EP3681390A1

EP3681390A1 - An electrode structure for measuring electrical signals

Info

Publication number: EP3681390A1
Application number: EP18855516.3A
Authority: EP
Inventors: Tommi TUULENMÄKI; Kirsi VANHATALO; Atte JOUTSEN
Original assignee: Clothing Plus MBU Oy
Current assignee: Clothing Plus MBU Oy
Priority date: 2017-09-14
Filing date: 2018-09-13
Publication date: 2020-07-22
Also published as: WO2019053331A1; EP3681390A4; FI20175817A1

Abstract

An electrode structure (100) for measuring electrical bio signals comprises a body structure (103) with first and second sides (103A, 103B), and first (101) and second (102) snap portions. The first snap portion (101) is typically arranged to the first side (103A) of the body structure (103) and arranged to functioning as an electrode interface for collecting the electrical bio signals from the user during the use of the electrode structure. The second snap portion (102) is arranged to the second side (103B) of the body structure (103). The first and/or second snap portions (101, 102) are advantageously introduced, such as punched through said body structure (103) and pressed and electrically and mechanically coupled together so that the body structure (103) is located between said first and/or second snap portions (101, 102).

Description

ELECTRODE STRUCTURE FOR MEASURING ELECTRICAL

SIGNALS

TECHNICAL FIELD OF THE INVENTION The invention relates to an electrode structure for measuring electrical signals from a user wearing the electrode structure.

BACKGROUND OF THE INVENTION

Different kinds of electrodes may be used to sense biopotentials or electric signals being response to a physiological activity of the user. These μν to mV scale potentials are generated by muscle and nerve cells. In principle any conductive material can be used as an electrode, but their properties dictate the feasibility of their use in each application. For example in short term ECG monitoring disposable self-adhesive gel electrodes are used in clinical applications and conductive polymers and knits in consumer sports applications. For convenient use the electrodes are attached to textiles for example for the short term ECG monitoring, heart rate monitoring and EMG monitoring for example during sport activity and bio-impedance sensing for measuring body composition or respiration. In long term and repeated short term ECG monitoring there is no established method that is technically feasible and at the same time comfortable to the user. The gel and adhesive in the disposable electrodes may irritate the skin, especially in long term or repeated short term monitoring where the electrode is in place for extended periods of time or the adhesive is detached and attached to the same skin locations repeatedly.

Conductive polymers or knits do not offer a solution either. The polymer tends to adhere to the skin and may cause rash-like reddening when removed. The knit's soft and porous structure keeps the electrode-skin interface well ventilated, which is important for comfort, but may lead to poor signal quality. Therefore electrolytes (like tap water) may be needed for the sensor to function well. Electrolyte use is often also encouraged with polymer electrodes. SUMMARY OF THE INVENTION

Embodiments of the invention may provide a cost effective, biocompatible, durable and reliable electrode structure for measuring electrical signals being response to a physiological activity of a user to mitigate a need for electrolyte or conductive gel to be used and to provide improved user comfort, such as for both in long term and repeated short term use.

Embodiments of the invention relate to an electrode structure for measuring electrical bio signals according to claim 1. According to an embodiment of the invention an electrode structure for measuring electrical signals from a user wearing the electrode structure comprises a body structure. The body structure may take the form of a flexible and/or stretchable substrate, polymer, PET (polyethylene terephthalate), polyimide material, textile or fabric of a garment like a strap, belt, bra, pants, shirt, sock, hat, armband or wristband. The body structure comprises first and second sides, where the first side points towards the user skin during use and the second side points opposite direction than the first one.

In addition the electrode structure may include an electrically conducting first snap portion functioning as an electrode interface for collecting the electrical bio signals from the user during the use of the electrode structure. The electrode structure may also include a second snap portion mechanically coupled with the first snap portion and mechanically supporting the first snap portion to the body structure. The second snap portion may also be electrically conducting and be electrically coupled with the first snap portion. The first snap portion may be arranged to the first side of the body structure. The first snap portion comprises a snap cap and post portions, where the snap cap portion is arranged to the first side of the body structure towards the user skin during use and the post portion is introduced, such as punched through the body structure. In addition the second snap portion may be arranged to the second side of the body structure. The second snap portion comprises a stud, washer, socket and/or eyelet portions, where at least one portion is configured to receive (or be received by) the first snap portion when the post portion is introduced, such as punched through the body structure, for example. According to an embodiment of the invention the first and/or second snap portions punched through the body structure are pressed against each other, thereby coupling these portions electrically and mechanically together. The punching and/or pressing cause transformation of the material of the first and/or second snap portions (like a post) thereby providing mechanical and electrical coupling. In embodiments of the invention the body structure or at least portion of it may be located between the first and second snap portions after the coupling.

