Researchers from the University of California, Berkeley, have created a new material that changes color based on the amount of pressure or force applied.
In the new material, thousands of microscopic ridges are etched onto a single thin silicon wafer. These ridges reflect a very specific wavelength of light. This is in contrast to colors we typically see reflected from everyday objects and in nature. In those objects, the unique chemical composition of the object (think chemical dyes and pigments) absorbs most colors in white light, and what we see reflected back are the colors that were not absorbed. This novel material takes a different approach: the structure of the material defines the color observed, rather than it’s chemical composition.
In the UCBerkeley material, the spacing between the ridges on the silicon wafer define the color observed. Flexing or bending of the material changes the space between the ridges, thus changing the color we see. The silicon material is unique in that it has high reflection efficiency (we see most of the color reflected) and it can tolerate flexing and bending. Other materials, such as metallic surfaces, were too inflexible, inefficient, or brittle.
Imagined applications include display technologies, camouflage, and defect-sensors in buildings, bridges, and aircrafts, where slight changes in the amount of bend or extension would lead to color changes notifying engineers of structural weaknesses. Less referenced is the potential this technology has for the fashion industry--clothing that would change color at the slightest movement, transforming an entire look. Some designers are already using nature’s original version of this technology, which can be observed in butterfly and beetle wings. They have incorporated these wings into their work (see image of Mathieu Mirano work). A synthetic material to achieve this look would be more sustainable, malleable, and longer-lasting, and has the potential to disrupt the textiles and fashion industry.
Link to the Science Daily article:http://www.sciencedaily.com/releases/2015/03/150312100728.htm
Link to the original paper:
Li Zhu, Jonas Kapraun, James Ferrara, Connie J. Chang-Hasnain. Flexible photonic metastructures for tunable coloration. Optica, 2015; 2 (3): 255 DOI: 10.1364/OPTICA.2.000255