An artificial eye which is capable of being powered by sunlight could in due time, be used as a visual aid for people who have lost the privilege to see.
At the Hong Kong University of Science and Technology, Zhiyong Fan and his colleagues have developed a round visual sensor that looks more like the structure of the human eye. And just like the human eye, this artificial eye is made up of a lens to focus light. And it also has a hemispherical retina, the section at the back of the eye where photosensitive cells generate electrical impulses that are sent to the brain.
Just as an adult eye is about 2 centimeters in diameter and filled with a gel called vitreous humour, the artificial eye is precisely 2 centimeters in diameter but filled with a conductive fluid. Its retina is constructed from porous aluminium oxide filled with firmly packed nanowires. These wires are sensitive to light and are made from a compound known as perovskite, which is generally known to be used in solar cells. They act in the same way as the nerve cells in the human eye, transmitting electrical signals when they are triggered by light.
To test how well the artificial eye works, Zhiyong Fan and his team projected images of letters onto the lens. Without any problems, a computer connected to the eye was able recognised the letters E, I and Y. According to the team, this artificial eye could, as a matter of principle, be connected to an optic nerve to do the same, and also to test whether the device was medically safe to use in a real person.
Currently, the model of the eye requires an external power source, but the team are planning to make it self-sufficient in future.
“Each nanowire can function as a small solar cell. In that case, we don’t need any external power at all.” says Zhiyong Fan
The eye has yet another limitation though, it has a low image resolution compared with commercial sensors like the ones in smartphones. moreover, existing visual prosthetic devices uses a flat object for image sensing, which doesn’t conform to the spherical shape of the human eye, says Fan. For that reason, it limits the possible field of view compared with a human eye, which on a normal day has a field of vision of about 150 degrees.