WO2023085961A1

WO2023085961A1 - Protective facce mask comprising a capacitive sensor with embroidered silver plated polyamide electrodes and sensitive polyester layer

Info

Publication number: WO2023085961A1
Application number: PCT/RS2022/000009
Authority: WO
Inventors: Goran Stojanovic; Milan Radovanovic; Ankita Sinha; Mitar SIMIC; Adrianos STAVRAKIS
Original assignee: Faculty Of Technical Sciences, University Of Novi Sad
Priority date: 2021-11-12
Filing date: 2022-05-30
Publication date: 2023-05-19
Also published as: RS20211394A1

Abstract

Face mask with embroidered sensor (101) with an interdigitated capacitor made by stitching of a silver-coated polyamide conductive thread on a modern embroidery machine. A disposable face mask (100) was used as the base on which the sensor was made. After making the sensor on the embroidery machine, a sensitive layer (102) is applied in between the sensor structure. This sensitive layer (103) allows the measurement of changes in humidity or temperature difference in inhaled and exhaled air. The appearance of the mask on the face of the user 104 and the position of the sensor when using the mask with the embroidered sensor are shown in fig. 1. Two different non-conductive threads were used to make the sensitive layer, based on spun polyester and extrusion-based polyester.

Description

PROTECTIVE FACCE MASK COMPRISING A CAPACITIVE SENSOR WITH EMBROIDERED SILVER PLATED POLYAMIDE ELECTRODES AND SENSITIVE POLYESTER LAYER

Technical field

The invention belongs to the field of arrangement for application in medical sciences and diagnostics. The designation is according to the International Patent Classification (IPC) is: A61B 5/6803, A61H 33/12, G16Z 99/00, GOIN 33/48.

Background art

In recent years, we have witnessed a pandemic of COVID-19, which has imposed the mass and daily use of protective face masks that all citizens over the age of 10 are obliged to wear indoors. However, why should masks only serve to protect against virus transmission? Within the scope of this patent, we propose a way to enrich the mask with smart sensors, so that the mask could be used as a diagnostic tool for the detection of many parameters and bacteria or viruses from our breath. This patent proposes a new design, fabrication and characterization of a capacitive sensor on face masks whereby the electrodes are embroidered with silver-coated polyamide thread. As we breathe, the capacitance of this sensor changes, and a correlation can be established between the breath parameters we want to measure and thus key user health parameters can be identified.

The invention relates to the production of a capacitive sensor, embroidered on a face mask where a conductive silver-coated polyamide thread is used to make the sensor.

State of the art

Sensors are among the most commonly used electronic components, starting with the automotive and aerospace industries, and are increasingly used in medicine to measure a growing number of health parameters crucial for monitoring the condition of both sick and healthy people. The corona-virus pandemic has imposed the use of face masks indoors and in some countries outdoors. This mass use of masks leads to the idea of installing certain sensors that would collect information from the user's breath, such as respiratory rate, which in addition to being an important indicator for characterizing health, is also a reliable indicator for determining anaerobic threshold (AP), also known as lactate threshold, in athletes. AP is defined as the highest level of exercise that can be maintained without inducing metabolic acidosis; this level is strongly associated with athletic performance. In most clinical settings (e.g. hospital emergency rooms), respiratory rate is usually measured by observing the patient from a distance and counting inhalations and exhalations. Although this method is simple, it is subjective and provides little data. It is also challenging and impractical to visually monitor individual patients for extended periods of time. There are however, dedicated biomedical instruments which accurately monitor respiratory rate. These instruments typically use sound, airflow, and chest movement, with airflow being the most commonly used in clinics. A temperature sensor is usually used as an auxiliary for detection, because exhaled air is usually warmer than inhaled air, and a cyclic change in temperature can be converted and associated with respiratory rate.

