Harvard has reported a breakthrough flat artificial eye just 30 microns in depth which can exceed the capabilities of the human eye. The technology, which builds on so-called metalens technology by adding electrically-controlled flexible muscles, could make a real impact in all manner of optical fields, including those in cameras, telescopes, microscopes, glasses and even virtual reality.
The prototype device can make simultaneous adjustments for image focus, image shift and astigmatism, all of which can cause blurred images, and which are adjustments beyond what our own eyes can do. The technology can also focus in real time, just as our eyes can.
"All optical systems with multiple components … have slight misalignments or mechanical stresses on their components … that will always cause small amounts of astigmatism and other aberrations, which could be corrected by an adaptive optical element," explains Alan She, an author of the research. "Because the adaptive metalens is flat, you can correct those aberrations and integrate different optical capabilities onto a single plane of control."
The metalens She refers to is a flat silicon nanostructure which focuses light. But this eye goes further by adding the surrounding artificial muscle, which posed some real challenges to the team.
The first of these was to make the metalens much bigger, as earlier prototypes were no larger than a piece of glitter. Scale that up to a 1-cm (0.4-in) lens, and the team discovered that the data needed to describe the design of the lens could amount to terabytes, thanks to the complexity of the nanostructures involved.
To overcome the problem, the team developed an algorithm capable of describing lens production which reduced the data down to a manageable size, and made it compatible with technology used to make integrated circuits. If the lenses could be made in more or less the same way as circuits, as the research suggests, this is a considerable boon for the commercial viability of the technology.
The next challenge was in attaching an artificial muscle to the lens without significantly compromising its optical performance. The team chose a dielectric elastomer – an elastic polymer which could be controlled by applying electricity via carbon nanotube electrodes. The researchers identified an elastomer which allowed light to pass through without much loss due to scattering.
The team intends to work towards further improvements, including reducing the voltage needed to control the eye and improving its speed of response.
The research was carried out at the Harvard John A. Paulson School of Engineering and Applied Sciences. The team's paper has been published in Science Advances.
Update March 15, 2018: Alan She got back to us to let us know that, due to the electricity needed by the eye, applying the technology to a human implant would be hard. "That said, it might be possible to hook up the soft metalens to the existing ciliary muscle within the eye," She added. "I don't know whether a medical technique to do so exists or not. To that end, I think it is straightforward to make the soft metalens bio-inert and biocompatible by using the appropriate materials."
Source: The Harvard Gazzette
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