Screen-printed wet electrode, electrocardiogram system, and method

Abstract

An electrode unit (100) for acquiring health related signals from a skin includes a flexible substrate (102), a first electrode (104) printed on the flexible substrate (102), a first electrode gel layer (108-1) printed on a first part (104A) of the first electrode (104), and a first adhesive gel layer (110-1) printed around the first electrode gel layer (108-1).

Description

SCREEN-PRINTED WET ELECTRODE, ELECTROCARDIOGRAM SYSTEM, AND METHODCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 568,086, filed on March 21 , 2024, entitled “FULLY SCREEN-PRINTED WET ECG ELECTRODE FOR BIOELECTRICAL SIGNAL MONITORING,” the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTIONTECHNICAL FIELD

[0002] Embodiments of the subject matter disclosed herein generally relate to a screen-printed wet electrode, electrocardiogram (ECG) system, and method of using the screen-printed wet electrode for monitoring a heart condition, and more particularly, to a wet electrode that is entirely screen-printed and is integrated with a processing circuit and an antenna for wireless transmission of the collected data.DISCUSSION OF THE BACKGROUND

[0003] It is estimated that cardiovascular diseases caused 20.5 million deaths in 2021 , and their incidence is rising worldwide, impacting over 500 million people globally. Therefore, there is a pressing need to develop tools for early diagnosis and therapies for personalized health monitoring. The ECG is frequently used fordiagnosing cardiovascular diseases and monitoring the health of the human heart. A 12-lead ECG system is used for diagnostic purposes, whereas 1 , 3, or 6 leads are used for monitoring the heart’s rhythm. Recent advances in electrode technology have led to wearable ECG systems for monitoring the heart’s health, which may decrease the need for users to visit the hospital visits.

[0004] In hospitals, the traditional ECG systems use commercially available disposable Ag / AgCI wet ECG electrodes or reusable vacuum cup electrodes. Disposable, single use, Ag / AgCI wet ECG electrodes costs are still high per electrode. The reusable vacuum cup electrodes are uncomfortable and result in sore skin and rashes. In addition, the vacuum cup electrodes require decontamination and can spread antibiotic-resistant pathogens even after decontamination or due to inadequate decontamination.

[0005] Therefore, disposable Ag / AgCI wet ECG electrodes are preferred over reusable vacuum cup electrodes. However, the disposable Ag / AgCI wet ECG electrodes remain expensive for a broader audience, for example, undeveloped or developing countries. To date, vacuum cup electrodes are still in practice in many parts of the world. Additionally, the price per Ag / AgCI wet ECG electrode increases when gentle-to-skin and easy removal features are added, further increasing the overall usage cost of ECG systems.

[0006] Wearable ECG systems for personal health monitoring use commercially available wet ECG electrodes or custom dry electrodes. Commercially available dry electrodes need some pressure in the form of a wearable belt to improve contact with the skin to acquire a good ECG signal. Applying or removingthese electrodes cause significant discomfort to the patient and results in sore skin and rashes for patients with sensitive skin.

[0007] Depending on the type of application, dry and wet ECG electrodes have advantages and disadvantages. The dry electrodes are suitable for long-term ECG monitoring, for example, during exercises, and they show comparable performance to the commercial wet ECG electrodes as soon as perspiration fills the skin-electrode gap. The wet ECG electrodes (commonly used commercial disposable ECG electrodes) perform better than the dry electrodes in the clinical settings, and hence, they are routinely being used in the clinical practice to date.

[0008] Numerous efforts have been made to fabricate dry ECG electrodes using various functional materials, such as silver nanowires (AgNWs) deposited on or embedded in poly(dimethylsiloxane) (PDMS) [1 -4], a zwitterionic polymer brush coated on Au / PDMS, graphene, carbon nanotube composites, conductive textiles, nanomaterial-polymer composites, 3D electrodes, poly(ionic liquid) nanofiber membranes, and conductive polymers blended with other materials for improved flexibility and adhesiveness. A common challenge to the fabrication of the dry ECG electrodes is that the production cost of these electrodes is higher than that of commercially available wet ECG electrodes, owing to the inclusion of multiple complex manufacturing processes such as spin-coating, multiple lithography processes, casting, coating, electrode connection via snap connectors or soldering the wires, and manual handling. Thus, many potential ECG electrodes that have been fabricated at the laboratory scale are unsuitable for large-scale production. Thismeans that hospitals still have to use expensive Ag / AgCI wet ECG electrodes or uncomfortable vacuum cup electrodes for clinical diagnosis.

[0009] Electronics printing methods such as roll-to-roll and screen-printing allow for the manufacturing of large-area, high-volume, and low-cost production of flexible electronic components [5]. Dry ECG electrodes have been screen-printed from conductive inks, polymers, and carbon [6-9]. However, these efforts were mainly focused on the development of dry ECG electrodes for ECG monitoring purposes.

[0010] Recent interest in telehealth, precision medicine, and the Internet of Things or Internet of Medical Things has led to an emerging trend of sending health data to smartphone apps for continuous monitoring and remote diagnosis. Such applications require, in addition to the ECG electrode, an antenna for wireless communication, which should provide a reasonable gain across the whole bandwidth used by the communication protocols and easily integrate with a wearable ECG system. The antenna-on-package (AoP)

[0010] fully utilizes the system’s volume and expands the design freedom to provide better performance. An AoP also serves as the packaging / enclosure, which saves considerable space, weight, and cost compared with other antenna design options known in the literature.

[0011] The miniaturization of ECG devices is desired for practical application by improving mobility and ease of use. For instance, typical ECG devices for neonatal monitoring use long wires that connect electrodes to a readout device on the side of the infant’s bed (i.e. , not worn). This reduces access and mobility forparental care as well as for clinical processes. References [11-17] address some of the problems noted above but none fully solves all these problems.

