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Nanoscale braids and weaves

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Maypole dance. Image courtesy of WIkimedia Commons/Grenville Burrows.

Within all living cells, precisely arranged protein complexes use energy from ATP to perform mechanical work. Researchers have sought to emulate these biological machines by manipulating individual atoms and molecules into custom structures. Exploiting recent advances in colloidal science, Carl Goodrich and Michael Brenner (pp. 257–262) describe a proof-of-principle strategy for the autonomous assembly of microscopic-scale braids and weaves driven by self-propelled charged particles. Using short-range attractive forces and photolithographic micropillars, which are fixed structures that act as pivot points, the technique precisely guides the motion of colloids attached to long semiflexible filaments. As the particles move in concert between and around the micropillars, the motion is akin to a maypole dance, a European folk custom in which participants holding colored ribbons circle a pole in opposite directions, weaving among one another to form a braid. The authors propose a number of schemes to achieve such motion without external input, a fundamental characteristic of biological systems, and demonstrate the method using Brownian dynamics simulations. According to the authors, the approach can be customized to generate motion along topologies suitable for a range of applications. — T.J.