Researchers at Wageningen University in the Netherlands developed a 3D printing material that changes colour depending on the angle of the light source.

The material has a red brown colour normal light. However, when there is a light source placed behind it, the colour changes to translucent purple.

The print material is based on the polymer PVA (polyvinyl alcohol), mixed with gold nanoparticles. To the gold particles, citric acid is added. In certain quantities this mixture becomes dichroic.

The researchers used the material to 3D print a cup inspired by the Lycurgus cup from the British Museum, an object from the 4th century that changes colour from red to green, depending on the light. This effect is also reached by nanoparticles, gold and silver in this case.

With 3D printing, the material can turned into any shape, like lenses that let through selective light.

Photos: Wageningen University