[0012] Thus, there is a need for an inexpensive wet ECG electrode which can be easily manufactured at scale, and a small and lightweight wearable device that can be connected to the wet ECG electrode for collecting health related data, partially processing the health related data, and wirelessly transmitting this processed data to a data server.SUMMARY OF THE INVENTION

[0013] According to an embodiment, there is an electrode unit for acquiring health related signals from a skin, and the electrode unit includes a flexible substrate, a first electrode printed on the flexible substrate, a first electrode gel layer printed on a first part of the first electrode, and a first adhesive gel layer printed around the first electrode gel layer.

[0014] According to another embodiment, there is a portable and wireless monitoring system for acquiring health related signals from a skin. The monitoring system includes an electrode unit configured to be directly attached to the skin to record a signal, a readout device configured to process the signal, a connecting unit physically and electrically connecting the electrode unit to the readout device through first and second pogo pins, and an antenna package electrically connected to the readout device and configured to transmit a processed signal in a wireless manner. The antenna package is shaped to receive as a base the readout device.

[0015] According to yet another embodiment, there is a method for screenprinting an electrode unit for acquiring health related signals from a skin. The method includes providing a flexible substrate, screen-printing an electrode on the flexible substrate, screen-printing an electrode gel layer on a first part of the electrode, and screen-printing an adhesive gel layer around the electrode gel layer.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0017] FIG. 1 is a cross-section view of a wet ECG electrode that is fully screen-printed;

[0018] FIGs. 2A and 2B are cross-sections views of other wet ECG electrodes that are fully screen-printed;

[0019] FIGs. 3A to 3C are top views of various wet ECG electrodes that are fully screen-printed;

[0020] FIG. 4 is a flow chart of a method for manufacturing a screen-printed wet ECG electrode;

[0021] FIG. 5 schematically illustrates the various stages of manufacturing the screen-printed wet ECG electrode made with the method of FIG. 4;

[0022] FIG. 6 is a schematic diagram of a screen-printed wet ECG electrode integrated with a readout device and an antenna module, in communication with an application on a smartphone;

[0023] FIG. 7 schematically illustrates the scree-printed wet ECG electrode attached to the readout device and antenna module with a connecting unit;

[0024] FIG. 8 is an exploded view of the connecting unit and how the wet ECG electrode and the readout device fit into the connecting unit;

[0025] FIG. 9 schematically illustrates the antenna module integrated with the readout circuit and the screen-printed wet ECG electrode;

[0026] FIGs. 10A and 10B show overall views of the integrated system that includes the screen-printed wet ECG electrode, the readout circuit, and the antenna module.DETAILED DESCRIPTION OF THE INVENTION

[0027] The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a fully screen- printed wet ECG electrode that is integrated with a miniaturized readout device, which is packaged inside a printed antenna module. However, the embodiments to be discussed next are not limited to fully screen-printed electrode, or readout device packaged inside a printed antenna module, but may use non-printed electrodes or readout devices that are packaged outside the printed antenna module.

[0028] Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0029] According to an embodiment, a novel fully screen-printed wet ECG electrode unit, which may be integrated with a miniaturized ECG readout device that includes a custom-designed printed circuit board (PCB) packaged inside a 3D-printed antenna module (e.g., AoP). The electrode unit provides soft and gentle contact with the human skin while acquiring a high-quality ECG signal on both 12 lead ECG diagnosis system and miniaturized ECG monitoring readout device. The readout device is user-friendly and has a better communication range than commercial chip antennas. Having the fully screen-printed wet ECG electrode unit with all its three components (i.e. , AgNWs-based conductive part, electrode gel, and adhesive gel) printed on a single substrate is not only conducive to large scale manufacturing, but also resulting in an inexpensive product. The inventors also developed an atypical electrode-device interface that connects the electrode unit to the wireless readout device in a plug-and-play manner without the need for snap connectors or conductive epoxy for soldering.

[0030] FIG. 1 illustrates a wet ECG electrode unit 100 (also called “electrode unit” in this document) that is entirely manufactured by screen-printing. The wet ECG electrode unit 100 has a flexible substrate 102. The flexible substrate may be made of, for example, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) plastic sheet. Other flexible materials may be used. The term “flexible” is understood in this document as a characteristic of a material to bend at least 90 degrees. Two electrodes 104 and 106 are printed (e.g., screen-printed) on top of the flexible substrate 102. Although FIG. 1 shows the flexible substrate 102 to be a single part, in one embodiment, it is possible that each of the electrodes 104 and 106 are independently printed on corresponding flexible substrates, separated from each other. The two electrodes may be made to be identical (i.e., shape, geometry,properties, material, etc.). In one embodiment, AgNW ink is used for printing the two electrodes.

[0031] Then, selected parts 104A and 106A of the electrodes 104 and 106 are fully covered (e.g., by scree-printing) with an electrode gel to form corresponding electrode gel layers 108-1 and 108-2. Each electrode 104 and 106 has its own electrode gel layer. Note that the remaining parts 104B and 106B of the electrodes 104 and 106 are not covered by the electrode gel. An adhesive gel is then screen- printed around the electrode gel layers 108-1 and 108-2, to form adhesive gel layers 110-1 and 110-2. Each electrode 104 and 106 has its own adhesive gel layer. In one embodiment, the adhesive gel layer 110-1 (110-2) fully encloses the electrode gel layer 108-1 (108-2). In this or another embodiment, a top surface of the adhesive gel layer 110-1 , 110-2 is flush with a top surface of the electrode gel layer 108-1 , 108-2. In another embodiment, a top surface of the layers 108-1 , 108-2 or 110-1 , 110-2 is printed to be higher than the other one of the layers 110-1 , 110-2 or 108-1 , 108-2. For example, FIG. 2A shows a wet ECG electrode unit 100A having the top surface of the electrode gel layer 108-1 (108-2) being higher than the top surface of the adhesive gel layer 110-1 (110-2) and FIG. 2B shows a wet ECG electrode unit 100B having the top surface of the adhesive gel layer 110-1 (110-2) being higher than the top surface of the electrode gel layer 108-1 (108-2). Note that the electrode gel layers 108-1 , 108-2 are configured to achieve good contact between the wet ECG electrode unit 100 and the user’s skin while the adhesive gel layers 110-1 , 110-2 are configured to achieve good adhesion between the wet ECG electrode 100 and the user’s skin. FIG. 1 also shows a hole 104C formed in the free part 104B of theelectrode 104 and a similar hole 106C formed in the free part 106B of the electrode 106. The hole may extend through the entire thickness of the substrate 102.

