**3.2 3D type EVC vibrator**

3D type EVC vibrator has more degrees of freedom compared with 2D type EVC vibrator. Thus, it has more flexibility and modulation ability to fabricate the structured surface than 2D type EVC vibrator. However, the structure was more complicated and it is difficult to control the structure size, which may influence the potential applications. In recent 10 years, the flexure-based 3D type EVC vibrator developed rapidly. In general, there are three commonly used piezoelectric actuator configurations, i.e. three perpendicular piezoelectric actuators configuration, two parallel and one perpendicular piezoelectric actuators configuration, and four parallel piezoelectric actuators configuration. Here are some typical examples following below.
