Sensor patch positioning

Abstract

A sensor patch configured to be positioned on a user using a belt, the sensor patch having a first surface with electrodes configured to contact the user's skin and a second surface opposite the first surface with a curved protrusion disposed opposite a portion of the first surface on which the electrodes are positioned. To minimize movement of the sensor patch relative to the user's skin, the invention aims to isolate the sensor patch from movement of the belt in a plane transverse to the skin while maintaining a pressure of the belt perpendicular to the user's skin. A system including the sensor patch and the belt is also provided.

Description

[Technical field]

[0001] The present invention relates to sensor patches, and more particularly to the positioning of sensor patches on a user. [Background technology]

[0002] The specification of US20140062508A1 discloses a non-resistive contact sensor assembly including an electric field sensor device including a dry electrode component for receiving an electrical signal from an object of interest and a signal processing component for processing the electrical signal, and a casing in which the signal processing component is surrounded or embedded.

[0003] WO2017108215A1 discloses a health monitor patch having at least one physiological sensor and a digital processor, the patch being configured to be adhered to the skin of a subject.

[0004] US20110279963A1 discloses an electronic device for long-term adhesion to an animal. The device includes a housing with electronic components.

[0005] Wearable devices with electrodes can be used to determine a user's vital signs. One of their uses includes pregnancy monitoring, such as monitoring fetal and maternal heart rates and uterine activity in pregnant women. Such devices typically use wet electrodes, which require a gel to be placed between the electrodes and the user's skin to enhance skin contact and signal transmission. Wet electrodes are often attached to the skin using an adhesive that combines an adhesive function with the gel.

[0006] Before attaching the wet electrodes, the user's skin must be prepared. This requires skin abrasion with sandpaper to ensure good contact and minimize movement and static artifacts. Because they require gel, the wet electrodes are one-time use and are discarded after the measurement.

[0007] Relatively recently, wearable devices using dry electrodes have been introduced. Dry electrodes can be reused, can be washed, have a longer life span, and in principle do not require skin preparation. However, like with wet electrodes, measurements are sensitive to motion artifacts.

[0008] Another type of reusable electrode is the semi-dry electrode, which requires only a small amount of electrolyte solution stored in a reservoir inside the electrode structure and can be reused a limited number of times depending on the amount of electrolyte solution left in the reservoir. Their setup is quick and convenient, similar to that of dry electrodes. Summary of the Invention [Problem to be solved by the invention]

[0009] There is currently considerable attention being paid to positioning reusable electrodes on a user, with one major problem that needs to be solved being the reduction of motion artifacts caused by the displacement of the electrodes relative to the user's skin.

[0010] Among other things, it is an object of the present invention to provide a sensor patch having features that allow for minimizing movement of the sensor patch relative to the user's skin, thus leading to reduced movement artifacts. [Means for solving the problem]

[0011] The invention is defined by the independent claims. Advantageous embodiments are defined in the dependent claims.

[0012] A first aspect of the present invention provides a sensor patch configured to be positioned on a user by a belt, the sensor patch comprising: a first surface having electrodes configured to contact the skin of a user; and a second surface opposite the first surface, the second surface having a curved protrusion disposed opposite the portion of the first surface on which the electrode is positioned; has.

[0013] An advantage of this sensor patch is that the belt exerts a normal force on the sensor patch, mainly at the area where the electrodes are located, ensuring contact between the electrodes and the user's skin, and optimizing friction between the electrodes and the user's skin. Another advantage of this sensor patch is that the curved protrusions allow the belt to slide over the curved protrusions and therefore the sensor patch, while the frictional force caused by the normal force ensures that the electrodes stay in place without more than minimal movement of the sensor patch relative to the skin. When the sensor patch has multiple electrodes on the first side, preferably the second side has protrusions opposite each electrode.

[0014] The sensor patch may be used to monitor a user's physiological parameters, such as, for example, cardiac electrical activity, brain electrical activity, or pregnancy monitoring, e.g., fetal heart rate, maternal heart rate, maternal uterine contractions, maternal respiratory rate.

