Experimental study on non-Newtonian droplet in microfluidic device under the influence of electric field

• Main Author: Chiew, Say Kiat
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/63666
• Institution: Nanyang Technological University

In this project, investigation of the influence of AC electric field on droplet size generated in a flow focusing geometry microfluidic device is carried out. Applied voltage and frequency are varied with different flow rate in the study of non-Newtonian in Newtonian fluid system. Fabrication procedures of microfluidic device are detailed in this report and making of devices are completed prior the conduct of experiment. The two distinct regions of non-Newtonian droplet formation, pre-stretch and self-thinning are observed which differs greatly from Newtonian droplet. The filament thinning rate under the influence of electric field is also studied and found to follow similar trend to that without electric field but at a slightly faster rate. In addition, satellite droplets resulting from self-thinning is noticed to be non-uniformly larger at higher voltage. In the study of the influence of electric field, an increase in applied voltage has shown to decrease droplet size while frequency variations have lesser influence as compared to voltage. Maxwell stress from electric field is accounted for the decrease in droplet diameter. The effect of electric field is further investigated using different orifice widths of 25μm and 75μm and is found to exhibit similar behaviour to that without orifice. Smaller droplet diameter is observed with the decrease in orifice width for the same capillary number.