The present invention relates to an improved EPD which comprises the in plane switching mode. The treating unit is constructed by a cage-shaped supporting structure which defines an interior space for containing the microbial cell therein. The substrate is arranged at the side opposite to the lid relative to the terminal block, and deviated from the position facing an aperture of the connector retain hole. Such clusters can be ionized by electron bombardment or other means, permitting the gas clusters to be formed into directed beams of known and controllable energy. The active compounds are characterized by the following formula : .