[0015] The electrode may be any electrode, preferably a reusable electrode, such as a dry electrode or a semi-dry electrode. The use of dry or semi-dry electrodes offers advantages over the use of wet electrodes, such as reusability, no need for skin disinfection, and longer life. A further advantage of dry electrodes is that they are more reusable and washable compared to semi-dry electrodes.

[0016] Although typically using wet type, sensor patches using other types of electrodes (e.g. semi-dry, dry) are also attached to the skin using adhesive. According to the present invention, the sensor patch is configured to be positioned on the user using a belt. One advantage is that the sensor patch is washable. In contrast, it is very difficult to make a sensor patch using adhesive washable, since water or other cleaning agents will damage the adhesive, even if the adhesive is protected by a film. Also, a sensor patch configured to be positioned on the user using a belt is more robust and has a longer life than a patch configured to be positioned on the user using an adhesive, since the adhesive, even if protected by a film, will be damaged, for example, by environmental conditions, aging, etc. Furthermore, the solution using a belt allows reusability, and there is the freedom to reposition and slide the patch on the skin, even during operation, with no limit on the number of times it can be done. Such repositioning or sliding is not possible or limited for a sensor patch designed to be positioned using an adhesive.

[0017] The location of the sensor patch on the user may depend on the measurement of interest, e.g., for pregnancy monitoring, the sensor patch should preferably be placed on the user's abdomen. To position the sensor patch on the user, a belt that completely or partially covers the sensor patch is fastened around the user's body or body part, e.g., the belt is fastened around the user's waist when the sensor patch is placed on the abdomen, or around the user's torso when the sensor patch is placed on the chest.

[0018] To reduce sensor patch movement relative to the user's skin, the present invention aims to isolate the sensor patch from belt movement in a plane transverse to the user's skin, while maintaining a pressure of the belt perpendicular to the user's skin, which may occur when the user is moving or changing position. To achieve this goal, the sensor patch may have the features detailed below.

[0019] Such a feature is that the sensor patch is designed to be separate from the belt, so that the electrodes used to measure the user's physiological parameters are not integrated into or secured to the belt, for example, with hooks, buttons or any other fastening system.

[0020] The first side of the sensor patch is configured to contact the user's skin and has one or more electrodes. A curved protrusion on the second side of the sensor patch serves the purpose of being a contact area with the belt. Through this curved protrusion, the belt presses the sensor patch against the user's skin, ensuring contact between the electrodes and the skin. Furthermore, due to the curved surface of this protrusion, the belt can slide over the sensor patch while pressing the sensor patch against the user's skin. Thus, when the user is moving, the belt can slide over the sensor patch, while the sensor patch, and therefore the electrodes, remain in contact and do not move relative to the user's skin. As a result, motion artifacts are reduced.

[0021] A further advantage of the sensor patch being separate from the belt is that the sensor patch is easily cleaned, for example with a wet cloth or with alcohol.

[0022] The sensor patch may have multiple curved protrusions on the second surface, the effect of which is that the multiple curved protrusions act as multiple contact areas with the belt, further improving the contact between the sensor patch and the user's skin.

[0023] The sensor patch can have a first surface with a number of electrodes and a second surface with a number of corresponding curved protrusions arranged on opposite sides of the electrodes. The effect is that the belt can slide over the sensor patch and press the electrodes against the user's skin via the curved protrusions. As a result, the contact of the electrodes with the user's skin is improved while the movement of the electrodes with respect to the user's skin is reduced.

[0024] The sensor patch may have a first friction element on a first surface, the benefit of which is to create additional friction between the sensor patch and the user's skin.

[0025] The sensor patch may have a first friction element disposed on the first surface next to the electrode, the benefit of which is that it creates additional friction between the sensor patch and the area of ​​skin in contact with the electrode, which inhibits movement of the electrode relative to the skin.

