Chinese scientists have developed artificial eyes based on the hemisphere's retina

, an artificial eyeball reportedly integrates dense nanoscale light sensors into a component similar to a hem spherical retina. Some of its sensory abilities are comparable to its biological rivals.Robots with artificial eyes and bionic eyes connected to the human brain to restore blind vision are common in science fiction. A lot of effort has been put into developing this device, but making spherical human eyes -- especially the hexal retina -- is a huge challenge, severely limiting the function of artificial and bionic eyes. In a paper published recently in the journal Nature, Fan Zhiyong of the Hong Kong University of Science and Technology reported on an innovative, concave hemomethic retina consisting of a series of nanoscale light sensors (photoreceptors) that mimic photoreceptor cells in the human retina. The researchers applied the retina to electrochemical eyes, which have as many functions as the human eye and are able to accomplish the basic function of obtaining image patterns.The retina of the human eye is heme spherical, and its optical layout is more refined than that of a flat image sensor in the camera: the dome-like shape of the retina naturally reduces the amount of light transmitted through the lens, making the focus sharper. The core component of Fan Zhiyong's team's bionic electrochemical eye is an array of high-density photosensitive elements for the retina. The photosensitive element is formed directly in the pores of the alumina hemispheric membrane (Al2O3).Thin soft wires made of liquid metals (cocrystalline palladium-indium alloys) are sealed in hoses and transmit signals from nanowire light sensors to external circuits for signal processing. These wires simulate the nerve fibers that connect the human eye and brain. A layer of palladium between the liquid metal wire and the nanowire improves the electrical contact between the two. The artificial retina is secured by a socket made of silicone resin to ensure proper alignment between the wire and the nanowire.Lenses combined with artificial irises are placed at the front of the device as if they were in the human eye. The rear retina is combined with the front hexal shell to form a spherical cavity ("eyeball"); The chamber is filled with an ionic liquid that mimics the glass body -- a gel that fills the space between the human eye crystal and the retina. This arrangement is necessary for electrochemical operation of nanowires. The overall structure of the artificial eye and the human eye is similar, which gives the device a wide field of view of 100 degrees. In contrast, the vertical field of view of the static human eye is approximately 130 degrees.The artificial eye's structural imitation is impressive, but what really stands out from previously reported devices is that many of its sensory abilities are pretty good compared to natural eyes. For example, artificial retinas can detect a wide range of light intensity, ranging from 0.3 microwatts to 50 milliwatts per square centimeter. At the lowest intensity measured, each nanowire in the artificial retina detects an average of 86 photons per second, comparable to the sensitivity of human retinal photoreceptotic cells. This sensitivity comes from the calcium-titanium ore material used to make nanowires. Calcium-titanium compounds are promising materials for a wide range of photoelectronics and photon applications. The calcium-titanium ore used by thelead iodized salt, which was chosen for its excellent photoelectrelectrelectrient properties and good stability.The response rate of the nanowires (measuring the current generated per watt of incident light) is almost identical to the frequency of all visible spectra. In addition, when the nanowire array is stimulated by a regular fast pulse, it can generate an current that responds to the pulse within 19.2 milliseconds and then recovers (back to inactive) at the end of the pulse in just 23.9 milliseconds. Reaction and recovery times are important parameters because they ultimately determine the speed at which artificial eyeballs react to light signals. For comparison, human retinal photoresponsive cells react and recover between 40 and 150 milliseconds.Perhaps most impressive is the high-resolution imaging of this artificial retina, which is due to the high density of nanowire arrays. In previous artificial retinas, photoreceptors were first made on a flat, hard substrate; This limits the density of the imager units because there must be space between them for transmission or folding.In contrast, the nanowires in the new device are formed directly on the surface, allowing them to bind more closely together. In fact, nanowires have a density of up to 4.6 million cm-2, which is much higher than the optical receptors on the human retina (about 100,000 cm-2). Signals from each nanowire can be obtained individually, but the pixels in the current device are made up of three or four nanowires.Bridging the gap between artificial vision andthe overall performance of this artificial eye represents a leap forward for such devices, but much remains to be done. First of all, the photoelectric sensor array is currently only 10 × 10 pixels, the difference between pixels is about 200 -? m; This means that the light detection area is only 2 mm wide. In addition, the manufacturing process involves expensive and low-volume steps - for example, researchers use an expensive process called focused ion beam etching to prepare holes for the formation of each nanowire. In the future, high-volume manufacturing methods must be developed to significantly reduce costs and produce larger photosensitive component arrays.Second, in order to improve the resolution and size of the retina, the size of the liquid metal wire needs to be reduced. The outer diameter of the wire is about 700 um, but this should be equivalent to the diameter of the nanowire (a few microns). The challenge now is to reduce the diameter of the liquid wire to this size.Third, more tests are needed to determine the life of the artificial retina. The researchers reported no significant decline in performance after nine hours of operation, but the performance of other electrochemical devices declined over time. Finally, the authors note that their devices have less response and recovery time at the higher concentration of ionic liquids, but at the cost of light transmission in the liquid. In order to solve this problem, the composition of ion-liquid needs to be further optimized.Still, the work adds another to the breakthroughs of the past few decades, not only by imitating camera-like eyes, such as those of humans, but also by imitating insect-like eyes. Given these advances, it seems likely that we will witness the widespread use of artificial and bionic eyes in everyday life over the next decade. (Bio Valley Bioon .com)