In what may be either the most discreet or the most conspicuous of wearable electronics, a team of researchers led by Desheng Kong of Nanjing University has developed a prototype stretchable stopwatch sticker that can be adhered to the back of a person's hand. Using nanotechnology, the new timepiece is not only bright enough to read in indoor light but runs at voltages low enough to be safe for human skin.
Electronic stickers or temporary tattoos, aren't new. Such technology has a wide range of potential applications, especially in the medical field, but Alternating-Current Electroluminescent (ACEL) displays that have been recently developed leave much to be desired. This is because for such devices to be bright enough to be practical, they have to operate at voltages that could be hazardous next to human skin.
To make a stopwatch sticker that's a bit less shocking, Desheng's team sandwiched an electroluminescent layer consisting of light-emitting microparticles set in a stretchable dielectric material between two flexible silver nanowire electrodes. But the clever bit is that the dielectric material is made of ceramic nanoparticles embedded in a rubbery polymer. These have the property of concentrating the electric field on the phosphor, making it light up much brighter at much lower voltages.
So far, the four-digit stopwatch sticker has been tried out on a volunteer's hand and is bright enough to be seen in indoor lighting conditions. The hope is that the technology could one day find applications in soft robotics and human-machine interfaces.
The research was published in ACS Materials Letters.
Source: American Chemical Society