The increasing prevalence of ocular diseases and severe ocular injuries has increased the demand for artificial eyes worldwide. However, current prosthetic eyes cannot restore vision. Scientists have now created a biomimetic, electrochemical bionic eye with image detection functionality.
The human eye is nature at its best. Due to its spherical shape and hemispherical photosensitive retina, a highly specialized and refined instrument is an extreme manufacturing challenge for biomimetic devices.
The human brain obtains over 80% of its environmental information from the eyes. The human eye has a wide field of vision of 150 to 160 degrees, excellent resolution, and great sensitivity to light, mainly due to the cloudy shape of the retina (above the flat image sensors of the cameras) and its vast number of cellular photoreceptors (about ten million per square centimeter). The creation of artificial bionic eyes that mimic these features is of particular interest in the field of robotics and the development of prosthetic optical devices.
Artificial Eye-Technical characteristics
The new artificial electrochemical eye includes a hemispherical retina made of aluminum oxide, which contains a dense arrangement of many photosensitive sensors from perovskite in its pores. This promising material has begun to be used in the new solar panels. These sensors mimic photoreceptor cells in the human retina. Very thin and flexible nanowires of liquid metal with a diameter of 700 micrometers (millionths of a meter), which mimic the nerves that connect the human eye to the brain, transmit the signals of artificial photoreceptors to an external electronic circuit (the “brain”) to process them. The synthetic retina at the back of the artificial eye and the lens and an artificial iris at the front of the device are surrounded by a silicone polymer, forming a spherical bulb filled with a liquid gel between the retina and lens, as in the human eye. So far, the biomimetic eye has a low resolution, as it contains only 100 pixels (each pixel has three or four nanowires), while its field of view has a range of 100 degrees, i.e., smaller than the human. It can also detect light at intensities of 0.3 microwatts to 50 milliwatts per square centimeter. Each nanowire of the artificial retina detects an average of 86 photons per second, having a sensitivity proportional to the photoreceptors of the human retina.
3D Technical Eye
The world’s first 3D artificial eye with capabilities beyond those of existing bionic eyes and, in some cases, even human eyes was developed by an international team of scientists at Hong Kong University of Technology (HKUST), raising new hopes for visually impaired patients.
Scientists have been trying for decades to reproduce the structure and sharpness of the biological eye. However, the vision provided by existing prosthetic eyes – mainly in external wired lenses – is still low-resolution, with 2D, flat image sensors. The Electrochemical Eye (EC-Eye) developed at HKUST, however, not only reproduces the structure of the natural eye for the first time but may also provide better vision than the human eye in the future, with additional features such as infrared detection in the dark.
Electrochemical Eye (EC-Eye)
The “key” element that gives the EC-Eye such capabilities is its 3D retina, which is made of an array of nanosensors made from nanowires that mimic human retinal photoreceptors. This 3D retina was developed by Professor Ziyong Fan and Dr. Leiley Guo of the Department of Electronics and Computer Engineering at HKUST.
The researchers connected the nanosensors from nanowires to liquid metal cables that acted as nerves behind the artificial hemispherical retina they created. They could copy the transmission of the visual signal to reflect what the eye saw on a computer screen. In the future, nanowire light sensors can connect directly to the nerves of patients with visual impairments.
The theory behind the new artificial eye
The theory behind the new artificial eye is based on an electrochemical process adopted by a type of solar cell. Theoretically, any artificial retina photosensor can function as a nano-solar cell. With some further modifications, the EC-Eye can become an image sensor that will be self-powered without needing an external power source. This is expected to make it much easier to use compared to existing artificial light sensors used in visually impaired people.