# Self-organization of a mesoscale bristle into ordered hierarchical helical assemblies

This paper demonstrates that this elastocapillary force can be used to self-assemble stiff and upright nano-pillars to helical clusters and even coiled large-area structures. The fundamental theory involves the following parameters: $r$: circular radius of the nano-pillars $L$: length of nano-pillars $d$: distance between adjacent nano-pillars $E$: Yong's modulus $B~Er^4$: bending stiffness of the nano-pillars $J$: adhesive energy per unit area $\gamma$: interfacial tension of the evaporating liquid
$\tau=\pi$