We probably all killed spider or two in the past, but what if that arachnid’s corpse could be turned into something useful? By injecting dead spiders with air to capture small objects, researchers at Rice University in Texas think it could, and does, pioneer the field of “necrobotics.”
Daniel Preston, assistant professor of mechanical engineering at Rice University, set up his lab and graduate student Faye Yap explained why a dead spider in the corner of the room had twisted legs. It turns out that spiders extend their legs using hydraulic pressure from fluid pumped into their legs from a central cavity, which means that when they die, their legs retract permanently. By injecting them, Preston or Ya are able to force hydraulic air into the spider’s legs. They found they could, and their research was published on this terrifying opportunity to develop a biological scavenger Advanced Science Monday.
“[Spiders] they actually only have flexor muscles,” Yap said in a video call, noting that spiders can pull their legs in, but don’t have the muscles to extend them. “The way they extend their legs is using hydraulic pressure.”
This pressure comes from the spider’s prosoma – the cephalothorax where its legs are attached to its body – which allows the arachnid to walk by sending fluid to its legs – the individual legs are controlled by the opening and closing of valves in the spider’s anatomy. Preston, Yap and colleagues found that if they carefully inserted a syringe into the prosoma of a dead spider, they could extend and retract all of the spider’s legs at once by simulating hydraulic pressure with air. This meant that the spider could be used as a handle. So why try something so disturbing?
“We’re interested in using them for things like sample collection,” Preston said. “Because of this hydraulic or pneumatic actuation that we can implement, they have internal compatibility, which helps protect fragile specimens or even other live insects, such as those we want to collect in the field.”
The properties of the repurposed arachnid are incredibly promising: The team found that the spider’s gripper can last more than 1,000 on/off cycles and can be used to lift 130% of its own body weight.
The researchers used wolf spiders for the work in this particular manuscript, but believe other spider species could be used as well. Interestingly, Yap says, the group found that spiders with larger body masses, such as Goliath spiders, can only lift objects 1/10th of their body weight, while smaller spiders – such as jumping spiders – can. twice its body weight.
As for how those outside the lab have reacted to the project, Preston said he’s been most supportive and even excited to see how effective the catcher has been. Others weren’t too happy about having spiders around.
“One of our front office employees really doesn’t like spiders. So when another delivery arrived for us to use for the project, we had to call the front office and just let them know,” Preston said with a laugh. The team ordered their spiders from a biological supply company, but unfortunately, some of them didn’t die. Read More said: “Sometimes they are lifeless, but sometimes we have to euthanize them. So we look for the most humane way to kill them in literature.”
While the project may seem odd, Preston believes his lab is well-suited to the research field for studying soft robotics. “We’re looking at anything at the intersection of energy, materials and fluids,” he says. “Soft robotics typically uses unconventional materials, things that don’t have the typical hard plastic metals, but instead things like hydrogels and elastomers, and unique modes of motion like magnets and light.” Preston and Yap are very interested in using this as a jumping-off point for other research on necrobotic grippers, such as learning how the individual legs open and close.
While researchers around the world were working on bio-inspired robotics, Preston, Yap and the rest of the team cut to the chase and harnessed biology itself, plucking it from their lab floors. This creative, nature-inspired work is downright mad science at its best.
