In recent years, we’ve seen a number of robotics grippers inspired by the wide range of motion and gripping ability of animals. Now, mechanical engineers at Rice University have repurposed deceased spiders as mechanical grippers that can blend into natural environments while picking up objects, like other insects, that outweigh them.
Unlike people and other mammals that move their limbs by extending and contracting opposing muscles, spiders move their legs by hydraulic pressure. Internal valves in the spider’s hydraulic chamber, or prosoma, allow them to control each leg individually. The Prosoma chamber located near their heads contracts to send blood to limbs, forcing them to extend. When the pressure is relieved, the legs close back in.
The Rice University team, led by Prof. Daniel Preston and graduate student Faye Yap, set out to see if they could manually trigger such movements in dead wolf spiders. They had the grippers manipulate a circuit board, move objects and even lift another spider. A study in Advanced Science outlines the process by which researchers harnessed a spider’s physiology in the first step toward a novel area of research they call “necrobotics.”
To set up necrobotic grippers, Yap tapped into the prosoma chamber with a needle, attaching it with a dab of superglue. The other end of the needle was connected to one of the lab’s test rigs or a handheld syringe, which delivered a minute amount of air to activate the legs almost instantly. An air is subsequently pushed into the chamber, causing the legs to open up and when air is drawn back out of the chamber, the legs close.
The lab ran one ex-spider through 1,000 open-close cycles to see how well its limbs held up and found it to be fairly robust. “It starts to experience some wear and tear as we get close to 1,000 cycles,” Preston said. “We think that’s related to issues with dehydration of the joints. We think we can overcome that by applying polymeric coatings.”
The testing showed that the necrobotic grippers could grasp objects with irregular geometries, lift more than 130% of their own body weight, and sometimes much more.
Preston said a few necrobotic applications have occurred to him. “There are a lot of pick-and-place tasks we could look into, repetitive tasks like sorting or moving objects around at these small scales, and maybe even things like an assembly of microelectronics,” he said. “Also, the spiders themselves are biodegradable. So we’re not introducing a big waste stream, which can be a problem with more traditional components.”