HOUSTON — This is something straight out of a horror movie. Mechanical engineers have turned dead spiders into robots.
In a new study, engineers repurposed dead spiders to serve as mechanical grippers that can blend into natural environments while picking up objects that outweigh them. They call these zombie spiders “necrobotics.”
“It happens to be the case that the spider, after it’s deceased, is the perfect architecture for small scale, naturally derived grippers,” says Daniel Preston, of Rice’s George R. Brown School of Engineering, in a university release.
Preston and his colleagues use nontraditional materializes for their soft robotic systems, as opposed to hard plastics, metals, and electronics.
“We use all kinds of interesting new materials like hydrogels and elastomers that can be actuated by things like chemical reactions, pneumatics and light,” explains Preston. “We even have some recent work on textiles and wearables.”
“This area of soft robotics is a lot of fun because we get to use previously untapped types of actuation and materials. The spider falls into this line of inquiry. It’s something that hasn’t been used before but has a lot of potential,” the researcher continues.
How do spiders move?
Rice engineers used wolf spiders for their necrobotics research. They were able to lift more than 130 percent of their own body weight and had the grippers manipulate a circuit board, move objects, and lift another spider. Spiders use hydraulics to move their limbs and a chamber near their heads contracts to send blood to limbs, forcing them to extend. The legs contract when the pressure drops.
Researchers say smaller spiders can carry heavier loads in comparison to their size. Larger spiders, on the other hand, carry a smaller load in comparison to its own body weight. Lead author Faye Yap says their research began in 2019.
“We were moving stuff around in the lab and we noticed a curled up spider at the edge of the hallway,” notes Yap. “We were really curious as to why spiders curl up after they die.”
Spiders curl up after death because they don’t have antagonistic muscle pairs, like biceps and triceps in humans.
“They only have flexor muscles, which allow their legs to curl in, and they extend them outward by hydraulic pressure. When they die, they lose the ability to actively pressurize their bodies. That’s why they curl up,” explains Yap. “At the time, we were thinking, ‘Oh, this is super interesting.’ We wanted to find a way to leverage this mechanism.”
Researchers say that internal valves in the spiders’ hydraulic chamber, or prosoma, allow them to control each leg individually. This will be the subject of future studies.
“The dead spider isn’t controlling these valves,” says Preston. “They’re all open. That worked out in our favor in this study, because it allowed us to control all the legs at the same time.”
How did engineers turn dead spiders into robots?
For the study, engineers tapped into spiders’ prosoma chamber with a needle and attached it with superglue. Researchers connected the other end of the needle to one of the lab’s test rigs or a handheld syringe, which delivered a small amount of air to activate the legs immediately. One dead spider completed 1,000 open-close cycles to see how well its limbs held up.
“It starts to experience some wear and tear as we got close to 1,000 cycles,” says Preston. “We think that’s related to issues with dehydration of the joints. We think we can overcome that by applying polymeric coatings.”
Preston believes their necrobotic research will turn into useful technology in the future.
“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 assembly of microelectronics,” explains Preston.
Even though some might be wary of this type of experiment, researchers say turning dead spiders into robots doesn’t qualify as reanimation.
“Despite it looking like it might have come back to life, we’re certain that it’s inanimate, and we’re using it in this case strictly as a material derived from a once-living spider,” says Preston. “It’s providing us with something really useful.”
The study is published in the journal Advanced Science.
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