A Relaxor Ferroelectric Crystal Based Two-DOF Miniature Piezoelectric Motor with Fish Body Structure

Multi-dimensional movements and miniaturization are required for robotic joints motion, multi-axis optical alignments and other multiple degree-of-freedom (DOF) actuation scenes. However, it is a challenge for piezoelectric motors to guarantee multi-DOF movements, miniaturization, high load capacity and high resolution simultaneously. Inspired by synergic movement of body and caudal fin of fish in nature and the construction idea of metamaterials, we proposed a two-DOF linear piezoelectric motor (4mm^Height×3mm^Length×3mm^Width) based on the artificial elongation 31_z and shear 35_x/y mode by using Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIMNT) relaxor ferroelectric single crystal as piezoelectric elements. The results demonstrate that the motor is capable of achieving bidirectional motion in both X and Y axes, with the PIMNT crystal-based motor reaching a velocity of up to 94.8 mm/s. Its mechanical loading capacity per unit volume reaches as high as 1.39 mN/mm³, which exceeds the load capacity of currently reported two-DOF motors by 10 times. Moreover, it exhibits an exceptional step resolution of 5 nm, outperforming existing two-DOF motors by 1-2 orders of magnitude in terms of precision and accuracy. Furthermore, by modulating the driving signals of this motor, it can traverse any trajectory within the XY plane. The proposed ultrasonic motor has potential for applications in micro-robots, nano-precision motion, automatic visual systems and haptic interfaces.