Dual-Scale Pattern Formation in Nanoparticle Assemblies

Abstract

A pseudo-3D lattice gas-based Monte Carlo simulation is used to reproduce dual-scale nonequilibrium structures formed from drying colloidal nanoparticle solutions. Morphologies possessing multiple length scale features are recreated by coupling the chemical potential to the solvent density, modeling a film thickness-dependent disjoining pressure. By assigning a sigmoidal form to the chemical potential, a switch in the dewetting mechanism at a threshold solvent density is capable of producing nanoparticle patterning at two length scales. Dual-scale cellular networks, and nanoparticle ring and fingering structures coexisting with small scale patterning, can all be generated in this way with suitable simulation parameters. Extensive exploration of the model's parameter space maps the temperature-dependent spinodal line and demonstrates the influence of nanoparticle concentration on morphology.

Bio-inspired Murray materials for mass transfer and activity

“…Evaporation-driven self-assembly of the NPs dispersed in hexane was used to obtain the macro–meso–microporous film with the required macroporous structures on various substrates. Holes induced by the spontaneous evaporation of hexane could nucleate and expand, forming macroporous rings2829. The NPs are pushed to the edges and aggregated by the expanding holes, resulting in compact walls composed of mesopores between the NPs30.…”

Nanomaterial Patterning in 3D Printing

“…This can mitigate the coffee‐ring phenomenon, which Song and co‐workers demonstrated by assembling polystyrene nanoparticles to form a range of microstructures from flat disks to dome structures with an increasing height to diameter ratio 231. In addition to counter‐acting the coffee‐ring effect, nonequilibrium dewetting processes can be leveraged to produce a plethora of patterns through the modification of factors such as nanoparticle concentration in the ink, the solvent used to form printable ink, method of deposition, and the free surface energy of the substrate237 For example, isolated islands,254–256 worm‐like domains,257 interconnected cellular networks with continuous labyrinthine structures,258–261 and ring structures262–264 have been reported with gold, latex, and silver nanoparticles.…”

Temporal dynamics of site percolation in nanoparticle assemblies

“…The strength of the NNN energies are 1/ √ 2 of the corresponding NN terms. For comparison with other studies which use the NN interactions only, here the values of the total interaction energy summing from nearest and next-nearest neighbors are therefore divided by the factor 1 + √ 1/2 [7,8]. μ is the value of chemical potential which determines the equilibrium state of solvent lattice sites on the surface.…”

“…For each MCS, a number of L × L attempted updates (diffusion of the nanoparticles, evaporation and condensation of the solvents) are examined according to the Metropolis algorithm [7,9]. To reduce the artifact due to the choice of boundary condition and the finite-size effect, the system with area coverage of nanoparticles p will be classified as having a percolating cluster if the n max 0.5.…”

“…For some cases with slower convergence, the simulations are terminated at t = 4000 MCSs as argued in Ref. [7].…”