Wearable contactless respiration sensor based on multi-material fibers integrated into textile

In this paper, we report on a novel sensor for the contactless monitoring of the respiration rate, made from multi-material fibers arranged in the form of spiral antenna (2.45 GHz central frequency). High flexibility of the used composite metal-glass-polymer fibers permits their integration into a cotton t-shirt without compromising comfort or restricting movement of the user. At the same time, change of the antenna geometry, due to the chest expansion and the displacement of the air volume in the lungs, is found to cause a significant shift of the antenna operational frequency, thus allowing respiration detection. In contrast with many current solutions, respiration is detected without attachment of the electrodes of any kind to the user’s body, neither direct contact of the fiber with the skin is required. Respiration patterns for two male volunteers were recorded with the help of a sensor prototype integrated into standard cotton t-shirt in sitting, standing, and lying scenarios. The typical measured frequency shift for the deep and shallow breathing was found to be in the range 120–200 MHz and 10–15 MHz, respectively. The same spiral fiber antenna is also shown to be suitable for short-range wireless communication, thus allowing respiration data transmission, for example, via the Bluetooth protocol, to mobile handheld devices

A Novel smart jacket for blood pressure measurement based on shape memory alloys

Smart textiles with medical applications offer the possibility of continuous and non-invasively monitoring which benefit patients and doctors. To measure blood pressure in premature infants a miniature actuator that can be sewn to the fabric is required. For this reason, an actuator based on shape memory alloys has been designed so that it compresses as a conventional air cuff but with 3.5W power consumption and can be controlled by applying different Pulse-Width Modulation (PWM) signals, thus offering several levels of compression. In addition, the first concept prototype of the smart jacket is achieved; made of a natural fiber fabric that incorporates: an optical sensor, a capacitive pressure sensor with great accuracy, the force actuator and a Lilypad Simblee control board which can be sewn to the fabric, is washable and has a Low Energy Bluetooh module (BBE) to connect to other devices. All this allows the systolic, diastolic and cardiac pressure to be measured for the first time in the world with the smart jacket by a semi-occlusive method. Altogether with a mobile application which allows doctors to monitor the patient at every moment, perform remote control, data measurement and recording in a comfortable and intuitive way that satisfies the necessity for a better clinical management to the growing number of patients and is a source of savings for the clinical services

Development of Form-Fitted Body-Worn Force Sensors for Space and Terrestrial Applications

University of Minnesota M.S. thesis. December 2016. Major: Design, Housing and Apparel. Advisor: Lucy Dunne. 1 computer file (PDF); iv, 137 pages.Sensing force on the body is useful in the design of many on-body systems, including gas-pressurized space suits, for design diagnostics (e.g., determining where an on-body system is exerting potentially dangerous amounts of force) and for in-use monitoring. Mechanical Counter-Pressure (MCP) space suits have advantages over gas suits, and are an example of where measuring on-body force would be necessary. The development of an unobtrusive and practical means of measuring force in an MCP suit has yet to be established. Reasons for the absence of an established method for force-sensing within an MCP suit lie in the difficulties associated with integrating a force sensor, unobtrusively, into the under-layers of the user’s garment. If the sensor introduces pressure points (e.g., is rigid or bulky), it will potentially cause harm to the user. This thesis describes the process of developing a soft and unobtrusive force sensor that avoids the use of a stiff apparatus. Specifically, the criteria for sensor selection and initial characterization of a variety of candidate sensor configurations when exposed to an applied load will be discussed. This thesis focuses on three experiments that were performed. The first experiment featured a commercial piezoresistive flex sensor as well as a custom coverstitched stretch sensor that were adapted to respond to normal forces and evaluated in a laboratory compression test. The flex sensor response displayed considerable noise, particularly evident in recovery artifacts when the load was fully removed from the sensor. The coverstitch sensor, on the other hand, had a more consistent, linear response in relation to the load being applied. Based on the findings and analysis of the first test, a second experiment was performed to examine the accuracy and performance of different lengths and widths of the coverstitched stretch sensor. The findings concluded that the thin 2’’ coverstitched sensor displayed the most promising results in terms of overall correlation with applied load and standard deviation between trials in relation to the other coverstitched samples that were tested. The final experiment extended the findings from the second experiment to test two different support structure substrates, rubber and silicone, each implemented in a topography of small hemispheres in varying size (small-diameter hemispheres, medium-diameter hemispheres, large-diameter hemispheres, and a flat topography). The results of the third experiment showed promise for the flat topography, which exhibited the strongest correlation between sensor response and applied load for both elastomer rubber and silicone substrate materials. Results were less favorable for the more extreme large-diameter hemisphere topography, which exhibited a weaker correlation indicating the larger the diameter the hemisphere was in the substrate material, the weaker the correlation between the load being applied to the sensor that was overlaid on the substrate material and the sensor’s response (resistance readings). The development of an unobtrusive, form-fitted stretch sensor that measures force is a significant step forward for MCP suit design and controllability, as well as for many other domains in which sensing forces on the body is important. The results of this thesis study illustrate the difficulties associated with implementing a flex sensor onto a pliable surface. Additionally, this thesis study illustrates the potential that the coverstitched stretch sensor has for force-sensing applications

