Figure 5. Assessment of the bundles' propensity to bend.

We consider two vertical bundles each blocked by the rest the network, with typical mesh size ξ (a). Thermal fluctuations or internal network stresses may cause the two filaments to deform and come into contact (b). Denoting by the binding free energy associated with the binding of a crosslinker and by the typical distance between crosslinks, we assess whether such configurations are energetically favourable by comparing the energy bonus due to crosslinker binding to the energy penalty ≈k_BTL_p/ξ because of filament bending, where L_p is the persistence length of the bundle. The latter exceeds the former for mesh sizes smaller than , (≃3 μm with the parameters of the main text). Our treatment of bundles as rigid is thus justified in these networks.