Advection kinetics induced self assembly of colloidal nanoflakes into microscale floral structures

TL;DR

This study investigates how internal hydrodynamics and advective transport within evaporating colloidal droplets influence the self-assembly of nanoflakes into floral patterns, highlighting the effects of fluid composition and nanomaterial concentration.

Contribution

It provides new insights into the role of solutal Marangoni advection in controlling nanoflake self-assembly and pattern formation during droplet evaporation.

Findings

Self-assembled rose-like floral structures observed.

Nanostructure size depends on fluid composition and nanomaterial concentration.

Internal advection regimes influence clustering and aggregation.

Abstract

This article explores the governing role of the internal hydrodynamics and advective transport within sessile colloidal droplets on the self assembly of nanostructures to form floral patterns. Water acetone binary fluid and Bi2O3 nanoflakes based complex fluids are experimented with. Microliter sessile droplets are allowed to vaporize and the dry out patterns are examined using scanning electron microscopy. The presence of distributed self assembled rose like structures is observed. The population density, structure and shape of the floral structures are noted to be dependent on the binary fluid composition and nanomaterial concentration. Detailed microscopic particle image velocimetry analysis is undertaken to qualitatively and quantitatively describe the solutal Marangoni advection within the evaporating droplets. It has been shown that the kinetics, regime and location of the internal advection are responsible factors towards the hydrodynamics influenced clustering, aggregation and self-assembly of the nanoflakes. In addition, the size of the nanostructures and the complex fluids.