A Miniature Two-Degree-of-Freedom Bipedal Piezoelectric Motor Driven by Low Voltage

The demand for miniaturized, multi-degree-of-freedom (DOF) piezoelectric motors with high power density and low driving voltage is growing across advanced technology fields. Achieving compact size while maintaining multi-DOF motion and superior performance remains challenging. This study presents a bio-inspired two-DOF bipedal piezoelectric motor (BPM), which is fabricated via the multilayer co-fired technology. The motor consists of a 1.9 mm^Height × 1.9 mm^Width × 7 mm^Length bipedal piezoelectric stator (BPS) that is equipped with two friction tips, and the motor operate in coupled longitudinal and bending (L_1,XB_2,Z and B_2,YB_2,Z) vibration modes. At a peak-to-peak driving voltage of 3.3 V_PP, the motor achieves velocities of 115 mm s⁻¹ (X-axis) and 110 mm s⁻¹ (Y-axis), maximum loads of 120 mN (X-axis) and 110 mN (Y-axis), as well as minimum step resolutions of 0.41 µm (X-axis) and 0.33 µm (Y-axis). Notably, it achieves a power density per unit voltage of 25.64 mW cm⁻³ V⁻¹, which is more than 40 times higher than previous reported multi-DOF piezoelectric motors. These results demonstrate the motor's potential for applications in micro-nano processing, portable electronics, and biomedical devices.