Engineers at Cornell University have created stretchable surfaces with programmable 3D texture morphing, a synthetic 'camouflaging skin' inspired by octopus and cuttlefish camouflage.
In the natural world, octopus and cuttlefish are able to instantaneously change their skin colour and pattern to camouflage themselves. They can also quickly morph their skin into a textured, 3D surface in order to mimic their surroundings.
With the help of cephalopod biologist Roger Hanlon of the Marine Biological Laboratory (MBL), the engineers, led by James Pikul and Rob Shepherd, created a controllable soft actuator. The material is pneumatically activated to create the 3D bumps, or papillae that cephalopods can quickly deploy and deactivate.
“Lots of animals have papillae, but they can’t extend and retract them instantaneously as octopus and cuttlefish do,” explained Hanlon.
Without a shell, these soft-bodied molluscs depend upon their morphing skin for their primary defence.
Papillae are muscular hydrostats, biological structures consisting of muscle with no skeletal support. The tongue is another type of muscular hydrostat. The shape of the surface depends on how the muscles in the hydrostat are arranged.
According to Pikul, an assistant professor in the Department of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, engineers have developed a lot of sophisticated ways to control the shape of soft, stretchable materials, but the team wanted to do it in a simple way that was fast, strong, and easy to control.
“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,” he explained.
This bio-inspired engineering could be further extended, for example, by having the material morph to reflect light and absorb light, allowing applications where the temperature of the material is manipulated.
[Image: An example of a silicone-mesh composite membrane pressurised with air. Credit: J.H. Pikul et al., Science (2017)]