Electrophysiological sensor and method for detecting electrophysiological signals

Abstract

This application discloses a wearable electrophysiological sensor comprising a flexible substrate and one or more dry electrodes for sensing electrophysiological signals. Each of the one or more electrodes is located on the skin-facing surface of the flexible substrate. Each dry electrode has a non-solid pattern configured to flexibly conform to the contours of the patient's skin. In some examples, the electrophysiological sensor may be configured for use as an electrocardiogram (ECG) sensor. Methods for using the wearable sensor, methods for detecting electrophysiological signals, and methods for manufacturing the wearable sensor are also disclosed.

Description

[Technical Field]

[0001] The present disclosure relates to a wearable electrophysiological sensor, a method of using a wearable sensor, a method of detecting an electrophysiological signal, and a method of manufacturing a wearable electrophysiological sensor. Certain specific examples relate to wearable electrocardiogram (ECG) sensors. [Background Art]

[0002] Electrophysiological signals are electrical signals generated by biological cells and tissues. Since electrophysiological signals from the human body provide useful information about a subject and how well the subject's body functions, there is great interest in detecting and measuring such signals. Electrophysiological sensors have many applications, including monitoring patients, generating data for scientific research, confirming any abnormalities in patients, or assessing an individual's health status.

[0003] Examples of electrophysiological signal measurement include, but are not limited to, ECG (electrocardiogram), EMG (electromyogram), EEG (electroencephalogram), EOG (electrooculogram), and ECoG (electrocorticogram). ECG can be used for detecting cardiovascular problems and for overall assessment of cardiac health. ECG measures the electrical activity of the heart over repeated cardiac cycles by detecting differential voltages between electrodes placed at different locations on the skin. ECG can enable detection of cardiovascular problems and assessment of cardiac health. ECG (electrocardiography) is particularly difficult because it requires accurate detection of very small differential voltages.

[0004] ECG is normally performed in a hospital with the patient lying down. A number of leads are attached to electrodes placed at various locations on the patient's body. A standard 12-lead ECG has a total of ten electrodes, six of which are placed on the chest, and one electrode is placed on each of the four limbs. A 12-lead ECG only has ten electrodes, but since some electrodes are attached to two or more leads, there are twelve leads.

[0005] To minimize skin electrode impedance and generate a stronger signal, ECGs typically use wet electrodes. Wet electrodes use a conductive gel for contact with the skin, improving the acquisition of electrical signals. Ag / AgCl electrodes are commonly used wet electrodes. Ag / AgCl electrodes consist of an Ag / AgCl electrode surrounded by a conductive gel. This gel is usually surrounded by an adhesive layer for attachment to the skin. These electrodes can be uncomfortable, drying out over time and known to cause irritation and allergies in some patients. Furthermore, during prolonged or extended signal acquisition, the electrode gel can dry out and denature, causing signal loss and, furthermore, leading to the need to either replace the electrode or continuously add more electrode gel. In addition, conventional electrophysiological sensors are bulky and have multiple cables, which limits patient mobility.

[0006] Any discussion of documents, acts, materials, devices, articles, etc., contained herein shall not be deemed to acknowledge that any or all of these matters constitute common knowledge in the art relating to this disclosure, such as forming part of the foundation of the prior art or existing prior to the respective priority dates of the attached claims. [Overview of the project]

[0007] A first aspect of the present disclosure provides a wearable electrophysiological sensor comprising a flexible substrate and one or more dry electrodes for sensing electrophysiological signals, each of which is located on a skin-facing surface of the flexible substrate, wherein each dry electrode is a planar electrode comprising several electrode tracks arranged in a non-solid pattern connected to each other to form a labyrinthine structure, the labyrinthine structure being configured to flexibly conform to the contours of a patient's skin while maintaining contact with the skin.

[0008] A second aspect of the present disclosure provides a wearable electrocardiogram (ECG) sensor for attachment to a patient's skin, the wearable ECG sensor comprising: a flexible substrate having a first surface for attachment to a patient's skin and a second surface opposite to the first surface; one or more dry electrocardiogram (ECG) electrodes on the first surface of the flexible substrate, each dry ECG electrode including a non-solid pattern filling its respective two-dimensional electrode area, different portions of the non-solid pattern being movable relative to one another to correspond to the contour of the surface of the patient's skin, and the non-solid pattern including a plurality of electrode tracks together forming a plurality of concentric circles, each concentric circle being connected to an adjacent concentric circle.

[0009] In some examples, one or more dry electrodes may be formed from a conductive thin film layer having a thickness of 120 nm to 5 microns. In some examples, each electrode track may have a width of 30 to 500 microns, and the gap between adjacent electrode tracks is 30 to 500 microns or less. In some examples, the electrode tracks are substantially uniform in width, except for the outer periphery.

[0010] A third aspect of this disclosure includes the use of a wearable sensor in the first or second aspect for sensing electrophysiological signals, such as electrocardiogram signals, on a patient's skin, without limiting the scope of use.

[0011] A fourth aspect of the present disclosure provides a method for detecting electrophysiological signals, comprising attaching a wearable sensor according to the first or second aspect to a patient's neck or torso, and transmitting an electrophysiological signal sensed by one or more electrodes to a measuring device via a wired connection or wirelessly.

[0012] A fifth aspect of the present disclosure provides a method for manufacturing a wearable sensor according to the first or second aspect, the method comprising providing a flexible substrate and forming one or more dry electrodes on the surface of the flexible substrate having a non-solid pattern configured to bend to conform to the contour of the surface of a patient's skin.

[0013] Further aspects and features of this disclosure are provided in the following description and the appended claims.

[0014] Herein, examples of the present disclosure will be described only as non-limiting examples, with reference to the attached drawings below. [Brief explanation of the drawing]

