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Writhing and Twisting: The Dynamics of Nanofilaments

Motivated by experimental work on hydrogel filaments and their prospect as microactuators, CSEM researchers have been studying the non-equilibrium dynamics of shape changes of nanofilaments under a sudden change in the parameters controlling the state of the filaments. A common theme that emerges in our study is that internal stress can lead to complex shape dynamics through redistribution of the deformation energy. The following example shows the intricate writhing dynamics induced by twisting an initially straight elastic rod in a viscous medium. In this case, relaxation of the twist deformation occurs by conversion to bending, which causes the initially straight rod to writhe into a helical structure through a sequence of complex motions. Insight into these motions may provide a basis for design of nanoscale systems capable of walking or swimming.

For further information, please contact Professor David Tirrell, team leader of IRG 1: (626) 395-3140 or tirrell@cheme.caltech.edu.