Experimental and theoretical investigation of frequency-dependent and conductivity-dependent threshold actuation voltage of electrowetting-on-dielectric and liquid dielectrophoresis on a one-plate device

Actuation voltage is critical in microfluidic manipulation using electrowetting-on-dielectric (EWOD) and liquid dielectrophoresis (LDEP). Compared to parallel electrode devices, the liquid manipulation of coplanar electrodes requires a higher actuation voltage due to its structure. This study derives an equation related to the threshold actuation voltage and all important parameters (droplet volume, fluid permittivity, fluid conductivity, applied frequency, surface tension, thickness and permittivity of dielectric materials, and electrode width). The equation is also used to analyze and explain frequency-dependent, and conductivity-dependent threshold actuation voltage on a coplanar electrode structure in the experiment. Three water-based solutions with different electrical conductivities (3 *10-4-10-2 S/m) were tested for the threshold voltage of liquid actuation using a wide range of signal frequencies (0.1-100 kHz). The theoretical and experimental data reveal that our model can successfully explain the effects of conductivity and frequency on liquid actuation. In addition, the effects of EWOD and LDEP on the threshold actuation voltage of microfluidics on a one-plate device are also discussed with the model and experiment. This study covers a common range for important parameters (applied frequency, and fluid con-ductivity) related to the actuation voltage in microfluidic actuation on a coplanar electrode structure. The theory and experimental data can be used to predict the applied voltage of EWOD and LDEP for a broad range of buffers and organic solvents.

Automated summary

This study derives an equation related to the threshold actuation voltage and all important parameters and successfully explains the effects of conductivity and frequency on liquid actuation. The theoretical and experimental data can be used to predict the applied voltage of EWOD and LDEP for a broad range of buffers and organic solvents.