[0015] [Figure 1A] A perspective view of a wearable electrophysiological sensor according to an example of this disclosure is shown. [Figure 1B] A cross-sectional view of a wearable electrophysiological sensor according to an example of this disclosure is shown. [Figure 2] A to F illustrate various non-limiting examples of electrode patterns that may be used in the wearable electrophysiological sensors according to this disclosure. [Figure 3] A to H illustrate steps in a process for manufacturing a wearable electrophysiological sensor according to an example of the present disclosure. [Figure 4] An example of a wearable electrophysiological sensor is shown in this disclosure. [Figure 5] This graph shows surface area versus resistance versus total track length for various electrode designs according to this disclosure. [Figure 6A] This is a schematic diagram illustrating the various sequences of cardiac depolarization and repolarization. [Figure 6B] Figure 6A shows the traces of the deflection waves corresponding to the sequence of depolarization and repolarization. [Figure 7a] This shows a subject in a lateral recumbent position. [Figure 7b] This image shows a subject in a lateral recumbent position with an electrophysiological sensor attached to their chest. [Figure 7c] The voltage over time under resting conditions when the subject is wearing the wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of this disclosure is shown. [Figure 7d]Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under physical stimulation when the sensor is worn on the chest of a subject in a recumbent position. [Figure 7e] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under mental stimulation when the sensor is worn on the chest of a subject in a recumbent position. [Figure 7f] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under both physical stimulation and mental stimulation when the sensor is worn on the chest of a subject in a recumbent position. [Figure 8a] Shows a subject in a sitting position. [Figure 8b] Shows a subject with an electrophysiological sensor worn on the chest in a sitting position. [Figure 8c] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under a resting state when the sensor is worn on the chest of a subject in a sitting position. [Figure 8d] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under physical stimulation when the sensor is worn on the chest of a subject in a sitting position. [Figure 8e] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under mental stimulation when the sensor is worn on the chest of a subject in a sitting position. [Figure 8f] Shows voltage versus time measured by a wearable electrophysiological sensor having hexagonal maze pattern electrodes according to an example of the present disclosure, under both physical stimulation and mental stimulation when the sensor is worn on the chest of a subject in a sitting position. [Figure 9a] Shows a subject in a standing position. [Figure 9b] Shows a subject with an electrophysiological sensor worn on the chest in a standing position. [Figure 9c]The voltage over time under resting conditions when the sensor is worn on the chest of a subject in an upright position is shown for measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of this disclosure. [Figure 9d] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn on the chest of a subject in an upright position. [Figure 9e] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is worn on the chest of a subject in an upright position. [Figure 9f] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the sensor is worn on the chest of a subject in an upright position. [Figure 10a] This shows a circular maze pattern electrode for an electrophysiological sensor. [Figure 10b] This image shows a subject in a supine position with an electrophysiological sensor attached to their chest. [Figure 10c] The voltage over time under resting conditions when the sensor is attached to the chest of a subject in a supine position is shown for measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to an example of the present disclosure. [Figure 10d] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is attached to the chest of a subject in a supine position. [Figure 10e] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is attached to the chest of a subject in a supine position. [Figure 10f]The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the sensor is attached to the chest of a subject in a supine position. [Figure 11a] This shows a circular maze pattern electrode for an electrophysiological sensor. [Figure 11b] This shows a subject in a seated position with an electrophysiological sensor attached to their chest. [Figure 11c] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time in a resting state when the sensor is worn on the chest of a subject in a seated position. [Figure 11d] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn on the chest of a subject in a seated position. [Figure 11e] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is worn on the chest of a subject in a seated position. [Figure 11f] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode, as illustrated in the example of this disclosure, show the voltage against time under physical and mental stimulation conditions when the sensor is worn on the chest of a subject in a seated position. [Figure 12a] This shows a circular maze pattern electrode for an electrophysiological sensor. [Figure 12b] This shows a subject with an electrophysiological sensor attached to their chest while standing. [Figure 12c] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time in a resting state when the sensor is worn on the chest of a subject in an upright position. [Figure 12d] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn on the chest of a subject in an upright position. [Figure 12e] The measurements from a wearable electrophysiological sensor having a circular maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is worn on the chest of a subject in an upright position. [Figure 12f] This figure shows the voltage against time under physical and mental stimulation conditions when the wearable electrophysiological sensor having a circular maze pattern electrode, according to an example of the present disclosure, is worn on the chest of a subject in an upright position. [Figure 13a] This shows a square maze pattern electrode for an electrophysiological sensor. [Figure 13b] This image shows a subject in a lateral recumbent position with an electrophysiological sensor attached to their chest. [Figure 13c] The voltage over time under resting conditions when the subject is wearing the wearable electrophysiological sensor with a square maze pattern electrode, as illustrated in the example of this disclosure, is shown. [Figure 13d] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is attached to the chest of a subject in a supine position. [Figure 13e] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is attached to the chest of a subject in a supine position. [Figure 13f] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the sensor is attached to the chest of a subject in a supine position. [Figure 14a] This shows a square maze pattern electrode for an electrophysiological sensor. [Figure 14b] This shows a subject in a seated position with an electrophysiological sensor attached to their chest. [Figure 14c]The voltage over time under resting conditions when the subject is seated and the sensor is attached to the chest is shown for measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to an example of this disclosure. [Figure 14d] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn on the chest of a subject in a seated position. [Figure 14e] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is worn on the chest of a subject in a seated position. [Figure 14f] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the sensor is worn on the chest of a subject in a seated position. [Figure 15a] This shows a square maze pattern electrode for an electrophysiological sensor. [Figure 15b] This shows a subject with an electrophysiological sensor attached to their chest while standing. [Figure 15c] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time in a resting state when the sensor is worn on the chest of a subject in an upright position. [Figure 15d] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn on the chest of a subject in an upright position. [Figure 15e] The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to the example of this disclosure show the voltage over time under mental stimulation when the sensor is worn on the chest of a subject in an upright position. [Figure 15f]The measurements from a wearable electrophysiological sensor having a square maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the sensor is worn on the chest of a subject in an upright position. [Figure 16a] This shows a hexagonal maze pattern electrode for an electrophysiological sensor. [Figure 16b] This image shows a subject in a lateral recumbent position with an electrophysiological sensor attached to their neck. [Figure 16c] The voltage over time in a resting state when the subject is wearing the wearable electrophysiological sensor with hexagonal maze pattern electrodes, as illustrated in the example of this disclosure, is shown. [Figure 16d] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage as a function of time under physical stimulation when the subject is wearing it around their neck in a supine position. [Figure 16e] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage as a function of time under mental stimulation when the subject is wearing it around their neck in a supine position. [Figure 16f] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode, as illustrated in the example of this disclosure, show the voltage against time under physical and mental stimulation conditions when the sensor is worn around the neck of a subject in a supine position. [Figure 17a] This shows a hexagonal maze pattern electrode for an electrophysiological sensor. [Figure 17b] This shows a subject in a seated position with an electrophysiological sensor attached to their neck. [Figure 17c] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time in a resting state when the subject is seated and wearing the sensor around their neck. [Figure 17d] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn around the neck of a subject in a seated position. [Figure 17e] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage as a function of time under mental stimulation when the sensor is worn around the neck of a subject in a seated position. [Figure 17f] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of this disclosure show the voltage against time under physical and mental stimulation conditions when the subject is seated and wearing the sensor around their neck. [Figure 18a] This shows a hexagonal maze pattern electrode for an electrophysiological sensor. [Figure 18b] This image shows a subject with an electrophysiological sensor attached to their neck while standing. [Figure 18c] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time in a resting state when the subject is wearing it around their neck in an upright position. [Figure 18d] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage over time under physical stimulation conditions when the sensor is worn around the neck of a subject in an upright position. [Figure 18e] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage as a function of time under mental stimulation when the subject is wearing it around their neck in an upright position. [Figure 18f] The measurements from a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to the example of this disclosure show the voltage against time under physical and mental stimulation conditions when the subject is wearing it around their neck in an upright position. [Figure 19] Figures a-d show the correlation of measurements obtained from a wearable electrophysiological sensor having a hexagonal labyrinth pattern electrode according to an example of the present disclosure having ideal 12-lead ECG parameters under different stimuli, specifically, a shows the time parameters of the chest region, b shows the amplitude parameters of the chest region, c shows the time parameters of the neck region, and d shows the amplitude parameters of the neck region. [Figure 20] Figures a-d show a comparison of amplitude parameters between a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of the present disclosure and a Welch Allyn device, specifically, a shows a comparison of P waves, b shows a comparison of R waves, c shows a comparison of T waves, and d shows a comparison of Q waves. [Figure 21] Figures a-d show a comparison of time parameters between a wearable electrophysiological sensor having a hexagonal maze pattern electrode according to an example of the present disclosure and a Welch Allyn device, specifically, a shows a comparison for PR waves, b shows a comparison for QT waves, c shows a comparison for P-wave intervals, and d shows a comparison for ST waves. [Figure 22] Figures a-d show the correlation of amplitude parameters between a wearable electrophysiological sensor having hexagonal labyrinth pattern electrodes and a Welch Allyn device under different stimuli in the chest region, specifically a for resting state, b for mental stimulation, c for physical stimulation, and d for both physical and mental stimulation. Figures e-h show the correlation of temporal parameters between a wearable electrophysiological sensor having hexagonal labyrinth pattern electrodes and a Welch Allyn device under different stimuli in the chest region, specifically e for resting state, f for mental stimulation, g for physical stimulation, and h for both physical and mental stimulation. [Figure 23] Figures A through C are schematic diagrams illustrating the difference between stretchability and flexibility. [Figure 24] Figures A through E are schematic diagrams illustrating examples of labyrinthine structures and Peano curve structures. [Figure 24] Figures A through F are schematic diagrams illustrating examples of labyrinthine structures. [Modes for carrying out the invention]

[0016] Throughout this specification, the word “comprise,” or variations such as “comprises” or “comprising,” shall be understood to imply the inclusion of the specified element, component, or step, or group of elements, components, or steps, but not to exclude any other element, component, or step, or group of elements, components, or steps. The term “includes” means inclusive of the inclusion, and the term “including” means inclusive of the inclusion. The term “based on” means at least partially based. The term “number” means any natural number greater than or equal to 1. The terms “a” and “an” are intended to indicate at least one of the specified elements.

[0017] Conventional ECG systems include multiple wet electrodes placed on the patient's limbs and chest, connected by multiple leads to an electronic data acquisition and processing device. ECGs are typically performed in a controlled hospital setting. The use of wet electrodes and numerous leads means that the system is not suitable for long-term monitoring or routine patient use, as electrodes are easily removed, disrupting ECG readings. Furthermore, conductive gels tend to dry out, making them unsuitable for extended use over several hours or days.

[0018] Other electrophysiological signal measurements also use multiple wet electrodes placed on the patient's skin and attached to leads. EMG (electromyography) measures the electrical activity of muscles, EEG (electroencephalography) measures the electrical activity of the brain, EOG (electrooculography) measures the electrical activity related to the eyes, and ECoG (electrocortical regulating) measures the electrical activity related to the ears.

