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Large-Scale Production of Compound Bubbles Using Parallelized Microfluidics for Efficient Extraction of Metal Ions

Abstract

Recent advances in microfluidic technologies have enabled production of micro-scale compound bubbles that consist of gaseous cores surrounded by thin liquid shell, achieving control and uniformity not possible using conventional techniques. These compound bubbles have demonstrated enormous utility as functional materials for drug delivery, as ultra-lightweight structural materials, as engineered acoustic materials, and also as a separating agent for extraction of metal ions from waste fluid streams. Despite these successful demonstrations, compound bubbles have largely remained at the laboratory-scale due to the slow production rates endemic to microfluidics (< 10 mL/hr). Although parallelization approaches have enabled large-scale production of simple emulsions and bubbles, its application to the production of higher order dispersions such as compound bubbles has been limited because the optimal processing window for the production of uniform compound bubbles is relatively narrow and the required channel geometry is quite complex. In this report, we demonstrate the parallelization of multi-stage flow focusing droplet generators that produce compound ternary bubbles. We parallelize 400 multi-stage FFG devices, generating up to 3 L (~ 1011 bubbles) of monodispersed (CV< 5 %) compound bubbles in less than 1 hour. We show that it is critical to use multi-height channels and operate each individual generator in a flow regime that is minimally sensitive to variations in the flow rate to reliably produce uniform compound bubbles. By taking advantage of the buoyancy and the high mass transfer rate that comes from the thin shells of gas-in-oil-in-water compound bubbles which reduces the diffusion length for the metal ions and thus accelerates the extraction kinetics, we demonstrate the utility of mass-produced compound bubbles from the parallelized device for highly efficient extraction of Nd ions from a model waste stream.

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Publication details

The article was received on 18 Nov 2018, accepted on 09 Jan 2019 and first published on 10 Jan 2019


Article type: Paper
DOI: 10.1039/C8LC01267A
Citation: Lab Chip, 2019, Accepted Manuscript
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    Large-Scale Production of Compound Bubbles Using Parallelized Microfluidics for Efficient Extraction of Metal Ions

    H. Jeong, Z. Chen, S. Yadavali, J. Xu, D. Issadore and D. Lee, Lab Chip, 2019, Accepted Manuscript , DOI: 10.1039/C8LC01267A

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