Necrobotics is a new area of interest for scientists. It includes the use of biotic materials as robotic components. The science of necrobotics mainly uses the combination of natural cells with artificial components to generate biocompatible small robots. This has been experimented with before, by replicating the locomotion mechanisms of cheetahs, but just recently a more purposeful and inspiring development happened as a group of scientists managed to ‘bring back a dead spider to life’.
Faye Yap, a mechanical engineer from Rice University, has been one of the leading scientists in the field of necrobotics, specifically in the spider case along with other mechanical engineer peers. The team found that the key to this new application of necrobotics was the mechanism used by spiders to move, grasp objects, or even stick to some surfaces such as tree barks for camouflage. Instead of the common locomotion mechanism of animals where muscles are involved in an antagonistic (contrasting) relationship with each other, spiders possess a unique way of moving: using the hydraulic pressure in their bodies. When alive, they use their blood pressure to push their legs in the direction of their need and thus, can move. Once they are dead, since the blood pressure is no longer existing, the legs curl close to the body of the spider.
Scientists made use of this property of spiders and thought of ways in which they can artificially put pressure back inside the spider and activate the body parts. Interestingly, the process they followed for this experiment only required the insertion of constant pressure using a needle and a syringe which took no more than 10 minutes per spider, but nothing more complex. The steps included the following.
- Selected spiders for experimenting from the Lycosidae family were euthanized (to kill an animal using humane ways, mainly because it is sick and would be dead anyways) by exposing the spiders to cold temperatures of about -4℃ for 5 to 7 days.
- A 25-gauge hypodermic needle is inserted into the prosoma of the spider (the connection point of the legs to the body) as naturally, this body part is responsible for the creation of movement in response to the blood pressure.
- The use of a hypodermic needle with a hollow tip is common practice in scientific studies as it works great as a sterile applicator, inhibiting any contamination of the injected fluid from the substances around. This property of hypodermic needles is mainly due to their smooth surface which doesn’t allow any particles from the air to stick to the needle. The sharp and hollow needles of these hypodermic versions also help with the creation of sterile environments as nearly no contaminants can easily enter from the hole.
- The needle is then glued onto the body of the spider to form an airtight seal to inhibit any air from disturbing the mechanism.
- After the glue has been dried, a syringe is connected to the needle to insert the necessary pressure inside the spider.
After experimenting with their design, the scientists were able to capture the capacity of their small biocompatible robot to carry out specific tasks: the gripping effect of the spider injected with artificial pressure was able to lift an object that is around 130% of its own mass, it could exert a gripping force of 0.35 mN and could withstand 700 actuation cycles before the onset of degradation. Furthermore, what was mainly of interest to the scientists was that they could use this artificial gripping effect of the spider to lift a variety of objects of different sizes, masses, and shapes.
With this design, the movement of the spider legs could easily be controlled by adjusting the level of pressure applied from the syringe. The resulting opening and closing movement of the legs could effectively be utilized as grippers, such as those in the machines full of toys or expensive materials in the arcade saloons. One of the main advantages and innovative ways of this experiment was that the team was able to make use of what nature itself offers to us. Normally, building a completely artificial robotic mechanism such as this would require a lot more effort, expertise, and budget. However, the spiders were already complex themselves that they only needed a small ‘push’ to work as great as any artificially designed equivalent. Furthermore, no waste would occur with this application as spiders are living creatures that can easily be decomposed by the nature and hence, are considered to be biodegradable.
” 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.”
Scientists consider using this small robot in the necrobotics field itself, as a helper applicator to grab on some small objects for more careful insertion of engineering materials. However, the design needs some improvements to extend the maximum number of times a spider can withstand the artificial pressure leading to the opening and closing of its legs which is probably related to dehydration of the joints as proposed by Daniel Preston, a mechanical engineer from Rice University involved with this research.
FUN FACT! Faye and her colleagues actually did not insert the needle into the prosoma region of the spider by expecting a direct result. Instead, they were just estimating regions where they possibly could lead the air towards the leg structures of the spiders. But luckily enough, they were successful at finding the right location to insert the pressure from in their first trial. Faye said in a video talking about the new discovery on the website of Rice University that “We had an estimate of where we wanted to place the needle. And when we did, it worked, the first time, right off the bat.”
Nelson, Felicity. “Scientists Are Turning Dead Spiders into ‘Necrobots’ and We Are so Creeped Out.” ScienceAlert, 26 July 2022, https://www.sciencealert.com/necrobotics-the-creepy-field-of-science-that-is-using-dead-spiders-as-robots.
Yap, Te Faye, et al. “Necrobotics: Biotic Materials as Ready‐to‐Use Actuators.” Wiley Online Library, 25 July 2022, https://onlinelibrary.wiley.com/doi/10.1002/advs.202201174.
Abraham, Nic. “What Is a Hypodermic Needle?” Medical Design and Outsourcing, 21 Aug. 2019, https://www.medicaldesignandoutsourcing.com/what-is-a-hypodermic-needle/.