The rapid co‐assembly of graphene oxide (GO) nanosheets and a surfactant at the oil/water (O/W) interface is harnessed to develop a new class of soft materials comprising continuous, multilayer, interpenetrated, and tubular structures. The process uses a microfluidic approach that enables interfacial complexation of two‐phase systems, herein, termed as “liquid streaming” (LS). LS is demonstrated as a general method to design multifunctional soft materials of specific hierarchical order and morphology, conveniently controlled by the nature of the oil phase and extrusion's injection pressure, print‐head speed, and nozzle diameter. The as‐obtained LS systems can be readily converted into ultra‐flyweight aerogels displaying worm‐like morphologies with multiscale porosities (micro‐ and macro‐scaled). The presence of reduced GO nanosheets in such large surface area systems renders materials with outstanding mechanical compressibility and tailorable electrical activity. This platform for engineering soft materials and solid constructs opens up new horizons toward advanced functionality and tunability, as demonstrated here for ultralight printed conductive circuits and electromagnetic interference shields.
Drop motion and deformation of a conducting drop in a perfect (or leaky) dielectric fluid and a leaky dielectric drop in a leaky dielectric fluid, in a non-uniform electric field is presented. The investigated non-uniform electrode configuration is of the pin-plate type. Systematic experiments and comparison with existing analytical models is carried out. The main results are summarized as follows: (i) The dielectrophoretic motion of a conducting drop in a non-uniform electric field is explained reasonably well assuming a spherical drop, although deviations are observed at large deformations. Thus dielectrophoretic motion shows a weak shape dependence. (ii) The deformation of a conducting drop in a non-uniform electric field has comparable contributions from the uniform and the non-uniform components of the applied field. (iii) The leaky dielectric nature of the medium results in three different states for a conducting drop (a) no movement, (b) near electrode cyclic motion, and (c) cyclic motion between the electrodes. The frequency of cyclic motion decreases with electric field for near electrode motion. On the contrary it increases with the applied field for electrode-electrode cyclic motion. The leaky dielectric system showing positive dielectrophoresis leads to the drop getting attached to the pin electrode causing emulsification at large field. A leaky dielectric drop suspended in a dielectric, system exhibiting negative dielectrophoresis shows oblate deformation which is augmented by the plate-drop hydrodynamic interaction.
The interaction and coalescence of a freely suspended drop pair, aligned in a uniform DC electric field is investigated using experiments, analytical theory, and numerical calculations (boundary element method (BEM)). The systems considered are a pair of perfect conductor drops in a perfect dielectric fluid and a pair of leaky dielectric drops suspended in another leaky dielectric fluid. The applied electric field induces a dipole in the drops that form a pair, leading to their approach and subsequent merger. The study focuses on the drop approach and the film drainage stages of drop-drop electrocoalescence. The shapes and motion predicted using BEM are in good agreement with the experimental results and analytical theory.
This study addresses the effectiveness of constant and pulsed DC fields in promoting coalescence of dispersed water drops in an oil-continuous phase. For this purpose, a train of drops of relatively uniform size is injected into a stream of flowing sunflower oil. This stream is then admitted to a coalescing section, where an electric field is applied between a pair of ladder-shape bare electrodes. The capability of this device to enhance coalescence of droplets in a chain is investigated at different field intensities, frequencies and waveforms. The effect of the initial inter-droplet separation distance on the process performance is also addressed under constant DC fields. The dominant coalescence mechanism is found to be due to dipole-dipole interaction at low field strength, whereas electrophoresis becomes predominant at higher field strength. Experiments reveal the existence of an optimal frequency, where the average droplet size enlargement is maximized, especially at low field strengths. The droplet size at the outlet of the coalescer is also found to be dependent on the field waveform.
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