When mechanical engineering graduate student Faye Yap saw a dead spider curled up in the hallway, she wondered if it could be used as a robotics component.
Turning dead spiders into mechanical tweezers might be the idea of a nightmare scenario for some people, but it could have tangible benefits. Spider legs can grasp large, delicate, and irregularly shaped objects firmly and smoothly without breaking them.
So, in collaboration with mechanical engineer Daniel Preston, Yap and his colleagues at Rice University discovered a way to make a dead wolf spider’s legs spread out and grab objects.
They called this new type of robotics ‘necrobotics’.
Strangely, spider legs don’t have muscles for extension, but instead move their legs through hydraulic pressure: they have what’s called a prosome chamber, or cephalothoraxthat contracts, sending internal body fluid to your legs, causing them to extend.
The team then inserted a needle into the spider’s prosome chamber and created a seal around the tip of the needle with a drop of superglue. Squeezing a small puff of air through the syringe was enough to activate the spider’s legs, achieving a full range of motion in less than a second.
“We took the spider, we put the needle in it without knowing what was going to happen,” says Yap in a video on the Rice University website.
“We had an estimate of where we wanted to put the needle. And when we did, it worked, the first time, right away. I don’t even know how to describe it, that moment.”
The team was able to get the dead spider to grab a small ball and used that experiment to determine a maximum gripping force of 0.35 millinewtons.
Next, they demonstrated the use of a dead spider to pick up delicate objects and electronic devices, which included this necrobotic tweezer removing a jumper wire connected to an electrical breadboard and then moving a block of polyurethane foam.
They also showed that the spider could support the weight of another spider of roughly the same size.
(Preston Innovation Lab/Rice University)
Since spiders extend their legs by exerting hydraulic pressure from their cephalothorax, when they die the hydraulic system no longer works. The flexor muscles of the spider’s legs enter into rigor mortisbut, since the muscles only work in one direction, the spider coils.
While most man-made robotic components are quite complex to manufacture, spiders are already complex, and (unfortunately for arachnophobes) they abound.
“The concept of necrobotics proposed in this work takes advantage of unique designs created by nature that can be complicated or even impossible to replicate artificially,” say the researchers in their paper.
Spiders are also biodegradable, so using them as robot parts would reduce the amount of waste in robotics.
“One of the applications we could see it being used for is micromanipulation, and that could include things like microelectronic devices.” He says Preston in the video.
One disadvantage of the dead spider caliper is that it begins to experience some wear after two days or after 1000 opening and closing cycles.
“We think it’s related to joint dehydration issues. We think we can overcome that by applying polymeric coatings.” Explain Preston.
The researchers experimented with coating the wolf spiders with beeswax and found that their mass decline was 17 times less than that of the uncoated spider over 10 days, meaning it held more water and its hydraulics could work longer. .
This study was published in advanced science.
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