Credit: Dongpeng Yang

Materials that change colour when pulled or squeezed could form the basis of display screens or sensors. But existing photonic gels, which change colour when deformed, cannot cover the entire rainbow or switch quickly.

Now, Jianping Ge at East China Normal University in Shanghai and his colleagues have created a material that can adopt every colour from red to blue and is more sensitive to pressure than previous efforts, while being just as durable. The team used a mixture of ethylene glycol and polyethylene glycol methacrylate in which silica spheres were fixed to create a softer and more elastic gel (pictured). Like other photonic gels, the new material works because it forms a crystalline array of spheres, which alter light reflection by shifting orientation when squeezed.

Adv. Funct. Mater. http://doi.org/rpn (2014)