Figure 5.

Equilibrium self-assembly of microtubules. (a) Microtubules at high concentration self-assemble into ordered arrays (a nematic crystalline phase). This research was originally published in⁷². © the American Society for Biochemistry and Molecular Biology. (b) The combination of microtubule aggregation due to depletion forces and forces exerted by cross-linkers capable of passively diffusing along the microtubule can give rise to contractile networks. Reproduced with permission from⁷⁶. (c) Microtubule asters can be assembled by end-specific attachment of microtubules to microspheres (left), or by polymerization of microtubules from the surface of microspheres (right). Adapted with permission from^{84, 88}. Copyright 2008, 2013 American Chemical Society.