Lai adapted Lasheras' tools to study snails and slugs. Snails are similar to our cells "in that they both have to move and adhere to a surface at the same time," she said. Lai's experiments echoed Eadweard Muybridge's famous stop-motion photographs from the late s. His photos — taken on what is now the Stanford campus — proved that all four of a horse's hooves are off the ground at the same time during a gallop.
In Lai's case, she used high-resolution videos to show that parts of a snail's foot lift off the ground as the waves of motion travel through it. If the snail's foot never lifted off the ground, then the animal would need the special mucus to achieve enough force to push itself across a horizontal surface.
But if, however, a part of the snail's foot lifted up as the waves traveled through it then the animal could produce enough thrust to push itself forward even without the special physical properties of the mucus. Lifting part of its foot reduces the amount of friction the snail has to overcome to move. This would be similar to a caterpillar, which lifts the middle part of its body up and stretches forward as it moves. Lai tracked the movement of snails on a horizontal glass surface, using a high-resolution camera placed underneath.
She measured the back-and-forth waves of muscle contractions by tracking the movement of distinctive speckles on the foot. She also used a laser to measure the distance that the foot waves moved up-and-down off the glass surface.
To measure forces, she placed the snails on a gel and measured how the gel deformed as the snails moved across it. She already knew how much force it took to deform the gel, so she was able to calculate how much force it took to produce the observed deformation. Based on their new measurements, the researchers found that the snails didn't require the special mucus to travel horizontally. The lifting of the snail's foot as the waves travelled through it produced enough force to propel the animal even without the slime.
The slime's adhesive ability still plays a crucial role, however, in allowing the animal to crawl upside down and up vertical surfaces. Apart from changing how we view snail locomotion, the work has practical applications as well. A number of other research groups have been making robots that move like snails. Lai is currently working on a more detailed mathematical model of snail movement that could help refine these robots.
Booseum: Make Snail Slime! Directions Pour 2 cups of cornstarch into your mixing bowl. Add 1 cup of water. If you want more or less slime than 2 cups worth, just mix the cornstarch and water to a ratio. Mix until combined. Add food coloring if desired. E-News Sign up. Yang shared her findings in a new study published last week in the Proceedings of the National Academy of Sciences.
Named PHEMA, after its chemical composition polyhydroxyethylmethacrylate , it is so effective that at first, Yang had trouble measuring its strength. The strength of an adhesive is measured by pulling until the attachment breaks. In the end, the team had to design straps made out of Kevlar — the material used in bulletproof vests — to pull the PHEMA apart. The adhesive holds tight when dry, but add some water and within a few minutes, PHEMA detaches, ready to be reused.
If immersed in water, they suck up water," said Yang. And when a hydrogel dries out, it becomes rigid. When squishy and wet, PHEMA is able to fit into the microscopic grooves and imperfections that are on all surfaces, even seemingly smooth materials like glass. While a the idea of a reversible superglue is new to humans, snails have been making something similar for millions of years.
Once it rains, the snails detach and continue crawling around. Only some snails make epiphragms.
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