[0032] FIG. 3A is a top view of the electrode unit 100, showing that the flexible substrate 102 supports the two electrodes 104 and 106, the two electrodes 104 and 106 are separated by a distance D, the parts 104B and 106B are not covered by the electrode gel layers 108-1 , 108-2 while the parts 104A and 106A are fully covered by the electrode gel layers 108-1 , 108-2. FIG. 3A also shows that each electrode 104 and 106 has a corresponding hole 104C and 106C, that extends all the way through the substrate 102. These holes are made for the purpose of attaching the electrode unit 100 to a connecting unit, which is discussed later. FIG. 3A further shows that each of the electrodes 104 and 106 extends along a same longitudinal axis X. In one embodiment, a longitudinal axis of the first electrode 104 and a longitudinal axis of the second electrode 106 coincide. While FIG. 3A shows the layers 104, 106, 108-1 , 108-2, 110-1 , and 110-2 having a circular shape, FIG. 3B shows the same layers having a square shape. One skilled in the art would understand that other shapes may be used for these layers. Further, FIGs. 3A and 3B show the adhesive gel layers 110-1 , 110-2 fully enclosing the corresponding electrode gel layers 108-1 , 108-2. However, it is possible, as illustrated in FIG. 3C, to screen print the adhesive gel layers 110-1 , 110-2 to partially enclose the electrode gel layers 108-1 , 108-2, so that the adhesive gel layers 110-1 , 110-2 does not cover the electrodes 104 and 106.

[0033] A method 400 of manufacturing the electrode unit 100 is now discussed with regard to FIG. 4. In step 402 (also illustrated in FIG. 5), a flexiblesubstrate 102 is provided. In one embodiment, any flexible plastic sheet can be used as a substrate provided good adhesion of silver nanowire ink onto the substrate. In this embodiment, a flexible 50 pm polyethylene terephthalate (PET) or 50 pm polyethylene naphthalate (PEN) plastic sheet was used as the substrate 102. In step 404, a silver nanowire ink is selected. The ink may be produced as follows. Ag NWs are synthesized by using a modified polyol method. Polyvinyl pyrrolidone (PVP) (Mw = 55,000, 0.8 g, Mw = 360,000, 0.8 g) was mixed in 200 mL of ethylene glycol (EG) and stirred until fully dissolved. Next, 2.1 g of AgNO3 (2 g) was added to the PVP solution. After complete dissolution, 30g of FeCla seed solution (0.6 mM in EG) was added to this mixture and stirred for a few minutes. Finally, the mixture was transferred to a round-bottom flask preheated at 120 °C. After 5 h, the heating was stopped, and the reaction mixture was allowed to cool down to room temperature. The Ag NWs were washed multiple times with acetone and finally left in acetone. The AgNW ink was prepared by adding 1 .5 g of PVP K120 (Mw = 2,000,000) to 27 g propanediol and 20 g ethanol and stirring at 600 rpm until dissolved. Finally, about 3 wt% AgNWs was added to the solution to obtain the ink.

[0034] A screen mesh with a mask containing the ECG electrode design was used to print in step 406 the AgNW ink on the flexible substraste, at a speed of 200 mm / s (see also FIG. 5). After the first printing cycle, an air dryer was used to dry the printed AgNW. In this embodiment, three printing cycles were used to print each of the electrodes 104 and 106. The microscopic structure of the electrodes 104 and 106 is shown in FIG. 5. The printed AgNW electrodes 104 and 106 were then dried, in step 408, at 80 °C for 10 min and then cooled. They were then immersed indeionized water for 30 min to remove the PVP and were then dried at 80 °C for 1 h. Next, the electrode gel layers 108-1 , 108-2 (e.g., Spectra 360 ECG electrode gel) were screen-printed in step 410 (see also FIG. 5) by aligning the AgNWs printed on the substrate 102 on the screen-printer. The electrode gel layers 108-1 , 108-2 were then used to cover the parts 104A and 106A of the printed electrodes 104 and 106. A high-tack silicone gel A4717 kit was used in step 412 (see also FIG. 5) to print the adhesive gel layers 110-1 , 110-2. Other types of gel material may be used for this step. For this specific silicone gel kit, parts A and B in the kit were mixed, and air bubbles were removed by using a vacuum desiccator. Then, the gel was ready for screen-printing. After alignment with the printed structures, the adhesive gel was screen-printed at a speed of 200 mm / s.

[0035] Next, the substrate 102 was cut in step 414 to a desired shape (see also FIG. 5), as shown in FIGs. 3A and 3B. Holes 104C and 106C were then formed through the electrodes 104 and 106 and through the substrate 102. Note that this step may be performed as soon as the electrodes 104 and 106 are made or at the end of the process. In one application, the through holes 104C and 106C extend only through the electrodes 104 and 106 and not through the substrate 102. Note that FIG. 5 shows, for simplicity, only half of the electrode unit 100. Also, in one embodiment, it is possible that the electrode unit 100 is not monolithic as illustrated in FIGs. 1 to 3C, but is actually made of two parts, a first part related to the first electrode 104 and a second part that is related to the second electrode 106, similar to what is shown in FIG. 5.

