Adam Weld

Multidisciplinary Madness

Piezoelectric EM stage

4DOF Piezoelectric Positioning Stage for Electron Microscope

One of my first hardware design engineering projects, but one that I am still very proud of. Working at desktop electron microscope company Project Voxa, I was tasked with working on a four-axis stage to move the sample around under the EM beam.

Because any kind of magnetic field will distort the microscope image, there are only a few types of motor that work in such a system. The most popular option is a piezoelectric motor, which I was tasked with prototyping as well as linear motion structure of the stage.

Here you can see a few of my rough prototypes of piezoelectric motors, and the final titanium wire-EDM machined flexure design for the final version. Piezoelectric motors work with a special type of ceramic crystal that lengthens and contracts a fraction of a percentage point when high voltages are applied across it. By using a saw-tooth wave and careful amounts of friction between the actuated end of the crystal and a plate, we can achieve linear motion by moving between static and dynamic friction.

Here is the captive-ball positioning stage I designed to hold the electron microscope sample.

The motors fit into every axis of the stage in small cut outs.