Electroporation is a process by which intense electric fields generate nano-scale defects within the cell membrane. These defects allow molecular exchange between the cell interior and the extracellular environment. We have developed a method by which a minimal amount of energy may be delivered to a cell suspension that will render the cells permeable while mitigating much of the thermal damage typically associated with such procedures. Using single square pulses at specific electric potentials and durations, cells are exposed to electric fields sufficient to generate long-lived pores within the membrane that render the cells in suspension permeable long after the cessation of the electrical pulse.