A new study describes how spheres can be transformed into twisted spindles thanks to insights from 16th century navigational tools. Researchers show how polymers can contract into spiral structures, known as loxodromes, that have complex patterning ten times smaller than the width of a human hair. Published in Physical Review Letters, the research was conducted by University of Pennsylvania graduate student Helen Ansell, postdoc Daeseok Kim, and professors Randall Kamien and Eleni Katifori in the School of Arts and Sciences, in collaboration with Teresa Lopez-Leon of the École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI).
Kim, who worked on this project at ESPCI before coming to Penn, was inspired by other studies showing that a mixture of polymer and liquid crystal took on a new shape when placed in a different solvent. It was a change that was also reversible and reproducible, with little to no energy required to cause the change in shape.
Changes - Kim - Lab - Theorists - Sense
To understand the interesting conformational changes that Kim had seen in the lab, he sought out theorists who could help make sense of how the polymer's geometry caused it to twist and contract. After seeing the microscopic images and data that was collected and analyzed by Kim, Ansell had an initial idea of what the spindle's structure might be: a loxodrome.
More commonly referred to as rhumb lines, a loxodrome is an arc that follows a constant angle as it cuts across a sphere. Sailors throughout the 16th-19th centuries used these lines to navigate, allowing them to set their compasses to a constant bearing so that their ship did not have to change its bearing.
Case - Ansell - Hypothesis - Loxodromes
"We tried to figure out if this was the case," Ansell says about investigating if her hypothesis was correct. "We think we found these loxodromes, so we had to...
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