Flexible LEDs for implanting under the skin

Flexible LEDs for implanting under the skin: "The research, led by John Rogers of the University of Illinois at Urbana-Champaign in the US, and published today in Nature Materials developed flexible arrays 2.5 μm thick and 100 x 100 μm square, which is much smaller than any commercially available array. They printed circuits directly onto a rigid glass substrate and then transferred them to an inexpensive biocompatible polymer called poly(dimethylsiloxane) (PDMS) to create a mesh-like array of LEDs and photodetectors.
The PDMS substrate is flexible enough that the circuits can still function even if twisted or stretched by even as much as 75 percent. Rogers said most research has concentrated on organic LEDs (OLEDs), which are extremely sensitive to water and oxygen, but the flexible arrays are encapsulated in a thin layer of silicon rubber, which makes them waterproof and allows them to function well when implanted or completely immersed in biofluids. The design also eliminates the mechanical constraints normally imposed on such devices by the inflexible semiconductor wafers that support them."