Wearable, Stretchable Memory Device Monitors Heart Rate

The device also improves on previous "wearable" monitors with higher memory performance, courtesy of gold nanoparticles.
After the stretchy monitoring device is assembled, the scientists transfer it to the skin like a sticker. | Jaemin Kim

Patients who need continuous heart rate monitoring could one day wear nothing more than an ultra-thin, stretchable, electronic device that easily laminates onto human skin like an adhesive sticker, suggests a new study appearing in the 1 January issue of the journal Science Advances.

In the past few years, several types of watches and bands designed to monitor heart rate and other health functions have popped up, yet the components of these devices cannot be used in situations that require extreme stretchability. In addition, there are often problems with the stability or efficiency of data storage in the watches and bands, and they typically do not get sufficiently close to the skin to detect heart rate with a high accuracy.

To address some of these issues, Dae-Hyeong Kim of Seoul National University and colleagues have designed a heart rate monitor that, unlike most wearable memory devices that are merely flexible, can sustain complicated mechanical deformations (or stretching) associated with movements a human wearer might perform.

"The technology in this work provides a new wearable platform for the flash memory and signal amplification devices that are important for continuous monitoring and data storage of a patient's healthcare information," said Kim.

The device also gets a memory performance boost, thanks to a touch of gold. The ultrathin circuit demonstrated in this study is made of a stretchable silicon membrane containing closely-packed gold nanoparticles, instead of more conventional conducting films. The gold nanoparticles have many advantages over the conventional films, including superb chemical stability and long-term memory storage.

The device consists of electrocardiogram (ECG) sensors and amplifiers that monitor heart rate while conforming to the skin, and contains heart rate and elapsed time data encoded in binary numbers, which can be subsequently converted to decimal numbers for readability.

Kim and colleagues show that their device can reliably store heart rate data obtained after exercise stress tests, as extracted from sample ECG signals. The heart rate data was retrieved and read again six hours later. The results hint at the possibility of using the stretchable circuit to design improved mobile and personalized health-monitoring devices.