Thermally assisted buckling of colloidal assemblies

We investigate the effect of thermal fluctuations on the buckling instability of colloidal assemblies. Using laser tweezers to grab the ends of, and push on colloidal chains assembled with critical Casimir forces, we probe the buckling instability analogous to the Euler buckling of macroscopic beams, in the presence of thermal activation. We find that buckling fluctuations diverge upon approaching the buckling point, while their time scale diverges similar to critical slowing down. Molecular dynamic simulations allow quantitative extraction of the corresponding critical exponents, which we identify as the mean-field critical exponents. Using an analytically solvable minimal model, we elucidate the origin of these exponents. The surprisingly rich physics of this simple thermal mechanical system highlights the interplay of thermal fluctuations and elasticity in the buckling stability of micron-scale architectures such as biomaterials.