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While we've seen a number of robotic grippers inspired by various animals, US scientists have now taken a much more "direct" approach. They've devised a method of using actual dead spiders to delicately grasp small objects.

Unlike mammals, which move their limbs by extending and contracting opposing muscles, spiders move their legs via hydraulic pressure. More specifically, they have a "prosoma chamber" located near their head which sends blood into the legs as it contracts this causes the legs to extend. When the pressure is released, the legs close back in.

Led by Asst. Prof. Daniel Preston and graduate student Faye Yap, a team at Texas' Rice University set out to see if they could manually trigger such movements in dead wolf spiders. The scientists have named the field of research "necrobotics."

The process begins with a spider being euthanized, after which a needle is inserted into its prosoma chamber. A drop of glue is then added at the insertion point, to keep the needle in place.

Using a syringe attached to that needle, a small amount of air is subsequently pushed into the chamber, causing the legs to open up. When air is drawn back out of the chamber, the legs close. In tests conducted so far, the spider-based necrobotic grippers were able to lift over 130% of the spider's own body weight.

According to the researchers, one spider carcass lasts for about 1,000 open/close cycles before its tissues begin to degrade. It is hoped that adding a polymer coating could increase longevity.Besides being the rather creepy subject of a scientific study, the necrobotic grippers could have some practical 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," said Preston. "Also, the spiders themselves are biodegradable. So we're not introducing a big waste stream, which can be a problem with more traditional components."

Source: Rice University