Summary
In the presented work an electronic controlled nanopositioning system based on piezoelectric motors was realized. First of all, different strategies of driving were investigated, particularly focusing on the waveform to being applied; then, after selecting trapezoidal waves as the best ones for our purposes, it was studied how they could be generated. Afterwards, an electronic driver for the piezoelectric motor was designed, with the ability to produce proper levels of tension. Several tests were performed on the piezoelectric motor eventually, using an home-made interferometer, totally built in the laboratory. Our studies pointed out the followings:
• the motor resolution is about 35 nm/V;
• with no load, the motor moves uniformly in both the directions.
Although digital-analog converters of 16 bit would have caused a minimum theoretic step of the motor extremely small (about 0,026 nm), due to mechanical, physical and electronic factors the minimum step reached was about 3 nm indeed.
RESOLUTION ≈ 35 nm/V MINIMUM STEP LENGHT ≈ 3 nm
MOVEMENT uniform in both the directions
Even if the obtained movement is more than acceptable, how to hold the motor in the target position is still an open question. The best solution seems to be the
Summary introduction of a feedback control. Moreover, it is necessary to lower the sensitivity of the motor to external electromagnetic fields and mechanical vibrations.
Future steps →
increase resistance to EM fields and mechanical vibrations develop a feedback control
This work is a development of a project started by the colleague Diego Barone, MD, with the aim to realize a nanopositioning XY stage. Thanks to this work the accuracy has been increased by 10 fold, but to integrate this system within a scanning electron microscope (SEM) or within an atomic force microscope (AFM), more work would be required.
Whenever this goal will be reached, the positioning of the sample will be much more accurate in comparison with the resolution of an electron beam which will become the limiting factor.