[0019] Dry electrodes do not use conductive gels and can come into direct contact with the skin. However, due to the high skin electrode impedance, dry electrodes tend to experience signal loss and fragile noise degradation. This makes it difficult to accurately measure small electrophysiological signals with dry electrodes. This problem is particularly noticeable when using dry electrodes for ECG, which is one of the most complex signals to acquire.

[0020] This invention proposes a wearable electrophysiological sensor comprising a flexible substrate and one or more dry electrodes for sensing electrophysiological signals. Each of the one or more dry electrodes is located on the skin-facing surface of the flexible substrate, and each dry electrode includes a plurality of (i.e., one or more) electrode tracks arranged in a non-solid pattern configured to flexibly conform to the contours of the patient's skin. The non-solid pattern means a pattern that includes one or more empty spaces surrounded by one or more electrode tracks formed of a conductive material. For example, each electrode may include a plurality of electrode tracks connected together, at least some of the plurality of electrode tracks being adjacent to one another, with space between adjacent electrode tracks.

[0021] Because the sensor has a flexible substrate, it can conform to the contours of the wearer's skin. This enhances comfort and helps maintain contact between the skin and the electrode. Since the electrode is a dry electrode, a conductive gel is not required, so the electrode can be worn for longer periods and is easier to use outside of specialized medical or hospital settings. Because the electrode has a non-solid pattern, it is more flexible than a solid electrode and can better conform to the contours of the wearer's skin and maintain contact in the absence of a conductive gel.

[0022] Compared to "solid" electrodes with a continuous, gapless planar surface, electrodes with a non-solid pattern can maintain contact with the skin over a larger area. Wet electrodes use a conductive gel to ensure electrical contact over a wide area, which is not possible with dry electrodes. Therefore, this invention proposes to provide an electrode having multiple electrode tracks arranged in a non-solid pattern configured to flexibly conform to the contours of the patient's skin.

[0023] One method for generating non-solid patterns is to use mathematical algorithms to generate fractal patterns or space-filling curves. Fractal patterns are patterns with a structure that branches into smaller parts and self-replicates on smaller scales. Space-filling curves are curves containing multiple repeating patterns that fill two-dimensional space. Therefore, these patterns can be applied to thin-film conductors by printing or etching, for example.

[0024] Another method for generating non-solid patterns is to use mathematical algorithms to generate maze structures or labyrinthine structures. A maze is a structure that contains a set of connection paths formed by gaps between walls (e.g., electrode tracks) that lead to a central point or an interior point. A labyrinthine structure refers to a pattern that has multiple connection paths formed by gaps between electrode tracks. Thus, the term labyrinthine structure is broader in that it includes maze structures but also patterns in which the paths do not necessarily lead to a central point and some or all of the paths are blocked by connections between adjacent tracks. One or more electrode tracks that form the walls of a maze are connected together so that they are at the same potential.

[0025] Another method for generating a non-solid pattern is to design an electrode containing multiple electrode tracks that together form multiple concentric rings, each ring connected to an adjacent ring. When each ring is connected to an adjacent ring, the rings are at the same potential. Each ring may, but is not limited to, a circular, elliptical, triangular, quadrilateral, square, hexagonal, or other polygonal shape, or a loop shape that completely or partially encloses the inner ring (or loop) or center point of the electrode. Each ring may contain one or more gaps (thus forming paths connecting the spaces on both sides of the ring). One or more gaps provide further flexibility.

[0026] It is possible to manually draw mazes, labyrinthine or concentric ring structures. However, these patterns can be generated using algorithms, which simplifies the design process and allows for filling any specified two-dimensional region with non-solid patterns. The maze, labyrinthine or concentric ring patterns can then be applied to thin-film conductors by printing or etching, etc.

[0027] The inventors unexpectedly found that the labyrinthine and concentric ring structures offered better performance compared to the fractal and space-filling curve structures. This is thought to be partly due to the high flexibility achieved by the labyrinthine and concentric ring structures, which allows them to conform better to the contours of the patient's skin. The labyrinthine and concentric ring structures allow different parts of the electrode to bend in both directions parallel and perpendicular to the plane of the electrode.

[0028] Fractal and space-filling curve patterns offer high extensibility but are not as good in terms of flexibility. Labyrinthine and concentric ring structures exhibit relatively high flexibility in that they conform to the contours of the patient's skin. Flexibility is more important than extensibility in maintaining multiple contact points with the patient's skin.

[0029] Figures 23A to 23C are schematic diagrams illustrating the difference between tensile strength and flexibility. Figure 23A shows a planar electrode in its original, undeformed state. Figure 23B shows how a planar electrode is stretched by the application of a force within the electrode's plane. Figure 23C shows how a planar sensor is bent by the application of a bending force. This bending force includes a component perpendicular to the electrode's plane.

[0030] Extensibility refers to the ability of a material to withstand stretching or elongation in a plane-like direction without causing permanent deformation or fracture, and to return to its initial state when the force is removed. Extensibility can be measured by the percentage of strain. Flexibility refers to the ability of a material to bend when a force is applied without breaking or permanent deformation. Flexibility can be measured by the bending radius achievable without causing fracture or permanent deformation. In some examples, the labyrinthine and concentric ring structure electrodes of this disclosure have a flexible bending radius of at least 4 mm, meaning they can bend around a cylinder having a diameter of at least 8 mm. In some examples, electrodes having a labyrinthine or concentric ring structure were tested and withstood 100 cycles of such bending.

[0031] Figures 24A to 24D show some examples of maze structures. Figure 24A shows an example of a hexagonal maze structure, while Figures 24B, 24C, and 24D show examples of circular, triangular, and square maze structures, respectively.

[0032] The labyrinthine structure may include multiple concentric rings, as in some cases, including the examples shown in Figures 24A to 24D, with each ring connected to an adjacent ring. The rings may have polygonal (e.g., hexagonal, triangular, quadrilateral) shapes, elliptical or circular shapes, or loop shapes. Figure 24A shows a structure having a first ring 501, a second ring 502, a third ring 503, a fourth ring 504, a fifth ring 505, and an innermost ring 506. In this example, the innermost ring 506 surrounds the center point of the electrode. These rings are connected to each other by intersections of patterns formed by portions that join adjacent electrode tracks.

[0033] This structure may allow different rings to move relative to each other in a plane perpendicular to the electrode plane, and different parts of the same ring to move relative to each other in a plane perpendicular to the electrode plane. At the same time, the connections between the rings may help prevent a large area of ​​the electrode from coming out of contact with the patient's skin. In contrast, the Peano curve structure shown in Figure 24E consists only of multiple repeating patterns without having an overall structure, and therefore individual repeating pattern units such as 601 or 602 in Figure 24E, or groups of repeating pattern units, can independently adhere to and detach from the skin, resulting in suboptimal performance as a sensor.

[0034] Figures 25A to 25F show exemplary variations of the hexagonal labyrinthine structure. The example shown in Figure 25A has three slits or openings 711, 712, and 713 in the first ring, three slits or openings 721, 722, 723, and 724 in the second ring, two slits or openings in the third ring, and one slit or opening in each of the fourth through sixth rings. The example shown in Figure 25B has two slits 811 and 812 in the first ring, and two slits 821 and 822 in the second ring. The more slits there are, the more flexible the electrode becomes, allowing the electrode to adapt to the contours of the skin and maintain contact. Figures 25D to 25F show more complex hexagonal labyrinthine structures with a greater number of slits within the rings. A similar principle applies to maze-like structures having rings of other shapes, including but not limited to triangles, squares, and circles. In some examples, the maze-like pattern has at least one break in the two outer rings, and in other examples, it has at least three breaks in the two outer rings. In some examples, the maze-like pattern has at least one break in each ring, and in other examples, it has at least three breaks in each ring.

[0035] Figure 25C shows an example of a maze-like structure that does not satisfy the strict mathematical form of a maze because there is no clear path from the center to the outside. The structure in Figure 25C is essentially identical to the maze structure in Figure 25A, except that additional sections 901, 902, and 903 have been added to block some paths. However, since the overall structure is derived from and similar to a maze, this structure can be considered maze-like and has the same advantages as described above.

[0036] In some examples, the present disclosure proposes a wearable electrophysiological sensor for attachment to a patient's skin. The wearable sensor comprises a flexible substrate having a first surface for attachment to the patient's skin and a second surface opposite the first surface. One or more dry electrodes are provided on the first surface of the flexible substrate. Each dry electrode comprises a non-solid pattern filling its respective two-dimensional electrode region, and different sections of the non-solid pattern are movable relative to each other to correspond to the contours of the patient's skin surface. The wearable electrophysiological sensor may be an electrocardiogram (ECG) sensor, and the dry electrodes may be dry electrocardiogram (ECG) electrodes for use when performing an ECG.

