Introducing the hemihelix.
All images: PLOS One
Update: I asked Harvard professor Katia Bertoldi, author of the study, to respond to the people who have said that she went and discovered a tangled up landline phone cord. Here's what she said:
"I totally agree that the shapes we observed in our simple experiments are familiar to all of us (helices and tangled up phone cords). However, we determined robust rules to obtain such 'twisted' shapes starting from 2D flat configurations. Following the simple recipe we provide, you exactly know which sort of 3D shape you will get (helix or hemihelix).
I believe this is the important point and I think this can have exciting applications. For example, complex 3D 'twisted' micro structures have been successfully use to manipulate light in very interesting and exciting ways. Typically, these 3D structures are fabricated directly. However, there are limitations regarding the sort of 3D shapes that can be fabricated. Our results indicate that it is possible to identify robust mechanisms to generate complex 3D shapes starting from flat 2D structures, paving the road to the fabrication of complex 3d structures that otherwise cannot be manufactured."
You probably thought you learned all the shapes—your circles, your squares, your triangles and rhombi—sometime in elementary school. You’d be mistaken. Using complex materials such as rubber bands, plastic cups, and paper clips, researchers at Harvard University have just observed and recreated an entirely new shape: the hemihelix.
It’s true, you probably won’t see the new shape much in nature (if at all), but, just in case, it looks like this:
In fact, it can be recreated fairly easily with some rudimentary materials, which we'll get to in a minute.
Why bother doing something like this at all? Like many things in science, it was kind of an accident. The Harvard team, led by Katia Bertoldi, a professor of applied mechanics, was setting out to try to create a new type of spring. To do that, they were intertwining two different strips of rubber bands that were different lengths and widths. During one of the tests, they accidentally formed a hemihelix, which is like a corkscrew that changes its chirality, or the way it’s proverbially screwing, halfway through. Think of it as a if someone put a mirror in the middle of a corkscrew.
Anyways, the discovery of this new type of shape led to more experiments. Bertoldi and her team quickly learned that by altering the width of the rubber bands, they could create more “perversions”—that is, they could make the helix switch directions many more times. Here’s what that looks like:
To actually create and observe these things, the team set up a deceptively simple contraption. At the top, they tied the rubber bands to free-rotating nylon strings. They then stretched the bands, using paper clips (the fancy kind that lets you clip dozens of papers at once), and connected the bottom to a weight—in this case, a paper cup with either small metal balls or water in it. They then started dropping weight, allowing the rubber bands to tense up. Depending on the setup, a different shape was formed. You can watch videos of the experiments here.
The focus now moves to finding applications for this—and to creating hemihelices out of other materials. In a paper published in PLOS One, Bertoldi noted that “it is highly probable that the reason hemihelices with multiple perversions have escaped notice in the past has been that most man-made materials, unlike [rubber bands], would fracture well before [they could be formed naturally].”
So it’s entirely possible that we won’t even be able to make the shape with anything all that useful. But they believe that the shape may be able to be used in nano devices and could be used to make new sensors. Or, maybe all we’ll have is a new thing to call a tangled up landline phone cord.