Scientists from United States and Hong Kong have built a “bionic eye’ that mimics a human eye in shape and function. This super human eye technology, with high imaging resolution, will be ready for integration into medical robots to take care of patients. It will even cater to the visually impaired when the researchers find suitable bio-compatible materials.
The research paper for this technology is published in the journal Nature.
Human eyes possess exceptional image-sensing characteristics such as an extremely wide field of view, high resolution and sensitivity with low aberration. Biomimetic eyes with such characteristics are highly desirable, especially in robotics and visual prostheses. However, the spherical shape and the retina of the biological eye pose an enormous fabrication challenge for biomimetic devices.
The researchers created an electrochemical eye with a hemispherical retina made of a high-density array of nanowires mimicking the photoreceptors on a human retina. The device design has a high degree of structural similarity to a human eye with the potential to achieve high imaging resolution when individual nanowires are electrically addressed. Additionally, the researchers demonstrate the image-sensing function of their biomimetic device by reconstructing the optical patterns projected onto the device. This work may lead to biomimetic photosensing devices that could find use in a wide spectrum of technological applications.
Biological eyes are arguably the most important sensing organ for most of the animals on this planet. In fact, our brains acquire more than 80% of information about our surroundings via our eyes. A human eye with a concavely hemispherical retina and light-management components is particularly notable for its exceptional characteristics including a wide field of view (FOV) , a high resolution and excellent adaptivity to the optical environment.
Particularly, the domed shape of the retina has the merit of reducing the complexity of optical systems by directly compensating the aberration from the curved focal plane. Mimicking human eyes, artificial vision systems are just as essential in autonomous technologies such as robotics. Particularly for humanoid robots, the vision system should resemble that of a human in appearance to enable amicable human–robot interaction, in addition to having superior device characteristics. In principle, a hemispherical image sensor design mimicking that of the human retina can achieve this goal. However, commercial charge-coupled device (CCD) and complementary-metal-oxide-semiconductor (CMOS) image sensors are mainly using planar device structures shaped by mainstream planar microfabrication processes, making hemispherical device fabrication almost impossible.
The researchers demonstrate an artificial visual system using a spherical biomimetic electrochemical eye (EC-EYE) with a hemispherical retina made of a high-density perovskite nanowire array grown using a vapour-phase approach. An ionic liquid electrolyte was used as a front-side common contact to the nanowires and liquid-metal wires were used as back contacts to the nanowire photosensors, mimicking human nerve fibres behind the retina. Device characterizations show that the EC-EYE has a high responsivity, a reasonable response speed, a low detection limit and a wide field of view. The EC-EYE also demonstrates the basic function of a human eye to acquire image patterns. In addition to its structural similarity with a human eye, the hemispherical artificial retina has a nanowire density much higher than that of photoreceptors in a human retina and can thus potentially achieve higher image resolution, which is bolstered by implementation of a single-nanowire ultrasmall photodetector.
News Source: Nature
