Nanoparticle assembly by confinement in wrinkles: experiment and simulations

We created hierarchically ordered structures of nanoparticles on smooth planar hydrophilic substrates by drying colloidal dispersions in confinement under macroscopic stamps with microscopically wrinkled surfaces. Experiments were carried out with model nanoparticle suspensions that possess high colloidal stability and monodispersity. The structures ranged from single parallel lines of particles to arrays of dense prismatic ridges. The type of observed structure could be controlled by the particle concentration in the initial dispersion. Confinement between two crossed stamps led to interconnected meshes of particles. The precise morphology could be predicted in all cases by Monte Carlo computer simulations of confined hard spheres. Our findings open up possibilities for versatile nanoparticle assembly on surfaces. We introduce drying of colloidal dispersions under confinement by wrinkled soft stamps for assembly of nanoparticles into quasi-1-d and 2-d-structures. Comparison of experimental results to MC-simulations allows the process control parameters to be identified.