In embodiments of the invention the first snap portion comprises a snap cap and/or post, which is punched through the body structure against the second snap portion. The second snap portion may include a stud, washer, socket and/or eyelet. The second snap portion may comprise a post, which is punched through the body structure against the snap cap, for example.

In addition the electrode structure may also comprise an electrically conductive conductor, which is electrically coupled with the first and/or second snap portions. The electrically conductive conductor may take the form of a printed trace or conductor or electrically conductive ink, for example silver ink, or conductive fabric as an example. Furthermore the first and/or second snap portions may also be punched through the electrically conductive conductor to press and secure the electrically conductive conductor between the first and/or second snap portions. In this way an electric coupling can be ensured between the electrically conductive conductor and the first and/or second snap portions.

According to embodiments of the invention the electrode structure may comprise an electrically conducting interface portion arranged between the first and second snap portions, or more specifically between the body structure and the second snap portion. The interface portion may be electrically coupled to the first and/or second snap portions, and include an electrically conducting fabric, woven or knit fabric, textile, carbon nanotubes or polymer, like TPU or silicone, or electrically conductive ink, for example.

According to an embodiment of the invention the interface portion can be used to secure electric connection between the electrically conductive conductor and the first and/or second snap portions by placing the interface portion in connection with the electrically conductive conductor and the first and/or second snap portions. In embodiments of the invention the diameter of the interface portion may be greater than the diameter of the first and/or second snap portions. In such a case the interface portion may extend over the first and/or second snap portions and thereby secure and ensure the electric contact between the portions. Alternatively the interface portion may also be arranged to extend other way over the peripheral area of the first and/or second snap portions, such as taking a form of a drop or ellipse extending from the first and/or second snap portions towards to the electrically conductive conductor.

According to an embodiment of the invention at least a portion of the second snap portion may be configured to form a snap output connector for an external device having a counterpart snap portion and thereby be coupled with said snap output connector, such as in a detachable manner. One example of this kind of snap connector is a snap faster or press-stud like device, which is in this invention used as the first and second snap portions. The external device might be a transmitter, for example, however not limiting to this only. In this embodiment the first snap portion, such as a snap cap portion can be used for measuring the electrical signals and the second snap portions, such as a socket or the like, can be used to output the detected electrical signal from the electrode structure. The first and second snap portions may be electrically coupled with each other for example by directly mechanically coupling and connecting them with each other. The external device to be coupled with the output connector may be e.g. a heart rate measurement unit or a wireless data transmitter to transmit measured data in a wireless way to another device, such as a watch or mobile phone. In embodiments of the invention the electrode structure may include a cover portion for example for providing mechanical protection, which may be arranged on the second side of the body structure. At least a portion of the second snap portion may be punched also through the cover portion thereby providing a snap output connector for transmitting sensed or measured electrical bio signals from the first snap portion to the snap output connector, and thereby for example to the external device, such as to the wireless data transmitter connected to the second snap portion.

In order to make the electrode structure durable against bending and twisting, such as for daily use, materials and/or manufacturing methods of the interface portion may be selected so that the modulus of elasticity, such as flexibility and/or stretchability of the interface portion is greater than the corresponding modulus of elasticity, such as the flexibility and/or stretchability of the first and/or second snap portions, body structure and/or the corresponding modulus of elasticity, such as flexibility and/or stretchability of the electrically conductive conductor. The flexibility and stretchability relate to or can be measured e.g. by modulus of elasticity of the material [measured e.g. by N/m²].

According to an embodiment of the invention the first and second snap portions (snap fastener or press-stud like portions) can be implemented by stainless steel electrodes integrated into garments or other body structures. For example, stainless steel electrodes have proved to be user acceptable when the garment is in use. The stainless steel alloys may be biocompatible (e.g. AISI 304, 316), and made of common and cost effective materials. In addition known sheet metal manufacturing methods can be used to produce the stainless steel electrode parts, the parts can be attached using existing snap punching techniques, and the stainless steel electrodes can be used to record sufficient quality data (tested e.g., in ECG/HR, EEG and bioimpedance). Furthermore the stainless steel electrode parts can be made very small and larger semi-flexible electrode surfaces can be formed by placing multiple stainless steel electrodes parts side-by-side and connecting those to the same signal conductor inside the garment.

