There is a paradigm shift in the way we provide healthcare, from curing to preventing to constant care, and from hospital-centered to patient-oriented health. We aspire to have medical technology that is not only accessible, accurate, and comfortable, but can also be functional anywhere and anytime to improve our health and wellbeing. There are currently two major classes of wearable electronics for healthcare: on-skin and textile electronics. Thin, soft and skin-like electronics in the form of a patch have been developed to monitor various physiological signals (e.g. electrophysiology, temperature, pulse oximetry, blood pressure, hydration, and others). However, they mostly have a soft, fragile nature, and require adhesive tape to laminate on the skin, restraining them from a long-term operation. They also require novel materials and micro-fabrication techniques to develop, making them relatively high-cost and challenging for mass manufacturing and large-scale deployment.

Textiles and clothing, on the other hand, are ubiquitous in daily life. We wear and wash them regularly, and they give us comfort and protection from the outside environments. Being the closest layer to our body, they provide an ideal  platform for sensing throughout dynamic activities and environments, where robustness and washability are critical as the substrate undergoes multiple stretching, friction, and is frequently exposed to dirts and humidity. With this, we have developed a technique of combining thin, customizable flexible-stretchable electronic devices including interconnected lines and off-the-shelf integrated circuits with plastic substrates that can be woven into knitted textile using an accessible and low-cost manufacturing approach. 

Similar to a compression garment, the nature of this electronic textile conformable suit (E-TeCS) will allow more intimate contact between electronics and the skin. In the end, we demonstrate the capability of this suit for distributed, wireless physiological and physical activity sensing, such as temperature, respiration, and heart-rate monitoring around the human body during various activities.

This project took a year to finish, starting in June 2018 at the MIT Media Lab. We were fortunate to be able to work in knitting and circuit factories in Shenzhen, China under the Media Lab's Research at Scale program.

The E-TeCS can detect skin temperature with an accuracy of 0.1°C and a precision of 0.01 °C, as well as heart-rate and respiration with a precision of 0.0012 m/s2 through mechanoacoustic inertial sensing. We integrated 31 sensor islands into the tailored bodysuit, including 30 temperature sensors spread across the upper-body region, and one accelerometer placed right below the sternum. We proposed a critical step in the design of high-performance e-textile suit, which is a compression garment patterning approach to ensure sufficient pressure (~25 mmHg) between all of the sensing points in our suit and the skin. This approach enables intimate sensor-skin contact and accurate sensor reading, while still maintaining overall comfortability.

Distributed skin temperature sensing has been widely used in sports science to evaluate athletic performance through thermoregulation efficiency, as well as to study the relationship between blood flow and skin temperature during intense physical exercise.

Skin temperature variations can also be used to inform the circadian phase, for the treatment of sleep disorders and jet lag. Another medical application of distributed skin temperature sensing is to indicate dermatome abnormality around the human body, which enables insights to symptoms caused by a regional nerve root damage. Most of skin temperature mapping involves IR cameras that limit the user movements and require the users to be naked. Our E-TeCS enables distributed skin temperature and other physiological sensing during dynamic activities and without the need to be naked. 

We have demonstrated a real case scenario at the gym, in which we tested E-TeCS on a subject and performed heart-rate, respiration, and temperature distribution sensing during intense physical exercise, and compare its temperature distribution performance with a commercial IR camera.

Yes, we have demonstrated the robustness of our approach with rigorous mechanical, breathability, and washability tests in a controlled environment to ensure acceptable characteristics towards proper end-use. Our test showed that the knit textile electronics can be stretched up to 30% under 1000 cycles of stretching without significant degradation in mechanical and electrical performance. We also performed cyclic washing tests (10 times), as well as demonstration, in which a textile electronic patch reads temperature and acceleration data continuously in real time while being washed in a washing machine. 

Due to the modular nature of our system, we can tailor the electronics to cover specific parts of the body. It is also straightforward to add any other available sensing modules to tackle other medical needs, such as humidity, pressure, optical, ultrasonic, gyroscope, gas, or magnetic field sensors. The multi-modal, multi-functional framework of E-TeCS would also enable a new strategy of personalized telemedicine for rapid prototyping and deployment, especially during extreme conditions such as pandemic or natural disaster relief efforts.

Several smart clothing products already exist in the market, with their specific functions and applications. We would need several years of further development to have this technology accessible and ready for use in clinics and at home, such as performing further system optimization and even more rigorous electromechanical and washability studies. 

Current on-skin sensors require wireless power transfer or batteries. The ones with near-field communication (NFC) readers require the sensors to be in the vicinity to power the electronics and collect sensor data. This method makes them challenging to be used while performing dynamic activities, which limit its applications outside the lab settings. Other wireless on-skin devices are integrated with batteries. However, having multiple devices with their independent power sources tend to be cumbersome when one needs to replace and charge every single device. These on-skin sensors are also somewhat reusable and not suitable for long-term operations. 

Our modular system-on-textile architecture and garment design approach enable the future realization of washable, comfortable, personalized-fit electronic textile bodysuits that could perform all or localized sensing needs. With E-TeCS, we only need to wear one garment as it already covers our whole body to perform spatiotemporal physiological and physical activity sensing.