The latest discovery by scientists at Rice University: a needle and some air are all it takes for the wolf spider necrobot to lift 130 percent of its body weight. Best of all, it can withstand nearly 1,000 opening and closing cycles. The latest research can be found published in the journal Advanced Science.
The spider itself lacks the extensor muscles used to stretch its legs, but it does have the flexor muscles for it. When spiders need to stretch their legs, they rely on the legs’ “hydraulic system.” The system is like a syringe for an injection, and when it is filled with fluid, the plunger pushes out and straightens the leg. When the spider dies, its body fluid will gradually drain out and the legs can no longer be straightened, so they are retracted under the action of the flexors.
The gripper, which the researchers made from the spider’s body, replaced the active mechanism for regulating the spider’s hemolymph pressure with external air pressure changes. When the spider’s internal pressure is higher than atmospheric pressure, it “kicks” its legs; otherwise, it retracts its legs. It does not matter whether the pressure change occurs spontaneously while the spider is alive, or whether it is added or subtracted artificially.
So how do you make a “zombie spider”?
The first step is to euthanize it, and the second step is to insert the needle and seal it.
To begin the research, a suitable spider carcass is needed. The researchers obtained the ideal sample by exposing a wolf spider to freezing temperatures (about -4°C) for 5 to 7 days. An image of the wolf spider ‘s patellofemoral joint was also scanned with an electron microscope to show exactly what the joint membrane looks like.
To make a necrobotic gripper, only one simple step is required now: insert a needle into the anterior extremity area of the deceased wolf spider and then tape the needle to the spider’s body to form a closed circle.
The amazing thing is that you do not have to do anything here and the glue can automatically fall onto the junction between the needle and the wolf spider. The reason for this is to minimize the energy required: first, the glue droplets are injected into the side of the needle where they settle and minimize the energy on the surface of the needle. Second, the glue travels down the needle and comes into contact with the surface of the spider’s cuticle or exoskeleton by gravity. When contact is complete, the glue droplets form a crescent-shaped pool at the junction between the needle and the spider’s cuticle. After curing, the glue eventually forms an airtight seal.
The entire process from insertion of the needle to dripping of the glue can be completed in about 10 minutes. The researchers mimicked this self-sealing mechanism on paper. The paper mimics the properties of the spider’s cuticle, and similar needles are inserted into the paper. Using a drop of blue colored glue on the paper, they were able to reproduce the airtight seal. This was done to demonstrate that dynamic energy minimization can indeed be achieved by dripping and spreading the glue on the junction between the spider’s exoskeleton and the needle. At the same time, the researchers mapped the needle’s insertion point on the spider using SEM, to show the tightness between the needle and the cuticle. They chose the spider’s forelimbs because the exoskeleton of the forelimbs is stiffer than that of the abdomen.
What can we use this for? Well, according to the researchers, we can have them pick up and place objects, perform repetitive tasks, sort and move objects in small areas, and even perform microelectronic assembly and similar tasks. Another application is to have the necrobotic spider catch smaller insects in nature and use its body as a natural master of camouflage. In addition, the spiders themselves are easily biodegradable, so no major waste was generated during the study.
That being said, while the research itself is interesting – and perhaps somewhat horrifying – we here at GiGadgets doubt this research will lead to any actual, practical uses.
