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We present a droplet-based microfluidic system for performing bioassays requiring controlled
analyte encapsulation by employing highly flexible on-demand droplet generation. On-demand droplet
generation and encapsulation are achieved pneumatically using a microdispensing pump connected to a
constant pressure source.
The system generates single droplets to the collection route only when the pump is actuated with a
designated pressure level
and produces two-phase parallel flow to the waste route during the stand-by state. We analyzed the effect of
actuation pressure on the
stability and size of droplets and optimized conditions for generation of stable droplets over a
wide pressure range. By
increasing the duration of pump actuation, we could either trigger a short train of identical size
droplets or generate a single larger droplet. We also investigated the methodology to control
droplet contents by fine-tuning flow rates or implementing a resistance bridge between the pump and main channels.
We demonstrated the integrated chip for on-demand mixing between two aqueous phases in droplets and
on-demand encapsulation of Escherichia coli cells. Our unique on-demand feature for
selective encapsulation is particularly appropriate for bioassays with extremely dilute samples,
such as pathogens in a clinical sample, since it can significantly reduce the number of empty
droplets that impede droplet collection and subsequent data analysis. 相似文献
2.
Even though isoelectric focusing (IEF) is a very useful technique for sample concentration and
separation, it is challenging to extract separated samples for further processing. Moreover, the
continuous sample concentration and separation are not possible in the conventional IEF. To overcome
these challenges, free flow IEF (FFIEF) is introduced in which a flow field is applied in the
direction perpendicular to the applied electric field. In this study, a mathematical model is developed for FFIEF to understand
the roles of flow and
electric fields for
efficient design of microfluidic
chip for continuous separation of proteins from an initial well mixed solution. A finite volume based
numerical scheme is implemented to simulate two dimensional FFIEF in a microfluidic chip. Simulation results
indicate that a pH gradient forms as samples flow downstream and this pH profile agrees well with
experimental results validating our model. In addition, our simulation results predict the experimental behavior of
pI markers in a FFIEF microchip. This numerical model is used to predict the separation
behavior of two proteins
(serum albumin and cardiac troponin I) in a two-dimensional straight microchip. The effect of
electric field is
investigated for continuous separation of proteins. Moreover, a new channel design is presented to increase the separation
resolution by introducing cross-stream flow velocity. Numerical results indicate that the separation
resolution can be improved by three folds in this new design compare to the conventional straight
channel design. 相似文献
3.
Panwong Kuntanawat Jirapat Ruenin Rungrueang Phatthanakun Phongsakorn Kunhorm Werasak Surareungchai Sompong Sukprasong Nimit Chomnawang 《Biomicrofluidics》2014,8(3)
A simple microwell-based microfluidic chip for microalgal cells trapping was
fabricated. An electrostatic
cell trapping
mechanism, enabled by a positively charged glass surface, was used. The chip was capable of capturing multiple algal
cell types.
In the case of filamentous Spirulina platensis, we observed single filament
occupancy of up to ∼30% available wells, as high as some previously proposed methods. Captured
filaments were not of any preferential size, suggesting well randomized cell trapping. It was found
that the electrostatic
attraction did not affect the cell
growth. Total replacement of liquid inside the wells could be achieved by pumping
new solutions via the inlet, making single cell experiments in controlled chemical conditions
possible. After the top layer of the chip was removed, cells in the wells could be simply transferred using a
micropipette, turning the chip into a platform for strain selection. 相似文献
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