2 research outputs found
Large-Scale Single Particle and Cell Trapping based on Rotating Electric Field Induced-Charge Electroosmosis
We
propose a simple, inexpensive microfluidic chip for large-scale
trapping of single particles and cells based on induced-charge electroosmosis
in a rotating electric field (ROT-ICEO). A central floating electrode
array, was placed in the center of the gap between four driving electrodes
with a quadrature configuration and used to immobilize single particles
or cells. Cells were trapped on the electrode array by the interaction
between ROT-ICEO flow and buoyancy flow. We experimentally optimized
the efficiency of trapping single particles by investigating important
parameters like particle or cell density and electric potential. Experimental
and numerical results showed good agreement. The operation of the
chip was verified by trapping single polystyrene (PS) microspheres
with diameters of 5 and 20 μm and single yeast cells. The highest
single particle occupancy of 73% was obtained using a floating electrode
array with a diameter of 20 μm with an amplitude voltage of
5 V and frequency of 10 kHz for PS microbeads with a 5-μm diameter
and density of 800 particles/μL. The ROT-ICEO flow could hold
cells against fluid flows with a rate of less than 0.45 μL/min.
This novel, simple, robust method to trap single cells has enormous
potential in genetic and metabolic engineering
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