Formation of Highly Ordered Spherical Aggregates from Drying Microdroplets of Colloidal Suspension

Abstract

The formation of highly ordered spherical aggregates of silica nanoparticles by the evaporation of single droplets of an aqueous colloidal suspension levitated (confined) in the electrodynamic quadrupole trap is reported. The transient and final structures formed during droplet evaporation have been deposited on a silicon substrate and then studied with SEM. Various successive stages of the evaporation-driven aggregation of nanoparticles have been identified: formation of the surface layer of nanoparticles, formation of the highly ordered spherical structure, collapse of the spherical surface layer leading to the formation of densely packed spherical aggregates, and rearrangement of the aggregate into the final structure of a stable 3D quasi-crystal. The evaporation-driven aggregation of submicrometer particles in spherical symmetry leads to sizes and morphologies of the transient and final structures significantly different than in the case of aggregation on a substrate. The numerical model presented in the article allows us to predict and visualize the observed aggregation stages and their dynamics and the final aggregates observed with SEM.

Sodium dodecyl sulfate microaggregates with diversely developed surfaces: Formation from free microdroplets of colloidal suspension

“…2(c)) were spherical. For initially smaller microdroplets, they had regularly ordered SiO 2 nanospheres at the surface, similar to the earlier ones we reported in [19]. However, aggregates obtained from larger droplets ( fig.…”

“…Recently, we reported a versatile DSA method [19,20] of formation of highly ordered spherical aggregates from drying microdroplets of colloidal SiO 2 suspension by the evaporation of single microdroplets levitated in the linear electrodynamic quadrupole trap [21][22][23]. The use of electrodynamic trapping of microdroplets of colloidal suspensions provide a contactless versatile solution.…”

“…The use of electrodynamic trapping of microdroplets of colloidal suspensions provide a contactless versatile solution. It allows unsupported drying of the solvent/dispersion media [24,25], control and retention of the droplets/aggregates [26] as well as singly deposition ("soft-landing") of the final products with well-defined symmetries [19,20]. The technique requires less material implementation from first principles and does not require any pre-treatment of the substrates on which the dried particles are deposited.…”

Numerical Simulation of Structure Formation of Surface-Modified Nanoparticles during Solvent Evaporation

“…Therefore, it is important to understand the dispersion and aggregation behavior of nanoparticles in a solvent and the structure for-mation mechanism of nanoparticles during solvent evaporation for the application of nanofluids in printed electronics. There exist a lot of experimental studies on the structure of nanoparticles after solvent evaporation (Nishikawa et al, 2005;Lee et al, 2010;Suhendi et al, 2013;Woźniak et al, 2015). There also exist numerical simulations of the structure formation of nanoparticles during solvent evaporation.…”

Effects of Silica Nanoparticles and Silica-Zirconia Nanoclusters on Tribological Properties of Dental Resin Composites

“…Nanoclusters are nanoparticle aggregates with controlled size and morphology, obtained prior to the dispersion process in the resin [25][26][27]. One of the methodologies used to obtain these aggregates is spray drying using nanoparticle dispersions [28][29][30]. Examples of dental materials that use nanoparticle aggregates are Filtek Supreme Body resins and Filtek Supreme Translucent resin (3M), which use aggregates of silica and zirconia nanoparticles [23,25].…”