Invisible Lenses Made of Grass express
When light hits a transparent plate, some of it bounces off the surface. For astronomers, that means losing precious photons from distant stars. New 3D-printed microlenses made from IPX Clear resin transmit visible and near-infrared light, but at the air boundary they lose about 8%.
The solution came from nature. A layer of aluminum oxide is grown on the glass, forming tiny blades of grass. Light passing through this 'lawn' encounters not a sharp boundary but a smooth transition from air to material. Reflection is suppressed, and transmission rises from 92% to 99%.
The authors applied this coating for the first time to printed microlenses made from IPX Clear resin. After treatment, the lenses reflect only 0.3% of light in the 400–850 nm range. This means telescopes with such lenses can collect more light from faint objects.
So far, the coating has been tested only over part of the resin's working range (up to 1700 nm), but the first results are promising. Future plans include adding a protective layer of silicon dioxide to shield the blades from moisture and temperature swings.
The 'grass' layer of aluminum oxide is so thin that its thickness is a thousand times smaller than the diameter of a human hair, yet it boosts light transmission by nearly 7%.
In Arthur C. Clarke's novel Rendezvous with Rama, the alien spacecraft has perfectly black surfaces that absorb all light — here the task is the opposite: to make surfaces that don't reflect light but transmit it.