[0036] The Ag NW ink ensures that the electrodes 104 and 106 have high conductivity and that they can acquire a high-quality ECG signal. The electrode gel layers 108-1 , 108-2 were made of a material that reduces an electrical impedance at the point of contact with the skin and results in a high-quality ECG signal. The biocompatible adhesive gel material is selected to create a soft adhesion and easy release from the skin. The printed wet ECG electrode unit 100 is gentle on the skin, and it is easier to remove than typical commercial ECG electrodes and avoid skin damage or irritation. The wet ECG electrode unit 100 can be used in a 12-lead ECG systems and wearable wireless ECG readout device for health monitoring. Using the screen-printing method to fabricate the ECG electrode unit 100 results in low cost and the process can be scaled up for mass production.

[0037] To obtain an ECG signal quality (for the electrode unit 100) comparable to that of the commercial ECG electrodes, the inventors evaluated different electrode sizes and number of printed layers of the Ag NW ink. Increasing the diameter of the electrodes 104 and 106 from 7 mm to 14 mm and printing three layers of Ag NW ink (for each electrode 104 and 106) with a sheet resistance of 0.72±0.03 Q / sq achieved a reasonable ECG signal quality. Printing three layers of AgNW ink also achieved an interfacial impedance close to that of the commercial ECG electrodes and less than the impedances of the electrodes with one or two layers of Ag NWs. Thus, ECG electrode units 100 with three printed layers of Ag NW ink were used in all subsequent measurements.

[0038] To assess the effect of the electrode shape on the ECG signal quality, the inventors tested circular electrodes (as shown in FIG. 3A) with a diameter of 14mm and square electrodes (as shown in FIG. 3B) with a similar surface area. All characteristics of the ECG peaks (PQRST) appeared in all ECG signals, and the calculated peak heights (i.e. , amplitudes) showed that the electrode shape did not significantly affect the ECG signal. However, the square electrodes acquired a lower interfacial impedance than the circular electrodes, and they performed similarly to commercial electrodes. A low interfacial impedance is desired for obtaining a reliable and sensitive ECG signal. Thus, the square electrodes were used in the subsequent studies on single-lead wireless and 12-lead ECG systems.

[0039] The screen-printed ECG electrode units 100 were found to be gentle on the skin because they use a biocompatible adhesive gel (high-tack silicone gel A4717) that sticks well to the skin, which allows the electrodes to acquire a high- quality ECG signal while easily separating from the skin compared to commercial ECG electrodes. The inventors conducted a peel test to assess the ease of removing the printed ECG electrodes compared to the commercial ECG electrodes. The inventors found that the adhesion of the printed ECG electrode is sufficient to acquire the ECG signal, and require approximately 2.5 times less force during the peel test compared to the commercial ECG electrode. This demonstrates the gentle- to-skin and easy removal features of the printed ECG electrode unit 100. To assess the operational stability and reliability of the printed ECG electrode units 100, cyclic bending and twisting tests were conducted. The inventors found that the ECG signal remained unaffected even after 50,000 bending cycles and 24 hours of twisting, indicating the operational stability of the ECG electrode unit 100.

[0040] The screen-printed ECG electrode unit 100 is light in weight and uses less material than commercial wet ECG electrodes. On average, a printed-ECG electrode 104 or 106 uses 0.86±0.05 mg of silver nanowires as a conductive part, which is 265 times less metal than the commercial wet ECG electrode (227.72±2.48 mg of metal as a conductive part). In addition, the ECG electrode gel (2.57±0.47 mg) used in the screen-printed ECG electrode unit 100 is 176 times lighter than the commercial wet ECG electrode (453.73±43.55 mg). The screen-printing method 400 is versatile and the AgNW ink can be printed on different substrates such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and Polyimide (PI). The screen-printed electrode unit 100 is expected to be cheaper than the existing ECG electrodes. Hence, the screen-printed electrode unit 100 is expected to be made with a low-cost manufacturing at an industrial scale while being gentle on the skin.

[0041] As a complement to the screen-printed wet ECG electrode unit 100, the inventors have also developed a complete end-to-end ECG monitoring system 600 (see FIG. 6) that includes a miniaturized wireless readout device 610, a smartphone app 650 deployed on a mobile phone 652, and cloud server software installed on a cloud server 660 for storage and later analysis of collected ECG data. The ECG signal is acquired via the screen-printed electrode unit 100, which is directly attached to the human body. Then, the readout device 610 filters the signal for noise removal and then amplifies and digitizes the signal for Bluetooth Low Energy (BLE) transmission to the smartphone app 650. The smartphone app 650presents the ECG waveform to the user and sends it to the cloud server 660 for storage and possible post-processing in the future, such as with artificial intelligence.

[0042] The readout device 610 is shown in FIG. 6 including a filtering module 612, for example electrostatic discharge (ESD) filter for protecting the device against electrostatic discharge, and / or electromagnetic interference (EMI) filter for removing unwanted high-frequency noise. The filtering module 612 is connected to an amplifier 614 for amplifying the received signal. The received signal is then converted from analog to digital in an analog-to-digital converter 616 and the digital signal is supplied to a digital interface 618. The digital interface 618 serves as a port connection to another digital interface 620. The digital interface 620 is in communication with a processor 622 for processing the digital signal, and a memory 624 that stores a processing code (application code). The processor 622 is in communication with a bluetooth radio 626 that sends the processed signal, through an antenna package 628, to the application 650 stored in the phone 652. The readout device 610 further includes a power source 630, for example, a battery, but other devices may be used. The power supplied by the power source 630 is regulated by a power regulator 632 prior to being supplied to the elements of the readout device 610.