According to an embodiment of the invention an exemplary manufacturing method of the electrode structure may include the following steps and portions. The parts can include but are not limited to snap cap, post and washer. The snap cap and post can be fixed together by stamping and/or pressing, for example. According to an embodiment of the invention there may be included: cover textile, adhesive membrane, conductor (conductive textile, conductive polymer, conductive ink print or similar), adhesive membrane, and cover textile. A hole may be cut or made to the skin side textile, adhesive and conductor, through which the post is pushed. The washer can be placed on the post and punched such that the snap cap and post are mechanically fixed to the material stack. A reliable electrical connection may thus be formed between the stainless steel electrode part and the conductor. An outside cover textile with an adhesive membrane may be placed on top of other components described here and heat bonded to the assembly. Conventional lamination and punching methods used in the textile industry are suitable. Therefore additional cost and effort may be mitigated. In embodiments of the present invention for a short term (e.g., 10 min) and long term (e.g., 48 h) ECG measurements several electrode materials are tested. In the latter the measurements were made intermittently at 0 h, 24 h and 48 h. The tested materials were conductive polymer, silver knit, stainless steel, silver plated flex, platinum plated flex. The electrodes were placed on the skin without skin preparation or electrolyte. Stainless steel showed the highest ECG signal-to-noise ratio in the 10 min measurement. In the 0 h, 24 h and 48 h measurement stainless steel had the highest SNR in steady state. In the long term measurement, the Pt-flex electrode performed slightly better than the stainless steel when movement provocation added to the experiment. None of the materials showed skin irritation, however conductive polymer is known to have a tendency to cause skin irritation in long term. That may have been minimized here by the small electrode size (20 mm diameter).

The electrodes' impedances were measured from their connectors after clamping them face-to-face. Measurements were performed before and after SFS-EN ISO 6330 machine washing test. All metal-based materials had impedances in the range of tens of milliohms to ohms before and after washing. The conductive polymer was -300 ohms before and 1000 ohms after washing. In microscope viewing before and after washing the other materials showed some scratching, whereas the stainless steel had no visible changes.

In conclusion stainless steel performs well in short and long term measurements and retains its form and low impedance in machine washing. In addition the present invention offers numerous advantages over the known prior art, such that it is easy to implement to almost any garment ranging from outerwear to underwear, electrode elements can be tiled to form larger measuring surfaces, and snap punching can be used to form an electrical connection between the stainless steel electrode and various electrically conductive materials (conductive polymer, conductive knit, printed wiring, traditional (copper) wire). In addition the snap punching/attachment is a widely applied and cost effective method e.g. in punching conventional snap fasteners or stud-like devices in a conventional clothing industry. The stainless steel parts are cost effective when produced in mass, and stainless steel is a common material, and its properties are well known. Moreover stainless steel is skin friendly, biocompatible, and medical grade. Still stainless steel is chemically very stable, there is no staining, or colour change etc. Additionally stainless steel electrodes do not restrict the use or care (e.g. washing / chemical wash / autoclave) of the garment. The electrode structure, such as the garment or the like, having the electrode structure according to the invention can be used and machine washed as regular clothing. In addition stainless steel electrode-to-conductor interface materials do not need to be specially prepared, for example no additional solvents, glues, adhesives or the like are needed before punching, nor do they need special shielding materials after punching. In embodiments of the invention the provided mechanical contact is enough to produce a well conducting path from the stainless steel part to the conductor material. Still the electrode structure or a product having the electrode structure according to the invention can be sold as a modular approach. The measurement and operation is reliable offering high SNR even without electrolyte, provided that the surface area is large enough relative to the activity level. Further especially the electrodes according to the invention are robust, and does not wear or scratch easily (so is mechanically stable).

The exemplary embodiments presented in this text are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this text as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific example embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

Figures 1A-1 G illustrate a principle of an exemplary electrode structure for measuring electrical bio signals according to an advantageous embodiment of the invention, and

Figures 2-6 illustrate exemplary electrode structure for measuring electrical bio signals according to an advantageous embodiment of the invention.

DETAILED DESCRIPTION

In embodiments of the present invention, for comfort in long term and repeated short term monitoring the electrodes may be integrated into garments that the user would wear regardless. The electrodes may be biocompatible, of cost effective material, relatively simple to manufacture and integrate in garments, and provide sufficient quality data for analytics. Electrode attachment to garments may be accomplished using familiar and established methods in the textile industry. Figures 1A-1 D as well as Figures 2-6 illustrate exemplary electrode structures 100 for measuring electrical bio signals according to embodiments of the invention. Electrode structure 100 includes a body structure 103 with first and second sides 103A, 103B, and electrically conducting first snap portions 101 , 101 A and second snap portions 102, 102A. The exemplary first snap portion 101 includes a snap cap portion 101 B and post portion 101 C. In the illustrated embodiments the post portion 101 C is punched through an aperture 108 in the body structure 103, and pressed against the second portion 102/102A thereby coupling the portions electrically and mechanically together. As can be seen in the Figures the body structure 103, or at least portion of it, may be arranged between the first and second snap portions 101 , 102 after they are pressed, fit or otherwise mechanically coupled to one another. In addition and depending on the application the form of the first and second snap portion 101/101 A and 102/102A may vary. As an example the snap portions may be made of steel and have forms illustrated in Figures, like circular forms, but may naturally vary not limiting to those examples only.

