Along with their unique propulsion system and ability to change color, octopi are also known for their grabby tentacles. Now, Korean scientists have developed a material that mimics the sucker discs on those tentacles. It could be used for adhesive pads that are reversible, reusable, fast-acting, and effective even in wet conditions.
A real octopus sucker disc has a hollow cavity in the middle, surrounded by a ring of muscle tissue. The size of the cavity is controlled by the octopus making that tissue thicker or thinner – the thinner the muscle tissue, the larger the cavity, and the lower the air pressure within it. A larger cavity creates more suction, while a smaller one causes the disc to release.
The scientists, from the Korea Institute of Science and Technology (KIST) and Ulsan National Institute of Science and Technology (UNIST), made their pad using rubbery polydimethylsiloxane (PDMS) studded with an array of tiny pores. Each of those pores is lined with a thermally-responsive polymer.
At room temperature, the polymer stays relaxed, and the pad doesn't stick. Once the temperature of the material is raised to 32 ºC (89.6 ºF), however, the polymer contracts. This causes the pores to open up, each one acting like a tiny sucker disc. As a result, the pad sticks to whatever surface it's laid upon.
Amongst other possible applications, it is hoped that the pads could be used as a substrate for bandages or medical sensors that stick to the skin at normal body temperature, but that can be released simply by exposure to cold water.
A paper on the research was recently published in the journal Advanced Materials.