The science of superheroes

Some very real science has inspired the superheroes that capture our imagination in movies.

Today’s superheroes, whether dark knights or galactic guardians, attract massive fan followings, star A-list celebrities and generate enormous revenues at the box office. 2017 alone saw the release of the hugely successful Wonder Woman, Spider-man: Homecoming, and Guardians of the Galaxy vol.2, with the highly anticipated Justice League and Thor: Ragnarok slated for release later in the year.

Technological revolution in the form of special effects and advanced computer graphics has driven at least part of this upsurge in the success of comic book movies. We love to watch Superman fly, Spider-man swing through the city on his webs, and Cyclops shoot lasers out of his eyes. Interestingly, many of these impressive superhuman abilities have close counterparts in the biological world around us. And sometimes, the latter plays a direct role in inspiring the former.

The Amazing Spider-Man

One of the best-known examples of this is Spider-Man. A brainchild of Stan Lee and Steve Ditko, the first Spider-Man comic was published in 1962. Bitten by a radioactive spider, the teenage Peter Parker gains abilities that resemble a spider’s, including enhanced agility, increased strength, and perhaps most iconic, the ability to cling to and climb walls.

Without the aid of their silk lines or any kind of adhesive, spiders scale perfectly smooth surfaces that do not provide any kind of grip or purchase. What makes spiders such adept climbers?

Unlike insects and frogs that use sticky fluids to adhere to surfaces, spiders employ dry adhesion, wherein weak Van der Waal forces supply all the force necessary for attachment. These forces are born out of close interactions between atoms on a surface and dense tufts of microscopic hairs present on claws at the ends of spiders’ legs. These tufts are known as scopulae and are made up of small hairs known as setae, which in turn have even finer hairs known as setules. Together these hairs greatly increase the surface area for attachment, providing the combined force necessary to hold the spider in its place.

One interesting feature of this mode of adhesion is that very little force is required for the spider to detach itself from a position. Instead of expending a lot of energy to break the adhesive forces holding it to a surface, all the spider needs to do is angle its foot slightly, allowing it to peel off easily. This is key to ensuring that the spider does not die of exhaustion after taking three steps, said Tobias Seidl from Westphalian University of Applied Sciences in Germany, who has studied adhesive mechanisms in invertebrates extensively. “Having superglue in your shoes is not a good idea if you want to walk up a building,” he said.

So, can we do what a spider can? Efforts are underway to replicate the spider’s dry adhesion in several forms, from stickers to robots. Perhaps the biggest application lies in space travel, where vacuum conditions prevent the use of many fluid adhesives.

The gold standard for attachment in space is Velcro; but spider-inspired adhesion has one big advantage—it only requires one prepared surface, unlike the two surfaces required for Velcro. Climbing robots that use spider-like mechanisms to scale surfaces have been developed, and may find uses in remote surveillance and rescue operations. And perhaps one day, we may also see a suit coated in such materials, making wall-scaling Spider-Men a common sight in our cities.

Mysterious Mystique

Spider-Man isn’t alone in possessing abilities that hail from nature. Shape-shifters such as the Marvel villain Mystique can change their appearance at will. Like Mystique, some animals can change the color and texture of their skin easily, sometimes within milliseconds. The specialists here are cephalopods—octopuses, squids, and cuttlefish, who use their dynamic camouflage powers to carry out functions as diverse as avoiding predators, confusing prey, and communicating with peers.

These marine animals achieve this using multilayered skin with specialized cells known as chromatophores, iridophores, and leucophores. Some of these cells absorb, reflect, and scatter light in various ways, while others contain pigments of different types. These cells are often densely innervated or mechanically activated, allowing rapid changes in the animal’s appearance.

And just like the spider’s adhesive pads, scientists have been trying to reverse engineer cephalopods’ approach to camouflage in the laboratory. “We developed a way to make very large amounts of a protein that plays a key role in cephalopod cells, and then we took that protein and used it to form coatings that have very basic color-changing properties,” said Alan Gorodetsky from the University of California, Irvine. “Based on things that we learned from those coatings, now we are developing more advanced, completely artificial materials.”

Materials with such properties may benefit a number of different fields such as the military and textile and fashion industries, where dynamic clothing that adapts to the wearer’s needs is likely to find a big following among consumers. Gorodetsky suggested a shirt that may look like a T-shirt or a Tuxedo depending on specific conditions.

As movies and comic books continue to bring superheroes into our homes, who knows what scientific discoveries they may inspire or how many movies will be prompted by the latest news coming from the laboratory? Researchers delving into these superpowers in the natural world may one day soon make fiction reality.