Electrified Coaxial Jets Technology
The core of the Yflow technology consists in the formation of a very thin coaxial jet of two immiscible liquids by the action of the electro-hydro-dynamic (EHD) forces.
The core of the Yflow technology consists in the formation of a very thin
coaxial jet of two immiscible liquids by the action of the electro-hydrodynamic
(EHD) forces. The liquids are injected through two coaxial needles
connected to a high voltage power supply. Under the action of the electric
field, the compound meniscus adopts a conical shape (the so called compound
Taylor cone); a very thin electrified coaxial jet (ECJ) being issued from the
apex cone. The diameter of the coaxial jet is independent on those of the
needles, and it can be tailored into the micro or nanometric size range by
suitably tuning of the flow rates and liquids properties, mainly the electrical
conductivity. The electrical stresses are transmitted towards the bulk by
viscosity and the stretched outer flow deforms the inner meniscus and put it
into motion. As shown in the video of the homepage, inner and outer liquids
flow coaxially to form the steady EJC. The evolution of this ECJ may lead
either to the formation of micro/nanocapsules or micro/nanofibers, with
well defined core-shell structure. C apsules are obtained from the breakup of a coaxial jet while fibers can be obtained if the outer liquid
solidifies before the jet breakup. This novel one-step method to fabricate core-shell nanoparticles is highly competitive with other existing
strategies based on either templates and molecular self-assembly. In fact, chemical or physical adherence onto the surface of the template
depends on case-specific interactions i.e., a particular approach may not even be adaptable to the synthesis of a chemically similar material.
Furthermore, the first synthetic step is the design of a nanotemplate, which is not necessarily a trivial task. Therfore, the use of solid templates
invariably leads to a multistep approach: template design, growth of the structure on or around the template, and ultimately its selective removal
from the precursor (composite) structure. On the contrary, the ECJ approach is mostly free of these constraints since, firstly, the coaxial shape is
obtained by the use of physical forces (EHD) rather than chemical interactions and, secondly, the inner liquid plays the role of the template to
obtain hollow/coaxial structures.
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