Inventions keep science marching. The scientific manifestation of artificial as well as bionic eyes got a breakthrough by the efforts of Gu and Colleagues, published in Nature. A concave hemispherical retina consisting of an array of nanometer-scale light sensors that mimic the photoreceptor cells in the human retina has got several capabilities comparable to those of human eye.
STRUCTURE
The resemblance to the original eyes are as follows:
Retina – Composed of a high-density array of photosensors. The photosensors were formed directly inside the pores of the hemispherical membrane of Aluminum oxide just like they are arranged in retina of our eye.
Nerve fibre – The flexible wires made of liquid metal sealed in soft rubber tubes transmit signals from the nano photosensors.
Vitreous Humor – A lens combined with artificial iris is placed at the front of the device, just as in the human eye. The retina at this back combines with the hemisphere shell at the front to form a spherical chamber resembling the “eyeball”. This chamber is filled with an ionic liquid that mimics the vitreous humour.
The uniqueness of the structure of artificial eye lies in its sensoring capabilities matching with the natural eye. It detects a large range of light intensities. Also, the responsivity of the nanowire which measures the current produced per watt of incident light is almost the same for all frequencies of the visible spectrum. The response and recovery are important parameters because it ultimately determines how quickly the artificial eye can respond to a light signal. In Gugs and colleagues artificial eye, it takes 19.2 milliseconds to as little as 23.9 milliseconds to recover. Last but not least, the high resolution of the image resulting from the high density of nanowire array makes it versatile.
Improvisation paves in perfection. Much needs to be done in widening the light detecting region of the photosensor array and cost reduction of the fabrication process associated with the production of nanowire formation.
Second, to improve the resolution and scale of the retina, the size of the liquid metal wires need to be reduced.
Third, more testing is needed to establish the operational lifetime of the artificial retina. Gu et al report that there’s no obvious
reduction in its performance after 9 hours of operation, but the performance of other electrochemical devices can deteriorate over time. Lastly, the optimization of the ionic liquid is required to address the reduction of response and recovery time at the expense of light transmission through the liquid.
The collaborative endeavour by Gu and Colleagues’ has achieved mimicking not only human eyes but also compound eyes similar to those of insects. It seems feasible that we might witness the use of artificial and bionic eyes in daily life within the next decade.
–Gokul M Nair
Reference: nature
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