The reduction in zm due to the bottom electrode is an important factor for controlling the levitation effect. Fig. 6(a) illustrates that the equilibrium position decreases for increasing electrode potential. As observed in the simulation, zm is still independent of Vc provided VP0 is proportional to Vc. Furthermore, for increasing plate potential the position in z at which the force density becomes negative increases and eventually equals zm. This effect is depicted by the data in Fig. 10(a). Fig. 6(b) illustrates a finite element simulation of the potential around
a comb at z = 1 μm, Vc = 10 V and VP0 = 3.33 V.