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Converting Dead Spiders Into Gripping Tools

Researchers at Rice University have developed a novel method, to control and use the dead bodies of spiders for gripping micro-sized objects.

Some may view spiders as creepy and dangerous and might prefer them dead. But did you know that researchers have found a way to make tools out of their dead bodies?

While it might sound startling, spiders have been found to naturally have the perfect build for small-scale gripping tasks. Engineers at Rice University have managed to devise a way to use the dead spiders to grip weights larger than their own and that can camouflage into natural environments.

This study, published in Advanced Science, details how the lead author Faye Yap, under the guidance of Assistant Professor Daniel J. Preston at Rice University’s George R. Brown School of Engineering, developed a method to manipulate spider physiology for specialised uses, pushing the frontiers of this new field of research named “necrobiotics”.

The Preston lab specialises in soft robotic systems that utilise novel, unexpected materials, compared to the commonly used electronics, hard plastics, and metal. “We use all kinds of interesting new materials like hydrogels and elastomers that can be actuated by things like chemical reactions, pneumatics, and light,” he said. “We even have some recent work on textiles and wearables.

“This area of soft robotics is a lot of fun because we get to use previously untapped types of actuation and materials,” Preston said. “The spider falls into this line of inquiry. It’s something that hasn’t been used before but has a lot of potential.”

The mechanism behind spider mobility is vastly different from that of mammals as the spiders’ limb movements are achieved through the use of a hydraulic system. A chamber close to the spider’s head controls the blood pressure in the limbs, causing them to extend when the blood pressure rises and contract when it falls.

The materials used in this system were courtesy of deceased wolf spiders, which were exceptionally strong and were able to support weights amounting to 130 per cent of the spider’s original body weight. The engineered system was able to move objects, lift other similar spiders, and modify a circuit board.

During their search for a suitable spider to be used as tweezers, the researchers also discovered that smaller spiders had legs that were able to support larger loads. To design systems that can bear larger loads, the researchers are looking into other species of spiders smaller than the wolf spider.

This entire project was inspired by a curled-up, dead spider in the lab hallway, which sparked curiosity in the researchers as they wanted to better understand the mechanics behind the spider’s leg movement.

An internet search instantly gave them their desired answers: “Spiders do not have antagonistic muscle pairs, like biceps and triceps in humans,” Yap said. “They only have flexor muscles, which allow their legs to curl in, and they extend them outward by hydraulic pressure. When they die, they lose the ability to actively pressurise their bodies.”

Keen to exploit these features of the spiders, the researchers attached a needle and syringe or a test rig to each prosoma—the blood-activated hydraulic chamber individually connected to each spider leg—with superglue, where the movement of the legs could be controlled by the injection of small amounts of air.

This process was repeated over and over to achieve 1,000 cycles of the opening and closing movements of the spider legs to test their durability, and they were found to be surprisingly sturdy. To increase the durability of the spider legs to withstand more than 1,000 cycles of the abovementioned movements, the researchers hypothesise that the application of polymeric coatings will help to solve the wear-and-tear thought to be caused by the dehydration of the spider joints that negatively impacts the mobility of the spider legs.

The researchers believe that their creation may be used for tasks requiring fine motor control, like the sorting and movement of various small components, and may potentially be used for motorised assembly for micro-scale electronics.

Besides uses in manufacturing, their creation may also be useful for retrieving insects during fieldwork as they are grippers that are both biodegradable and able to blend into the background.

Addressing concerns that their work is worrying due to the assumptions that the spiders are revived, the researchers have clarified that their work does not count as reanimation and people should not be concerned that they might be bringing spiders back to life.

“Despite looking like it might have come back to life, we’re certain that it’s inanimate, and we’re using it in this case strictly as a material derived from a once-living spider,” Preston said. “It’s providing us with something really useful. [APBN]

Source: Yap et al. (2022). Necrobotics: Biotic Materials as Ready‐to‐Use Actuators. Advanced Science, 2201174.