Bioinspired electronic eye offers simple solution

Bio-inspired electronic eye based on an all-solution-processed transparent retina. (Top left) Schematic illustration of the electronic eye based on a fully transparent retina. Inset shows the transparent retina attached on an eyeball model. (Top right) Optical transmission spectra of the transparent retina. (Bottom left) Schematic illustration of transparent retina perceiving UV light from all directions. (Bottom right) Reconstructed images of letter ‘E’ and ‘·’ captured by an electronic eye prototype. The numbers 0–25 represent plane space location of the sensing units. The color bar represents the greyscale values.

The simple and compact hemispherical eyes of living organisms offer inspiration for next-generation imaging systems. But fabricating artificial hemispherical electronic eyes is challenging using conventional processing methods. Now researchers report a straightforward solution-based route for fabricating bio-mimicking electronic eyes [Gao et al., Materials Today (2023), https://doi.org/10.1016/j.mattod.2023.06.004].

“Currently, extreme processing routes for electronic eye devices, requiring high temperature and vacuum conditions, significantly limit applications,” explains Zhan Gao of City University of Hong Kong. “We wanted to come up with a low-cost, facile process.”

Together with coworkers at Hong Kong Centre for Cerebro-Cardiovascular Health Engineering and The Chinese University of Hong Kong, the team led by Hua Zhang, Zhiyuan Zeng, and Xinge Yu developed an electronic eye system featuring a fully transparent artificial retina fabricated using a room temperature solution-based method.

“By our all-solution process, we can fabricate electronic eye systems with higher throughput and at low cost,” points out Gao.

The artificial retina is made up of a 16 x 16 light-sensing ZnO nanoparticle/MoS2 nanosheet composite photodetector array served by Ag nanowire conductive interconnects and electrodes embedded in a transparent PVA film on a PMMA substrate. The hemispherical PMMA dome mimics the shape of a natural eyeball, while the photodetector array acts as the retina. The device shows a reliable UV response and high transparency across the visible and IR ranges, enabling the sensing of light from all angles.

Eyes in nature, meanwhile, can be concave or convex: the human eye, for example, relies on a light-sensitive concave surface with a retina for high resolution image formation while the compound eyes of spiders are convex in structure, enabling wide fields of view and high motion sensitivity. Thanks to the combination of solution processing and fully flexible transparent materials used, the researchers fabricated both concave and convex hemispherical electronic eye prototypes in a single configuration. The combination of concave and convex devices enables double-sided imaging.

“Compared with other approaches for electronic eyes, our approach shows greater advantages in terms of fabrication cost and efficiency,” says Gao. “[Our approach] could make bio-inspired electronic eyes with higher system-level efficiency practical.”

The simple, low-cost fabrication process is compatible with a wide range of materials and the team now plan to develop stretchable electronic eye systems based on soft materials. These bio-inspired devices could also be integrated with energy harvesting systems such as solar cells to create self-powered, miniaturized, portable electronic eyes.

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