<p>An actuator for an ink jet printer includes: an ink tank comprising a thick substrate (21) having a cavity structure with a vibrating plate (22) covering a cavity (20), and a piezoelectric/electrostrictive working portion comprising an upper electrode layer (25), a lower electrode layer (23) and a piezoelectric/electrostrictive layer (24). The piezoelectric/electrostrictive working portion is disposed on the ink tank so that the lower electrode (23) layer contacts with the vibrating plate (22). The upper electrode is laser trimmed only in the portion where the piezoelectric/electrostrictive layer (24) covers the vibrating plate (22) so as to control the effective electrode area and adjust an ink jet volume to be appropriate. In this way risk of damage to the vibrating portion (22) is minimized. <IMAGE> <IMAGE></p>
