This thesis is divided into two parts. First, the field modulated surface tension of aligned carbon nanotubes (aligned-CNTs) is discussed and demonstrated. Electric fields are found capable of changing contact angle of liquid droplet on surfaces of aligned carbon nanotube arrays, and the surface tension is calculated according to the experimental data using the Owens-Wendt model and Young’s equations. Second, we discuss the effect of different ion concentrations on electro-wetting. By applying the same voltage, the contact angle of droplet varies with different ion concentrations, and the relationship between droplet contact angle and ions is also discussed.