Dead Spider Becomes Robot Gripper: It’s Necrobotics!

Robot arms and grippers do important work every hour of every day. They’re used in production lines around the world, toiling virtually ceaselessly outside of their designated maintenance windows.

They’re typically built out of steel, and powered by brawny hydraulic systems. However, some scientists have gone for a smaller scale approach that may horrify the squeamish. They’ve figured out how to turn a dead spider into a useful robotic gripper.

The name of this new Frankensteinian field? Why, it’s necrobotics, of course!

Working With Nature

Scientists and engineers have long held reverence for the achievements of the natural world. Tiny insects are capable of feats far exceeding those of our greatest robots, and can operate independently for days or weeks without ever needing to be plugged in. The intricate mechanical systems of spiders and beetles are beyond even our finest engineering to date.

Spiders are particularly impressive. They have eight legs of surprising strength, especially given their weight and power requirements. Rather than try to create something to match these capabilities from scratch, a group of researchers at Rice University decided to simply hack the spiders themselves.

The process of making necrobiotic grippers with wolf spider carcasses. Credit: Preston Innovation Laboratory, Rice University

Spider legs only have muscles for retraction, while extension is achieved via a hydraulic mechanism. In the spider’s body, a chamber filled with blood expands and contracts to control the movements of the creature’s legs. Each leg has a valve that allows the spider to control their movement individually. After death, all these valves open up and the spider’s hydraulic system loses pressure. This is what causes a spider’s legs to curl up after death.

The researchers realised that they could tap into this hydraulic system to extend and contract the spider’s legs at will. With a dead spider, all the individual leg valves typically fail open, so control is limited to extending or contracting all the legs at once. This causes the dead spider to act like a robot gripper, just like you might see on an skill tester arcade machine.

Researchers worked with wolf spiders, and began by euthanizing them in cold temperatures. A needle was then inserted into the spider’s body, and sealed with glue. This allowed the hydraulic passages inside the spider to be pressurized with air to extend the legs. Releasing the pressure lets the legs contract again into the curled up position.

Testing and Applications

The dead spiders are surprisingly robust. In testing, the group was able to get over 1,000 open-close cycles out of a single spider carcass. Some wear and tear was notable at the higher end of this range, which the team believes is primarily due to the dehydration of the spider body. Research is ongoing as to whether this problem can be solved with special polymeric coatings to keep the body from drying out.

Lifting power was also impressive. Wolf spider bodies were reliably able to lift 130% of their own body weight. Some bodies would exceed this figure by a great amount, too. Of course, variability is to be expected when working with a carcass as an engineering material.

The team believes that dead spiders could serve as useful actuators for small-scale pick-and-place tasks. Demonstration from the team included using a spider gripper to pull a jumper out of an electronic breadboard. Other examples involved moving small objects and even lifting another spider. The benefit of the necrobotic gripper is that the spider’s eight legs are good at gripping objects of odd shapes and sizes.

The team also cite the renewable nature of the necrobotic gripper. “The spiders themselves are biodegradable,” said Daniel Preston, assistant professor of Mechanical Engineering at Rice University. “We’re not introducing a big waste stream, which can be a problem with more traditional components,” he adds.

However, the necrobotic grippers as shown do have some limitations. A usable service life of 1,000 cycles is relatively low for a robotic gripper, particularly one to be used in a mass-production environment. There’s also a lot of variability in dead spider bodies that isn’t seen with regular engineered robotic components. Additionally, while the spider carcasses themselves are biodegradable, the needles, glues, and plastic fittings are not. Plus, the production of spider grippers is time-consuming, fiddly work. Then there’s the significant investment required in spider husbandry facilities.

The Future For Necrobotics

The research is compelling, and shows off reliable control of a stable spider carcass after death. It’s also much simpler than other insect-robotics projects that use electrodes inserted into cockroach brains for control. There’s no need to manipulate a living creature’s brain, or fight against its natural instincts to make it complete a given task.

However, the research would raise ethical hackles for some. It’s less troubling than electronically enslaving living beings, perhaps. Regardless, humans have always had strong feelings around the proper treatment and respect of mortal remains. Using spiders is likely to draw far less condemnation than if the same research were carried out with a mouse or hamster, for example. Try the same feat with a cat or a dog, and you might expect your lab to be closed with remarkable haste.

Just to be clear, we don’t think you’ll be using a spider-based pick-and-place any time soon. But work in the field of necrobotics will likely teach us a lot about how the bodies of animals and insects work. They may also guide the development of our own robotic or biomechatronic creations. In any case, the quest for knowledge often presents us with strange and meandering paths to follow. And sometimes, just sometimes… those paths are covered in spiders.



46 thoughts on “Dead Spider Becomes Robot Gripper: It’s Necrobotics!

      1. The problem is an energy supply. You can do it only once, while there is still an ATP inside muscle cells. And without entire living body to resupply, it is quickly deployed and all you have is a dead meat. Galvani was only able to observe that phenomenon because frog was freshly killed.
        It is different with spiders. They do not have muscles in their legs. Bending is achieved by regulating pressure of the fluid inside. This is why dead spider defaults to the position with legs bent maximally under the body. But it you are able to manipulate pressure inside, you can bent them back.

  1. Wolf spiders are what is used in the article. Wolf spiders body size can be over 2 inches or >50 MM. They can live for more than 2 years. I’m thinking with a big enough spider I can pick and place my coffee cup. That wouldn’t wierd out the co-workers, nahhhhhhhhh not at all:)

  2. Just the project in time for scaring those pesky Trick-or-Treaters… make the spiders dance to The Who’s “Boris The Spider”… or maybe David Bowie’s “Ziggy Stardust” if you can make a miniature guitar one of them to play.

  3. So… take the ink reservoir out of a bic type pen, cut ~5mm off the end.. put thin wire down each side internally, seal off end and hold wire in place with dot of (hot) glue… then place drip of saturated salt solution into end of tube, then hold spider leg in end of tube and seal it in with dot of glue… now…. you got electrically activated spider leg actuator, put 3V on the electrodes and gas evolved creating pressure in system… experimentation required to discover how long it takes gas to diffuse and pressure to release, and how many “shots” you get out of small drip of electrolyte… Tuning of electrolyte used to vary rate of gas diffusion (high with low atomic weight hydrogen I should think, low with N2) possible. Wondering actually if some electrolytes will let you “suck” gas bubbles back in by reverse polarity… if they haven’t got too far away.

    Anyhoo, be cool to make mini paper RC aeroplanes with elevons controlled by spider leg actuators lol.

    1. Alternate halloween novelty, print skeletal hand and broken off arm bones, where the arm bones contain one side the electrolyte cell, other side, battery and single transistor oscillator, slow blink rate, and fingers are 5 spider legs encased in 3d printed finger bone skins…. and it will clench and retract pulling itself across a desk lol.

    1. That is one tiny wolf spider. I once extracted one out of my garage the size of a large mans hand. It was very angry with me as it had its babies with it. I did allow the babies to crawl under the clear container with it. When i let it out it lept at me and tried to murder me. It was staring right at me. Rather smart those things.

    1. Scientists and engineers sometimes need to do something weird to keep their minds fresh. This may seem a waste of public money, but I think, ultimately, allowing such craziness is beneficial.

    1. There are some sects in India that take harming of insects seriously… but I think they also regard the body as an empty shell, so probably okay with the whole deal if you collect naturally expired spiders.

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