Experimental and numerical study of temperature-actuated droplets within microfluidics
Date
2019-04-30
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Abstract
Droplet microfluidics (DM), which involves the production of nano-/micro- droplets and particles using immiscible phases, reveals an impressive evolutionary trend that have been widely used to establish highly sensitive, robust, and flexible multitasking microsystems. Droplets generated by DM systems can operate thousands of parallel reactions without increasing device size or complexity which facilities the possibility of developing miniaturized fully integrated high‐throughput screening devices. The high surface-to-volume ratio offered by micro-drops ensures the rapid heat and mass transfer and makes thermal stimulation a powerful actuation technique to perform exquisite transporting, mixing, melting, and changing the volume formed droplets. The work aims to numerically and experimentally analyze the droplet generation and behavior when heat is applied to a flow-focusing microstructure under variable flow conditions. The study focused on two main topics; (1) Studying the effect of temperature variation on the behavior water droplets emulsified in mineral oil when heat is applied to the downstream channel. (2) Examining at 37C the size and generation regimes of agarose droplet dispersed in mineral oil. The study had several parts: designing and manufacturing a microchannel network to allow experimental investigation of the characteristics of the droplets, heater calibration and location determination to best fit the selected applications, and applying numerical simulations to understand the hydrodynamics and physics controlling the droplets. Results obtained from temperature alteration of water-in-oil micro-dispersions indicate that the temperature has a dominant effect on the size and the local stability of the droplets in the micro-channels. While, the results observed from exploring the formation of agar-in-oil emulsion demonstrate the significance of capillary number Ca and fluids flow rate ratios �� on the droplet size and the transformation from squeezing into dripping or jetting regimes. The findings of this work assist the future works of performance optimization of on-chip DNA amplification devices and encapsulating bacteria and live cells in agarose droplets for drug delivery applications.
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Keywords
Droplet generation - Water-in-oil emulsion - Agar-in-oil emulsion - Heat transfer - Non-Newtonian fluids - Agarose droplets - Multi-phase flow - Droplet manipulation - Flow-focusing -
Citation
Ali Khater, A. A. E. A. (2019). Experimental and numerical study of temperature-actuated droplets within microfluidics (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.