When Faye Yap, a graduate student in mechanical engineering, saw a dead spider curled up in the hallway, it made her wonder if it could be used as a robotic component.
Turning dead spiders into mechanical claws may be some people’s idea of a nightmare scenario, but it could have tangible benefits. Spider legs can firmly and gently grip large, delicate and irregularly shaped objects without breaking them.
So, working 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 hold of objects.
They called this new type of robotics “necrobotic”.
Oddly, spider legs have no muscles for extension, but move their legs by hydraulic pressure – they have what’s called a prosomal chamber, or cephalothorax, which contracts, sending internal body fluid into their legs, causing them to stretch out.
So the team inserted a needle into the spider’s prosoma chamber and created a seal around the tip of the needle with a globe of superglue. Squeezing a small puff of air through the syringe was enough to activate the spider’s legs, performing a full range of motion in less than a second.
“We took the spider, we put the needle in there not knowing what was going to happen,” Yap explains 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 off the bat. I don’t even know how to describe it, that moment.”
The team managed to get the dead spider to adhere to a small ball and used this experiment to determine a maximum grip force of 0.35 millinewtons.
They then demonstrated the use of a dead spider to pick up delicate objects and electronics, including having this necrobotic claw remove a jumper wire attached to an electric breadboard, then move a block of foam of polyurethane.
They also showed that the spider could support the weight of another spider of about the same size.
As 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 go into rigor mortis, but, since the muscles only work in one direction, the spider curls up.
While most human-made robotic components are quite complex to make, spiders are already complex and (unfortunately for arachnophobes) are in abundance.
“The concept of necrobotics proposed in this work takes advantage of unique designs created by nature that may be complicated or even impossible to reproduce artificially,” the researchers state 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 this being used for is micro-manipulation, and that could include things like micro-electronic devices,” Preston explains in the video.
A disadvantage of the Dead Spider Clamp is that it begins to experience some wear after two days or after 1000 cycles of opening and closing.
“We believe this is related to joint dehydration issues. We believe we can overcome this by applying polymer coatings,” says Preston.
Researchers experimented with coating wolf spiders in beeswax and found that its decrease in mass was 17 times less than that of the uncoated spider over 10 days, meaning it retained more energy. water and that its hydraulic system could work longer.
This study was published in Advanced science.