As can be seen especially in Figures 1A-1 D, the first snap portion 101 may function as a skin electrode or interface for collecting the electrical bio signals via contact with the user skin during the use of said electrode structure. Snap portion 101 is shown arranged to the first side 103A of the body structure 103. The second snap portion 102/102A is mechanically and electrically coupled with the first snap portion 101 and mechanically supports the first snap portion 101 to the body structure 103. The second snap portion 102/102A is shown arranged to the second side 103B of the body structure 103. In more details the electrically coupling between the first and second snap portions 101 , 102 / 102A is implemented by directly coupling the first and second snap portions 101 , 102 / 102A with each other (as is the case in Figures 1A-D). The second snap portion 102 / 102A may function as a snap output connector for an external device, such as a wireless transmitter or the like, having a counterpart snap portion on a connector therefore and thereby to be coupled with said snap output connector, such as in a detachable manner

Figures 1 E-1 G still illustrate examples of how the portion of the electrode structure 100 can also be implemented, where the snap portion comprises an open prong ring 101 D and post portion 101 C, as well as a capped prong ring 101 E and a socket 101 F.

Referring now more particularly to Figures 2-6, electrode structures 100 are shown to additionally include an electrically conductive conductor 105, such as a printed conductor or a copper wire or other conductor discussed in this document. Conductor 105 may be electrically coupled between the first and/or second snap portions 101 , 102, such as by being mechanically arranged between the first and second snap portions 101 / 101 A, 102 / 102A, as is the case in Figures 3 and 4, for example. The coupling may be implemented by punching the first and/or second snap portions 101 / 101 A, 102 / 102A through the body structure 103and electrically conductive conductor 105. Conductor 105 may thus be pressed tightly between the first and second snap portions 101 / 101A, 102 / 102A and secured mechanically and electrically between the conductor 105 and the first and/or second snap portions 101 / 101 A, 102 / 102A.

In the embodiment of Figure 3 there may be two different first portions 101 , 101 A, where the first portion 101 is a cap portion for sensing electrical signals and the second portion 101 A supports the another second portion 102A and electrically couples the electrical connector 105 to the second portion 102A. The first second snap portion 102 is for supporting the first cap portion 101 and also pressing and electrically connecting the electrical connector 105 with the first cap portion 101. The electrical connector 105 is also pressed between the second first 101A and another second 102A snap portions. The electrical connector 105 couples electrically the first end portions 101 , 102 with the second end portions 101 A, 102A. Electrode structure 100 may also include an electrically conducting interface portion 104 as can be seen, e.g., in Figures 4 and 6. The interface portion 104 may be arranged between the first 101 and second 102 snap portions, or more specifically between the body structure 103 and the second 102 snap portion. In addition interface portion 104 is electrically coupled to the first and/or second snap portions 101 / 101A, 102 / 102A. The interface portion 104 may be used to secure electric connection between the electrically conductive conductor 105 and the first and/or second snap portions 101 / 101 A, 102 / 102A by placing the interface portion 104 in connection with the electrically conductive conductor 105 and the first and/or second snap portions 101 / 101A, 102 / 102A. For example, in the electrode structure 100 of Figures 3 and 6 the diameter of the interface portion 104 is greater than the diameter of the first and/or second snap portions 101 / 101 A, 102 / 102A so that the interface portion 104 extends over the first and/or second snap portions 101 / 101 A, 102 / 102A and thereby ensure the electric contact between the portions.

Electrode structure 100 may also include cover portions 106, 107, as is shown in Figures 2, 3, 4 and 6. The cover 106 may be arranged on the second side of the body structure 103. Another cover (not shown) may be arranged to the first side of the body structure 103. When not so include body structure 103 may function as a cover enough against the skin of the user and all the conductors and electrical elements or devices may be arranged to the second side of the body structure 103. When the cover portion 106 is included, at least portion 102A of the second snap portion 102 may be punched through the cover portion 106 thereby providing for example a snap output connector 102A for transmitting the sensed or measured electrical bio signals from the first snap portion 101 to the snap output connector 102A.

