Ultrafast microfluidic droplet sorter extension work Kong, Luke; Wu, Samuel
This project builds on work done by a previous APSC 459 group, who developed fluorescence- based droplet sorting device similar to that described by Agresti et al. up to the point where it could detect the fluorescence of droplets up to a rate of 1kHz. However, it was unable to sort droplets; this project sought to add droplet sorting functionality to their microfluidic chip design. Our project aimed to demonstrate droplet actuation with use of the existing experimental setup. This consisted of three main objectives: 1. Model effect of electrode design and geometry on droplet actuation using finite-‐ element analysis (implemented in COMSOL). 2. Demonstrate actuation of droplets, redesigning microfluidic chip if necessary. 3. Optimize setup towards droplet sorting at speeds on the same order (1-2 kHz) as exisiting work (Agresti, 2010). Using COMSOL we determined the factors that will most strongly affect the dielectrophoretic force on a droplet in a channel. From these results we redesigned the droplet sorter chip from the previous group and fabricated chips with a new electrode design (microfluidic channels to be filled with low-melting-point alloy). We then went on to demonstrate droplet redirection at a rate of at least 100Hz. Although droplet redirection, the main focus of this project, was successfully demonstrated, much work remains to be done on this project. The redirection needs to be coupled to the previous 459 group’s droplet detection setup in order for controlled droplet actuation. Recommendations were made about electrode fabrication, droplet transfer from generator to sorter and high voltage switching.
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