Bendable LEDs as biomedical tattoos

U. ILLINOIS (US) — It may soon be possible to implant tiny light emitting diodes (LEDs) under the skin for a wide range of biomedical applications, including health monitors and drug delivery.

Advancements in biocompatible electronics have been challenging because current technology is tied to hard, rigid technologies such as the silicon wafers found in electronics devices, or because of the difficulty in integrating newer materials like carbon nanotubes into current manufacturing methods.

The materials used in the current research take advantage of an established semiconductor, gallium arsenide, and conventional metals to create flexible electronic circuits that work even when stretched repeatedly as much as 75 percent and when immersed in biological fluids.

The gallium arsenide and metal diodes and detectors are stamped onto a flexible plastic film; interconnecting coiled metal wires are deposited onto the plastic, creating a mesh-like structure that is then encapsulated in a piece of rubber.

The compatibility of the bendable, stretchable device with biological tissue opens up exciting new possibilities for its use in medicine, says John Rogers, professor of engineering at the University of Illinois.

Details of the research are published in Nature Materials.

“Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics,” the researchers write.

“Light-emitting sutures, implantable sheets and illuminated plasmonic crystals that are compatible with complete immersion in biofluids illustrate the suitability of these technologies for use in biomedicine.

“Waterproof optical-proximity-sensor tapes capable of conformal integration on curved surfaces of gloves and thin, refractive-index monitors wrapped on tubing for intravenous delivery systems demonstrate possibilities in robotics and clinical medicine.”

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