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“Spiderman suit” may be on the way

Aug. 28, 2007
Courtesy Institute of Physics
and World Science staff

In theory, a “Spi­der­man suit” can work—a sticky out­fit that enables people to climb walls and ceil­ings, the author of a new stu­dy claims.

Only re­cently have scientists learned how spi­ders and geckos ef­fort­lessly scut­tle up walls and hang from ceil­ings. But re­search­ers doubted whether this nat­u­ral form of ad­he­sion would ev­er be strong enough to hold a per­son in place.

The tokay gecko, native to southeast Asia. (©  M. Moffett)

Gecko feet from various species. (Courtesy U.S. Nat'l Science Foundation)
New calculations show it can, ac­cord­ing to a pa­per to ap­pear Aug. 30 in the re­search pub­lica­t­ion Jour­nal of Phys­ics: Con­densed Mat­ter.

“it may not be long be­fore we are see­ing peo­ple climb­ing up the Em­pire State Build­ing with noth­ing but sticky shoes and gloves to sup­port them,” said the author, Ni­co­la Pu­gno, an en­gi­neer and phys­i­cist at Pol­y­tech­nic of Tu­rin, It­a­ly.

Research published earl­ier, in the Sept. 17, 2002 issue of the journal Pro­ceed­ings of the Na­tion­al Ac­ad­emy of Sci­ences, found that Ge­ckos and spi­ders get their stick­ing pow­er from so-called van der Waals forc­es. These are weak el­ec­tri­cal at­trac­tions be­tween mo­le­cules that are very close to­geth­er. Ti­ny hairs on spi­ders’ feet at­tract the mo­le­cules of sur­faces, even glass, and keep them in place. 

In the new stu­dy, Pugno de­s­c­ribes a com­bina­t­ion of ad­he­sive forc­es he says can sus­pend a per­son’s full weight against a wall or on a ceil­ing, while al­so be­ing easy to de­tach.

The pa­per is en­ti­tled “To­wards a Spi­der­man suit: large in­vis­i­ble ca­bles and self-clean­ing re­leas­a­ble super-ad­he­sive ma­te­ri­als.”

The tech­nol­o­gy would con­sist of mi­nus­cule hooks and loops that work like Vel­cro, made from car­bon nan­o­tubes—large mo­le­cules of car­bon atoms shaped like tubes of chick­en wire. 

This would be used in con­junc­tion with van der Waals forc­es and cap­il­lary ad­he­sion, a phe­nom­e­non in which two sur­faces stick to each oth­er if pressed to­geth­er with a small amount of wa­ter in be­tween. “There are many in­ter­est­ing ap­plica­t­ions for our the­o­ry, from space ex­plora­t­ion and de­fense, to de­sign­ing gloves and shoes for win­dow clean­ers of big skyscrap­ers,” Pugno said.

A bo­nus is that, as with spi­ders’ and ge­ckos’ feet, the hooks and hairs can be self-clean­ing and wa­ter-resistant, Pugno pre­dic­ted. This means they won’t wear or get clogged by bad weath­er or dirty sur­faces, and could with­stand some of Earth’s harsh­est habi­tats, in­clud­ing the deep sea.

But there remains work to be done before the “Spi­der­man suit” be­comes a re­al­ity, Pu­gno con­ced­ed. “There are a num­ber of oth­er me­chan­ics that need ad­dress­ing,” he said. “Size ef­fects” need fur­ther re­search, he added, ex­plain­ing that this refers to the fact that the geck­o-like stick­ing strength drops as the ar­ea that needs to stick in­creases. For­tu­nate­ly, it should be pos­si­ble to com­pen­sate for this, as the geck­o uti­lizes just a small per­cent­age of the ad­he­sion strength that van der Waals forc­es the­o­ret­ic­ally offer, he con­tin­ued.

Anoth­er prob­lem to address is that a per­son’s mus­cles dif­fer greatly from a ge­cko’s. “We would suf­fer great mus­cle fa­tigue if we tried to stick to a wall for many hours,” Pugno noted.

* * *

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Physicists claim to have found the formula for a Spiderman suit. Only recently has science come to understand how spiders and geckos effortlessly scuttle up walls and hang from ceilings. But it was doubted that this natural form of adhesion would ever be strong enough to hold a person against a wall or ceiling. New research shows it can, according to a paper published Aug. 30 in the research publication Journal of Physics: Condensed Matter. A previous study in 2002 found that van der Waals forces—a weak attraction molecules have for each other when very close together—are responsible for creepy crawlies’ amazing sticking power. It is the tiny hairs on spiders’ feet that attract to the molecules of surfaces, even glass, and keep them steady. In the new study, Nicola Pugno, engineer and physicist at Polytechnic of Turin, Italy, describes a combination of adhesive forces he said can suspend a person’s full body weight against a wall or on a ceiling, while also being easy to detach. The paper is entitled “Towards a Spiderman suit: large invisible cables and self-cleaning releasable super-adhesive materials.” The technology would consist of minuscule hooks and loops that would function like Velcro, made from carbon nanotubes—large molecules of carbon atoms shaped like tubes of chicken wire. This would be used in conjunction with van der Waals forces and capillary adhesion, a phenomenon in which two surfaces will stick together if pressed together with a small amount of water in between. “There are many interesting applications for our theory, from space exploration and defense, to designing gloves and shoes for window cleaners of big skyscrapers,” Pugno said. A bonus is that, as with spiders’ and geckos’ feet, the hooks and hairs are self-cleaning and water-resistant, Pugno said. This means that they will not wear or get clogged by bad weather or dirty surfaces and will be able to withstand some of Earth’s harshest habitats, including the deep sea. But there is still work to be done, Pugno conceded. “There are a number of other mechanics that need addressing before the Spiderman suit can become a reality,” he said. “Size effects” need further research, he added, explaining that this refers to the fact that the gecko-like sticking strength drops as the area that needs to stick increases. Fortunately, it should be possible to compensate for this, as the gecko utilizes just a small percentage of the adhesion strength that van der Waals forces can theoretically provide, he continued. Another problem is that a person’s muscles differ greatly from a gecko’s. “We would suffer great muscle fatigue if we tried to stick to a wall for many hours,” Pugno said. “However, now that we are this step closer, it may not be long before we are seeing people climbing up the Empire State Building with nothing but sticky shoes and gloves to support them.”