People often try to become one with nature, sometimes literally by using camouflage, such as military suits. Some animals, like squid or octopuses, do not need clothing to achieve this. They can change the colour and even texture of their skin to blend in with their surroundings. New research has discovered a way to artificially make material just like that, changing colour and texture when stretched.

The material, invented by Luyi Sun, associate professor of chemical and biomolecular engineering, collaborator Dianyun Zhang, assistant professor of mechanical engineering, and Songshan Seng, PhD student in Sun’s lab, was developed in the lab of UConn’s Institute of Materials Science in Connecticut, US. They were inspired by two sea-creatures, the jellyfish and the squid. The skin of the jellyfish is usually flat and transparent, but when it wrinkles, it causes a deformation that creates an opaque appearance. The squid is capable of changing colour by contracting, causing pigment cells to expand.

Following the example of these animals, a thin, stretchable and squishy material was developed. The material is two-layered, made from a rigid film, and a layer of soft, stretchable elastomer. The top layer has cracks and folds, but when it is stretched, the surface becomes rough and scatters so that the light that comes through, changing the material’s transparency. When released, it becomes transparent again.

In several experiments, different kinds of dye were added to the material, causing it to change colour or even become fluorescence when stretched. A different kind of experiment involved material that wrinkles when it is exposed to moisture, which can be engineered to be reversible or non-reversible.

The base materials are low cost and the process of making the material is quite simple. The researchers, planning to partner with industries, see many possibilities for the new colour changing material, from toys to clothing. They also see a future for smart windows that turn opaque when stretched, or for making anti-glare computers. It could even be used in encryption, as text can be made to appear when the material is stretched, only to disappear again when released.

For now, the colour change is only activated by UV-light, but the aim of the researchers is to have it activated by any kind of light. The researchers are now working on improving the material and are experimenting with other biobased materials, which results should be published next summer.

Courtesy photos: Uconn