Assembly and Rearrangement of Particles Confined at a Surface of a Droplet, and Intruder Motion in Electro-Shaken Particle Films

Abstract

Manipulation of particles at the surface of a droplet can lead to the formation of structures with heterogeneous surfaces, including patchy colloidal capsules or patchy particles. Here, we study the assembly and rearrangement of microparticles confined at the surface of oil droplets. These processes are driven by electric-field-induced hydrodynamic flows and by ‘electro-shaking’ the colloidal particles. We also investigate the motion of an intruder particle in the particle film and present the possibility of segregating the surface particles. The results are expected to be relevant for understanding the mechanism for particle segregation and, eventually, lead to the formation of new patchy structures.

Electric Field-Driven Assembly of Sulfonated Polystyrene Microspheres

“…For the particles sulfonated for short periods of time, the low dielectric constant and electric conductivity ( Table 2 ) yield DEP and dipolar forces that are ~2–3 orders of magnitude smaller than the EHD drag force. Consequently, EHD circulation flows govern the dynamics of PS particles sulfonated for short periods of time (4 min), i.e., the particles follow the EHD flows and are brought to the droplet equator where they form a ribbon-like structure ( Figure 7 b) [ 23 , 62 ]. For these particles, we do not observe any direct electrical interactions (e.g., electrophoretic motion or dipolar interaction between the particles).…”

Role of Surface Energy of Nanoparticle Stabilizers in the Synthesis of Microspheres via Pickering Emulsion Polymerization

“…Pickering emulsions can be biocompatible if the oils and stabilizing particles are biocompatible such as starch [ 9 ]. The emulsion droplet protected by an armor of self-assembled monolayers of nanoparticles, referred to as colloidosomes [ 14 ], are attractive vehicles for microencapsulation and cascade reactions [ 15 ], or even as platforms for fundamental studies for interfacial dynamics such as diffusion, interaction, 2D assembly of particles at liquid–liquid interfaces [ 23 , 24 , 25 , 26 ], etc. The application potential of Pickering emulsions technology in manufacturing nano and microstructures can be greatly expanded by combining it with complementary methods; for example, micron sized hollow spheres decorated with catalyst nanoparticles could be obtained [ 27 ] from combining Pickering emulsification with non-solvent induced phase separation (NIPS) method.…”

Particle-covered drops in electric fields: drop deformation and surface particle organization

“…[1][2][3][4] This is because they are promising for a variety of practical applications, such as in food technology, 5 the oil industry, 6 biofuel processing, 7 and for improving pharmaceutical products. 8 Moreover, such drops possess characteristics that make them useful as experimental model systems for studying, for example, particle effects on interfacial tension, 9 particle crystal growth and ordering or particle layer buckling on curved interfaces, [10][11][12][13] particle assembly and rearrangement on drop surfaces, 14,15 and particle detachment from drops. 16 Particle-covered drops can additionally be employed for fabricating porous structures, 17 granular or colloidal capsules of different mechanical properties, morphologies, or shapes, 18,19 and adaptive structures.…”

“…Removing particles from a drop is also possible through tip-streaming mechanisms 42 and strong EHD flows. 14 The applicability of the abovementioned approaches depends on the electric properties of both the particles and the liquids. For example, the dielectrophoretic force (force exerted on an object subjected to a non-uniform electric field) acting on drop surface particles is very small (and cannot be used to manipulate particles) when the dielectric properties of those particles are similar to those of the drop and surrounding liquid.…”