Researchers from Harvard set out to develop a new type of spring that could be used in an imaging project inspired by cephalopods. While experimenting on a few rubber bands to develop the new springs, scientists accidentally happened upon a new type of shape.
The researchers who found the new shape have named it the "hemihelix." As the name implies, the hemihelix is a type of helix, which is basically a curve with three dimensions. Helixes are often common in nature and the shape can be observed in plants and some animals. Unlike normal helixes, however, the hemihelix rarely occurs naturally. It can spiral clockwise and counterclockwise several times.
After stumbling onto the hemihelix while working with rubber bands, the researchers from Harvard's School of Engineering and Applied Sciences got curious about the strange-looking helix. The research team then tried to figure out how the shape was produced. Specifically, the scientists tried to see whether the shape was formed randomly or whether there were certain factors that could affect the formation of the hemihelix. The researchers published their findings in the online journal Plos ONE.
Discovering and observing a new type of shape is one thing, but for scientists to understand the complexities and possible applications of novel shapes and structures, a deeper understand of how the shape is produced is required. In particular, scientists are interested in the possible applications of the hemihelix in other fields, such as nanotechnology or in biotechnology.
"Once you are able to fabricate these complex shapes and control them, the next step will be to see if they have unusual properties; for example, to look at their effect on the propagation of light," said Harvard SEAS associate professor Katia Bertoldi.
At first glance, the hemihelix might look like a convoluted helix. The basic helix shape can be seen in a variety of everyday objects such as screws. The curve of a normal helix turns in a single direction, which is referred to a chirality. Looking at the hemihelix, the researchers noticed a number of perversions in the shape's curve. These perversions happen when the chirality of the helix suddenly changes. The researchers then attempted to understand how and when these perversions occurred.
"We see deterministic growth from a two-dimensional state -- two strips bonded together -- to a three-dimensional state," said Harvard SEAS graduate student Jia Liu. "The actual number of perversions, the diameter, everything else about it is entirely prescribed. There is no randomness; it's fully deterministic. So if you make 100 of these, they'll always perform exactly the same way."
The researchers say that their findings on the inner workings of the hemihelix may help pave the way for developing new fabrication methods using flat shapes similar to the rubber bands. The hemihelix may also have applications in mechanics since the shape is basically a spring. Moreover, slight changes in the shape's geometry could also produce other novel types of springs.
"Intellectually, it's interesting, and we believe it is significant, too," said Harvard SEAS Materials professor David R. Clarke. "There are a variety of complex shapes in nature that arise as a result of different growth rates. We stumbled quite by accident on a way to achieve fully deterministic manufacture of some three-dimensional objects."
