Seulki Lee, Researcher, Holst Centre/imec08.24.16
Most people are familiar with smart watches, but what about smart clothing? Can this attire be accurate enough for doctors to monitor their chronic patients in daily life? And can it also be fashionable and comfortable? The answer is a resounding yes. Take a look at the recent prototype of the first loose-fit medical-grade ECG T-shirt developed at Holst Centre/imec.
A Smart Watch or a Smart T-Shirt?
Wearable technology that measures body parameters (e.g., heart rate, heart rate variability, body temperature, activity levels, etc.) has become increasingly popular in recent years. Among several wearable technologies, the wristband or smart watch is the most popular platform to be used for the fitness field. It can measure heart rate and activity level, and therefore, energy expenditure of the user. It has several drawbacks, however, for use in medical applications, such as the limited types of bio-signal modality. For example, electrocardiogram cannot be measured in those form factors—only heart rate is available. In addition, it is very prone to the motion of the hand, which will degrade the signal quality significantly.
On the other hand, a smart garment is the ideal platform since a person covers most of his or her body with clothing for virtually every occasion. Measurement location is, therefore, not limited to specific body parts, and it can be used at any time and in any place.
Smart Compression Shirts Available Today
Sensory clothing that is on the market today is mainly focused on athletes and fitness applications. Most of these compression shirts measure the heart rate and acceleration of the body, and sends the data to the wearer’s smart phone. But some of them also measure the electrocardiogram and/or respiration. The main challenge in the smart garment is to have a loose fit while also maintaining good signal quality. With the current technology, good signal quality with a dry electrode is only possible when the shirt is very tight to the skin. This is the reason they are in the compression shirts form factor and only being used in sports applications.
A Loose-Fit ECG T-Shirt
In Holst Centre/imec (Netherlands), smart garments that can deliver medical grade data through looser fit, every day clothes are being developed. The t-shirt can monitor various bio-signals such as electrocardiogram, real respiration, and activities performed, and extract information such as heart rate, heart rate variability, breathing rate, breathing volume, and calories burned. It shares the data and information over the cloud via a smart phone, tablet, or PC. The t-shirt combines flexible smart fabric interconnect technology and ultra-low power miniaturized electronics.
Small, Low-Power Electronics
The ultra-low power miniaturized electronics are integrated into the form factor of an extended SD card. The electronics contain imec’s high accuracy, ultra-low power, multi-sensor data acquisition chip (MUSEIC), which can measure three channels of electrocardiogram, two channels of bio-impedance, and one channel of acceleration. With the signals obtained, its embedded processors can extract and calculate the features based on imec’s robust signal processing algorithm. The total size of the electronics module is only 1.5 cm (W) x 2.0 cm (L) x 2.0 mm (H), and it weighs only 7 grams including the battery. Since the technology is extremely small and lightweight, the user doesn’t notice the presence of the electronics any differently from other products on the market. In addition, the power consumption of the electronics is very low, enabling a wearer to be continuously monitored without recharging a battery. This functionality will enable medical applications that require longer monitoring time beyond sports applications to leverage the technology.
Unique Interconnect Technology
The flexible, stretchable interconnect technology preserves the original properties of the fabric. In other words, the t-shirts remain flexible, stretchable, breathable, lightweight, and washable. It also gives the complete freedom in placing sensors, actuators, and electronics to ensure the highest data quality. An important part of the research is dedicated to find the best locations for the electrodes. The best location is the one that combines good data quality with a comfortable fit. The electrodes used are dry Ag/AgCl electrodes. So no gel is required to make good contact with the body. There is some height added in the electrode area to have better skin contact while having a loose fit. All steps for producing these smart garments, including the lamination and interconnect technology, are fully compatible with the most standard material production processes and conventional textile manufacturing processes.
As Good as Conventional Monitoring
Currently, the t-shirts have been tested with healthy volunteers who do not have any cardiac or pulmonary diseases. While wearing the t-shirts, bio-signals of the wearer were recorded and sent to the cloud to be processed further. After applying the signal processing techniques, features such as heart rate and heart rate variability from electrocardiogram, and respiration rate and volume from bio-impedance can be achieved. Acquired data shows high correlation result with the reference devices, which means that the smart garment can substitute the existing devices with better comfort and are more suitable for longer-term monitoring.
Seulki Lee received her B.S., M.S., and Ph.D. degrees from KAIST, Daejeon, South Korea, in 2007, 2009, and 2012 respectively, all in electrical engineering. Her research focused on low power IC design and wearable system development for wearable body area network, such as for a sleep monitoring system. In March 2012, she joined the Holst Centre/imec in The Netherlands as a researcher with the Body Area Network (BAN) team, and has been working on wearable healthcare applications, mainly using a bio-impedance platform. Smart garment activity is one of her research interests as it is a promising platform to enable convenient healthcare monitoring in everyday life.
