Over the past year, wearable consumer electrocardiogram (ECG/EKG) devices have become more commonplace thanks to the introduction of the Apple Watch Series 4, but that’s not the final word in heart monitoring — measurements can become more accurate and continuous with sensors mounted elsewhere on your body. Now researchers at the University of Texas at Austin have developed a light, thin, and stretchable “electronic tattoo” that can be worn over your heart, simultaneously creating ECG and seismocardiograph (SCG) readings.

While lead researcher Nanshu Lu has been working on so-called e-tattoos for years, her team’s major new innovation has enabled a typically rigid SCG sensor to become super thin and stretchable, contouring to the wearer’s chest. The e-tattoos aren’t thick patches, instead using a conductive plastic material named polyvinylidene fluoride to achieve mere 28-micrometer thinness — that’s 0.028 millimeters.

The combined ECG and SCG sensor enables the reading of both heartbeats and associated chest movements. Just as a seismograph detects vibrations in the earth, the seismocardiograph detects vibrations in the chest, and can be precisely positioned directly above the heart for stronger readings. “We can get much greater insight into heart health by the synchronous collection of data from both sources,” explained Lu, compared with only ECGs.

Lu’s system is smartphone-powered and can continuously monitor the wearer’s heart for days at a time; a prototype app can track and even display heart data in real time. No tape is needed to keep the e-tattoo on a chest, where it occupies a 63.5mm by 38.1mm space, using a serpentine mesh pattern.

For the time being, the researchers are working on enhancing the tattoo’s ability to gather and store data independently, as well as ways to keep it powered wirelessly for extended periods. Assuming those issues can be solved, classic sticky chest electrodes and even cutting-edge consumer ECG devices could soon become too bulky and cumbersome to consider wearing for heart monitoring purposes.