[0037] These sensors may be compact and lightweight so that they are easily wearable devices. They have many applications, but are not limited to, monitoring motor function, outpatient care, outpatient use, long-term monitoring of individuals at home, work, or in everyday environments, or convenient use in hospitals in bedside settings. The potential for long-term use in home care is particularly attractive because it can reduce costs and detect health problems earlier, as is its use in monitoring patients after discharge from the hospital. In some examples, sensors may have a wireless module for wirelessly transmitting the data collected by the sensor. In this way, the need for leads is avoided, and the wearer can continue to move.

[0038] Figure 1A shows an example of a wearable electrophysiological sensor 100 according to the present disclosure. Figure 1B shows a portion of the wearable sensor 100 in cross-section. The wearable sensor 100 comprises a flexible substrate 110 and one or more dry electrodes 120 for sensing electrophysiological signals. The electrodes 120 are located on the skin-facing surface 112 of the flexible substrate. Each electrode includes one or more electrode tracks 122 arranged in a non-solid pattern 200 configured to flexibly conform to the contours of the patient's skin.

[0039] Dry electrodes can be planar electrodes that have a substantially flat surface when not in use before being applied to the patient's skin. That is, the electrode is a planar electrode with a flexible surface that conforms to the contour of the patient's skin, rather than a needle electrode with multiple pointed ends that contact the skin. The electrode may be a direct contact electrode, where the conductive material of the electrode is in direct contact with the surface of the skin, and not an indirect contact electrode or capacitive electrode with an insulating layer between the conductive material of the electrode and the skin.

[0040] The flexible substrate 110 may have two surfaces. The first surface may be a skin-facing surface 112 for attachment to the patient's skin. The second surface 114 may be on the opposite side of the first surface. Each electrode 120 may include a non-solid pattern 200 filling its respective two-dimensional electrode region, and different portions of the non-solid pattern may be movable relative to each other to correspond to the contours of the patient's skin surface. Figures 2a to 2f show non-limiting examples of non-solid patterns 200 that may be used.

[0041] Examples in Figures 1A and 2A–2F show three electrodes on the surface of a flexible substrate, but other examples may have one, two, or more than three electrodes. Many applications require at least two electrodes to measure the potential difference or differential voltage between two electrodes. Then, if there are three or more electrodes, in some examples the electrodes may be substantially equidistant from each other. In this context, equidistant is measured from the periphery or outermost edge of the electrodes; for example, in the case of three electrodes, the shortest distance from the periphery of the first electrode and the periphery of the second electrode is substantially equal to the shortest distance from the periphery of the first electrode and the periphery of the third electrode, and substantially equal to the shortest distance from the periphery of the second electrode and the periphery of the third electrode. This arrangement of equidistant electrodes mounted on a flexible substrate allows the sensor to cover the Einthoben triangle for ECG sensing with the correct electrode spacing between the third and fourth intercostal spaces.

[0042] The design of individual electrodes plays a crucial role in sensor performance. By using dense geometric patterns, it is possible to increase the contact area between the skin surface and the electrode while maintaining the advantages of non-solid electrode patterns. As can be seen in Figures 2A to 2F, these patterns can be relatively dense, along with the majority of the electrode area occupied by the conductive electrode track. Figures 2B and 2F show fractal or space-filling curve patterns, while Figures 2A and 2C to 2E show labyrinthine patterns.

[0043] A non-solid electrode pattern includes one or more spaces 124 surrounded by one or more electrode tracks 122 formed of a conductive material. For example, a non-solid electrode pattern may include multiple electrode tracks connected together. When multiple electrode tracks 122 are connected together, they are at the same potential and form a single electrode.

[0044] To achieve high density, at least some of the multiple electrode tracks may be adjacent to each other with space between them. For example, an electrode may include multiple substantially parallel electrode tracks, or tracks having substantially parallel sections, and gaps between parallel electrode tracks or parallel track sections. Multiple electrode tracks are connected together, for example, by electrode connection sections, so that various tracks form a single electrode.

[0045] In some examples, for each electrode, the empty space occupies less than 75% of the surface area occupied by the electrode. In this way, the electrode has flexibility due to the space or gap, but has a large contact area with the skin. A larger contact area reduces impedance. In some examples, the electrode tracks occupy 20% to 75% of the surface area occupied by the electrode (the remainder being the space between the electrode tracks). This occupancy range or density of the electrode tracks has been found to provide a good balance between a large contact area on the one hand and greater flexibility and adaptability to the contours of the patient's skin on the other. Electrodes with a higher density, where more than 75% of the surface area is occupied by electrode tracks, have been found to actually perform worse because such electrodes are less able to adapt to the contours of the patient's skin.

[0046] In some examples, each of one or more electrodes has an electrical resistance of less than 3 ohms. Regarding electrical impedance, each electrode may have an electrical impedance of less than 10 kOhm for currents with frequencies between 0.1 and 10 kHz. Reducing electrical resistance and impedance allows for more sensitive and accurate measurement of smaller signals. This is useful for applications such as ECG, which measure very small electrical signals.

[0047] In Figures 2B and 2F, the electrodes comprise one or more electrode tracks that together form a fractal-like structure or space-filling curve structure containing multiple repeating patterns. Figure 2B shows an example of an electrode pattern in the shape of a Peano curve, an example of a two-dimensional space-filling curve. Mathematically, a space-filling curve reaches all points in a two-dimensional unit space, but in this disclosure, the term is used more generally to mean a curve containing multiple repeating patterns to fill a large portion of the two-dimensional space, e.g., more than 70 percent, with points on the curve. Figure 2F shows a Hilbert curve, an example of a fractal-like structure. In this application, the term fractal does not necessarily have to strictly adhere to the mathematical definition of a fractal, but rather refers to a pattern that has a structure that branches into smaller parts that self-replicate on a smaller scale.

[0048] The inventors have found that electrodes comprising multiple electrode tracks connected together to form a labyrinthine structure function well and can adapt to the contours of a patient's skin while maintaining a high degree of contact with the skin. Examples of such patterns are shown in Figure 2A, which illustrates a triangular labyrinth; Figure 2C, which illustrates a circular labyrinth; Figure 2D, which illustrates a hexagonal labyrinth; and Figure 2E, which illustrates a square labyrinth. A labyrinth is a collection of connection paths formed by gaps between electrode tracks, where the connection paths lead to a central point or an internal point. In the context of this disclosure, labyrinthine means that the electrode has a number of connection paths formed by gaps between electrode tracks. However, it is not necessary for the paths to reach a central point, and some or all of the paths may be blocked by connections between adjacent tracks.

[0049] In some examples, the electrodes have multiple electrode tracks that together form multiple concentric rings, with each ring connected to an adjacent ring. Each ring may, but is not limited to, a circular, triangular, square, hexagonal, or polygonal shape, or the rings may have a loop shape that completely or partially encloses the inner ring or center point of the electrode. Similar to a maze, the comprehensive structure of concentric rings provides flexibility and the ability to adapt to the contours of the patient's skin while maintaining multiple contact points with the patient's skin.

[0050] In some examples, one or more dry electrodes are formed from conductive thin film layers having a thickness of 120 nm to 5 microns. The use of thin film layers facilitates mass production because the electrode patterns can be applied using printing, lithography, etching, and other such techniques. Furthermore, the properties of electrodes formed by thin film conductors or layers are well understood and easy to model because the material can be uniform. This is in contrast to nanowire deposition of electrode tracks, which is difficult to scale and also difficult to model and provide predictable electrical properties due to anisotropic properties, quantum confinement effects, and the high aspect ratio of nanowires.

[0051] In some examples, each electrode track has a width of 30 to 500 microns, and the gap between adjacent electrode tracks is 30 to 500 microns or less. These are small enough to cover a relatively dense two-dimensional electrode area, but large enough to avoid quantum confinement effects and other problems associated with high aspect ratios and very thin electrode tracks.

[0052] In some examples, the electrode track is substantially uniform in width, except for the outer circumference, which may have one or more wider sections. This is in contrast to structures with solid electrode contacts (e.g., solid metal disks) connected by meandering tracks, in which the majority of the skin contact area passes through the solid electrode contacts rather than the connecting meandering tracks, which reduce the elasticity to the skin contour, as if one or more solid electrode contacts were losing contact with the skin performance of the electrode. In contrast, when the electrode track is substantially uniform, the contact points are very well distributed, and the performance is not significantly affected even if a small area of ​​the electrode loses contact with the skin, and multiple units can help ensure that the majority of the track is in contact with the skin. In some examples, the electrode does not have solid sections wider than the electrode track, and / or solid sections wider than 500 microns.