[0026] The sensor patch may have one or more lateral extensions, the second surface of which has a curved protrusion to press the lateral extension toward the skin to ensure that the lateral extension remains in contact with the skin.

[0027] The lateral extension may have a second friction element on the first surface, which creates additional friction between the lateral extension and the skin. The additional friction from the second friction element prevents the lateral extension from moving, twisting, or curling as the belt slides over the curved protrusion of the lateral extension. Twisting or curling of the lateral extension becomes relevant when the sensor patch or a portion of the sensor patch, such as a portion of the lateral extension, is made of a flexible material.

[0028] The first and second friction elements may be made of a non-slip material, such as plastic, rubber, or fabric, that prevents sliding or movement of the sensor patch relative to the skin. The advantages of using these materials are that they are robust, washable, reusable, and have a long lifespan, thus contributing to the robustness and reusability of the sensor patch. Due to these advantages, it is not preferred to use an adhesive material instead of the first and / or second friction elements.

[0029] The sensor patch may be flexible, which provides the advantage that it can better follow the curvature of the user's skin, e.g., follow the shape of the abdomen. The sensor patch, or parts of the sensor patch, may be elastically or plastically deformed.

[0030] The curved protrusions may be made from a low friction material, i.e. a material with frictional properties such that the belt can slide over the sensor patch without causing more than minimal movement of the sensor patch relative to the skin. The advantage of this is that the friction between the belt and the sensor patch is low enough to ensure that the sensor patch does not move relative to the user as the belt slides over the sensor patch. Thus, these frictional properties of the curved protrusions make it easier for the belt to slide over the sensor patch.

[0031] The curved protrusions may be separate from one another and may be separably or non-separably attached to the first surface, where the first surface is made partially or solely from a flexible material. The advantage of this configuration is that the sensor patch can better follow the contours of the body, thus improving contact between the electrodes and the user's skin.

[0032] The sensor patch may include one or more motion sensors, such as an accelerometer and / or an optical motion sensor. An advantage of an optical motion sensor is that it can directly detect the motion and / or velocity of the sensor patch relative to the skin, the signal of which can therefore provide an input to improve measurements that suffer from motion artifacts.

[0033] In a second aspect of the present invention, there is provided a system for monitoring a subject, the system comprising a belt and a sensor patch, the sensor patch having one of the features described in the first aspect of the present invention, wherein said sensor patch is separate from the belt. It will be appreciated that the advantages described in the first aspect of the present invention can also be achieved by the second aspect of the present invention.

[0034] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0035] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] FIG. 1 shows a known sensor patch. [Diagram 2] FIG. 2 shows an example of a sensor patch according to the present invention. [Figure 3a] FIG. 3a shows an example of a device according to the invention illustrating the force exerted on the sensor patch by the belt. [Figure 3b] FIG. 3b shows an example of a device according to the invention illustrating the force exerted on the sensor patch by the belt. [Figure 4a] FIG. 4a shows another example of a sensor patch according to the present invention. [Figure 4b] FIG. 4b shows another example of a sensor patch according to the present invention. [Diagram 5] FIG. 5 shows another example of a sensor patch according to the present invention. [Figure 6] FIG. 6 shows another example of a sensor patch according to the present invention. [Figure 7] FIG. 7 shows another example of a sensor patch according to the present invention. [Figure 8] FIG. 8 shows another example of a sensor patch according to the present invention. [Figure 8a] FIG. 8a shows another example of a sensor patch according to the present invention. [Figure 9] FIG. 9 shows an example of a system including a sensor patch and belt according to the present invention. [Figure 10] FIG. 10 shows another example of a system having a sensor patch and belt according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present invention will be described with reference to the drawings. The detailed description and specific examples, while showing exemplary embodiments of the apparatus and method, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus and method of the present invention will be better understood from the following description, appended claims and accompanying drawings. The figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to denote the same or similar parts.

[0037] The present invention provides a sensor patch for monitoring a physiological parameter of a user using electrodes, the sensor patch being configured to be positioned on the user by means of a belt. A known solution is to fix the electrodes to the belt, and Figure 1 shows an example of how such a known arrangement can be implemented.

