Ultra-compact piezoelectric motor with simplified stick–slip design for 3D constrained environments

This work presents the design and construction of a novel ultra-compact piezoelectric motor (PM) that employs a miniaturized piezoelectric tube (PT) measuring 8 mm in length and 3.65 mm in outer diameter. The PT is externally coupled with a curved copper-beryllium (CuBe) spring and a sapphire shaft guided by a zirconia rail to achieve precise linear motion control. The structural design employed the high hardness and wear resistance of sapphire, along with the low-friction properties of zirconia, to ensure precise linear motion and long-term durability. Operating on the inertial stick-slip principle, the PM utilized a modified sawtooth voltage waveform to induce controlled lateral bending of the PT. The spring transmitted motion to the shaft during slow deformation and allowed relative slip during rapid retraction. Experimental results revealed step sizes ranging from 0.1 to 0.8 μm, a threshold voltage of 45 V, and excellent long-term stability (±15 nm drift over 15 h). The design effectively held small loads with high stability, making it well suited for coarse positioning applications. Its compact footprint, simplified assembly, and bidirectional control capabilities underscore its potential for integration into coarse approach mechanisms of scanning tunnel microscopes and other high-resolution instrumentation platforms where space constraints, accuracy, and long-term reliability are critical. This work lays a foundation for future developments in ultra-compact, non-magnetic, application-specific nanopositioning motors.