Why bother to design your own robots when you can just reuse what nature created?
This was the thought process behind a research project from engineers at Rice University who successfully transformed dead spiders into robotic gripping claws. The scientists have dubbed their new area of research “necrobotics” and say it could create cheap, effective, and biodegradable alternatives to current robotic systems.
So why spiders? Well, while humans move their limbs using pairs of antagonistic muscles, like biceps and triceps, spiders’ legs contain only a single flexor muscle that draws the leg inward. This is opposed by a hydraulic system: a chamber in the center of the spider’s body (known as a prosoma) pushes out fluid to open the leg, with separate valves allowing the animal to control each limb independently. Incidentally, this is why spiders always curl up when they die; there’s no pressure in the system to oppose the legs’ flexor muscles.
Armed with this knowledge, the team from Rice University discovered they could artificially operate this hydraulic system simply by sticking a needle into a dead spider’s prosoma, pushing air in and out to open and close the spider’s legs like an arcade claw machine.
“It happens to be the case that the spider, after it’s deceased, is the perfect architecture for small scale, naturally derived grippers,” Daniel Preston of Rice’s George R. Brown School of Engineering said in a press statement. The spiders can lift more than 130 percent of their body weight and run through 1,000 open-close cycles before the joints degrade.
The team from Rice University, led by graduate student Faye Yap, has published a paper describing their work in the journal Advanced Science. In it, they note that humanity has a long history of repurposing the remains of dead organisms for new uses — from the hides of animals worn as clothes to bones sharpened into arrowheads and tools. In this context, turning a dead spider into a robot gripper is not as unusual as it might first appear.
The scientists also note that roboticists frequently draw inspiration for their designs from the natural world, copying the adhesive surface of geckos’ feet or the undulations of a fish’s tail, for example. But, they reasoned, why copy when you can steal? Especially when Mother Nature has already done the hard work of developing effective mechanisms through millions of years of evolution.
As they write in the paper, “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.”
The group ordered their test subjects from a biological supply company, reports Gizmodo, which created some problems for arachnophobic colleagues. As Rice’s Preston told the publication, “One of the employees that works in our front office really doesn’t like spiders. So we had to give a call to the front office whenever we had another delivery coming in for us to use for the project and just kind of give them a heads up.”
The work is essentially a proof of concept for now, but Preston said it could have many future applications. “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,” he said in a press statement.
Another use might be collecting animal samples in nature, said Yap, as a spider grabber is “inherently camouflaged.”