[0038] FIG. 1 shows a known sensor patch 1000 in which one or more electrodes 15 are integrated into or hooked onto a belt 400. The electrodes 15 are arranged on a first surface 10 of the sensor patch 1000 that is configured to contact the skin 30 of a user. A drawback of such an arrangement is that when the belt 400 moves or rotates, as indicated by the arrow in FIG. 1, the electrodes 15 fixed to the belt 400 also move or rotate relative to the skin 30. Such movements result in undesirable movement artifacts. Furthermore, in such an arrangement in which the electrodes 15 are fixed to the belt 400, a good fit of the belt 400 with the body is required to ensure that the electrodes are located at the appropriate positions on the user's body. Thus, multiple belt shapes or sizes are required to fit different users, e.g., different belts are required for pregnancy monitoring according to the abdominal shapes of various pregnant women.

[0039] 2 shows an example of a sensor patch 100 according to the present invention. The sensor patch 100 has a first side 10 and a second side 20. The first side 10 faces the skin of a user. An electrode 15 is disposed on the first side 10, the electrode 15 configured to contact the skin 30 of the user. The electrode 15 may be a reusable electrode. The sensor patch 100 or a portion of the sensor patch 100 may be flexible. The sensor patch 100 may be made of any suitable material, for example a polymer or a metal, and may be sufficiently flexible to allow conformal application to the surface of the skin 30.

[0040] The second surface 20 faces the first surface 10. The sensor patch 100 is positioned on the user's skin 30 using a separate belt (not shown in FIG. 2), which applies the required force F perpendicular to the user's skin 30, as shown in FIG. 3a. per This force F per ensures good contact between the user's skin 30 and the electrodes 15 and creates friction between the sensor patch 100 and the user's skin 30 , which resists movement of the sensor patch 100 relative to the skin 30 .

[0041] The belt is subjected to a lateral force F parallel to the plane of the user's skin 30, as shown in FIG. lat may be applied to the sensor patch 100. This force appears when the user moves or changes position due to the fact that the belt is fixed to the user's body or part of the body and therefore adapts to the user's movements. Force F lat tends to move the sensor patch relative to the skin. lat To reduce this, the belt needs to slide over the second surface 20 to the point where the sensor patch does not move relative to the user's skin 30, effectively decoupling the forces acting on the sensor patch 100 in a plane parallel to the skin 30 from the sensor patch 100.

[0042] For this reason, the second surface 20 has a curved protrusion 21, which is arranged on the opposite side to the portion of the first surface 10 where the electrodes 15 are positioned. Although the curved protrusion 21 is shown in FIG. 2 as an integral part of the sensor patch 100, it should nevertheless be understood that the curved protrusion can also be separable from the sensor patch 100, as exemplarily shown in FIG. 8. The curved protrusion comprises a portion of the sensor patch 100 that is configured to be in contact with the belt. When the curved protrusion 21 on the second surface 20 is arranged on top of the electrodes 15, a force F perpendicular to the user's skin 30 exerted on the curved protrusion 21 from the belt is per extends to electrode 15.

[0043] The curved protrusions 21-25 are preferably smooth, preferably having a uniform and regular surface, and preferably having no perceptible sharp edges. A smooth surface reduces friction between the belt and the curved protrusions 21-25, thus facilitating movement of the belt relative to the sensor patch 100.

[0044] In the non-limiting example shown in FIG. 3b, the axis of the curved protrusion 21 perpendicular to the user's skin, passing through the center of gravity of the curved protrusion, is substantially coincident with the axis of the electrode 15 perpendicular to the user's skin, passing through the center of gravity of the electrode 15. In such a configuration, the force F perpendicular to the user's skin 30 per acts on the center of gravity of electrode 15. As a result, a uniform pressure distribution is achieved along the radius of electrode 15, minimizing any torque about the center of mass (centre of gravity) of electrode 15, thus improving the contact of electrode 15 with the user's skin.