In addition the electrode structure may include more than one first and second snap portions 101 , 102 and thereby more than one measuring electrode, as is depicted in Figure 5 and 6, for example. The snap portions 101 , 102 (e.g., stainless steel electrode parts) can be made very small and thereby larger semi-flexible electrode surfaces can be formed by placing multiple first and second snap portions 101 , 102 side-by-side and connecting those to the same signal conductor inside the structure, like a garment, for example.

The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of the inventive thought and the following patent claims.

The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

Claims

1. An electrode structure (100) for measuring electrical signals from a user wearing said electrode structure, said electric signals being response to a physiological activity of the user, wherein said electrode structure comprises - a body structure (103) comprising first and second sides (103A, 103B), said first side arranged to point towards the user skin during use and the second side arranged to point opposite direction than said first side,

- a first snap portion (101 ) arranged to the first side (103A) of the body structure (103) and arranged to function as an stainless steel electrode interface for collecting said electrical bio signals from the user during the use of said electrode structure,

- a second snap portion (102) arranged to the second side (103B) of the body structure (103),

wherein

- said first and/or second snap portions (101 , 102) being introduced through said body structure (103) and electrically and mechanically coupled together so that the body structure (103) is located between said first and/or second snap portions (101 , 102), and

- wherein the electrode structure (100) comprises an electrically conductive conductor (105), such as a printed trace or conductor or electrically conductive ink or conductive fabric, and wherein said conductor (105) is electrically coupled with said first and/or second snap portions (101 , 102).

2. The electrode structure of claim 1 , wherein said first and/or second snap portions (101 , 102) is/are introduced, such as punched through said electrically conductive conductor (105) to press said electrically conductive conductor (105) tightly between said first and/or second snap portions (101 , 102) thereby providing electric coupling between said electrically conductive conductor (105) and said first and/or second snap portions (101 , 102). 3. The electrode structure of any previous claims, wherein said electrode structure (100) comprises an electrically conducting interface portion (104) arranged between said first (101 ) and second (102) snap portions, and more specifically between said body structure (103) and said second (102) snap portion, and being electrically coupled to said first and/or second snap portions (101 , 102).

4. The electrode structure of claim 3, wherein the diameter of said interface portion (104) is greater than the diameter of said first and/or second snap portions (101 , 102) and/or wherein said interface portion (104) extends over the peripheral area of the first and/or second snap portions (101 , 102) thereby providing electric connection between said electrically conductive conductor (105) and said first and/or second snap portions (101 , 102).

5. The electrode structure of claims 3-4, wherein the flexibility and/or stretchability of said interface portion (104) is greater than the flexibility and/or stretchability of said first and/or second snap portions (101 , 102), body structure (103) and/or the flexibility and/or stretchability of said electrically conductive conductor (105).

6. The electrode structure of claims 3-5, wherein said first and/or second snap portions (101 , 102) is/are introduced, such as punched through said interface portion (104) thereby providing said electric coupling between said interface portion (104) and said first and/or second snap portions (101 , 102).

7. The electrode structure of any previous claims, wherein at least portion (102A) of the second snap portion (102) is configured to form a snap output connector (102A) for an outer device having a counterpart snap portion and thereby to be coupled with said snap output connector (102A) in a detachable manner.

8. The electrode structure of any previous claims, wherein said electrode structure (100) comprises in addition a cover portion (106) arranged into the second side of the body structure (103), and wherein at least portion (102A) of the second snap portion (102) is introduced, such as punched through said cover portion (106) thereby providing a snap output connector (102A) for transmitting said measured electrical bio signals from the first snap portion

(101 ) to said snap output connector (102A).

9. The electrode structure of any previous claims, wherein the body structure (103) comprises a flexible and/or stretchable substrate, such as textile or fabric of a garment like a strap, belt, bra, pants, shirt, sock, hat, armband, wristband.

10. The electrode structure of any previous claims, wherein said first snap portion comprises a snap cap (101 ) and/or post, and said second snap portion

(102) comprises a stud, washer, socket or eyelet.

1 1. The electrode structure of any previous claims, wherein the electrode structure comprises plurality of the first and second snap portions, such as snap faster or press-stud like devices, (101 , 102) and thereby plurality of measuring electrode interfaces. 12. The electrode structure of claim 1 1 , wherein electrode structure (100) comprises an electrically conductive conductor (105) and wherein said plurality of the first and second snap portions (101 , 102) are electrically connected to said same electrically conductive conductor (105) thereby forming an electrode surface which has an area larger than the area of one first and second snap portion couple (101 , 102).