Focussing frustration for self-limiting assembly of flexible, curved particles

TL;DR

This paper demonstrates how geometric frustration in curved colloidal particles leads to self-limiting assembly sizes, controlled by particle shape, adhesion energy, and frustration escape modes, enabling programmable finite structures.

Contribution

It introduces a continuum and simulation framework showing how shape-induced frustration controls finite self-assembly sizes in deformable, curved particles, with tunable parameters.

Findings

Self-limiting stacks exceed individual particle dimensions.

Assembly size is controlled by the ratio of bending costs to adhesion energy.

Frustration escape modes can be suppressed to tune assembly size.

Abstract

We show that geometric frustration in a broad class of deformable and naturally curved, shell-like colloidal particles gives rise to self-limiting assembly of finite-sized stacks that far exceed particle dimensions. When inter-particle adhesions favor conformal stacking, particle shape requires {\it curvature focussing} in the stack, leading to a super-extensive accumulation of bending costs that ultimately limit the ground-state stack size to a finite value. Using a combination of continuum theory and particle-based simulation, we demonstrate that the self-limiting stack size is controlled by the ratio of the intra-particle bending costs to inter-particle adhesion energy, ultimately achieving assembly sizes that are tuned from a few, up to several tens of, particles. We show that the range of self-limiting assembly is delimited by the two structural modes of "frustration escape" which evade the thermodynamic costs of curvature focussing. Crucially, each of these modes can be suppressed through suitable choice of adhesive range and lateral patchiness of adhesion, providing feasible strategies to program finite assembly size via the interplay between shape-frustration, binding and deformability of colloidal building blocks.