[0045] Returning to FIG. 2 , the sensor patch 100 has a first friction element 16 disposed on the first surface 10, which increases friction between the sensor patch 100 and the user's skin 30. The first friction element 16 may be disposed next to the electrode 15. The first friction element 16 is made of a non-slip material, such as plastic, rubber, or fabric, that prevents the sensor patch 100 from sliding or moving relative to the skin 30. In the example shown in FIG. 2 , the first friction element 16 surrounds the electrode 15, but in other examples, the first friction element 16 may not surround the electrode 15.

[0046] The curved protrusions 21-25 of the sensor patch 100 may be made partially or completely from a low friction material, i.e., from a material with frictional properties that allow the belt to slide over the sensor patch 100 without causing more than minimal movement of the sensor patch 100 relative to the skin 30. Examples of such low friction materials are PTFE, polyetheretherketone, polyphenylene sulfide, nylon, polyoxymethylene or polyester. Examples of desired frictional properties are materials with a static coefficient of friction less than 0.5, preferably less than 0.3, more preferably less than 0.1. The above examples of materials with desired frictional properties are considered low friction materials in practical situations. The curved protrusions 21-25 allow the belt to slide over the sensor patch 100, but the use of such low friction materials can facilitate the belt to slide over the sensor patch 100. It should be understood that the sensor patch may have such material only in the curved protrusions 21-25 or in portions of the curved protrusions 21-25, while the remainder of the sensor patch 100 may be made from a different material.

[0047] The curved protrusions 21-25 of the sensor patch 100 may be partially or completely made of hard plastic. Examples of hard plastics are HDPE, UHMW, PVC or PP. Preferably, the static friction coefficient of the curved protrusions 21-25 is less than 0.5, preferably less than 0.3, more preferably less than 0.1.

[0048] The sensor patch 100 may also include a processor for processing signals received from the electrodes 15, a memory module for storing raw or processed data, a communication module for transmitting or receiving data via wired or wireless based communication techniques, and a power module for providing power to these modules of the sensor patch 100. It should also be appreciated that the sensor patch may include other modules that aid in the operation of the sensor patch 100 to monitor physiological parameters of the user.

[0049] In a further embodiment, the sensor patch 100 can have lateral extensions. Figure 4a shows a top view of a sensor patch 100 with two lateral extensions 2a and 2b, and Figure 4b shows a cross section thereof. Figure 5 shows a top view of another embodiment of a sensor patch with six lateral extensions. Figures 4a, 4b and 5 show just two examples of a sensor patch 100 with lateral extensions, these are non-limiting examples and many more shapes and layouts can be used.

[0050] In the example shown in Fig. 4b, electrode 18a is arranged on the first face 10 of lateral extension 2a and is surrounded by an optional friction element 12a, and electrode 18b is arranged on the first face 10 of lateral extension 2b and is surrounded by an optional friction element 12b. In other examples, friction elements 12a, 12b may not (completely) surround the corresponding electrodes 18a, 18b, or electrodes 18 may be arranged on the first face 10 without friction elements 12a.

[0051] Electrodes 15, 18a and 18b may all be the same type or all different, preferably medical grade electrodes, depending on the intended use and measurement. The electrodes may be silver chloride electrodes.

[0052] The cross section in Figure 4b shows that second surface 20 has curved protrusions 21, 22, and 23. Curved protrusion 21 corresponds to the area where the belt contacts the center of sensor patch 100, curved protrusion 22 corresponds to the area where the belt contacts lateral extension 2a, and curved protrusion 23 corresponds to the area where the belt contacts lateral extension 2b.

[0053] The friction elements 12a, 12b can have the same or different shapes and may be made from the same or different material, e.g., plastic, rubber or fabric, as the first friction element 16, which prevents sliding or movement of the sensor patch 100 against the skin of the user 30. The friction elements on the lateral extensions of the sensor patch 100 prevent relative movement of the lateral extensions against the skin, and possibly movement or rotation of the entire sensor patch 100, thus allowing the belt to slide over the sensor patch (e.g., caused by patient movement) while the sensor patch stays in place.