The main innovative steps within this patent are:

1. Determining key breath parameters

2. Capacitive sensor design for use on protective masks

3. Fabrication of capacitive sensors using a embrodery machine

4. Application of a sensitive layer or non-conductive thread in the space between the electrodes of the capacitive sensor

5. Characterization and testing of electrical properties of sensors

By connecting this capacitive sensor to conventional electronics, data related to breathing can be transferred to a smartphone or tablet for post-processing, and then optionally to the cloud. This reading tool provides a new, practical method of recording and analyzing breathing patterns.

The degree of innovation of the invention is reflected in the realization of a completely new capacitive and mechanically flexible sensor by embroidery technique where the use of a silver coated polyamide thread actually realizes the structure of the comb capacitor. After applying the sensitive layer, an innovative sensor for measuring breath parameters was obtained.

The following scientific papers are some of the presented solutions for making face masks with sensors.

Scientific paper: (1) B. Ghatak, S. Banerjee, S. Babar Ali, R. Bandyopadhyay, N. Das, D, Mandal, B. Tudu, "Design of a Self-powered Smart Mask for COVID-19", https://arxiv.org/abs/2005.08305, which describes a face mask that uses a textile triboelectric nanogenerator (TENG) to filter SARS-CoV-2. The proposed mask is designed with multiple protection sheets, in which the first two layers act as a triboelectric (TE) filter, and the outside is a smart filter. This smart mask can be used by many people due to its simple, self-propelled mechanism (collects mechanical energy from everyday activities such as breathing, talking or other facial movements, and efficient filtration, so it is expected to be potentially useful for slowing the devastating impact of COVID-19. The key difference from our invention is that only air filtration is performed here without any measurements.

Scientific paper: (2) Z. Gao, Z. Lou, S. Chen, L. Li, K. Jiang, Z. Fu, W. Han, G. Shen, "Fiber gas sensor- integrated smart face mask for room temperature distinguishing of target gases", NanoResearch, 2018, 11 (1), pp. 511-519, https://doi.org/10.1007/sl2274-017-1661-9. - This paper describes flexible gas sensors developed with carbon nanotubes (SWCNT), multilayer carbon nanotubes (MWCNT) and ZnO sensitive elements SWCNT (SWCNT s @ ZnO). By integrating these flexible gas sensors into face masks, the produced smart face masks could be used for selective detection of C₂H₅OH, HCHO and NH₃. Such face masks have great potential application. This realization of face masks with integrated sensors has a different application and a different fabrication technique compared to the sensors in our invention.

The following patents / patent applications represent some of the protected, known face mask enrichment solutions with sensors, for various applications.

Patent application CN201610031766.5A published on 18 January 2016 under the title "Power respiration mask with sensor" describes an invention which belongs to the technical field of masks, and in particular relates to masks for protection and measurement of air quality. The mask consists of a breathing mask body, an air supply valve, an air exhaust valve ,an air quality sensor and a controller. The air supply valve is equipped with a fan, and the fan and sensor are connected to the controller and that is subsequently connected to the battery. In addition, the controller is wirelessly connected to a receiver that is mobile, portable and independent of the mask body. The breather mask with controller can simultaneously meet the requirements for comfort, safety and high efficiency, and makes it convenient for the user to have information about the degree of environmental pollution in which the user is located. The main difference compared to our invention is that the sensor is used to measure the amount of air pollution, while in our invention the sensor is used to measure the number of inhalations and exhalations. CN105476116A - Power respiration mask with sensor - Google Patents

U.S. Patent No. 4,875,4777 July 9, 1987, entitled "Safety face mask with integrated sensor for monitoring live functions", describes a breathing mask with an integrated sensor for monitoring vital functions. No additional, possibly interfering aids intended for its installation are required to attach the sensor. For this purpose, the sensor is placed on the inside of the breathing mask. The difference from our invention is that a breathing aid mask is used here in which at least one sensor is placed, while our proposed sensor is placed on a standard face mask.