[0043] In one specific implementation, the miniaturized wireless readout device 610 was made of two components: an ECG data acquisition frontend (AFE) unit (elements 612 to 618 in FIG. 6) and a BLE transceiver (elements 620 to 626). The AFE acquired the ECG signal from the electrodes 104 and 106 and performed the initial filtering (bandpass filtering from 0.5 Hz to 28.35 Hz), amplification (20 V / V),and analog-to-digital conversion (128 samples per second, 18-bit samples). The digitized ECG signal was then stored in a memory buffer in the AFE, which was accessed by the BLE system-on-chip (SoC) over the serial peripheral interface. The BLE SoC acquired a digitized ECG signal from the memory buffer in the AFE and made it available for the smartphone app 650 using the BLE protocol. A Bluetooth virtual serial port was created over which data was transmitted to the smartphone app after a successful connection. The smartphone app 650 displayed the ECG data to the user and sent it to a cloud server 660 to be stored for later access or possible post-processing by a cardiologist or artificial intelligence models.

[0044] In one embodiment, the hardware of the ECG readout device 610 was designed on a four-layer printed circuit board (PCB) with a diameter of 1 .6 cm and thickness of 0.4 mm. Through, buried, and blind vias were used to fit all necessary routing within the available PCB area. To realize a seamless interface to the screen- printed electrodes 104 and 106, an innovative connection mechanism combining pogo pins (to be discussed with regard to FIG. 8) and a magnetic press device was designed (see also FIG. 7). Magnets 720A and 720B (see FIGs. 7 and 8) and screen-printed ECG electrodes 104 and 106 feature centric holes 104C and 106C at connection sites, which mate with circular poles (806-1 and 806-2) on the complementary part of the connector unit 710 for alignment and protection against slipping from the correct position. The size of the holes 104C and 106C and outside diameter of the poles 806-1 and 806-2 were matched.

[0045] FIG. 7 shows an actual implementation of the ECG system 600. Note that the ECG electrode unit 100 is attached with a magnet cap 720 to a connectingunit 710, the readout circuit 610 is attached to a base of the antenna package 628, and the readout circuit 610 is mechanically and functionally connected through a mechanical interface 730 to the connecting unit 710. In one embodiment, the antenna package 628 is shaped as a cylinder and the readout device 610 is shaped as a disk. The ECG system 600 shown in FIG. 7 is attached to the skin of the patient as a single unit. The ECG system 600 is configured to collect signals through the ECG electrode unit 100, partially process the signals in the readout circuit 610, and then transmit in a wireless manner, with the antenna package 628, the processed signals to a receiver, for example, a smartphone, a server, or a medical device within a medical facility. This means that the entire ECG system 600 is portable, wireless, and the ECG electrode unit 100 is disposable. After using the entire system 600 for a patient, it is possible to replace the ECG electrode unit 100 with a sterile one, and use the entire system 600 for another patient.

[0046] An exploded view of the ECG system 600 is illustrated in FIG. 8. The connecting unit 710 includes a pin mechanism board 802 and a base 810. The pin mechanism board 802 includes one set of pogo pins 804A for electrically connecting to the first electrode 104 and one set of pogo pins 804B for electrically connecting to the second electrode 106. Each of the set of pogo pins 804A and 804B may include one or more pogo pins. A pogo pin is known to include a pin that is biased by a spring. The pogo pins have one end on one face of the pin mechanism board 802 and another end on the opposite face of the pin mechanism board 802. The embodiment illustrated in FIG. 8 shows four pogo pins per set. However, fewer pogo pins may be used per set. The pogo pins are placed to directly face the electrodes104 and 106. The pogo pins extend through the pin mechanism board 802 (not visible in the figure), so that the back of the pogo pin may be connected to corresponding wires 730A and 730B that are removably attached to corresponding pins on the readout device 610.

[0047] A guiding pin 806-1 may be added to the pin mechanism board 802, facing the electrode unit 100, to receive the hole 104C for the first electrode 104 and a similar guiding pin 806-2 is also added to the pin mechanism board 802 for receiving the hole 106C for the second electrode 106. The guiding pins guide the electrode unit 100 relative to the connecting unit 710. The pogo pins 804A and 804B (four for each electrode are shown in the figure, but fewer or more may be used) are distributed around the guiding pins in this embodiment. To achieve a good electrical contact between the free part 104A of the electrode 104 and the pogo pins 804A, the magnetic cap 720 includes a first magnet 720A (and a second magnet 720B for the second electrode 106 and the pogo pins 804B) attached to a thin, flexible, transparent substrate 722. The magnets may have central holes 724 that are configured to fit on the corresponding guiding poles 806-1 and 806-2 so that they can press directly on the electrodes 104 and 106 against the pin mechanism board 802. In one embodiment, a distance between the holes 104C and 106C is the same as a distance between the guiding poles 806-1 and 806-2. In one embodiment, a line between the holes 104C and 106C coincides with the longitudinal axis X of the electrode unit 100. After the electrode unit 100 is placed over the guiding poles 806- 1 and 806-2, the magnetic cap 720 is placed over the electrode unit 100 to ensure that the electrodes 104 and 106 are secured (pressed against) to the pogo pins andgood electrical contact is achieved. The magnetic cap 720 also maintains the electrode unit 100 attached to the pin mechanism board 802.

[0048] The pin mechanism board 802 is configured to attach to the base 810. Both the base 810 and the pin mechanism board 802 may be made of plastic or another light, electrically insulating material. The base 810 includes two magnets 812A and 812B that are configured to magnetically attach (attract) to the magnets 720A and 720B, to hold the pin mechanism board 802 and the base 810 together, as a single unit, to form the connecting unit 710. This means that the magnet 720A’s north pole is facing the magnet 812A’s south pole and the same is true for the other pair of magnets. The magnets may be glued to the base 810.

