A wearable, ultra-thin and stretchable device that can provide continuous heart rate monitoring has been created by scientists using gold nanoparticles. The device was created by scientists in South Korea, who showed it could be used to reliably store heart-rate data – meaning one day it could improve personal and mobile health-monitoring systems.

Current devices used by people who need continuous monitoring include watches and bands, but these are problematic as they cannot be used in certain situations. The researchers, publishing their findings in the journal Science Advances, wrote: "Rapid developments in wearable electronics have led to an urgent demand for deformable electronic devices ... Most deformable memory devices reported so far, however, are just flexible. These kinds of memory devices are not compatible with wearable applications that require complicated modes of mechanical deformations such as stretching."

The team say, however, that they have managed to develop a fully-stretchable, wearable memory array, and a video of it being created shows the process – and the end product. The circuit is made from a stretchable silicon membrane containing very tightly-packed gold nanoparticles.

These particles are more stable and are better for long-term memory storage. On top of this, the device has ECG sensors and amplifiers that can be used to monitor heart rate while stuck on the skin. In the study, the authors showed how the device could be used to store heart rate data after an exercise stress test reliably.

"The advances in characterization and fabrication technologies reported in this paper will be an important stepping stone that will pave the way to a fully-integrated wearable system composed of the stretchable nanocrystal FG [floating gate] memory and other stretchable Si electronics toward mobile and personalised health monitoring," they wrote.