The researchers from University of Texas at Austin (UT Austin) and Seoul National University presented their work on August 20, 2018 at the 256th National Meeting & Exposition of the American Chemical Society (ACS).
"This is the first demonstration that you can use few-layer graphene and molybdenum disulphide to successfully fabricate an artificial retina," said Nanshu Lu, an associate professor at UT Austin’s Cockrell School of Engineering. "Although this research is still in its infancy, it is a very exciting starting point for the use of these materials to restore vision.”
Located at the rear of the eye, the retina contains photoreceptor cells that convert incoming light into nerve signals that are sent to the brain via the optic nerve. Macular degeneration, diabetic retinopathy and retinitis pigmentosa can damage or destroy retinal tissue, leading to vision loss or complete blindness.
There is no cure for many of these diseases, but silicon-based retinal implants can restore a degree of vision to some individuals. According to Lu, these devices are rigid, flat and fragile, making it hard for them to replicate the natural curvature of the retina. Consequently, silicon-based retinal implants can produce blurred or distorted images and can cause long-term strain or damage to surrounding eye tissue.
Lu and her collaborator Dae-Hyeong Kim, PhD, from Seoul National University, have developed a thinner, more flexible alternative that better mimics the shape and function of a natural retina.
The researchers are said to have used graphene and molybdenum disulphide, plus thin layers of gold, alumina and silicon nitrate to create a flexible, high-density and curved sensor array. The device reportedly conforms to the size and shape of a natural retina without mechanically disturbing it.
In laboratory and animal studies, photodetectors on the device absorbed light and passed it through a soft external circuit board. The circuit board housed the electronics required to digitally process light, stimulate the 2D retina and acquire signals from the visual cortex.
Based on these studies, the researchers determined that this prototype artificial 2D retina is biocompatible and successfully mimics the structural features of the human eye.
Lu is now looking at ways to integrate this technology into mechanically and optically imperceptible electronic tattoos that are laminated on the skin surface to gather real-time health information.
She said the team plans to add transistors to these transparent e-tattoos to help amplify signals from the brain or the heart so they can be more easily monitored and treated. These ultrathin sensors and electrodes can also be implanted on the surface of the heart to detect arrhythmias. Lu said doctors could potentially program them to act like tiny pacemakers, sending electrical impulses through the heart to correct anomalies.
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