For the octopus and cuttlefish, changing their skin colour and pattern to disappear into the environment is just part of their camouflage prowess, said researchers from Cornell University in the US.
These animals can also swiftly and reversibly morph their skin into a textured, three dimensional (3D) surface, giving the animal a ragged outline that mimics seaweed, coral, or other objects it detects and uses for camouflage.
The pneumatically-activated material developed by researchers takes a cue from the 3D bumps, or papillae, that cephalopods can express in one-fifth of a second for dynamic camouflage, and then retract to swim away without the papillae imposing hydrodynamic drag.
"Lots of animals have papillae, but they cannot extend and retract them instantaneously as octopus and cuttlefish do," said Roger Hanlon, from the Marine Biological Laboratory (MBL) in the US.
"These are soft-bodied molluscs without a shell; their primary defence is their morphing skin," said Hanlon. The breakthrough by the team was to develop synthetic tissue groupings that allow programmable, 2D stretchable materials to both extend and retract a range of target 3D shapes.
"Engineers have developed a lot of sophisticated ways to control the shape of soft, stretchable materials, but we wanted to do it in a simple way that was fast, strong, and easy to control," said James Pikul, assistant professor at the University of Pennsylvania in the US.
"We were drawn by how successful cephalopods are at changing their skin texture, so we studied and drew inspiration from the muscles that allow cephalopods to control their texture, and implemented these ideas into a method for controlling the shape of soft, stretchable materials," said Pikul.
"This is a classic example of bio-inspired engineering with a range of potential applications. For example, the material could be controllably morphed to reflect light in its 2D spaces and absorb light in its 3D shapes," Hanlon added.