Engineering researchers at Cornell University, in collaboration with a cephalopod biologist, have produced a dynamic and programmable “camouflaging” material based on how octopus and cuttlefish can quickly alter their skin color and pattern to hide from predators. With innovative stretchable materials increasingly being a focus for research, and soft robotics seen as important for use in proximity to humans – for instance, in the care of the elderly, the disabled and children – the team were motivated by how cephalopods control their texture to devise a way to influence the shape of soft and stretchable materials.

The pneumatically activated material, which was reported in Science [Pikul et al. Science (2017) DOI: 10.1126/science.aan5627], is inspired by the retractable 3D bumps, known as papillae, that cephalopods can express to quickly provide camouflage. Papillae are muscular hydrostats – biological structures that have muscle but no skeletal support – that can quickly and reversibly morph from a flat, 2D surface through a continuum of shapes until it reaches any of a number of final possible shapes depending on the arrangement of the muscles in the hydrostat.

The team therefore developed similar synthetic tissue groupings that allowed programmable transformation of 2D stretchable surfaces that could extend and retract into a range of target 3D shapes. These stretchable surfaces with programmable 3D texture morphing act as a synthetic “camouflage skin” in the same way that cephalopod’s camouflage themselves in their environment.

“I would love to integrate posture, color, and texture change into a single robot that can camouflage and display itself in similar ways to an octopus”Robert Shepherd

The groupings consisted of elastomeric membranes embedded with inextensible textile mesh that inflated to within 10% of their target shapes by using a simple fabrication method and modeling approach. The team designed an algorithm to translate the desired 3D shape into a 2D pattern of inextensible fabric – a fixed-length fiber mesh embedded in a silicone elastomer. When this rubber sheet was inflated, the fabric pattern guides the inflation into positive, zero or negative curvatures that could theoretically produce any shape.

As co-leader Robert Shepherd told Materials Today, “I would love to integrate posture, color, and texture change into a single robot that can camouflage and display itself in similar ways to an octopus”. Such bio-inspired engineering could offer various applications, including being controllably morphed to reflect light in its 2D spaces and absorb light in its 3D shapes, thereby manipulating a material’s temperature. One day such materials could also change their texture to provide information to the visually impaired, and be used in interfaces for immersive virtual or augmented reality experiences.