[0049] FIG. 8 shows that the mechanical interface 730 of the readout device 610 is accommodated by the base 810, in a corresponding trench 814, which extends between the two magnets 812A and 812B. The electrical interface 730 may accommodate, on its back, the two wires 730A and 730B. The first wire 730A is configured to electrically connect to the first set of pogo pins 804A and the second wire 730B is configured to electrically connect to the second set of pogo pins 804B. The wires 730A and 730B are attached to the back of the pogo pins 804A and 804B, achieving an electrical connection between the electrode unit 100 and the readout device 610.

[0050] The ECG readout device 610 uses an electrically small antenna package 628 to overcome the challenges of achieving an adequate gain and bandwidth within a limited space. As shown in FIG. 9, the antenna package 628 configuration achieves dual functions, radiation and protection, and it utilizes theavailable space to mitigate size limitations. The antenna package 628 was specifically designed for on-body application, and its on-body performance was verified via simulation and measurements without the readout circuit 610. The antenna package 628 shown in FIG. 9 was completely fabricated by printing. However, the antenna package is not limited to this manufacturing method. Any known method may be used for making the antenna package. The substrate 902 was 3D printed, and the conductor 912 was printed with silver paste. Thus, the fabrication followed the concept of additive manufacturing to reduce material waste. A thickness of 0.5 mm for the substrate 902 gave the optimal balance between mechanical strength and dielectric loss. However, other numbers may be used for the thickness. Note that the substrate 902 has a hole 904 that is sized to receive the readout circuit 610. A thin cap 906 (only partially visible in the figure) was 3D-printed and installed under the ground plane 902 to protect the electronic chips on the exposed PCB during integration with the wireless ECG readout device 610. This cap 906 also helps maintain the proper distance between the antenna package 628 and the skin for stable performance. Four snap fits were used to integrate the thin cap 906 with the rest of the antenna package 628 and make it easy to remove and install. The cap 906 has a thickness of only about 0.5 mm, so it had a very slight effect on the antenna package radiation. A conductor 908 was manually printed with a mask. The conductor 908 provides the signal from the readout circuit 610 for being transmitted by the antenna. One or more shorting stubs 910 were also added to the antenna package for adjusting the frequency of the emitted signal. Parameters such as the height, power, and speed were optimized to obtain an accurate pattern width.Then, tape was wrapped around the antenna package 628 and a silver paste was printed afterward to form the radiating element 912. Then, the semi-finished sample was placed in an oven for 3 h at 70 °C to cure the silver paste. The optimal temperature was determined as 70 °C, which resulted in good conductivity and minimal damage to the substrate. After the silver paste was cured, conductive epoxy was used for mechanical fixing and electrical connections. A connector (not shown) was connected to the RF signal input 908 for measurements. A chip capacitor (not shown) was inserted in the sideline for impedance matching.

[0051] For testing the antenna’s performance, the entire antenna package 628 was placed on a volunteer’s chest, and the smartphone performed as a receiver in the forward direction, and the received power was recorded at different distances in the open area. The output power of the BLE chip 626 was set to be OdBm, and the received power was compared to a commercial chip antenna. The received power was approximately 11 dB larger than the commercial chip antenna. Because the sensitivity of the smart phone is -96 dBm, the communication range of the proposed antenna package 628 was estimated to be 142 m, which is 4 times longer than the commercial chip antenna.

[0052] The designed antenna package 628 is integrated with the ECG readout device 610 and an electrode interface (730A, 730B). The RF output of the readout device 610 and the coplanar waveguide (CPW) 908 of the antenna package 628 are connected by conductive epoxy. The front side of the antenna package 628 is open to allow for battery replacement, as illustrated in FIG. 10A. FIG. 10A also shows the radiating element 912 having a portion 912A that extends toward a central axis Z(also called a longitudinal axis) of the antenna package 628. The ground plane 902 is located underneath the radiator 912 to isolate the antenna 628 from the human body, to reduce the degeneration owing to the loss from the tissue, as well as protect the patient from electromagnetic radiation. FIG. 10B shows the readout circuit 610 being attached to the bottom of the antenna package 628 and electrically connected to the connecting unit 710.

[0053] The ECG monitor system 600 was tested on actual patients. ECG measurements were performed with adult volunteers to validate the practical applicability of the fully screen printed wet ECG electrode unit 100 and the readout device 610. The acquired data was compared to those of commercially available Ag / AgCI wet ECG electrodes. The wearable ECG monitor system 600 was evaluated under various scenarios, such as rest-exercise-rest, and over extended measurement intervals to assess its suitability for daily use. It was found that the wearable ECG system 600 accurately measures changes in the ECG during these scenarios. The volunteer's heart rate increased from 76 BPM, during the resting state, to a peak of 145 BPM, during exercise, and then returned to 80 BPM, during the subsequent resting state. It is noted that as the volunteer began walking and running on the treadmill, the noise in the ECG signal increased, primarily affecting the P and T peaks. However, the R peaks remained clearly visible, allowing for accurate heart rate measurements. This phenomenon occurs because, with the increase in speed (from rest to walking and running), the muscle movements generate stronger electromyography (EMG) signals compared to the ECG signal, leading to a baseline drift.

[0054] To validate the accuracy of the ECG system 600, the inventors also utilized a commercially available single-lead wireless ECG system, which also exhibited a baseline drift trend. This confirmed that the baseline drift was not an artifact of the electrodes 104 and 106 or the ECG readout circuit 610. Overall, the signal quality of the ECG system 600 was adequate to measure the heart rate of the volunteer during different scenarios.

