Versatile on-demand droplet generation for controlled encapsulation |
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| Authors: | Minsoung Rhee Peng Liu Robert J Meagher Yooli K Light Anup K Singh |
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| Institution: | 1.Sandia National Laboratories, Livermore, California 94550, USA;2.Joint BioEnergy Institute, Emeryville, California 94608, USA |
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| Abstract: | 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. |
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| Keywords: | biological techniques bioMEMS cellular biophysics drops encapsulation lab-on-a-chip microfluidics microorganisms multiphase flow size control |
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