AbstractsComputer Science

Droplet formation on demand at a microfluidic T-junction

by Kelly Min He

Institution: University of British Columbia
Department: Electrical and Computer Engineering
Degree: Master of Applied Science - MASc
Year: 2015
Record ID: 2061547
Full text PDF: http://hdl.handle.net/2429/52271


Microfluidic aliquot dispensing technologies have been utilized in many chemical or biological high throughput assays to provide high-speed deposition of high-resolution droplets. Particularly, these aliquots can be used to dispense a controlled volume of liquid into multi-well plates in drug screening applications. However, existing platforms are often designed to print a limited set of materials where each material is handled by an independently actuated nozzle. A more convenient and scalable technology that could allow digital output of multiple materials on demand must be explored. Monodispered droplets can be formed continuously in a microfluidic T-junction when two input flows of immiscible fluids are maintained. However, it is difficult to form stable air separated aliquots in a simple T-junction configuration. Electrowetting-on-dielectric (EWOD) is commonly used to control individual droplets in a planar configuration. But it is not usually used in microfluidic channels. In this device, a new method for creating air separated aliquots on demand using EWOD at a microfluidic T-junction was demonstrated. Since air is the carrier fluid, these aliquots can be dispensed without further liquid processing. A device that consists of SU-8 channels with electrodes in alignment with the channels was designed and fabricated. A double wedged junction was incorporated at the dispersed channel to create a barrier pressure that allows the meniscus location to be controlled by the applied pressures. Droplets of approximately 15 nL can be generated by applying a voltage at the electrode at the junction. Liquid flow is stopped when the voltage is removed. This mechanism can be used as a digital valve to generate a sequence of aliquots of different materials for a multi-material printing platform.