[0053] In some examples, each of one or more electrodes may have a thickness of 50 nm to 500 nm. In some examples, each of one or more electrodes may have a thickness of 50 nm to 200 nm. This makes the electrodes more flexible and able to conform to the contours of the patient's skin. The thickness is the dimension shown by t in Figure 1A and represents the distance between the skin-facing surface of the flexible substrate and the skin-facing surface of the upper part of the electrode.

[0054] In some examples, each electrode includes one or more electrode tracks, each electrode track having a width of 30 to 500 microns, preferably 50 to 450 microns. In some examples, each electrode includes one or more electrode tracks, and adjacent electrode tracks are separated by a gap of 50 to 700 microns, preferably 140 to 650 microns. In some examples, each electrode track may have a width of 30 to 500 microns, and the gap between adjacent electrode tracks is 30 to 500 microns or less. The width of the electrode track is the dimension indicated by w in Figure 1A. Having narrow electrode tracks helps to provide a high-density structure that is flexible to adapt to the contours of the patient's skin, but also has a large number of contact points due to the large number of electrode tracks that can be accommodated within the electrode area.

[0055] In some examples, each electrode includes one or more electrode tracks, and for each electrode, the total length of one or more electrode tracks is at least 600 mm, preferably at least 1000 mm. The length of an electrode track refers to the length that the track extends in the electrode plane along its longest dimension, and the total length refers to the sum of the lengths of all electrode tracks.

[0056] Because the pattern can be very dense, the total path length may be relatively large compared to the overall surface area of ​​the electrode. In this context, the surface area of ​​the electrode refers to the total area covered by the electrode, including both the tracks and the spaces or gaps between the tracks; that is, the two-dimensional footprint of the electrode.

[0057] The total length of one or more electrode tracks, or the total path length, refers to the total length of all electrode tracks on the electrode.

[0058] The surface area or footprint of an electrode is different from the contact area of ​​the electrode. The contact area of ​​an electrode refers to the total area occupied by the electrode tracks, but not the gap. In a design where each electrode track has the same width, the contact area may be equal to the total length of all electrode tracks multiplied by the electrode track width. In some examples, each electrode occupies a two-dimensional surface area between 50 square millimeters and 500 square millimeters.

[0059] In some examples, for each electrode, the ratio of the total length (mm) of one or more electrode tracks to the surface area (mm²) of the electrode is at least 3, preferably at least 4, and in some examples 4 to 10. This provides a relatively dense electrode pattern that reduces impedance.

[0060] In some examples, wearable sensors are configured to detect electrical signals with a low voltage of 0.05 mV. Due to the low impedance and high density of the electrode pattern, at least a portion of the above structure of a dry electrode can detect electrical signals with this low voltage level. This makes the sensor suitable for use in applications such as ECG, where the detection of small electrophysiological signals is required.

[0061] One or more electrodes are formed from a conductive material. In some examples, the material is a metal, or contains a metal, including halides, alloys, and composites thereof. In some examples, one or more electrodes contain or consist of a metal, a metal halide, a metal composite, or a conductive polymer. Preferably, the material is biologically inert so as not to chemically react with the biological tissue of the subject during use. In some preferred embodiments, the electrodes contain or consist of one or more metals selected from Au, Ag, Cu, Sn, Pt, Ti and their alloys. Other examples of possible metallic electrodes include, but are not limited to, Au, Ag, Ag / AgCl, Ti, Sn, Pt, Cu, brass, and stainless steel. In one example, one or more electrodes contain or consist of a noble metal (e.g., the electrodes are Ag, Ag / AgCl, Au, Pt, Pd, etc.). In another embodiment, one or more electrodes contain or consist of Group 11 metals (for example, the electrodes may be Cu, Ag, Ag, Ag / AgCl, etc.). Metallic electrodes not only have good conductivity but also tend to be long-lasting and resistant to degradation. The electrodes may be formed from biotardant metals, and because they are biotardant metals, they do not chemically react with the biological tissue of the subject during use. In some examples, the electrodes may be formed from conductive polymers, which may be biotardant conductive polymers.

[0062] Flexible substrates are often thin films made of flexible materials. In some examples, flexible substrates include polymers or elastomers that can be thin films. Suitable polymers or elastomers include, but are not limited to, polyimide (PI), polyethylene terephthalate (PET), and polydimethylsiloxane (PDMS). Preferably, the polymer or elastomer is bioinert or biocompatible.

[0063] In some examples, one or more electrodes are deposited either physically or chemically, including by electrodeposition, machining, assembly, printing, or photolithography on a flexible substrate.

[0064] According to examples of the present disclosure, a method for manufacturing a wearable sensor may include providing a flexible substrate and forming one or more dry electrodes having a non-solid pattern configured to bend to conform to the contour of a patient's skin surface. This method may be used to create any of the above wearable sensors and may incorporate any of the above features. For example, the flexible substrate may be a thin polymer film, and the one or more dry electrodes may be formed from a bioinert metal-based material. In some examples, the one or more dry electrodes are formed by depositing a conductive (e.g., metal) layer on the substrate and etching the conductive layer by photolithography to form one or more electrodes.

[0065] Figures 3A to 3H illustrate an example method for manufacturing a wearable electrophysiological sensor according to the present invention. Photolithography can generate very fine and high-density patterns. However, depending on the electrode design and density, other techniques such as electrodeposition or printing may be used in some mounting configurations.

[0066] Figure 3A shows a first step in which a wafer, which may be a first substrate, is provided. Figure 3B shows a subsequent step in which a flexible substrate, such as a polymer substrate, is deposited on the first substrate. Figure 3C shows a further step in which a photoresist layer is deposited on the flexible substrate. For example, the photoresist layer may be deposited by spin coating. Figures 3D and 3E show further processes in which the photoresist layer is photoetched. For example, as shown in Figure 3D, the layer may be exposed to ultraviolet light via a maskless aligner or a masked aligner to form a desired pattern of electrodes, and as shown in Figure 3E, the photoresist layer may be developed using a photoresist developer to dissolve or remove portions of the photoresist layer that were not exposed to ultraviolet light. Then, as shown in Figure 3F, a conductive material (e.g., a metal) for electrodes may be deposited. In some examples, gold may be used as the conductive material. Subsequently, as shown in Figure 3F, the photoresist is removed, leaving a conductive material that forms one or more electrodes with a desired pattern(s). Then, as shown in Figure 3G, the first substrate may be removed or peeled off from the flexible substrate, leaving a flexible substrate with multiple patterned electrodes on its upper surface.

[0067] Figure 4 shows a schematic exploded view illustrating the components of a wearable electrophysiological sensor according to the present disclosure, further including a wireless module. In the example of Figure 4, the wearable sensor 400 includes a flexible substrate 110, which may be formed from, for example, polyimide, and has a first (skin-facing) surface 112 and a second (non-skin-facing) surface 114. As previously stated, there are one or more electrodes 120 having a non-solid pattern on the first surface. In addition, there is a wireless module 410 mounted on the second surface of the flexible substrate 110, which may be, for example, a Bluetooth, cellular communication, or Wi-Fi module. The wireless module 410 is electrically connected to one or more electrodes 120 and is configured to wirelessly communicate information to external devices such as mobile devices, computers, access points, clouds, or servers based on the sensed electrophysiological signals.

[0068] The wearable sensor 400 further comprises a second flexible layer 420 for positioning on the flexible layer 110 to attach the flexible layer to the user's skin 1. For example, the second flexible layer may be an Allevyn® dressing.

[0069] A wearable sensor described in any of the examples above may be used to sense detectable electrophysiological signals in a patient's skin. For example, as described above, a wearable sensor having two or more non-solid patterned electrodes may be used to detect a voltage difference between two of the electrodes. Wearable sensors may, but are not limited to, be used to sense electrocardiogram signals or other electrophysiological signals such as EMG (electromyography), EEG (electroencephalography), EOG (electrooculography), or ECoG (electrocortical regulating).

[0070] Wearable sensors can be attached, for example, to a patient's neck or torso. Wearable sensors can transmit electrophysiological signals, sensed by one or more electrodes, to a measuring device via a wired connection or wirelessly. In some examples, multiple such wearable sensors can be attached to different locations on the patient's body (e.g., limbs, chest, back, posterior neck, head, etc.) to measure signals at different locations or the difference between signals at various locations. Wearable sensors can be easily attached to different parts of the body because they can be secured by adhesive dressings or a second flexible layer.

