Effect of Electrode Geometry on Droplet Splitting in Digital Microfluidic Platforms

This paper studies the effect of the electrode aspect ratio on droplet splitting in a digital microfluidics (DMF) chip including an array of 3 electrodes in which the middle electrode is kept square while the two side electrodes have different aspect ratios. The aspect ratio is changed from 0.9 to 1.3 while the surface area of the electrodes is kept constant for all cases. Results show that changing the aspect ratio can severely change the required voltage for splitting with a nonlinear behavior. It is also shown that for a constant gap between the top and bottom plates and a constant volume of the droplet, the relation between the threshold voltage and the aspect ratio is parabolic, for which there is an aspect ratio with a minimum threshold voltage. Changing the volume of the droplet changes the threshold voltage and hence the aspect ratio corresponding to the minimum threshold voltage required for splitting.