Los Angeles Times
: A hemihelix, an unusual spiral whose direction changes repeatedly, is not a common shape in nature. Katia Bertoldi of Harvard and her colleagues stumbled on a way to produce the shape in the lab and then spent two years figuring out how the spiral formed. They had stretched a thin rubber band and then joined it lengthwise to a longer, unstretched band and allowed the material to relax. Instead of forming a normal helix as expected, it settled into the hemihelical shape. The researchers were able to determine that the cross-sectional shape of the rubberbands controlled the resulting shape. When the cross section is flat, the rubber band forms normal helices. When it is more square, the rubber band is more likely to form a hemihelix.