[0071] [Examples] Using gold as the electrode material, electrodes were manufactured according to each of the electrode patterns shown in Figures 2A to 2F. The electrodes had a thickness of 150 nm. Table 1 below shows the design parameters for each electrode pattern. In Table 1, the term "footprint" refers to the combined surface area of ​​all electrodes in the sensor (the example sensor in Figure 3 has three electrodes). The term "surface area" refers to the surface area of ​​a single individual electrode, while the total length of the electrode track refers to the total length of the track of a single individual electrode. Electrode distance refers to the distance between the outer edges of adjacent electrodes, while electrode thickness and resistance refer to the thickness and resistance of a single individual electrode.

[0072] [Table 1]

[0073] Figure 5 shows a comparison of surface area, resistance, and the total length of one or more electrode tracks ("total path length") for each electrode design.

[0074] Three equidistant electrodes of various types were formed on a substrate, and the resulting sensors were tested.

[0075] Acquisition of ECG signals under different postures and stimuli Measurements were performed by placing electrodes in the posterior cervical and anterior thoracic (fourth intercostal space) regions. Similar studies have been conducted in the posterior cervical region because it may be used to provide information on cardiac arrhythmias and palpitations that may be attributable to underlying stress, exercise, medication, or underlying medical conditions. Increased neural activity in the cervical region and electrodes that interface directly in this region have the additional advantage of having a larger total pathway length for a given region. This helps to have better fit and more regional coverage. ECG signals were acquired from subjects for different stimuli, namely complete rest, mental stimulation (MS), physical stimulation (PS), and mental + physical stimulation (PS+MS), using different postures, including sitting, standing, and lying down. For each specific electrode configuration, a total of 12 measurements (various posture and stimulation combinations) were obtained to conduct an extensive study. Of the designs considered, the hexagonal maze, square maze, and Hilbert curve designs were found to be suitable for ECG signal acquisition in both regions, as shown in Table 2 below. The hexagonal maze was the best candidate due to its relatively good fit and ability to establish close contact in both the anterior chest and posterior neck regions. The Peano curve design was found to be unsuitable for the neck region, and while suitable for the chest region in some situations, it was not suitable in all situations. As will be discussed later, the Hilbert curve can be used in both the chest and neck regions, but the extremely high density of the electrode pattern in the Hilbert curve design (occupation of more than 85% of the space by electrode tracks) was a contributing factor to performance degradation in practice.

[0076] [Table 2]

[0077] Compatibility of ECG electrodes in the chest and neck regions Table 2 provides a comprehensive list of each electrode and its suitability in different regions of placement across all locations and stimuli. Evaluations revealed that the hexagonal labyrinth-based design performed best overall across all different stimuli and in both the thoracic and cervical regions. Electrode suitability was evaluated based on the following criteria: (i) how well the electrode fits into the placement area; (ii) its ability to acquire ECG signals with minimal data loss and noise; (iii) its ability to acquire ECG signals in both the anterior thoracic and posterior cervical regions; and (iv) its ability to acquire ECG signals under different stimuli.

[0078] The hexagonal maze-based design was found to have the best response among the designs considered, and when placed in the chest region spanning the fourth intercostal space, its performance was comparable to that of commercially available portable ECG monitors. This was evaluated based on how well the electrodes could conform to the subject's skin and the quality of the ECG signal acquisition. The hexagonal maze shape was found to have a relatively small surface area, as seen in Figure 5 and Table 1, while the total length of the electrode track provided one of the longest minimum resistances, and it had the ability to increase the contact points with an increased area at the examination site. The hexagonal maze-based electrode design was also found to have one of the lowest resistances of 0.295 Ω among all electrode designs. Measurements were performed by placing the ECG electrodes on the anterior chest along the posterior neck and fourth intercostal space, which were the regions under consideration, and covering them with a commercially available Allevyn® bandage. This particular bandage was used for its antibacterial effect and its ability to provide additional conformity of the ECG sensor along the curvature of the skin. The non-adhesive yet adhesive properties of this bandage help to reinforce the locking of the ECG device in place. Figure 4 shows a schematic diagram of how the ECG electrode is sandwiched between the epidermis of the skin (target area) and the Allevyn® bandage.

[0079] ECG wave tracing Typical cardiac function involves the progression of depolarization and repolarization, tracking the deviations of these waves as shown in Figure 6. The mechanism and sequence are as follows: (i) The first step in this mechanism is the initiation of atrial depolarization by the SA node, which gives rise to the P wave. (ii) This is followed by the completion of atrial depolarization, with the impulse delayed at the AV node, which constitutes the PR interval. (iii) Ventricular depolarization begins at the apex, giving rise to the QRS complex (atrial repolarization occurs). (iv) This is followed by the completion of ventricular depolarization, resulting in the ST interval. (v) Ventricular repolarization then begins at the apex, giving rise to the T wave (vi), which is finally followed by the completion of ventricular repolarization.

[0080] From the perspective of the 3-lead wearable ECG sensor applicable to this device, it is possible to view key cardiac parameters indicating cardiac activity and events. These include flatline ECG, which can be (a) cardiac electrical activity but no pulse, non-contractile (characterized by the absence of pulse and electrical activity), and pulseless electrical activity (PEA). Asystole is a serious medical emergency and requires immediate intervention due to cardiopulmonary resuscitation (CPR), (b) absence of P waves which may indicate sinus dysfunction or the presence of fibrillation or flutter waves, (c) heart rate variability (HRV) from RR wave data, as well as (d) QT interval prolongation, (e) display of ST wave elevation / depression, and (f) other ventricular activity abnormalities such as T wave depression.

[0081] ECG acquisition in the anterior chest region Figure 7 shows the ECG response of a hexagonal maze-designed sensor placed in the anterior chest region along the fourth intercostal space to the right of the sternum in a lateral recumbent position, under the following stimuli: rest, mental stress, physical stress, and physical + mental stress. Figures 8 and 9 show the ECG response of the hexagonal maze-designed sensor under the same test conditions in a sitting and standing position, respectively. The sensor was able to acquire high-quality signals in all these different positions under different stimuli. Figures 10-12 show the ECG response of a circular maze-designed sensor in lateral recumbent, sitting, and standing positions under different stimuli, while Figures 13-15 show the ECG response of a square maze-designed sensor in lateral recumbent, sitting, and standing positions under different stimuli. The sensor was also able to acquire high-quality signals in these positions and stimuli, but the circular maze design was found to be less suitable for the lateral recumbent position than the other designs tested.

[0082] Time parameters - chest region ECG signal interpretation is a structured evaluation of the waves and intervals present / absent in the acquired ECG signal. An ECG signal essentially consists of time parameters along the x-axis and amplitude parameters along the y-axis. Some of the main time parameters are PR, QT, ST, and P wave intervals. [Table 3] Table 3 | Time parameters of various electrode designs: anterior chest.

[0083] The PR segment acts as an equipotential line (baseline) of the ECG curve, reflecting slow impulse conduction through the atrioventricular node. Furthermore, the amplitude of any wave is measured by using the PR segment as the baseline. Table 3 shows the time parameters measured from ECG signals in the lateral recumbent position. Typically, the PR interval ranges from 0.12 to 0.22 seconds. We found that the PR segment was approximately 0.17 to 0.21 seconds when acquired from hexagonal labyrinth electrodes. QT duration is measured from the start of the QRS complex, and the QT interval increases as heart rate decreases and decreases as heart rate increases. QT duration is then used to determine the corrected QT duration (QTc), which is...

number

[0084] Amplitude parameters - chest region The amplitude parameters are shown in Table 4 for the reclining position measured using various electrode designs. The main amplitude parameters are the P, R, Q, and T waves. The R wave should ideally be approximately 0.2 mV, and we obtained 0.22–0.23 mV for the R wave duration using a hexagonal maze design. The amplitude response of the P wave should be within 0.25 mV, and we obtained a P wave response of 0.1 mV from our hexagonal maze design. The R wave should be within 1.6 mV, and we obtained a value of 0.5 mV for the measured R wave. The measured Q wave was 0.5 mV, which is about 40% of the R wave. The T wave, which should be in the range of 0.1–0.5 mV, was measured at 0.08 mV. These slight deviations are as expected in ECG measurements used during walking. Note that the Hilbert curve electrode showed poor performance for the Q wave compared to the maze design. This is thought to be partly due to the design's inferior ability to adapt to the contours of the skin while maintaining high density and sufficient contact with the skin, compared to a labyrinthine structure.

