I try to appreciate nifty engineering, and a replacement for a moving parts mechanism with a non-moving parts mechanism always seems to fit the definition of nifty. Oh, here’s one now!
At Stanford University, engineering researcher Nina Vaidya designed an elegant device that can efficiently gather and concentrate light that falls on it, regardless of the angle and frequency of that light. A paper describing the system’s performance, and the theory behind it, is the cover story in the July issue of Microsystems & Nanoengineering, authored by Vaidya and her doctoral advisor Olav Solgaard, professor of electrical engineering at Stanford.
“It’s a completely passive system – it doesn’t need energy to track the source or have any moving parts,” said Vaidya, who is now an assistant professor at the University of Southampton, UK. “Without optical focus that moves positions or need for tracking systems, concentrating light becomes much simpler.”
The device, which the researchers are calling AGILE – an acronym for Axially Graded Index Lens – is deceptively straightforward. It looks like an upside-down pyramid with the point lopped off. Light enters the square, tile-able top from any number of angles and is funneled down to create a brighter spot at the output.
In their prototypes, the researchers were able to capture over 90% of the light that hit the surface and create spots at the output that were three times brighter than the incoming light. Installed in a layer on top of solar cells, they could make solar arrays more efficient and capture not only direct sunlight, but also diffuse light that has been scattered by the Earth’s atmosphere, weather, and seasons. [Stanford News]
Importantly, at least to me:
The basic premise behind AGILE is similar to using a magnifying glass to burn spots on leaves on a sunny day. The lens of the magnifying glass focuses the sun’s rays into a smaller, brighter point. But with a magnifying glass, the focal point moves as the sun does. Vaidya and Solgaard found a way to create a lens that takes rays from all angles but always concentrates light at the same output position.
I was concerned that this was going to be a ‘miracle’ device that requires a miracle to manufacture at scale, but this reference to current optical tech as well as 3D printing gives me hope:
After exploring many materials, creating new fabrication techniques, and testing multiple prototypes, the researchers landed on AGILE designs that performed well using commercially available polymers and glasses. AGILE has also been fabricated using 3D printing in the authors’ prior work that created lightweight and design-flexible polymeric lenses with nanometer-scale surface roughness. Vaidya hopes the AGILE designs will be able to be put to use in the solar industry and other areas as well. AGILE has several potential applications in areas like laser coupling, display technologies, and illumination – such as solid-state lighting, which is more energy efficient than older methods of lighting.
Fascinating and potentially impactful and far-reaching.
