How geckos climb smooth walls without falling

HostI was watching a tiny lizard on my porch window last night. It just ran straight up the glass like it was a flat sidewalk. No slipping, no falling, not even a moment of hesitation. It really feels like they're breaking the rules of how things should work. I mean, glass is so smooth that there's nothing for a claw to grab onto. How are they doing that without falling off?

GuestIt looks like a magic trick until you zoom in really, really close. Most of us think they must have sticky pads, like tape, or maybe little suction cups on their toes. But if you look at a gecko foot under a powerful lens, it's actually covered in millions of tiny hairs. And those hairs have even smaller hairs on the ends. It's like a forest of split ends that are so thin they can get right up against the actual atoms of the wall.

HostBut hair isn't sticky. If I press my hair against a window, I just slide right down. There has to be some kind of spit or glue involved to make them stay put.

GuestNo glue at all. That's the wildest part. It's a completely dry grip. If they used glue or spit, they would get stuck to the floor or pick up every bit of dust they walked on. Instead, they use a trick of physics. When those billions of tiny hair tips get close enough to a surface, the bits of energy in the lizard foot and the bits of energy in the wall start to talk to each other. They create a tiny pull. On its own, one hair doesn't do much. But when you have millions of them all pulling at once, the force is strong enough to hold up the whole lizard, even if it's hanging by just one toe.

HostOkay, wait. Energy talking? That sounds like you're saying they're magnetic. But glass isn't magnetic, so that doesn't seem right.

GuestIt's not quite magnetism, but it lives in the same family. Think of it like this. Every atom has a little cloud of energy around it. Usually, that cloud is balanced. But for a split second, the cloud can shift to one side. That makes one side of the atom a bit positive and the other side a bit negative. When the gecko hair tips get close enough, they sync up with the atoms in the glass. The positives and negatives line up and pull toward each other. It's a very weak force, but because the gecko has so many points of contact, it adds up to a massive amount of grip.

HostIf the grip is that strong, how do they ever move? It seems like they would be welded to the wall. I have seen them sprint. They aren't exactly struggling to pull their feet up.

GuestThis is where the shape of those hairs really matters. The grip only works when the hairs are pulled at a certain angle. It's a lot like a piece of sticky tape. If you try to pull tape straight up, it's hard to move. But if you peel it back from one edge, it comes right off. The gecko does the same thing. It uncurls its toes to change the angle of those hairs. As soon as the angle shifts, the atomic pull just snaps off. Then they can move the foot and slap it down somewhere else to turn the grip back on.

HostSo they're basically peeling themselves off the wall with every single step. But what happens if the wall is dusty? Or if the lizard walks through some sand? My tape stops working the second it touches a bit of lint.

GuestThat's another trick they have. Their feet are self-cleaning. The dirt particles on a wall are actually bigger than the tips of those tiny hairs. Because the hairs want to stick to the wall more than they want to stick to the dirt, the dirt just gets pushed aside or falls off. As the gecko walks, it actually cleans its own feet. Scientists have tried to make gecko feet dirty in labs, and within a few steps, the lizard is back to full grip. It's a system that never gets clogged up.

HostThis is making me wonder why we don't have gecko gloves yet. If it's just about the shape of the hairs, we should be able to copy that, right?

GuestWe're trying, but it's incredibly hard to do. Those hairs are so small that we struggle to make them in a factory. Also, when we try to make them, the hairs tend to clump together and get tangled. The gecko has a way of keeping every single hair separate and ready to work. Plus, our skin is soft and sweaty, which ruins the dry grip. We're getting closer, but nature is still way ahead of us on this one.

HostIs there anything they actually can't climb?

GuestTeflon. You know, the stuff they use in non-stick frying pans. The atoms in Teflon are so tightly packed and so balanced that they don't give the gecko hairs anything to grab onto. There's no shift in the energy cloud for the hairs to sync up with. If you put a gecko on a Teflon sheet and tilt it, the lizard just slides right off. It's the one thing that beats their physics trick.

HostSo the ultimate climber meets its match in a kitchen pan. It's funny to think that the whole system relies on being just the right kind of messy at a tiny level.

GuestOne single gecko could technically hold up the weight of two full grown humans if every one of its tiny hairs made contact at the same time.

HostThose little lizards on the porch window aren't just sticky; they're actually reaching out and grabbing onto the tiny bits of energy that hold the whole world together.