A miniature piezoelectric actuator with fast movement and nanometer resolution

To accomplish fast movement and high positioning capability, a miniature self-moving piezoelectric actuator (MSPA) is developed with two groups of polyphenylene sulfide (PPS) transducers operating in the symmetric bending (SB) or counter symmetric bending (CSB) vibration. Each group includes the inner and outer legs, whose vibrations are orthogonal and horizontal to the ground, respectively; this interestingly imitates the stepping and swing functions of the forelimbs and hindlimbs of the gorilla in the 'running on all fours' gait. To examine the validity, first, by utilizing the model on the basis of Krimhertz transmission theory, the resonant frequency of the CSB vibration was structurally tuned to approach that of the SB vibration. Then, a MSPA prototype with the size of 30 mm × 45 mm × 49 mm and the weight of 25.2 g was fabricated to assess the moving, carrying, and positioning performance. In a tethered manner, the MSPA yielded the maximal speed of 562 mm/s (18.73 body length per second), the maximal payload of 485 g (19.25 times of its own weight), and the towing force of 0.5 N (corresponding to the towing force density of 19.8 N/kg). Moreover, it achieved the turning movements (whose directions, angular speeds, and steering radii are changeable) and in-situ rotations, climbed the slope of 12.5°, and moved on the curved floor. In an untethered manner, the MSPA produced the minimal step displacement of 31.9 nm. These results demonstrate that the MPSA possesses the large speed and the nanometer resolution owing to the bionic operating principle and the employment of PPS, and provides a new approach to design lightweight piezoelectric actuators.