A Smart Watch or a Smart T-Shirt?
Wearable technology that measures body parameters (e.g., heart rate, heart rate variability, body temperature, activity levels, etc.) has become increasingly popular in recent years. Among several wearable technologies, the wristband or smart watch is the most popular platform to be used for the fitness field. It can measure heart rate and activity level, and therefore, energy expenditure of the user. It has several drawbacks, however, for use in medical applications, such as the limited types of bio-signal modality. For example, electrocardiogram cannot be measured in those form factors—only heart rate is available. In addition, it is very prone to the motion of the hand, which will degrade the signal quality significantly.
On the other hand, a smart garment is the ideal platform since a person covers most of his or her body with clothing for virtually every occasion. Measurement location is, therefore, not limited to specific body parts, and it can be used at any time and in any place.
Smart Compression Shirts Available Today
Sensory clothing that is on the market today is mainly focused on athletes and fitness applications. Most of these compression shirts measure the heart rate and acceleration of the body, and sends the data to the wearer’s smart phone. But some of them also measure the electrocardiogram and/or respiration. The main challenge in the smart garment is to have a loose fit while also maintaining good signal quality. With the current technology, good signal quality with a dry electrode is only possible when the shirt is very tight to the skin. This is the reason they are in the compression shirts form factor and only being used in sports applications.
A Loose-Fit ECG T-Shirt
In Holst Centre/imec (Netherlands), smart garments that can deliver medical grade data through looser fit, every day clothes are being developed. The t-shirt can monitor various bio-signals such as electrocardiogram, real respiration, and activities performed, and extract information such as heart rate, heart rate variability, breathing rate, breathing volume, and calories burned. It shares the data and information over the cloud via a smart phone, tablet, or PC. The t-shirt combines flexible smart fabric interconnect technology and ultra-low power miniaturized electronics.
Small, Low-Power Electronics
The ultra-low power miniaturized electronics are integrated into the form factor of an extended SD card. The electronics contain imec’s high accuracy, ultra-low power, multi-sensor data acquisition chip (MUSEIC), which can measure three channels of electrocardiogram, two channels of bio-impedance, and one channel of acceleration. With the signals obtained, its embedded processors can extract and calculate the features based on imec’s robust signal processing algorithm. The total size of the electronics module is only 1.5 cm (W) x 2.0 cm (L) x 2.0 mm (H), and it weighs only 7 grams including the battery. Since the technology is extremely small and lightweight, the user doesn’t notice the presence of the electronics any differently from other products on the market. In addition, the power consumption of the electronics is very low, enabling a wearer to be continuously monitored without recharging a battery. This functionality will enable medical applications that require longer monitoring time beyond sports applications to leverage the technology.
Unique Interconnect Technology
The flexible, stretchable interconnect technology preserves the original properties of the fabric. In other words, the t-shirts remain flexible, stretchable, breathable, lightweight, and washable. It also gives the complete freedom in placing sensors, actuators, and electronics to ensure the highest data quality. An important part of the research is dedicated to find the best locations for the electrodes. The best location is the one that combines good data quality with a comfortable fit. The electrodes used are dry Ag/AgCl electrodes. So no gel is required to make good contact with the body. There is some height added in the electrode area to have better skin contact while having a loose fit. All steps for producing these smart garments, including the lamination and interconnect technology, are fully compatible with the most standard material production processes and conventional textile manufacturing processes.
As Good as Conventional Monitoring
Currently, the t-shirts have been tested with healthy volunteers who do not have any cardiac or pulmonary diseases. While wearing the t-shirts, bio-signals of the wearer were recorded and sent to the cloud to be processed further. After applying the signal processing techniques, features such as heart rate and heart rate variability from electrocardiogram, and respiration rate and volume from bio-impedance can be achieved. Acquired data shows high correlation result with the reference devices, which means that the smart garment can substitute the existing devices with better comfort and are more suitable for longer-term monitoring.
Seulki Lee received her B.S., M.S., and Ph.D. degrees from KAIST, Daejeon, South Korea, in 2007, 2009, and 2012 respectively, all in electrical engineering. Her research focused on low power IC design and wearable system development for wearable body area network, such as for a sleep monitoring system. In March 2012, she joined the Holst Centre/imec in The Netherlands as a researcher with the Body Area Network (BAN) team, and has been working on wearable healthcare applications, mainly using a bio-impedance platform. Smart garment activity is one of her research interests as it is a promising platform to enable convenient healthcare monitoring in everyday life.