Wearable ECG garment with seamless knitted sensors allows for continuous cardiac monitoring
Over the past few years, it has be exciting for Seamless Knitting Solutions (SKS) to be part of HealthWatch Technologies’ effort to develop the world’s first medical grade smart sensing garment. The goal was to design a wearable ECG garment with seamless knitted sensors that would allow for continuous cardiac monitoring. The project presented many technical knitting issues that were challenging, and ultimately, gratifying to help solve. The potential societal health benefits of this project and of the whole line of hWear digital garments are immense. hWear garments, now available in 3-15 lead ECGs versions for men and women, is part of HealthWatch’s larger vision to integrate comprehensive, continuous cardiac monitoring into everyday life. The hWear digital garments are machine washable and require no time-consuming shaving for a typical ECG – users simply ‘wear and forget’. Furthermore, HealthWatch’s proprietary technology enables automatic self-placement of electrodes, helping save valuable clinical time by removing the need for medical professional guidance. Many people have asked how I became involved in the continuous cardiac monitoring project, and since this project illustrates how many project engagements come about for SKS, I thought I would share its development with the knitting community. Many aspects of hWear digital garment’s development were unique to the field of medical technology, but other stages simply were part of SKS’s product development.
One evening back in 2014, I received a phone call from Mac Cheek, who was standing in a parking lot in Tel Aviv, Israel talking to some friends from a company called Health Watch Technologies. Mac said HealthWatch wanted to develop a wearable ECG vest (ECG or EKG*) with knitted ECG sensors. Mac, knowing I had extensive experience with knitted heart rate monitoring sensors from previous projects, told them that the Seamless Knitting Solutions (SKS) Lab was the place to develop the proof of concept garment.
To launch the proof of concept, I spoke briefly with them, and we planned to talk soon. The next day after a Non-Disclosure Agreement was signed, I received a call from Boaz Shoshani of HealthWatch Technologies, and we discussed the project in detail. The concept was to have a wearable garment with 13 knit-in electrodes that had knitted traces that led to a central portion, where a Bluetooth® transmitter could be plugged in. At the proof of concept stage, we are not sure how several steps will work. The first thing we needed to ascertain was, can one knit sensor read the electrical pulse from the heart beat? and if so, can we achieve an ECG quality signal? After this launch call and an understanding of the technical problem we were trying to solve, I began to make numerous sensors in different shapes, sizes, thickness, knit selections and yarns. I sent many sensors to Israel for ECG testing. Throughout the process, there were many tests done and many improvements made. After several months, we concluded that we could knit one sensor into a wearable garment and get an ECG quality signal.
Now, a new technical challenge was to knit thirteen ECG sensors into the garment to touch the skin in thirteen different places. We had to decide what size each individual sensor would be and the exact placement on the garment. We also had to knit traces to an area where snaps could be plugged into a Bluetooth® device.
After several more months, we had a wearable concept garment with thirteen knit-in sensors that also had knitted traces to an area with snaps to hook it directly to an ECG recording device. At this point in testing, HealthWatch Technologies sent Seamless Knitting Solutions a working ECG machine with a technical representative from HealthWatch. After several days of testing the garment in the SKS Lab and some minor changes, we had our proof of concept – a working ECG wearable prototype.
Yet, we were still far from done. Now that we knew the concept would work, we had an entirely new set of issues. After solving the initial technical challenge, we had to put some thought into the look and feel of the garment. In keeping with its goal to integrate continuous cardiac monitoring into everyday life, HealthWatch needed the garment to be nice-looking as well as functional. Furthermore, in order to keep the user from stretching or repositioning the ECG sensors, the company also required a zipper in front, so that the continuous cardiac monitoring garment didn’t have to be pulled over the wearer’s head. The final location for the Bluetooth® transmitter, as well as how it would be connected from the knit-in leads to the ECG sensors, were issues that took time to resolve. Another issue was ensuring that the knit-in leads to the sensors did not touch the body. With each of these challenges, Seamless Knitting Solutions was mindful that every specification developed in the Lab had to be practical in production. With 30 years of experience, there aren’t many seamless knitting challenges that I haven’t seen; but I can honestly say, this continuous cardiac monitoring project brought some new ones to my attention. It was enjoyable to work with HealthWatch Technologies to help develop this breakthrough garment for wearable sensing technology.
* EKG came from the German, Elektrokardiogramm (in English, electrocardiogram) as German physicians were pioneers in the field in the early part of the 20th century. AMA Style and American medical journals now refer to the ECG instead of EKG.