Octopus-inspired 'synthetic skin' changes colour and texture on demand

"Bumps or grooves of a range of sizes - from the sub-micrometre scales of visible-light wavelengths up to millimetres - affect how a surface scatters light. This can make a material more or less dull, or change its colour when observed from different angles. Molluscs, such as octopuses and cuttlefish, use tiny muscles embedded in their skin to produce these effects for camouflage or communication."

"Siddharth Doshi, a materials scientist at Stanford University in California, and his collaborators built what they call metasurfaces out of PEDOT:PSS, a type of polymer that has been used in solar panels and printable electronics. They chose the material because it swells on contact with water, but in a reversible way: it will release the water and shrink when exposed to other liquids, such as certain alcohols."

"To create materials with a controllable texture, the researchers put a layer of the polymer on a substrate and used an electron beam to create regions capable of absorbing varying amounts of water, producing a 'landscape' of bumps on the surface. The result was materials that could drastically change their appearance when wet. When used practically, the surfaces could be covered by a transparent film - allowing the flow of water to be controlled."

Researchers engineered metasurfaces from PEDOT:PSS that can switch surface texture and optical properties by absorbing or releasing water. The polymer swells when exposed to water and shrinks reversibly when exposed to certain alcohols such as 2-propanol. Electron-beam patterning produced regions that absorb varying water amounts, forming a landscape of bumps and grooves across sub-micrometre to millimetre scales. Those topographic changes alter light scattering, producing matte-to-shiny transitions and angle-dependent colour effects. The surfaces can be sealed beneath a transparent film to control the delivery of water or water–alcohol mixtures, enabling reversible appearance changes for consumer and architectural uses.

Read at Nature