[0055] For long-term measurements, an ECG signal was recorded for a volunteer for more than an hour while sitting in an office environment. Minor fluctuations in the ECG signal were observed; however, a high-quality ECG signal was obtained during this period where all ECG peaks (PQRST) can be identified clearly with an average heart rate of 73 BPM. Additionally, to compare the long-term usage and wearability of the ECG system 600 with the commercial wet ECG electrodes, both the printed wet ECG electrodes 104 and 106 and the commercial wet ECG electrodes were worn for 24 hours. The volunteer followed normal daily routine, including daytime activities and sleep, throughout this period. The ECG readings (not shown) obtained from both electrodes were measured during the 24- hour period. From the data, the inventors observed that after 16 hours of use, the performance of the commercial wet ECG electrode significantly degraded (approximately 30%) compared to the initial measurement at 0 hours.

[0056] In contrast, the screen-printed wet ECG electrode unit 100 demonstrated better performance, maintaining functionality until 20 hours (approximately 15% decrease in signal) compared to the commercial wet ECG electrode. Both electrodes showed a decrease in the R-peak value of approximately35% after 24 hours of wearability. This decline is attributed to the drying of the ECG electrode gel in both cases, caused by water vaporization from the hydrogels, leading to signal decay and noise in the ECG signal. However, the R-peak signal loss was slower in the case of the printed wet ECG electrode unit 100. Additionally, screen-printed wet ECG electrodes 104 and 106 showed no signs of irritation / rashes on the skin after 24 hours, unlike the commercial wet ECG electrodes, which indicates that these electrodes could be useful for monitoring purposes.

[0057] The smart and wearable ECG system 600 offers gentle-to-skin fully screen-printed wet ECG electrodes 104 and 106 and a more extended communication range, which are useful for monitoring the human heart. The acquired ECG data is wirelessly transmitted to a smartphone app and can be stored on a cloud server. The results of an adult volunteer study showed that the ECG electrodes 100 provide an easier-to-use option for ECG measurements and a similar ECG signal quality compared to the commercial ECG electrodes.

[0058] The antenna package 628 encases the readout device 610 and provides a longer wireless communication range than a commercial chip antenna. The gentle-to-skin wet ECG electrode units 100 were tested with a 12-lead ECG system. It was shown that the ECG electrode units 100 could be used in hospitals and detect abnormalities in the ECGs, such as early repolarization, short PR, and poor R wave progression, similar to the commercial ECG electrodes. The wet ECG electrode units 100 were fabricated by a screen-printing method, which has the potential to produce high-quality ECG electrodes at the industrial scale. This has thepotential to offer affordable and gentle to the skin ECG measurements for all age groups.

[0059] The term “about” is used in this application to mean a variation of up to 20% of the parameter characterized by this term.

[0060] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first object or step could be termed a second object or step, and, similarly, a second object or step could be termed a first object or step, without departing from the scope of the present disclosure. The first object or step, and the second object or step, are both, objects or steps, respectively, but they are not to be considered the same object or step.

[0061] The terminology used in the description herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used in this description and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or" as used herein refers to and encompasses any possible combinations of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Further, as used herein,the term "if" may be construed to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context.

[0062] The disclosed embodiments provide a miniature delivery system that has needles that directly attach to the human body for delivering a desired fluid. It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

[0063] Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.

[0064] This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

[0065] The entire content of all the publications listed herein is incorporated by reference in this patent application.[1] Kim, J. H.; Kim, S. R.; Kil, H. J.; Kim, Y. C.; Park, J. W. Highly Conformable, Transparent Electrodes for Epidermal Electronics. Nano Lett. 2018, 18, 4531-4540.[2] Liu, L.; Li, H. Y.; Fan, Y. J.; Chen, Y. H.; Kuang, S. Y.; Li, Z. B.; Wang, Z. L.; Zhu, G. Nanofiber-Reinforced Silver Nanowires Network as a Robust, Ultrathin, and Conformable Epidermal Electrode for Ambulatory Monitoring of Physiological Signals. Small 2019, 15. No. 1900755.[3] Kisannagar, R. R.; Jha, P.; Navalkar, A.; Maji, S. K.; Gupta, D. Fabrication of Silver Nanowire / Polydimethylsiloxane Dry Electrodes by a Vacuum Filtration Method for Electrophysiological Signal Monitoring. Acs Omega 2020, 5, 10260-10265.[4] Maithani, Y.; Choudhuri, B.; Mehta, B. R.; Singh, J. P. Self-adhesive, stretchable, and dry silver nanorods embedded polydimethylsiloxane biopotential electrodes for electrocardiography. Sensor Actuat. A-Phys. 2021 , 332, No. 113068.[5] Matsuhisa, N.; Kaltenbrunner, M.; Yokota, T.; Jinno, H.; Kuribara, K.; Sekitani, T.; Someya, T. Printable elastic conductors with a high conductivity for electronic textile applications. Nat. Commun. 2015, 6, No. 7461.[6] Sinha, S. K.; Noh, Y.; Reljin, N.; Treich, G. M.; Hajeb-Mohammadalipour, S.; Guo, Y.; Chong, K. H.; Sotzing, G. A. Screen-Printed PEDOT:PSS Electrodes on Commercial Finished Textiles for Electrocardiography. Acs AppL Mater. Inter. 2017, 9, 37524-37528.[7] Xu, X. W.; Liu, Z. F.; He, P.; Yang, J. L. Screen printed silver nanowire and graphene oxide hybrid transparent electrodes for long-term electrocardiography monitoring. J. Phys. D. AppL Phys. 2019, 52, No. 455401.[8] Huttunen, O. H.; Behfar, M. H.; Hiitola-Keinanen, J.; Hiltunen, J. Electronic Tattoo with Transferable Printed Electrodes and Interconnects for Wireless Electrophysiology Monitoring. Adv. Mater. Technol-Us 2022, 7, No. 2101496.[9] Chansaengsri, K.; Tunhoo, B.; Onlaor, K.; Thiwawong, T. Preparation of Conductive Screen-Printing Ink for High-Performance Bendable and Wearable ECG Electrodes on Fabric Substrates. IEEE Sens. J. 2022, 22, 23683-23691.

