Electroporation (EP) is a method of introducing foreign substances, such as nucleic acids and proteins, into cells by controlling the permeability of the cell membrane using a high-energy electric field. EP does not require external reagents and can be used for a wide range of applications. In addition, it is easy to operate and can be used even at a low biosafety level. However, EP is highly cytotoxic because it applies high-energy electrical pulses to cells. Previously, we reported water-in-oil droplet electroporation (w/oEP), in which electrostatic charges, a low-energy pulsed electric field, are applied to cells to reduce the cytotoxicity of EP [1]. However, since w/oEP uses contact charge electrophoresis (CCEP) [2], the droplets need to move through the oil. This unstable droplet motion results in a decrease and unstability for transfection efficiency. In this work, we have developed a device to realize the electrical energy condition of w/o EP without CCEP.  A device was designed to apply an electric field similar to that of w/oEP. The electrical energy applied to the droplet was limited by connecting a capacitance in series with the droplet. The capacitance was calculated by regarding the droplets in oil as spheres of conductors in the insulator.A coil was connected in parallel to the droplet and capacitor to apply a periodic pulsed electric field. The plasmid vector (pCMV-EGFP) was introduced into adherent cells (HEK293 cells) and floating cells (Jurkat T cells) using this device. 4 µL droplets containing 50-1000 ng/µL plasmid DNA and 4000 cells were subjected to the voltage. The circuit parameters were as follows: inductance of the coil was 47 μH, capacitance of the capacitor was 7.33 pF or 1000 pF, and the processing time was 5-60 s. When the capacitor discharges, an electric field of reverse polarity is applied to the droplet, but no reverse voltage is applied to the w/o EP. Furthermore, the cytotoxicity of the bipolar voltage had been experimentally elucidated by conventional methods. Therefore, we eliminated the reverse voltage with a parallel diode. Using this device, we introduced pCMV-EGFP into HL60 cells. Two days after transfection, cells were observed by fluorescence microscopy and the number of cells with fluorescence signal was counted by ImageJ. EGFP-positive Jurkat T cells were observed for 30 s and 60 s. EGFP was not observed in HEK293 cells at any application time under the condition of 7.33 pF capacitance. However, EGFP was observed in HEK293 cells treated for 5 s under the condition of 1000 pF electrostatic capacity. The HL60 cell transfection was performed according to the conditions described previously. Two days after the gene transfection, EGFP-positive cells were found only in the condition with connected the diode. This suggests that the application of bipolar voltage may have had a negative effect. These results suggest that this novel method can be applied to various types of mammalian cells by examining the conditions.