[0085] [Table 4]

[0086] The number in parentheses appended to the Q-wave value represents the amplitude percentage relative to the R-wave.

[0087] ECG acquisition in the posterior cervical region Further measurements were performed in a lateral recumbent position, as shown in Figure 16, by attaching a hexagonal maze-designed base sensor to the posterior cervical region under the following stimuli: rest, mental stress, physical stress, and physical + mental stress. Figures 17 and 18 show the same conditions in a sitting and standing position, respectively. The sensor was able to acquire good quality signals in all these different postures under different stimuli, as shown in Tables 3 and 4, and was able to distinguish between subjects at complete rest and under stress.

[0088] Time parameters - cervical region Table 5 shows the time parameters measured from ECG signals in the lateral recumbent position. Typically, the PR interval is in the range of 0.12–0.22 seconds. We found that the PR segment was approximately 0.17–0.21 seconds when acquired from hexagonal labyrinth electrodes. The ST interval is typically in the range of 0.05–0.15 seconds. When tested using a hexagonal labyrinth design, the ST segment values ​​were in the range of 0.09–0.14 seconds. The normal QT wave interval is 0.34–0.44 seconds, and we found that this device exhibits QT values ​​of 0.38–0.41 seconds. The P wave interval is ideally 0.11 seconds, and we found that the P wave ranged from 0.10–0.12 seconds. [Table 5]

[0089] Amplitude parameter - Cervical region The amplitude parameters are shown in Table 6 for the reclining position measured using various electrode designs. The primary amplitude parameters are the P, R, Q, and T waves. The R wave should ideally be less than 0.2 mV. Using a hexagonal labyrinth electrode, we obtained R wave durations of 0.22–2.25 mV. Typically, the amplitude response of the P wave should be within 0.25 mV. We measured P wave responses between 0.06–0.24 mV from a hexagonal labyrinth design. The R wave should be within 1.6 mV, and we obtained a value of 1.25 mV for the measured R wave. The Q wave is approximately 25% of the R wave, and we obtained a value of 0.5 mV for the Q wave, which is 22% of the measured R wave. The T wave, which should be in the range of 0.1–0.5 mV, was measured at 0.08 mV. These slight deviations are as expected in ECG measurements taken during walking, and therefore, a closely correlated index can be established for the cervical region as well. [Table 6]

[0090] The number in parentheses appended to the Q-wave value represents the amplitude percentage relative to the R-wave. Again, please note that the Hilbert curve electrode exhibited poor performance in terms of the Q-wave compared to the labyrinth design.

[0091] Comparison with an ideal (standard) 12-lead ECG monitor Following this, the properties of responses obtained from both regions were compared and correlated against an ideal 12-lead ECG response under lateral recumbent conditions (corresponding to the standard posture for ideal 12-lead ECG sensing) across different stimuli. As with typical walking-use measurements, response parameters are usually corrected by certain coefficients that correlate with typical 12-lead ECG measurements. Figures 19a–19d show the time and amplitude parameters of the hexagonal maze-design-based sensors, as well as the ideal 12-lead ECG response. As shown in Figure 19a, for the chest, the time parameters (PR, QT, ST, and P wave intervals) are closely correlated. Figure 19c shows the time parameters obtained from the cervical region, which were found to be closely correlated for both locations, as well as the deviations when the stimulus was applied. The amplitude parameters of the hexagonal maze-design-based sensors for the chest and cervical regions are shown in Figures 19b and 19d. It can be seen that the P, Q, and T wave parameters are closely correlated, and the differential R wave parameter is retained as device-specific variation and correlates with standard ECG measurements. We can also obtain a clear distinction between the subject's state, i.e., whether the subject is at rest or under a certain level of stress. These device-specific responses can be considered during the development phase of ECG sensors incorporating specific electrode configurations. By obtaining more datasets across different categories of subjects (number, age, body composition, health status), we can gain a more comprehensive understanding and correlation metrics for calibrating and relating these device-specific ECG measurements.

[0092] Comparison with commercially available portable 12-lead ECG monitors: Welch Allyn (registered trademark) Readings from the sensor according to this disclosure, which has high-density non-solid pattern electrodes, were compared with readings from a 12-lead Welch Allyn ECG device. Figure 20 shows the amplitude parameters obtained from the sensor having hexagonal labyrinth electrodes according to this disclosure compared with ECG sensing responses obtained from a commercially available Welch Allyn wireless 12-electrode ECG device for different stimuli in a lateral recumbent position. Figure 21 shows the time parameters obtained from the sensor having hexagonal labyrinth electrodes according to this disclosure compared with ECG sensing responses obtained from a commercially available Welch Allyn wireless 12-electrode ECG device for different stimuli in a lateral recumbent position.

[0093] A comparison of the hexagonal maze-designed sensor with the Welch Allyn monitor is shown, and their correlation is presented in Figure 22. The correlation of amplitude parameters can be seen in Figure 22(a-d). As these are devices used during walking, each device exhibits slight device-specific variability in measurement. This can be used to calibrate the devices to match the expected ideal 12-lead ECG response. As shown in Figure 22(b-d), when stimuli are applied, there is a significant change in the amplitude response as expected, indicating that the subject is being forced. The overall time response parameters of the devices and their correlations are shown in Figure 22(e-h). As seen in Figure 22e, under stationary conditions, the PR, QT, and ST waves, as well as the P wave interval, appear to be closely correlated.

[0094] Under different applied stimuli, the developed hexagonal maze-design-based ECG sensor was found to correlate more closely with the ideally expected ECG values, as seen in Figure 22(f~h). The Welch Allyn® device also showed closely correlated values ​​for almost all time parameters except the P-wave interval. These slight deviations can be attributed to the inherent electronic system design and device-dependent acquisition during walking.

[0095] From a signal acquisition perspective, it was found that the fabricated ECG sensor can operate with the potential capabilities of a wearable ECG sensor patch. It was also found that the range of deviations in time and amplitude parameters between the hexagonal maze design-based ECG sensor reported herein and a commercially available portable Welch Allyn ECG device may be related to the fact that the wired 12-electrode Welch Allyn monitor has complex electronic and amplification circuits that can compensate for signal gain and signal-to-noise ratio (SNR). The reported sensor is a simpler 3-electrode type, lightweight, compact, and proposed as an ECG patch that provides portable and wireless ECG sensing capabilities. The Welch Allyn device is relatively bulky and weighs 200 grams. The total weight of the electrode patch is 5 grams, packaged with the Allevyn® dressing and battery, the net weight is 12 grams, and the compact footprint is 6.5 cm (length) × 6.5 cm (width) × 1.2 cm (height). Furthermore, while Welch Allyn devices use a thick paste (wet electrode gel) of silver / silver chloride (Ag / AgCl) material, our device is based solely on a dry electrode incorporating a gold (Au) thin film that is 150 nm thick and less than the diameter of a human hair, so the electrode gel plays no role in ECG signal acquisition.

[0096] A fully functional, compact wearable ECG sensor was also prototyped, incorporating a thin film of dry electrodes to enable continuous monitoring of cardiac activity. Bluetooth wireless measurements were performed using a custom-designed Bluetooth module. The BLE module was designed using surface-mount devices (SMDs). The Dialog Semiconductor GmbH DA14531MOD-00F01002 was the selected BLE 5.1 ​​SMD component, capable of operating at frequencies from 2.4GHz to 2.4835GHz with an output of 2.2dBm and a sensitivity of -93dBm. The BLE module was powered by a 3.3V coin cell battery. The BLE signal communication range was approximately 40m.

[0097] The wireless device has the advantage of being able to be attached to both the anterior chest and posterior neck of the developed ECG device, which is of great significance in monitoring exercise capacity, neonatal care, rehabilitation, elderly care, patient transport, cardiac monitoring of patients with pacemakers, and dementia patients, where continuous and uninterrupted acquisition of ECG is paramount, while ensuring that the device is not easily interrupted by the user. This developed three-electrode, wireless ECG device has the ability to provide key cardiac information and can be used as a screening device in a POC environment. As disclosed herein, the use of dry electrodes having a high-density non-solid pattern on a flexible substrate enables such wireless sensors, which is difficult or impossible when using conventional 12-lead ECG devices with wet electrodes.

