A linear piezoelectric motor with self-lubricating frictional contact for scanning probe microscopy (SPM) precision positioning

This work presents an ultra-compact linear piezoelectric motor (PM) for precision positioning in scanning probe microscopy (SPM). The motor consists of a 9-mm-long piezoelectric scanning tube (PST), a trapezoidal zirconia sliding shaft, and a customized beryllium–copper (BeCu) spring ring. The BeCu spring ring provides a stable radial preload and presses the zirconia shaft against the Au-coated inner wall of the PST, forming knife-edge contacts. Microscopic observations show that repeated axial sliding forms a relatively smooth and stable track at the contact interface, suggesting that this interface may help reduce direct wear and improve frictional stability during operation. The developed PM shows a threshold voltage of ∼30 V, a maximum travel range of about 5 mm, and a load-driving capacity exceeding 30 g at 90 V. In a simulated SPM coarse-approach procedure, no obvious parasitic displacement was observed under a 200 V probing waveform at 25 Hz for ∼2 h. Compared with reported piezoelectric-tube-based motors, the proposed PM shows a favorable combination of compact size, low threshold voltage, large travel range, and high load-driving capability. The motor was further used to construct a scanning tunneling microscope (STM), and atomic-resolution imaging of highly oriented pyrolytic graphite was obtained under ambient conditions. These results demonstrate that the proposed PM is suitable for compact SPM systems and other space-constrained nanopositioning applications.