Opening and Closing of Particle Shells on Droplets via Electric Fields and Its Applications

Abstract

Active, tunable, and reversible opening and closing of particle shells on droplets may facilitate chemical reactions in droplets and enable various small-scale laboratory operations, including online detection, measurement, and adjustment of droplet liquid. Manipulating various types of particle shells in a controlled manner requires new routes. This work provides a new strategy for controlling the spatial arrangement of particle-covered oil droplets using electric fields that expands the application of responsive droplets beyond the abovementioned examples. The behavior of stimulated particle-covered droplets is exploited in multiple ways: to form an active smart device, fabricate Janus and patchy shells, create an online diagnostic tool, and produce a tool for fundamental studies. Electric fields are used here to manipulate particle films on oil droplets through the synergetic action of droplet deformation and electrohydrodynamic liquid flows. First, the effects of electric field strength and liquid viscosity on droplet deformation, surface particle arrangements, and dynamics are examined in detail. Then three examples of applications of responsive particle-covered droplets are demonstrated. Our results show that the reversible opening and closing of the droplet’s shells, composed of various types of particles, can be conveniently achieved through electric fields, opening up a new possibility for applications in optics, clinical diagnostics, microfluidics, and material engineering.

Electro-Hydrodynamics of Emulsion Droplets: Physical Insights to Applications

“…Manipulating particles anchored on the droplet interface is one of the promised techniques for designing functional droplet. Using active structuring of a particle-covered droplet under the electric field, Rozynek et al demonstrated a millimeter-sized optical diaphragm [ 162 ] ( Figure 10 E). Li et al redistributed aluminum nanoparticles on an o/w emulsion droplet via an electric field for generating a Janus droplet [ 163 ] ( Figure 10 F).…”

“…( D ) Stabilizing the shape of deformed colloidal particles by the interfacial jamming of nanoparticles [ 121 ]. ( E ) Optical diaphragm based on the particle self-assembly [ 162 ]. ( F ) Generation of an aluminum Janus particle using an electric field [ 163 ].…”

Electric-field-induced deformation, yielding, and crumpling of jammed particle shells formed on non-spherical Pickering droplets

“…14,15 Moreover, particle-covered droplets facilitate the fabrication of new materials [16][17][18] and can be designed to form novel adaptive structures. 19,20 Pickering droplets can also be used in basic research, e.g., as model systems for mimicking the physical properties of red blood cells 21 or for studying particle crystal growth and ordering or particle layer buckling on curved interfaces. [22][23][24][25][26] In many research areas, knowledge of the stability and mechanics of an individual Pickering droplet is essential, e.g., for the efficient fabrication of Pickering emulsions, 27 for designing emulsions with controlled stability, 28,29 and, in general, for the further development of the abovementioned research fields.…”

Effect of the Dispersion Medium Viscosity on the Electrorheological Behavior of Halloysite Suspensions in Polydimethylsiloxane

“…Along with other "smart" materials, ERFs are widely used in technology in various devices such as shock absorbers, control valves, dampers and in microfluidics, robotics, sensors, etc [2]. The modern applications of the ER effect include sensors for rapid plague diagnostics and nanodiaphragms with adjustable aperture [3,4]. The several qualities are essential to the wide practical application of ERFs, namely significant change of rheological properties under electric field, low conductivity, chemical, aggregate and thermal stability.…”