Interfacial Targeting of Sessile Droplets Using Electrospray

Area of Science:

• Colloid science
• Surface chemistry
• Materials science

Background:

• Controlling nanoparticle assembly at liquid interfaces is crucial for fabricating ordered structures.
• Electrospray atomization offers a method for precise delivery of materials to liquid surfaces.

Purpose of the Study:

• To investigate the use of electrospray atomization for delivering nanoparticles and surfactants to sessile droplets.
• To explore the role of surfactants in controlling interfacial particle transport and deposit morphology.
• To demonstrate a scalable method for creating structured colloidal monolayers.

Main Methods:

• Utilized electrospray atomization to deposit solvent-free nanoparticles and surfactants onto sessile droplets.
• Investigated interfacial particle motion under varying surfactant conditions (none, high-molecular-weight, small surfactants).
• Employed numerical modeling (lattice Boltzmann-Brownian dynamics) to confirm particle transport mechanisms.

Main Results:

• Nanoparticles adsorbed at the droplet interface and mapped to the substrate upon evaporation, forming deposits.
• Small surfactants (e.g., sodium dodecyl sulfate) induced solutal Marangoni flow, driving particles to the droplet apex.
• High-molecular-weight surfactants and absence of surfactants did not induce significant interfacial convection.
• Numerical simulations corroborated the observed particle transport driven by surfactant-induced surface tension gradients.

Conclusions:

• Electrospray atomization combined with sacrificial targets enables scalable fabrication of structured colloidal monolayers.
• Small surfactants are key to inducing directed particle motion via Marangoni flow for controlled deposit patterning.
• The findings provide a novel approach for creating organized nanoparticle assemblies.