Abstract
Although buckling is a prime route to achieve functionalization and synthesis of single colloids, buckling of colloidal structures---made up of multiple colloids---remains poorly studied. Here, we investigate the buckling of the simplest form of a colloidal structure, a colloidal chain that is self-assembled through critical Casimir forces. We demonstrate that the mechanical instability of such a chain is strikingly reminiscent of that of classical Euler buckling but with thermal fluctuations and plastic effects playing a significant role. Namely, we find that fluctuations tend to diverge close to the onset of buckling and that plasticity controls the buckling dynamics at large deformations. Our work provides insight into the effect of geometrical, thermal and plastic interactions on the nonlinear mechanics of self-assembled structures, of relevance for the rheology of complex and living matter and the rational design of colloidal architectures.
Highlights
Due to recent advances in colloidal synthesis and interaction control, colloidal self-assembly has become a promising platform for designer materials with controlled internal architecture and tunable physical properties [1,2,3], such as unprecedented photonic [4], shape-changing [5,6], and mechanical properties [7]
By experiments, simulations, and theory, the mechanical instabilities of a slender self-assembled colloidal structure, observing a form of stochastic buckling where thermal fluctuations and associated entropic force effects are amplified in the vicinity of a buckling instability
The fluctuations decrease again and a kink appears at a well-defined large compressive displacement up
Summary
Due to recent advances in colloidal synthesis and interaction control, colloidal self-assembly has become a promising platform for designer materials with controlled internal architecture and tunable physical properties [1,2,3], such as unprecedented photonic [4], shape-changing [5,6], and mechanical properties [7]. There has been an extensive focus on the dynamical and structural aspects of self-assembly [14,15], while the mechanical instabilities of self-assembled objects have been experimentally much less explored; yet they play a crucial role in the response of soft materials [16,17,18,19,20] from biological networks [21] to mechanical metamaterials [22]. Potentially crucial factors such as the effective elastic interactions, the role of geometric nonlinearities, stochastic noise, and plasticity are virtually unexplored
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