[0098] Skin comfort of wearable 3-induction ECG sensors The waterproof sensor disclosed herein was worn by a user for 7 days to check biocompatibility. No skin irritation, rash, or allergy was observed by the end of the 7-day period. This makes the sensor suitable for long-term proof-of-concept (PoC) applications, as it can be maintained unaffected when the user showers, sweats, and during the user's daily activities.

[0099] conclusion As disclosed herein, a compact, waterproof, and comfortable three-electrode-based wearable ECG sensor using dry electrodes was tested for continuous monitoring of cardiac parameters. It could be used to observe abnormalities and palpitations and to distinguish between the user's resting and non-resting states. Various designs were tested and found to be suitable, and the hexagonal labyrinth design-based electrode design was found to give particularly good performance among the evaluated confined space designs. The dry pattern electrodes disclosed herein can establish more contact points on the skin surface and provide better signal acquisition while minimizing material consumption.

[0100] The three-electrode compact wearable ECG sensor using these electrode designs was compared to a commercially available Welch Allyn 12-lead ECG monitor and found to perform comparably. The sensor's lightweight, compact design, wireless measurement capabilities, ability to acquire ECG signals from both the chest and neck regions while distinguishing between resting and stress measurements under different stimuli, and ability to provide high-quality ECG sensing within a three-electrode configuration system indicate great potential for future applications of wearable ECG sensing, particularly in gait medicine and proof-of-concept (PoC) applications, where measurements can be performed with the device alone or integrated into wearable fabric.

[0101] In some cases, photolithography techniques were used to fabricate thin-film sensor electrodes. In some cases, AZ5214E ​​photoresist was used in the lithography process. The photoresist was spin-coated onto a polyimide film at a speed of 3000 rpm and an acceleration of 1000 rpm / sec for 30 seconds. This was then soft-baked at 95°C for 90 seconds. Gold (Au) was the selected electrode material. 30 nm of chromium (Cr) and 150 nm of Au were deposited as adhesive layers using e-beam deposition. Allevyn® Ag Gentle Border, an antimicrobial hydrocellular bandage based on silicone gel adhesive, was used as the dressing layer.

[0102] All features of various exemplary apparatuses disclosed herein (including any appended claims, abstracts, and drawings) and / or all blocks of any methods or processes disclosed herein may be combined in any combination, except for any combination in which at least some of such features and / or blocks are mutually exclusive.

[0103] Those skilled in the art will understand that numerous variations and / or modifications can be made to the embodiments described above without departing from the broad and comprehensive scope of this disclosure. Therefore, these embodiments should be considered in all respects as illustrative and not limiting. [Explanation of Symbols]

[0104] 1 skin 100 Wearable Sensors 110 Flexible substrate 112 First surface 114 Second surface 120 Dry electrodes 122 Electrode Track 124 Space 200 Non-Solid Patterns 400 Wearable Sensors 410 Wireless Module 420 Second flexible layer 501 The First Ring 502 The Second Ring 503 The Third Ring 504 The Fourth Ring 505 The Fifth Ring 506 Innermost ring 711 Opening 712 Opening 713 Opening 721 Opening 722 Opening 723 Opening 724 Opening 811th 812th 821st 822nd 901 Additional parts 902 Additional parts 903 Additional part

Claims

1. It is a wearable electrophysiological sensor, Flexible substrate and A dry electrode for sensing electrophysiological signals, wherein each of the dry electrodes comprises one or more dry electrodes located on the skin-facing surface of the flexible substrate, A wearable electrophysiological sensor in which each dry electrode is a planar electrode comprising several electrode tracks arranged in a non-solid pattern connected together to form a labyrinthine structure, the labyrinthine structure being configured to flexibly conform to the contours of the patient's skin while maintaining contact with the skin.

2. A wearable electrocardiogram (ECG) sensor for attachment to a patient's skin, wherein the wearable ECG sensor is A flexible substrate having a first surface for attachment to the patient's skin and a second surface opposite to the first surface, One or more dry electrocardiogram (ECG) electrodes on the first surface of the flexible substrate, The present invention comprises one or more dry ECG electrodes, each having a non-solid pattern filling its respective two-dimensional electrode region, wherein different sections of the non-solid pattern are movable relative to each other to correspond to the contours of the patient's skin surface. A wearable ECG sensor in which the non-solid pattern comprises multiple electrode tracks that together form multiple concentric rings, each ring being connected to an adjacent ring.

3. The wearable sensor according to claim 1 or 2, wherein one or more dry electrodes are formed from a conductive thin film layer having a thickness of 120 nm to 5 microns.

4. A wearable sensor according to any one of claims 1 to 3, wherein each electrode track has a width of 30 microns to 500 microns, and the gap between adjacent electrode tracks is 30 to 500 microns or less.

5. The wearable sensor according to any one of claims 1 to 4, wherein the electrode track has substantially uniform width in areas other than the outer circumference of the electrode.

6. The wearable sensor according to any one of claims 1 to 5, wherein, for each electrode, the electrode track occupies 20% to 75% of the surface area occupied by the electrode.

7. A wearable sensor according to any one of claims 1 to 6, wherein each electrode comprises one or more electrode tracks having a width of 30 microns to 500 microns, preferably 50 microns to 450 microns, and adjacent electrode tracks are separated by a gap of 50 microns to 700 microns, preferably 140 microns to 650 microns.

8. A wearable sensor according to any one of claims 1 to 7, wherein each electrode is provided with one or more electrode tracks, and for each electrode, the total length of the one or more electrode tracks is at least 600 mm, preferably at least 1000 mm.

9. The wearable sensor according to claim 10, wherein each electrode has a surface area, and for each electrode, the ratio of the total length of one or more electrode tracks to the surface area of ​​the electrode is at least 3, preferably at least 4, and in some examples 4 to 10.

10. A wearable sensor according to any one of claims 1 to 9, wherein each electrode occupies a two-dimensional area of ​​50 square millimeters to 500 square millimeters.

11. The wearable sensor according to any one of claims 1 to 10, wherein each of the one or more electrodes has an electrical impedance of less than 10 kHz for a current having a frequency of 0.1 to 10 kHz.

12. A wearable sensor according to any one of claims 1 to 11, wherein each electrode has a pattern selected from the group including triangular mazes, circular mazes, hexagonal mazes, and square mazes.

13. The wearable sensor according to any one of claims 1 to 12, wherein one or more electrodes include a metal, a metal alloy, a metal halide, a metal composite material, or a conductive polymer.

14. The wearable sensor according to any one of claims 1 to 13, wherein the flexible substrate comprises a polymer or elastomer, which may be a thin film.

15. The wearable sensor according to any one of claims 1 to 13, wherein one or more electrodes are formed on the flexible substrate by physical or chemical deposition, printing, or photolithography.

16. The wearable sensor according to any one of claims 1 to 15, comprising two or more, preferably three or more electrodes on the surface of the flexible substrate.

17. The wearable sensor according to any one of claims 1 to 16, wherein the wearable ECG sensor is configured to detect an electrical signal having a low voltage of 0.05 mV.

18. The wearable sensor according to any one of claims 1 to 17, further comprising a wireless module on a second (non-skin-facing) surface of the flexible substrate, wherein the wireless module is electrically connected to one or more electrodes and is arranged to wirelessly communicate information to an external device based on the sensed electrophysiological signals.

19. A wearable sensor according to any one of claims 1 to 18, further comprising a second flexible layer for positioning the flexible layer on the flexible layer in order to attach it to the user's skin.

20. Use of a wearable sensor according to any one of claims 1 to 19 for sensing electrophysiological signals in a patient's skin.

21. Use of a wearable sensor according to any one of claims 1 to 19 for sensing electrocardiogram signals in a patient's skin.

22. A method for detecting an electrophysiological signal, comprising: attaching a wearable sensor according to any one of claims 1 to 19 to the neck or torso of a patient; and transmitting the electrophysiological signal sensed by one or more electrodes to a measuring device via a wired connection or wirelessly.

23. A method for detecting an electrophysiological signal according to claim 22, comprising attaching a plurality of wearable sensors according to claims 1 to 19 to different locations on the patient's body.

24. A method for manufacturing a wearable sensor according to any one of claims 1 to 19, To provide a flexible substrate, A method comprising forming one or more dry electrodes having a non-solid pattern configured to bend to conform to the contour of the surface of a patient's skin on the surface of the flexible substrate.

25. The method according to claim 24, wherein the flexible substrate is a thin polymer film, and the one or more dry electrodes are formed of a bioinert metal.

26. The method according to claim 24 or 25, wherein the one or more dry electrodes are formed by depositing a metal layer and etching the metal layer by photolithography to form the one or more electrodes.

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