Low-frequency ac electro-flow-focusing microfluidic emulsification

Peng He; Haejune Kim; Luo, Dawei; Marquez, Manuel; Zhengdong Cheng
April 2010
Applied Physics Letters;4/26/2010, Vol. 96 Issue 17, p174103
Academic Journal
Applications of electric field, using either dc or high-frequency ac field, have shown many advantages in emulsification. We further develop this technique by a detailed study on low-frequency ac electro-flow-focusing (EFF) microfluidic emulsification. Counter-intuitively, the droplet size variation is not monotonic with the electric field, in contrary to the dc-EFF emulsification. This phenomenon originates from a relaxation oscillation of flow rate through the Taylor cone. Particularly, a continuous droplet size decrease was obtained at the voltage ramp-up stage. This emulsification process was modeled in analog to the accumulation and release of charges in an RC electric circuit with an adjustable resistor.


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