“Necrorobotics” is what researchers call a new technology with a spooky factor: They transform dead spiders into gripping tools by breathing new life into them, so to speak. Through fine pressure manipulations, they make the arms of the small carcasses open or close. In this way, objects can be gripped and lifted gently, but with considerable holding power. According to the scientists, the bizarre concept has application potential in the fields of technology and biology.
Nature is often the inspiration for new developments in robotics: researchers are inspired by the sophisticated concepts of various animal species in order to equip technical systems with new capabilities. Instead of plastics, metals and electronics, unconventional materials and drive systems are increasingly being used. Daniel Preston’s team at Rice University in Houston is also dedicated to the development of such innovations in robotics. “We use chemical reactions, light and pneumatics as drive systems and all kinds of materials such as hydrogels, elastomers or textiles as structural elements,” says Preston. With the new concept, however, there is no need to replicate the natural mechanics – the scientists use them directly.
A coiled spider provided the idea
As they report, there was a coincidence at the beginning of the development story: “We were just rearranging things in the laboratory and came across a dead spider with its legs curled up. So we asked ourselves why these animals adopt this characteristic posture after death,” says lead author Faye Yap. Research then quickly provided the answer: Unlike mammals, which move their limbs by synchronizing opposing muscles, spiders use hydraulics. A chamber near its head is contracted to direct a fluid to its limbs. By increasing the pressure, they then straighten and when it is released, the legs bend again. “When spiders die, they lose the ability to actively put pressure on their bodies. That’s why their limbs are in the curled-up state,” explains Yap.
So the team came up with the idea of translating this mechanism into a concept they call necrorobotics. “It turned out that after death, spiders provide the perfect structures for small, naturally derived claws,” says Preston. Apparently it is surprisingly easy to make them usable in a targeted manner. The researchers stuck a needle into the pressure chamber of newly deceased spiders and attached it with a blob of superglue. They then inject tiny amounts of air into the chamber via the needle and withdraw it again when necessary. This activates the hydraulic system of the spider’s musculoskeletal system: the eight legs can be stretched and then returned to their handy, curved position.
“Zombified” spiders grab
Experiments showed that this method can produce an effective gripping system. However, as the scientists found, it is not the tarantula and co that are the most efficient, because the larger the spider, the lower the load it can carry compared to its own body weight. Apparently, wolf spiders are well suited as necrorobotic grippers: They can lift objects with more than 130 percent of their own body weight. The researchers used the “zombified” arachnids to lift various objects, such as small electronic components. They also sounded out the potential for permanent stress: “Only when we approach 1000 gripping cycles does a certain amount of wear occur. We assume that this is related to the dehydration of the joints. It might be possible to prevent this by applying polymer coatings,” says Preston.
The scientists are now working on the refinement and further development of their necrorobotic system. Because, as they emphasize, it’s not just a bizarre curiosity – it has interesting application potential. “There are some pick-and-place tasks that we could consider: repetitive tasks like sorting or moving objects at small scales, and maybe even things like assembling microelectronics,” says Preston. “Another application could be to capture smaller insects in nature, since spiders are camouflaged by nature,” adds Yap. “Plus, spiders are biodegradable,” Preston points out. “So we don’t create a large waste stream, which can be a problem with traditional components. Spiders might actually provide us with something useful after they die,” says the researcher.
Source: Rice University, Article: Advanced Science, doi: 10.1002/advs.202201174
http://dx.doi.org/10.1002/advs.202201174
Video: Rice University