A substrate is levitated a first distance over a mother substrate when a first group of Coulomb islands are charged. A second group of Coulomb islands are charged and increase a separation to a second distance. When the magnitude of the potential of all Coulomb islands is decreased, the separation decreases from the second distance to the first distance. All potentials associated with the Coulomb islands have decreased yet the distance of separation equals to the first distance. Increasing the number of Coulomb islands in a substrate can reduce the magnitude of potentials applied to the Coulomb islands thereby reducing the concern of voltage stress.