[0054] It should be understood that the sensor patch 100 may be made of more than one material. For example, the material of the sensor patch connecting the curved protrusions 21, 22, 23 configured to contact the belt may be made of a flexible material, such as a flexible laminate, or an elastomeric material. Figure 6 shows an example where the curved protrusions 21, 22 and 23 are made of material 6a, e.g. a low friction material, and the material of the sensor patch 100 connecting the curved protrusions is made of material 6b, e.g. a flexible material.

[0055] FIG. 7 shows another example where some of the curved protrusions 21, 22 and 23 configured to contact the belt are made from material 7a, e.g., a low friction material, and the remaining part of the sensor patch 100 is made from material 7b, e.g., a flexible material such as a flexible laminate, an elastomeric material, which may also be a flexible electronic circuit incorporating wiring or other electronic components in a flexible substrate.

[0056] FIG. 8 shows an example in which the curved protrusions 21 , 22 , 23 , 24 and 25 are detachable from the sensor patch 100 .

[0057] In another example shown in Fig. 8, the friction elements 12c arranged on the first surface 10 are not arranged next to the electrodes, the purpose of which is to prevent movement of the first surface 10 relative to the skin.

[0058] 8, there are no electrodes positioned on the opposite side of the portion of the second surface 20 where the curved protrusions 24 and 25 are located. The purpose of the curved protrusions 24 and 25 is to increase the area where the sensor patch 100 contacts the belt, thereby further improving contact between the sensor patch 100 and the user's skin and further preventing the sensor patch 100 from shifting, twisting or curling.

[0059] Fig. 8a shows an example where the curved protrusions 21, 22, 23, 24 and 25 are not directly connected to each other, i.e. the protrusions are separated from each other. The curved protrusions 21, 22, 23, 24 and 25 are therefore segments with a second surface 20. Said curved protrusions are attached separably or non-separably to the first surface 10, which may be made of hard plastic or any other hard material, for example metal. Preferably, the static friction coefficient of the curved protrusions is less than 0.5, preferably less than 0.3, more preferably less than 0.1. The first surface 10 is partly or solely made of a flexible material, for example a flexible laminate or an elastomeric material, and / or the first surface 10 can also be a flexible electronic circuit incorporating wiring or other electronic components in a flexible substrate.

[0060] The curved protrusions are segments of the second surface 20 and are attached to the flexible surface 10 such that the flexible backing of the first surface 10 acts as a hinge between the segments or protrusions of the second surface 20. The advantage of this configuration is that the sensor patch 100 can better follow the contours of the body, thus improving contact between the electrodes 15, 18a, 18b, 18c and the user's skin.

[0061] In another example shown in Fig. 8a, the sensor patch 100 includes a motion sensor 19, such as an accelerometer, gyroscope, magnetometer, or optical motion sensor (such as those used in computer mice). Although the sensor patch 100 is designed to minimize movement of the sensor patch 100 relative to the user's skin, such movement may nevertheless still occur. For this reason, using a motion sensor to detect movement of the sensor patch relative to the user's skin can provide input to improve measurements that suffer from motion artifacts.

[0062] Accelerometers, gyroscopes and magnetometers generally detect motion, i.e., user motion, even when the sensor patch does not move relative to the skin, and thus motion artifact detection and / or prediction is achieved indirectly by processing the motion sensor signal using appropriate algorithms. On the other hand, optical motion sensors have the advantage that they can directly detect the motion and / or velocity of the sensor patch relative to the skin. In one example, only accelerometers, gyroscopes or magnetometers are used. In another example, only optical motion sensors may be used. In yet another example, optical motion sensors may be used together with accelerometers, gyroscopes or magnetometers to provide additional input to the accelerometer, gyroscope or magnetometer measurements to further improve motion artifact prediction and / or detection.

