Of all the super heroes with capes, why does only one get the title of “The Caped Crusader”? He wears a cape, and he’s waging an intense war against crime, but that’s basically every superhero in history, right? In that case, what makes “Bats” so special? Well, as a hardcore DC fanboy, I think the keyword here is “cape”, not “crusader”. Most heroes without a cape would still be just as super. Batman, however, is a special case.
First of all, if you remove the cape, all you have left is a “Rat-with-pointy-ears-man”. Second, it is just as important of a tool as the utility belt, if not more. It lets him glide, can be used in combat, and is fireproof to a large extent. Third, it might even be possible to make a real one. Let’s look at one of the best versions of the cape to understand it.
In Christopher Nolan’s Batman Begins (2005), Bruce Wayne goes to meet Lucius Fox looking for a lightweight fabric for his “adventure sport” of the week, you see the coolest fabric ever designed for a movie – and it has nothing to do with fashion!
Is it really possible to make a cape that has a relatively rigid shape under certain conditions and flexible under others? Theoretically…yes.
There are certain “smart materials” that possess the property of shape memory. These shape memory materials have a tendency to revert back to any programmed base shape that they’ve “memorized” when an external trigger (like heat, electricity or light) is applied.
This fascinating property of these materials is, as Lucius Fox states, due to molecular realignment. A commonly used shape memory material is Nitinol, which is an alloy (mixture of metals) composed of Nickel and Titanium. When Nitinol is heated to a high temperature (500ᵒ C), the molecular structure of the alloy can be programmed to attain a certain base state. After this, at low temperatures, the alloy can be deformed into almost any possible shape, but when it is heated past a certain transition temperature (which can range between 100ᵒC and -100ᵒC, depending on the composition of the alloy) it returns to its original base state.
These changes are similar to the changes between different states of matter. For example, when water is boiled, the amount of energy increases within the molecules and they move away from each other, giving us gaseous water vapor. Conversely, when water is frozen, the amount of energy within the molecules decreases and they move closer together, rearranging themselves to create a solid block of ice.
This is also the case with Nitinol, but within the solid state of Nitinol, there are multiple phases depending on the amount of energy of the molecules. Therefore, instead of the molecules diffusing away, the molecules rearrange themselves, while maintaining the solid state with a small increase in their energy.
Of course, there are technical limitations involved. Why else would we still be using elevators and escalators instead of capes and grappling guns? Also, it would be terribly expensive to create capes like this for everyone..
Nitinol can be used to create the exoskeleton of the cape, while parachute material could be used to help improve the glide, but how does electricity come into play?
One of the most common mechanisms for heating up an alloy is called Joule heating. Simply put, when an electric current is passed through any wire, the electrons moving across the length of wire bump into the molecules within the wire, which imbues them with energy, thus producing heat. This would make the “transformation” of the cape possible.
The cost of making such a nitinol alloy is huge, as it requires specific settings, such as high vacuum and temperature, as well as a very controlled environment. A second issue, and one which is much more difficult to solve, is that of the flight. The gliding can theoretically be achieved, as proven by some researchers, but it would be hard to “nail the landing” due to the high speeds reached during the glide.
For more gliding tips, check out this article: Can We Glide like ‘The Dark Knight’?