TECH

Elastic stopwatch brightens human skin

Flexible watch
Imagine a runner who does not have to carry a timer or cell phone to check his time: Just look at a brilliant timer on your wrist or the back of your hand.
These human-machine interfaces are no longer science fiction, but they still have a way to go before they become store-bought products.
A large portion of this journey has now been covered with the development of a flexible, stretchable light-emitting device that operates at low voltages, making it safe to stick to human skin.
Scientists have recently developed extensible light-emitting devices, called electroluminescent alternating current monitors, that can get stuck to the skin or other surfaces, such as a temporary tattoo. However, these monitors require relatively high voltages to achieve sufficient brightness, which can create safety concerns.
Now Desheng Kong and his colleagues at Nanjing University in China have developed an electroluminescent emitter that operates at lower voltages and is therefore safer for human skin.

Leather watch
The device consists of a sandwich with an electroluminescent layer made of light-emitting microparticles dispersed in an elastic dielectric material between two flexible silver nanowire electrodes.
The new dielectric material, in the form of ceramic nanoparticles embedded in a rubber type, was responsible for the increase in brightness compared to similar fabrics manufactured so far. The stretchy screen has shown itself to be bright enough to be seen under indoor lighting, but it needs to improve a little for those who enjoy running in the sun.
The team used this material to build a four-digit timer, which was assembled into a volunteer's hand for the first tests.
In addition to electronic tattoos, this release could find other applications in smart dressing technologies, light robotics, and human-machine interfaces, says the team.

Source: Stretchable High-Permittivity Nanocomposites for Epidermal Alternating-Current Electroluminescent Displays