A team of researchers from the United States, China, Korea, and Singapore have developed flexible ultra-thin sheets of inorganic light-emitting diodes (LEDs) and photodetectors for implanting under the skin. The flexible arrays measure 2.5 micrometers thick and 100 by 100 micrometers square, which is much smaller than any commercially available arrays.
The researchers printed circuits directly onto a rigid glass substrate, and then transferred them to a biocompatible polymer called poly dimethylsiloxane (PDMS) to create a mesh-like array of LEDs and photodetectors. The circuits can still function when the PDMS substrate is twisted or stretched by as much as 75 percent. The team also has encapsulated the flexible arrays in a thin layer of silicon rubber to make them waterproof, and they can function when implanted or completely immersed in biofluids.
The flexible LEDs could be implanted under the skin for a variety of biomedical uses.
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