Light-emitting diodes (LEDs) are all around us in the form of lighting, remote control devices and sensors, and soon they may be inside the human body.
Beckman Institute researcher John Rogers has been a pioneer in developing novel technologies, including electronics that can be stretched or integrated with silk, that have potential uses in consumer devices and, increasingly for Rogers, in biomedicine. Rogers, a member of Beckman’s 3-D Micro- and Nanosystems group, and his collaborators are now reporting on an implantable technology composed of inorganic LED semiconductors and photodetectors that is flexible and bio-compatible, ideal qualities for biomedical uses such as health monitors or in drug delivery. They detail their work in a recent paper in Nature Materials titled Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics.
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 by Rogers and his collaborators take advantage of an established semiconductor, gallium arsenide (GaAs), 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 GaAs 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, as the researchers write in their paper: “Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. … 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.”