An ink jet printing apparatus and an ink jet printing method which use a print head having a plurality of ejection port rows to enable high-quality printing without causing uneven density in a conveying direction by varying the printing distribution ratio of the ejection port rows in the print head depending on gray level. At least one opening can have at least one wall-like insulating barrier associated with it which consists of an electrically insulating material and with which it is possible for the air gaps and leakage paths between two adjacent openings to be increased. In one particular embodiment, the micromembrane can be likened to one of the plates of a capacitor and its deformation corresponds to a substantial increase in the capacitance of this capacitor, thus providing the electrical connection. The RDC authenticates the PDK based on received data and stores information to track customers and provide improved service. Combinations of various cell culture components disclosed and employed herein allow cells to be in high metabolic states useful for drug testing immediately after the start of cell culture.