US4875477A - Protective mask having a built-in sensor for monitoring vital functions - Google Patents

Patent US20040163648A1 published on October 16, 1999, entitled "Bio-mask with integral sensors" describes a gas mask with accompanying monitoring and control devices. This patent presents a device for monitoring a patient with sleep, breathing or post-anesthesia disorders. Several different sensors are placed on the mask, such as blood oxygen sensor, patient position sensor, eye movement sensor, leak sensor, EEG, EMG, EOG, ECG, PTT, microphones, pulse, blood pressure, temperature, light sensors and sensors for gas delivery. Another application enables the delivery of gas to the biomass, which is partially controlled by communication, from the pacemaker to the biomass controller. The present invention is similar to ours in the respiratory monitoring segment, the main difference being our flexible embroidered sensor.

US20040163648A1 - Bio-mask with integral sensors - Google Patents Patent US20020162556A1, issued May 7, 2001, entitled "Face mask incorporating respiratory flow sensor", describes a face mask with the addition of a respiratory monitoring sensor, and consists of a flexible mask made of a stretch fabric, such as spandex (artificial stretch fabric), which is designed to allow the installation of a flow measuring instrument or sensor in a way that does not require the instrument, i.e.. the sensor to be placed in the user's mouth, but it is still close to the user's mouth allowing accurate measurement. The main difference in relation to our invention is the sensor, which in our case was made with a new connection technique.

US20020162556A1 - Face mask incorporating respiratory flow sensor - Google Patents

Exposition of the essence of the invention

The invention is based on the fabrication or production of an interdigital capacitive sensor using the bonding technique, using a silver-plated polyamide thread on a professional embroidery machine. The next step in this invention is to apply a sensitive layer between the conductive electrodes, from a thread that is non-conductive. As a substrate on which the sensor is fabricated, standard disposable protective face masks were used, which are easily accessible and quite cheap. The design of the electrodes of the interdigital capacitive sensor was realized in a professional design program, after which the file was digitized into stitch code and then was transferred to the embroidery machine where the functional structure of the planar interdigital capacitor was obtained by utilizing a conductive thread. In order to increase the sensitivity of the sensor, non-conductive threads of different degrees of adsorption were embroidered between these electrodes, to form a sensitive layer. The next step was to characterize and test the proposed structure.

The use of embroidery machines for the production of electronic components is a cheap technique for prototyping in the field of textile electronics. The embroidery machine used to make the sensor is quite sophisticated and can handle non-standard threads such as in our case the silver-plated polyamide conductive one. Its proprietary software allows for adjustments in the design shape and stitch density. However, firstly, the desired structure is designed in one of the commonly available computer aided design (CAD) programs, which in our case is a comb capacitor. Here, based on the dimensions of the face mask, the dimension of the capacitor electrodes is determined, then the width of the conductive segments and the distance between them. The next step is to transfer the CAD file to the embroidery machine stitch calculator program, where the stitching mode, density and other important connection parameters are set. After that, the face mask is placed on the embroidery holder and positioned, followed by the creation of the desired structure by the embroidery machine. Lastly, aside from the interdigitated capacitor, a sensing layer is embroidered in between the design fingers, which completes the production of the embroidered sensor on the face mask. Brief description of the figures of the invention

The following figures complete the description of the invention:

Figure 1: Shows the design of the embroidered sensor on the face mask and the sensitive layer

Figure 2: Shows the measured values of the capacitance of the sensor depending on the frequency for different percentage values of relative humidity

Figure 3: Shows the measured values of the change in capacitance of silver-coated polyamide thread over time for different moisture values

Detailed description of the invention

The essence of the invention relates to the realization of a capacitive sensor in the form of interdigitated electrodes, by utilizing a silver-coated polyamide thread and a sophisticated embroidery machine, and subsequently apply a non-conductive thread-based sensing layer in between the capacitor fingers. The structure was designed in a design program, after which it was transferred to a program for adjusting connection parameters, where all parameters can be adjusted very precisely, the density of connections or conductive thread, the distance between each needle stitch, etc. After that, a sensitive layer of thread is applied, which enables the measurement of moisture from our exhalation or the difference in exhaled air and inhaled air, or the concentration of various parameters from our breath.

