not include any physical connector interface for forming a connection to the electronic unit  320 . 
     Electronic unit  320  may be similar to electronic unit  120 , except electronic unit  320  need not include any physical connector interface for forming a connection to the TFT unit  310 . Instead, the electronic unit  320  may be configured to be worn by the living being, such that the electronic unit  320  may be configured for fixed arrangement on the body part to which the TFT unit  310  may be attached. 
     The configuration of the TFT unit  310  and the electronic unit  320  may depend on the body part on which the TFT unit  310  and the electronic unit  320  are to be arranged. 
     For instance, the TFT unit  310  may be formed as a patch to be attached on a wrist or arm of a human being, and the electronic unit  320  may be formed as a wristwatch or bracelet for being worn on the arm, as illustrated in  FIG. 4 . 
     Alternatively, the TFT unit  310  may be formed as a patch to be attached to a chest of the human being, and the electronic unit  320  may be formed as a band to be worn over the chest of the human being. 
     As another example, the TFT unit  310  may be formed as a patch to be attached to a forehead of the human being, and the electronic unit  320  may be formed as goggles or glasses or some other device to be worn on a head of the human being. 
     In any case, the electronic unit  320  may be implemented by adaptation of presently available wearable devices. For instance, the electronic unit  320  may be implemented in a smart watch or smart bracelet; in a smart chest band (as used, e.g., with pulse measuring equipment), or in virtual reality goggles. 
     The electronic unit  320  may be specifically provided with an antenna for forming the wireless contact to the TFT unit  310 . The antenna may be arranged in the electronic unit  320  such that it will be in close relation to the TFT unit  310  when the electronic unit  320  is arranged on the body part. 
     The present disclosure has mainly been described with reference to a limited number of examples. However, it should be understood that examples other than the ones disclosed herein can be understood and effected from a study of the drawings, the disclosure, and the appended claims. 
     For instance, the TFT unit  110  may comprise a plurality of different sensors, such as comprising both electrodes and one or more photo-detectors.