[0063] In the example shown in Figure 8a, only one motion sensor 19 is shown, although more than one motion sensor may be used, preferably located near the electrodes.

[0064] In one embodiment, the sensor patch is safe for use in a magnetic resonance environment. The sensor patch can meet, for example, the U.S. Food and Drug Administration's Magnetic Resonance Conditional Device Recommendations: Testing and Labeling of Medical Devices for Safety in a Magnetic Resonance (MR) Environment, May 20, 2021.

[0065] In a second embodiment of the present invention, a system 200 comprises a belt 40 and a sensor patch as previously described herein. Figures 9 and 10 show such an example, in which the belt 40 contacts the sensor patch 100 at the curved protrusion 21 of the second surface 20.

[0066] The belt may be made of a stretchy fabric that ensures a good fit with the body regardless of the body shape and size, for example, one belt size may be used for pregnancy monitoring regardless of the shape or size of the abdomen of various pregnant women. Furthermore, the sensor patch may be positioned on the user using any belt with a suitable size or stretchability to be secured around the user's body or the user's body part of interest. The belt may be washable, for example in a washing machine, so that it can be cleaned before being reused.

[0067] In summary, the invention provides a sensor patch 100 configured to be positioned on a user using a belt, the sensor patch having a first side 10 with electrodes 15 configured to contact the user's skin 30 and a second side 20 opposite the first side, the second side having a curved protrusion 21 arranged opposite the portion on the first side 10 where the electrodes 15 are positioned. To minimize movement of the sensor patch relative to the user's skin, the invention aims to decouple the sensor patch from movement of the belt in a plane transverse to the skin, while maintaining a pressure of the belt perpendicular to the user's skin. A system 200 comprising the sensor patch and belt is also provided.

[0068] It should be noted that the above-described embodiments illustrate rather than limit the invention, and that those skilled in the art can design many alternative embodiments without departing from the scope of the appended claims. Any reference signs placed between parentheses in the claims shall not be interpreted as limiting the claim. The word "comprises" does not exclude the presence of elements or steps other than those listed in the claims. The absence of a plurality of elements does not exclude the presence of a plurality of the elements. The invention may be implemented by means of hardware comprising several distinct elements, and / or by means of a suitably programmed processor. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. Advantageously, means recited in mutually different dependent claims may be used in combination.

Claims

**Claim 1** A belt and, a sensor patch configured to be positioned over a user using the belt and separated from the belt In a system having, wherein the sensor patch has a first surface with electrodes configured to contact the skin of the user, and a second surface opposite the first surface, having a curved protrusion arranged on the side opposite to the portion of the first surface where the electrodes are positioned, and the sensor patch is such that the belt slides over the curved protrusion, and applies a force perpendicular to the sensor patch mainly at the portion where the electrodes are positioned, generating a frictional force between the electrodes and the skin of the user A system configured to enable this. **Claim 2** The system according to claim 1, wherein the second surface has a plurality of curved protrusions. **Claim 3** The system according to claim 1, wherein the first surface has a plurality of electrodes, and the second surface has a corresponding plurality of curved protrusions arranged on the side opposite to the electrodes respectively. **Claim 4** The system according to any one of claims 1 to 3, wherein the sensor patch has a first friction element on the first surface. **Claim 5** The system according to claim 4, wherein the first friction element on the first surface is arranged adjacent to the electrodes. **Claim 6** The system according to claim 1, wherein the sensor patch has a lateral extension having additional electrodes, and the second surface of the lateral extension has a curved protrusion on the side opposite to the additional electrodes. **Claim 7** The system according to claim 6, wherein the lateral extension has a second friction element on the first surface. **Claim 8** The system according to claim 1, wherein the sensor patch is flexible. **Claim 9** The system according to claim 1, wherein the curved protrusion has a low friction material. **Claim 10** The second surface has a plurality of curved protrusions separated from each other and attached to the first surface in a separable or inseparable manner, and the first surface is made of a flexible material partially or alone. **Claim 11** The system according to claim 1, wherein the sensor patch has a motion sensor.

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