Metallic nanoparticles have been used as glass colorant since the Roman Empire. One of the most famous piece of pottery from the Roman Empire is the Lycurgus cup. The nanoparticles embedded in this cup have an optical peculiarity as they present different colours depending on the angle of the illumination. This effect is called dichroism. Now, scientists from Wageningen University & Research have 3D printed objects showing dichroic effect.
This 21st-century invention was possible by synthesising special kinds of gold nanoparticles with different sizes. Those nanoparticles were then embedded in a common 3D printing material (PVA), available in any shop, and 3D printed with a standard off-the-shelf 3D printer.
A bit of gold
The amount of gold in the material is minute, a mere 0.07 weight percent. Such a small amount of gold doesn’t change the printability of the material, which remains the same as with normal material. However, even at this low amount of gold, the nanocomposite material shows a distinct dichroic effect showing a brown opaque colour in reflection (when the illumination and the observer are on the same side) and a violet transparent colour in transmission (when the illumination and the observer are on opposite sides).
New class of 3D printable nanomaterials
The material used in this new research is a standard material that can be printed with any off the shelf 3D printer and it opens the doors to a new class of 3D printable nanomaterials where the intrinsic properties of the nano world, in this case optical properties, are retained even in 3D printed objects. Such peculiar optical properties can be used not only by artists for their colours, but in the future also for nanocomposite based lenses and filters.
The researchers are now working on improving this methodology using different nanoparticles and different materials.