Why bother designing your own robots when you can simply reuse what nature has created?
That was the thought process behind a research project by Rice University engineers who successfully turned dead spiders into robotic grasping claws. The scientists have dubbed their new area of research “necrobotics” and say it could create cheap, efficient 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 one flexor muscle that draws the leg inward. This is opposed by a hydraulic system: a chamber in the center of the spider’s body (called the prosoma) expels fluid to open the leg, with separate valves allowing the animal to control each limb independently. It is for this reason that spiders always curl up when they die; there is no pressure in the system to oppose the flexor muscles of the legs.
Armed with this knowledge, the Rice University team discovered that they could artificially operate this hydraulic system simply by sticking a needle into the prosoma of a dead spider, pushing air in and the outside to open and close the spider’s legs like an arcade claw machine.
You can watch a video of their work in action below:
“The spider, after it dies, happens to be the perfect architecture for naturally occurring small-scale claws,” Daniel Preston of Rice’s George R. Brown School of Engineering said in a Press statement. Spiders can lift more than 130% of their body weight and go through 1,000 open-close cycles before joints break down.
The Rice University team, led by graduate student Faye Yap, published an article describing their work in the review Advanced science. In it, they note that humanity has a long history of repurposing the remains of dead organisms to new uses – from animal skins worn as clothing to sharpened bones into arrowheads and tools. In this context, turning a dead spider into a robot gripper is not as unusual as it might seem at first glance.
Scientists also note that roboticists frequently draw inspiration for their designs from the natural world, copying the adhesive surface of geckos’ legs Where the ripples 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 article, “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 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 who works in our front office really doesn’t like spiders. So we had to call the front office every time we had another delivery to use for the project and give them a whim.
The work is essentially proof of concept at the moment, but Preston said it could have many future applications. “There are a lot of pick-and-place tasks that we could look at, repetitive tasks like sorting or moving things around at these small scales, and maybe even things like microelectronics assembly,” he said in a press release.
Another use could be collecting samples from animals in the wild, Yap said, because a spider catcher is “inherently camouflaged.”