[0010] Z. Su; K. Klionovski; H. Liao; Li, W.; Shamim, a. A. A Fully-Printed 3D Antenna With 92% Quasi-Isotropic and 85% CP Coverage. IEEE Transactions on Antennas and Propagation 2022, 70, 7914-7922.

[0011] U.S. Patent Application no. US 2021 / 0324550 A1 .

[0012] U.S. Patent Application no. US10874854B2.

[0013] U.S. Patent Application no. US 2021 / 0236035 A1 .

[0014] Korean Patent Application no. KR20200113861 A.

[0015] U.S. Patent Application no. US 2021 / 0137381 A1.

[0016] International Patent Application no. WQ2020180186A1 WIPO.

[0017] U.S. Patent Application no. US 2021 / 0386379 A1 .

Claims

WHAT IS CLAIMED IS:1 . An electrode unit (100) for acquiring health related signals from a skin, the electrode unit (100) comprising: a flexible substrate (102); a first electrode (104) printed on the flexible substrate (102); a first electrode gel layer (108-1 ) printed on a first part (104A) of the first electrode (104); and a first adhesive gel layer (110-1) printed around the first electrode gel layer (108-1 ).

2. The electrode unit of Claim 1 , further comprising: a second electrode (106) printed on the flexible substrate (102); a second electrode gel layer (108-2) printed on a first part (106A) of the second electrode (106); and a second adhesive gel layer (110-2) printed around the second electrode gel layer (108-2).

3. The electrode unit of Claim 1 , wherein the first adhesive gel layer fully encloses the first electrode gel layer so that the first adhesive gel layer is partially on the first electrode.

4. The electrode unit of Claim 1 , wherein the first adhesive gel layer partially encloses the first electrode gel layer so that the first adhesive gel layer is not on the first electrode.

5. The electrode unit of Claim 1 , wherein a top surface of the first electrode gel layer is substantially flush with a top surface of the first adhesive gel layer.

6. The electrode unit of Claim 2, wherein the first and second electrodes extend along a same axis.

7. The electrode unit of Claim 1 , wherein the first electrode has a through hole on a corresponding second part, which is different from the first part, and the through hole extends through an entire thickness of the flexible substrate.

8. A portable and wireless monitoring system (600) for acquiring health related signals from a skin, the monitoring system (600) comprising: an electrode unit (100) configured to be directly attached to the skin to record a signal; a readout device (610) configured to process the signal; a connecting unit (710) physically and electrically connecting the electrode unit (100) to the readout device (610) through first and second pogo pins (804A, 804B); andan antenna package (628) electrically connected to the readout device (610) and configured to transmit a processed signal in a wireless manner, wherein the antenna package (628) is shaped to receive as a base the readout device (610).

9. The monitoring system of Claim 8, wherein the connecting unit comprises: a base (810) having first and second magnets (812A, 812B); a pin mechanism board (802) including the first and second pogo pins (804A, 804B) and first and second guiding poles (806-1 , 806-2); and a magnetic cap (720) having first and second magnets (720A, 720B) configured to engage the first and second magnets of the base.

10. The monitoring system of Claim 9, wherein the electrode unit comprises: a flexible substrate (102); a first electrode (104) printed on the flexible substrate (102); a first electrode gel layer (108-1 ) printed on a first part (104A) of the first electrode (104) a first adhesive gel layer (110-1 ) printed around the first electrode gel layer (108).1 1 . The monitoring system of Claim 10, wherein the electrode unit further comprises: a second electrode (106) printed on the flexible substrate (102);a second electrode gel layer (108-2) printed on a first part (106A) of the second electrode (106); and a second adhesive gel layer (110-2) printed around the second electrode gel layer (108-2).

12. The monitoring system of Claim 11 , wherein the first electrode has a through hole, which is sized to fit the first guiding pole and the second electrode has a through hole, which is sized to fit the second guiding pole.

13. The monitoring system of Claim 12, wherein a distance between the through hole of the first electrode and the through hole of the second electrode is equal to a distance between the first and second guiding poles.

14. The monitoring system of Claim 12, wherein a line between the through hole of the first electrode and the through hole of the second electrode is aligned with a longitudinal axis of the electrode unit.

15. The monitoring system of Claim 12, wherein the first electrode is electrically connected to the first pogo pin and the second electrode is electrically connected to the second pogo pin.

16. The monitoring system of Claim 14, wherein the electrode unit is sandwiched between the magnetic cap and the pin mechanism board and anelectrical interface of the readout device is sandwiched between the pin mechanism board and the base to electrically connect the first and second electrodes to a processor of the readout device.

17. The monitoring system of Claim 8, wherein the antenna package is shaped as a cylinder, the readout device is shaped as a disk, and the signal is an electrocardiogram signal.

18. A method (400) for screen-printing an electrode unit (100) for acquiring health related signals from a skin, the method (400) comprising: providing (402) a flexible substrate (102); screen-printing (406) an electrode (104) on the flexible substrate (102); screen-printing (410) an electrode gel layer (108-1 ) on a first part (104A) of the electrode (104); and screen-printing (412) an adhesive gel layer (110-1 ) around the electrode gel layer (108-1 ).

19. The method of Claim 18, wherein the adhesive gel layer fully encloses the electrode gel layer so that the adhesive gel layer is partially on the electrode.

20. The method of Claim 18, wherein the adhesive gel layer partially encloses the electrode gel layer so that the adhesive gel layer is not on the electrode.

Images