A team of applied physicists at Harvard University School of Engineering and Applied Sciences, Cambridge, MA, are developing a technology that coats a metallic object with an extremely thin layer of semiconductor, just a few nanometers thick. Although the semiconductor is a steely gray color, the object shows up in vibrant hues because the coating exploits interference effects in the thin films, similar to how an oil slick will appear to have an iridescent rainbow visible.
Through careful tuning in the laboratory, the coatings can produce a bright, solid pink or a vivid blue using the same two metals, applied with only a few atoms' difference in thickness.
They say that their advanced research building on previous work demonstrates that the ultrathin coatings could be applied to essentially any rough or flexible material, from wearable fabrics to stretchable electronics using just a tiny amount of material.
It was not immediately obvious that the same color effects would be visible on rough substrates, because interference effects are usually highly sensitive to the angle of light. However, the applied films are so extremely thin that they interact with light almost instantaneously, so looking at the coating straight on or from the side does not make much difference to the color.