2 research outputs found
Continuously Electrotriggered Core Coalescence of Double-Emulsion Drops for Microreactions
Microfluidically
generated double emulsions are promising templates for microreactions,
which protect the reaction from external disturbance and enable in
vitro analyses with large-scale samples. Controlled combination of
their inner droplets in a continuous manner is an essential requirement
toward truly applications. Here, we first generate dual-cored double-emulsion
drops with different inner encapsulants using a capillary microfluidic
device; next, we transfer the emulsion drops into another electrode-integrated
polydimethylsiloxane microfluidic device and utilize external AC electric
field to continuously trigger the coalescence of inner cores inside
these emulsion drops in continuous flow. Hundreds of thousands of
monodisperse microreactions with nanoliter-scale reagents can be conducted
using this approach. The performance of core coalescence is investigated
as a function of flow rate, applied electrical signal, and core conductivity.
The coalescence efficiency can reach up to 95%. We demonstrate the
utility of this technology for accommodating microreactions by analyzing
an enzyme catalyzed reaction and by fabricating cell-laden hydrogel
particles. The presented method can be readily used for the controlled
triggering of microreactions with high flexibility for a wide range
of applications, especially for continuous chemical or cell assays
A Simplified Microfluidic Device for Particle Separation with Two Consecutive Steps: Induced Charge Electro-osmotic Prefocusing and Dielectrophoretic Separation
Continuous
dielectrophoretic separation is recognized as a powerful
technique for a large number of applications including early stage
cancer diagnosis, water quality analysis, and stem-cell-based therapy.
Generally, the prefocusing of a particle mixture into a stream is
an essential process to ensure all particles are subjected to the
same electric field geometry in the separation region. However, accomplishing
this focusing process either requires hydrodynamic squeezing, which
requires an encumbering peripheral system and a complicated operation
to drive and control the fluid motion, or depends on dielectrophoretic
forces, which are highly sensitive to the dielectric characterization
of particles. An alternative focusing technique, induced charge electro-osmosis
(ICEO), has been demonstrated to be effective in focusing an incoming
mixture into a particle stream as well as nonselective regarding the
particles of interest. Encouraged by these aspects, we propose a hybrid
method for microparticle separation based on a delicate combination
of ICEO focusing and dielectrophoretic deflection. This method involves
two steps: focusing the mixture into a thin particle stream via ICEO
vortex flow and separating the particles of differing dielectic properties
through dielectrophoresis. To demonstrate the feasibility of the method
proposed, we designed and fabricated a microfluidic chip and separated
a mixture consisting of yeast cells and silica particles with an efficiency
exceeding 96%. This method has good potential for flexible integration
into other microfluidic chips in the future