Influence of Inclined Chip Angles on Dynamic Contact Angle Variations in Digital Microfluidics

¹ Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi 23460, Pakistan
² Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Pakistan.

^* Corresponding author: ali.turab@giki.edu.pk
gme2330@giki.edu.pk

Abstract

The impact of tilted angles on contact angles of water droplets in digital microfluidics was investigated. Experiments were conducted tilting the chip from 0 to 10 degrees at voltage increments of 50V from 250V to 400V DC. Both advancing and receding contact angles of the water droplets were measured at each angle and voltage combination. As the tilted angle increased from horizontal to 10 degrees, the advancing contact angle generally decreased whereas the receding contact angle increased. This trend held for all tested voltages. The changes were more pronounced at higher tilt angles above 5 degrees. Voltage was also found to influence the contact angles, with both advancing and receding angles decreasing with increasing driving voltage. The results provide insight into how tilted surface angles affect wetting properties in digital microfluidics. By understanding these relationships between contact angles, tilt angles and driving voltages, design parameters like maximum operational tilt angles before droplet pinning or instability can be better determined. The findings may assist in designing and optimizing tilted or three-dimensional digital microfluidic devices and applications.