The connection technique is a cheap technique in the new field of textile electronics. This technique is actually a standard connection technique using a sophisticated computer-controlled embroidery machine. In addition, in order to make a conductive structure with the connection technique, it is necessary to use a thread that has conductive threads in it, in our case, a thread with silver threads was used. Our proposed innovation shows for the first time the production of a mechanically flexible capacitive sensor on a standard, disposable face mask. The whole technique of making an embroidered sensor on a face mask involves making a comb condenser in a short period of time (less than 15 minutes) and in conditions that do not require a clean room and using expensive fabrication techniques.

Figure 1 shows a comb condenser that is embroidered on a standard face mask using an embroidery machine. A standard disposable face mask 100 was used for the base, ie the base on which the sensor was made, while the sensor structure is an interdigital comb capacitor 101 made by the connection technique on a soft embroidery machine, using a special thread with silver threads. This sensor is exported from the inside and its dimensions are determined by the dimensions of one strip of this protective mask (in the unstretched state). This embroidered layer does not interfere with the normal and usual stretching of the mask over the entire face when used. Also, in the specific application, it does not significantly increase the price of the mask, because the thread used is cheap and the material is present. After making the sensor on the binding machine, a sensitive layer 102 is applied, also by connecting different types of non-conductive thread depending on the parameter that is to be detected from our breath. Figure 1 also shows a graphical appearance 103 of the sensitive layer, which allows the measurement of humidity and the difference between the capacity of the inhaled and exhaled air. The appearance of the mask on the face of the user 104 and the position of the sensor when using the mask with the embroidered sensor are also shown.

The size and number of conductive electrodes of the comb capacitive sensor can be changed in accordance with the desired values we want to achieve, but the size of the face mask must be taken into account, which is the limiting factor here. By changing or increasing the surface of the conductive segments as well as the length of the fingers of the interdigital capacitor, we directly affect the increase in the capacitance of the structure, which ultimately results in greater sensitivity of the sensor.

After the component was realized by the binding machine, its testing was performed by measuring the capacitance as a function of frequency for different values of relative humidity using (Figure 2) HIOKI Chemical Impedance Analyzer IM 3590. Based on the graphs it can be concluded that the sensor structure has excellent sensitivity to changes in humidity, ie that changes in capacitance at lower frequencies with a change in humidity are very pronounced, while at higher frequencies this value decreases. The value of humidity varied in the range from 28% RH to 78% RH, while the value of capacitance varied from some 100 pF to more than 20,000 pF, from which it can be concluded that the sensor has excellent sensitivity.

Figure 3 shows the change in capacitance of the sensor structure at a constant frequency of 1 kHz, for two different types of non-conducting thread used as a sensitive layer to obtain different sensitivities.

Method of industrial or other application of the invention

The present invention involves the realization of a capacitive sensor structure on a face mask that is widely used, and as such, the present invention can find wide application primarily in medicine and diagnostics as well as in sports medicine.

In addition to its use for medical purposes, the present invention could also be used by athletes to measure some basic body parameters during training and exercise. By simply connecting to the electronics, it is possible to implement a smart application that would display all the important parameters on a phone screen, the number of inhalations and exhalations per minute, the difference between the temperature of inhaled and exhaled air, etc.

Claims

Patent claims:

1. Capacitive sensor 101 characterized by the technique of connections made of silver-plated polyamide conductive thread on a disposable protective face mask

2. Sensitive sensor layer 102, characterized in that a non-conductive thread is affixed between the electrodes of the comb capacitor

3. Application of two types of non-conductive thread (spun polyester and regular extrusion-based polyester) characterized in that they are used as a sensitive layer 102

4. Application of embroidered sensor on face mask 104 characterized in that the change in capacitance 201 for different humidity from our breath can be measured as parameter 202

5. Good change in capacitance increased from 4.20 pF to 10 pF for relative humidity changes from 28% to 78% for non-conductive spun polyester 301 thread

6. A good change in capacitance characterized by an increase from 3.81 pF to 7.73 pF in the case of using the extrusion-based polyester non-conductive thread as a sensitive layer 302, if the percentage of relative humidity varies from 36% to 74%.

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