In an upcoming paper, Nicola Pugno, a professor of structural engineering at the Polytechnic University in Turin, Italy, discusses formulas for fashioning carbon nanotubes into superadhesive gloves and boots that could be used to create a Spider-Man-like suit in the near future. He also outlines a theory for using carbon nanotubes to create large invisible cables that could act as human-strength cobwebs.
The designs for the materials are modeled from the adhesive properties of the gecko, a tropical lizard whose sticky feet can scale trees.
"A replication of the characteristics of the gecko or spider feet would enable the development of a self-cleaning, superadhesive and releasable hierarchical material and, with the conjunction of large invisible cables, of a preliminary Spider-Man suit," Pugno wrote in his paper, which will be published in an upcoming edition of the Journal of Physics: Condensed Matter.
Scientists have long studied the gravity-defying gecko for potential applications in the human world. (The practice of studying the natural world for industrial applications is.) Researchers at the University of California at Berkeley, for example, have that can keep objects from sliding down near-vertical surfaces. Other universities are working on materials to remove ice from windows based on the same principles.
What's special about the gecko feet is that they're covered with millions of tiny hairs. When these hairs brush against a surface, the molecules at the tip of the hairs adhere to the surface through van der Waals forces, a bond that forms between two molecules when they are close to each other. Although the bond between each hair and the surface is weak, it becomes strong when multiplied over millions of hairs.
Through their feet, geckos get both friction, which keeps them from sliding down, and adhesion, which makes it difficult to pull them off a surface. The challenge in creating nanotube materials strong enough to hold the weight of a human is that at such a large scope, the materials can either bunch up and become brittle; or they can become elastic, collapsing under their own weight, according to the paper.
Pugno proposed the use of "branched long carbon nanotubes...with a number of hierarchical levels sufficient to activate" a superadhesive suit.
"Mimicking nature, thanks to carbon nanotube-based technology, we suggest the feasibility of large invisible cables, as well as of self-cleaning, superadhesive and releasable hierarchical smart materials," Pugno wrote. "We found that a man can be supported by a transparent cable with a cross section of 1 cm squared and feasibly, with spider material gloves and boots, could remain attached even to a ceiling: a preliminary step towards a Spider-Man suit."