Spiderman Beetleman wall-crawl glove/boot tech invented
Does whatever certain kinds of beetle can
Boffins in the US say they have made a step upward in the quest for miracle switch-on, switch-off sticky devices that could allow people to walk on walls and ceilings in superhero crimefighter style.
The device, brainchild of US profs Paul Steen and Michael Vogel, works using the surface tension of water. Just as two glass slides will stick together when wet, Steen and Vogel think that a "palm sized" device could be made to grip a wall or ceiling and hold on against a weight of hundreds of pounds.
The secret lies in creating many blobs of water between the device and the surface, rather than just one. This trick is already employed in nature by certain beetles in Florida, apparently, able to hang onto leaves against forces of 100 times their own weight and yet instantly unstick themselves as desired.
"In our everyday experience, these forces are relatively weak," says Steen. "But if you make a lot of them and can control them, like the beetle does, you can get strong adhesion forces."
In the new beetlemimetic tech, the sticky plate has thousands of tiny holes in it, just microns across. An electric field - generated by a regular 9-volt battery - causes tiny droplets of water to be squeezed through the holes, each one generating a minuscule sticky blob in contact with the target surface.
The electrostatic pump is cunningly designed so that no more water can come out once it's switched off, so preventing the blobs running together and losing effectiveness. When the electric field is reversed, the droplets are sucked back into the holes and the sticking effect disappears.
Thus far a prototype with 1,000 300-micron holes has held 30 grams, and shown that Steen and Vogel's theoretical equations governing beetlemimetic adhesion plates seem to be correct. According to their calculations, a square-inch of plate using millions of 1-micron holes should be able to hold on against a 15lb+ pull, such that a gauntlet or bootsole unit 3"x5" would support 225lb.
That seems to be in the Spiderman - well, Beetleman - league, certainly. Though as ever it seems the surface to be stuck to might need to be nice and flat and strongly bound together: like most wall-crawler kit, beetlemimetics is perhaps best used on windows or glass ceilings.
But there would be other applications, according to Steen. The cunning multi-beetle-blob tech could also be used to exert outward force rather than creating stickiness, by putting a film over the tiny holes. The film would thus encapsulate the water blobs, and millions of little bumps would pop up on activation - apparently exerting powerful forces on the same scale as the stickiness app.
"You can think about making a credit card-sized device that you can put in a rock fissure or a door, and break it open with very little voltage," according to Steen.
"It's a fun thing to think about," he adds.
Well, for a while anyway. Full details on the latest in beetlemimetic electric droplet kit should be online shortly in the Proceedings of the National Academy of Sciences. ®