Textile-Based Sensors and Smart Clothing System for Respiratory Monitoring

Long-term respiratory monitoring provides valuable information for diagnostic and clinical treatment. Traditional measures of respiration require a mouthpiece or a mask, neither of which can be used as ubiquitous healthcare equipment. Using a smart clothing system seems to be a better alternative. Researchers in the field of smart textiles have focused on the development of health-related products since the 1990s, and textile-based sensors used for respiratory measurements have been discussed in several projects. Although the soft and flexible characteristics of textile-based sensors make them attractive, the flexibility of the materials also affects the signal quality. In a laboratory situation, where each sensor is tested as a single element, this is not as critical as in a user situation, where the sensor is integrated into the clothing and worn by different users engaging in different activities. The principal objective of this thesis was to explore the possibility of performing reliable respiratory monitoring using a clothing platform. The research began by investigating the possible methods and materials that can be used to produce textile-based sensors for respiratory monitoring applications. The aim was to determine the most suitable method for integrating the sensing function into the clothing system. Study results have shown that sensors made with a conductive coating demonstrated superior performance in terms of sensitivity, stability, and reliability. Therefore, five prototype systems based on conductive coating technique were developed. Sensor placement, signal collection techniques, and the clothing system configuration were the main concerns, while issues related to the sensor wearability, maintenance, and aesthetic appearance, as well as the environment and health, were also discussed. Knitting was found to be the most economical method for producing the textile-based sensors; however, sensors made of knit fabric do not perform as well as the coated ones. Therefore, elastic-conductive hybrid yarns have been created to improve the electro-mechanical properties of knitted-based sensors, and eventually, a prototype with two sensors and a built-in data-bus was made by fully-fashion knitting technique. Two smart clothing system prototypes, based on conductive coating technique, were tested systematically by ten subjects. The first prototype consisted of one sensing element, and the results show that the smart clothing system could successfully monitor the subjects’ breathing patterns during sitting, standing, and different forms of running. The system has also proven to be useful in the observation of sleep apnea disorder symptoms. The second prototype consisted of two sensing elements. Apart from all the characteristics of the first prototype system, a system with two sensing elements can be used to determine the relationship between the rib cage and abdomen compartments, which provides information for certain diseases, e.g., cardiac arrhythmias. The second smart clothing system prototype was compared with a conventional respiratory belt for validation. Signals from the clothing system and the respiratory belt were collected simultaneously with a self-designed LabVIEW program, and further processed with MATLAB. Quantitative analyses were conducted based upon different comparison techniques, such as Pearson’s correlation, ANOVA and Fast Fourier Transform analysis. The results demonstrate that the smart clothing system can provide reliable respiratory measurements, with signals of comparable quality to the conventional respiratory belt. In addition, the wearability and user acceptance were studied by means of a survey. The survey results indicate that users were more comfortable with the smart clothing system and that most believe that using a smart clothing system will improve both health condition and quality of life

Textile-Based Sensors and Smart Clothing System for Respiratory Monitoring

Long-term respiratory monitoring provides valuable information for diagnostic and clinical treatment. Traditional measures of respiration require a mouthpiece or a mask, neither of which can be used as ubiquitous healthcare equipment. Using a smart clothing system seems to be a better alternative. Researchers in the field of smart textiles have focused on the development of health-related products since the 1990s, and textile-based sensors used for respiratory measurements have been discussed in several projects. Although the soft and flexible characteristics of textile-based sensors make them attractive, the flexibility of the materials also affects the signal quality. In a laboratory situation, where each sensor is tested as a single element, this is not as critical as in a user situation, where the sensor is integrated into the clothing and worn by different users engaging in different activities. The principal objective of this thesis was to explore the possibility of performing reliable respiratory monitoring using a clothing platform. The research began by investigating the possible methods and materials that can be used to produce textile-based sensors for respiratory monitoring applications. The aim was to determine the most suitable method for integrating the sensing function into the clothing system. Study results have shown that sensors made with a conductive coating demonstrated superior performance in terms of sensitivity, stability, and reliability. Therefore, five prototype systems based on conductive coating technique were developed. Sensor placement, signal collection techniques, and the clothing system configuration were the main concerns, while issues related to the sensor wearability, maintenance, and aesthetic appearance, as well as the environment and health, were also discussed. Knitting was found to be the most economical method for producing the textile-based sensors; however, sensors made of knit fabric do not perform as well as the coated ones. Therefore, elastic-conductive hybrid yarns have been created to improve the electro-mechanical properties of knitted-based sensors, and eventually, a prototype with two sensors and a built-in data-bus was made by fully-fashion knitting technique. Two smart clothing system prototypes, based on conductive coating technique, were tested systematically by ten subjects. The first prototype consisted of one sensing element, and the results show that the smart clothing system could successfully monitor the subjects’ breathing patterns during sitting, standing, and different forms of running. The system has also proven to be useful in the observation of sleep apnea disorder symptoms. The second prototype consisted of two sensing elements. Apart from all the characteristics of the first prototype system, a system with two sensing elements can be used to determine the relationship between the rib cage and abdomen compartments, which provides information for certain diseases, e.g., cardiac arrhythmias. The second smart clothing system prototype was compared with a conventional respiratory belt for validation. Signals from the clothing system and the respiratory belt were collected simultaneously with a self-designed LabVIEW program, and further processed with MATLAB. Quantitative analyses were conducted based upon different comparison techniques, such as Pearson’s correlation, ANOVA and Fast Fourier Transform analysis. The results demonstrate that the smart clothing system can provide reliable respiratory measurements, with signals of comparable quality to the conventional respiratory belt. In addition, the wearability and user acceptance were studied by means of a survey. The survey results indicate that users were more comfortable with the smart clothing system and that most believe that using a smart clothing system will improve both health condition and quality of life