How Do Geckos Climb Walls?

A small lizard walks straight up a window, then upside down along the frame. In this episode of How Does Nature Do That?, we find out how geckos climb walls. It isn't suction and it isn't glue: each foot of a tokay gecko has nearly half a million tiny hairs, each hair splits into hundreds or even thousands of tinier tips, and together those roughly one billion tips get so close to a surface that a very weak pull, the van der Waals force, adds up to a strong grip. We see how strong that grip really is, how geckos peel their toes to let go, how their feet keep themselves clean, and why they can't grip every surface equally well, like dry Teflon or glass under water. Not every gecko can climb, either: leopard geckos have no sticky toe pads at all. Real footage is captioned with the species shown. Diagrams are original animations, labeled on screen (data charts are based on Autumn et al. 2000 and Stark et al. 2013). Chapters: 0:00 Intro: an upside-down climber 0:26 How do geckos climb walls? 0:47 Meet the geckos 1:33 Suction? Glue? 2:19 Zooming in on a toe 3:00 The van der Waals force 4:01 How strong is the grip? 4:50 Letting go 5:24 Self-cleaning feet 6:13 Where grip fails 7:07 Inspired by geckos 7:20 Recap 8:02 Next time Sources are in the pinned comment. CREDITS Photos and footage (via Wikimedia Commons): "Gekko gecko 161488397.jpg", Wich'yanan L, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Living gecko hunting the pointer of a mouse.webm", Basile Morin, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Gekko gecko (climbing) by Robert Michniewicz.jpg", Robert Michniewicz, CC BY 3.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Gekko gecko 14168715.jpg", Judy Gallagher, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Asian house gecko (Hemidactylus platyurus).jpg", Mark O’Shea, CC BY 3.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Eublepharis macularius 04.jpg", Σ64, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Tokay gecko @Vnm.jpg", BacLuong at Vietnamese Wikipedia, public domain, https://commons.wikimedia.org/wiki/Fi... "Uroplatus fimbriatus (3).jpg", TimVickers, public domain, https://commons.wikimedia.org/wiki/Fi... "Madagascan Day Gecko (9369358744).jpg", Bernard Spragg. NZ from Christchurch, New Zealand, CC0 https://creativecommons.org/publicdom..., https://commons.wikimedia.org/wiki/Fi... "Tokay foot.jpg", David Clements, public domain, https://commons.wikimedia.org/wiki/Fi... "Green gecko paw.jpg", Peter Heeling, CC0 https://creativecommons.org/publicdom..., https://commons.wikimedia.org/wiki/Fi... "Gekko gecko 226251330.jpg", Torrey Brownell, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Gekko gecko 221285.jpg", noamszoke, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Geco Tarentola mauritanica.JPG", Babo, public domain, https://commons.wikimedia.org/wiki/Fi... "Gold dust day gecko Phelsuma laticauda Hawaii 8107.jpg", ImagePerson, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Hemidactylus turcicus on teflon.webm", Michal Maňas, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... "Hemidactylus frenatus 170883357.jpg", Hopeland, CC BY 4.0 https://creativecommons.org/licenses/..., https://commons.wikimedia.org/wiki/Fi... Music: "Calmant" by Kevin MacLeod (incompetech.com), licensed under CC BY 3.0 (https://creativecommons.org/licenses/...) - https://commons.wikimedia.org/wiki/Fi... Some photos and clips were cropped to fit the frame. The gecko-on-a-screen clip in the intro does not identify the species. Narration voice: Kokoro-82M text-to-speech, af_heart voice (Apache 2.0, hexgrad/Kokoro-82M).