Carbon nanotubes and biological filaments each spontaneously assemble into kinked helices, rings, and ‘‘tennis racket’’ shapes due to
competition between elastic and interfacial effects. We show that the
slender geometry is a more important determinant of the morphology than any molecular details. Our mesoscopic continuum theory is
capable of quantifying observations of these structures and is suggestive of their occurrence in other filamentous assemblies as well