What is nanopositioning?
Posted in Queensgate Dec 8th 2022
Nanopositioning technology and where it’s used
Nanopositioning is the technology of moving, measuring and positioning a device or instrument to sub-micron levels of accuracy. By definition, this means movement over extremely small distances, often at high speeds; for example, in nanopositioning terms, a movement device that travels 1.0mm is considered to be operating at the extremes of the technology. More usually, a nanopositioning system will be designed to produce repeatable, high precision movement in increments of one nanometre or less, over a distance of a few microns.
A nanopositioning system is typically used to move and position devices such as a tools, probes, sensors or scanners. In each case, the requirement is normally to move the device to a set position and hold it precisely in place for extended periods, or to position, briefly hold and then reposition the device multiple times at high speeds.
Where are nanopositioning systems used?
The ability of nanopositioning systems to move rapidly yet consistently achieve nanometer levels of accuracy makes them ideal for a wide range of precision laboratory, research and manufacturing applications.
These include high performance linear stages used in the production of read/write heads in computer hard drives; medical devices such as laser mirror positioning in eye surgery, live cell imaging, DNA sequencing and multi-photon microscopes for neurosciences; and atomic force microscopy used in materials research.
How does a nanopositioning system work?
Although a nanopositioning system can be constructed in a number of ways, the most effective – and that pioneered by Queensgate, a brand of Prior Scientific – is based on proven piezoelectric technology.
The piezoelectric effect was originally discovered by Jacques and Pierre Curie in 1880. They found that when a mechanical force was applied to quartz or other crystals it generated an electric charge within the crystal. They were also able to show that an electrical field caused the crystal to expand or contract; this subsequently became known as the inverse piezoelectric effect.
A nanopositioning system exploits this phenomenon, using an electric signal to energise a stack of piezoelectric layers that expand in response to an applied voltage. By fixing one side of the mechanism to a reference base plate, or stage, while allowing the other to move, it is possible to create a linear actuator capable of sub-atomic resolution with extremely high mechanical stiffness.
As an example, a piezoelectric stack that is 20mm in length might typically have 200 layers, each 100 microns thick. For each 100 volts applied, the stack would expand by 15 microns and be able to generate a force of around 750N. The inherently high degree of stiffness results in correspondingly high resonant frequencies, enabling devices to move rapidly in a controlled manner.
Piezoelectric devices are, however, non-linear and exhibit hysteresis. They therefore require an external sensor to control their exact position. This is achieved using a capacitance sensor, which comprises two thin conducting films approximately 500 microns apart and separated by a dielectric air gap to give a set capacitance value.
Attaching one side of the sensor to the moving stage of the nanopositioning device and the other to the fixed stage allows any movement to be detected as a change in capacitance. Using this measurement as input to a feedback control loop enables the exact position of the moving stage to be determined, with exceptional resolution, linearity, stability and repeatability.
The system is completed with the addition of specially machined flexures, designed to guide each axis of motion, together with mechanical amplifiers and associated sensing and control electronics, creating a device that can make pure orthogonal motions with sub-nanometer levels of precision.
The nanopositioning experts
At Queensgate we have been designing, developing and manufacturing advanced nanopositioning systems for almost 50 years. We operate at the forefront of research into the science of sub-atomic movement, measurement and positioning, and have pioneered and perfected the application of piezoelectric and capacitance sensing technologies. Our systems are used around the world in sectors ranging from research, scientific and medical, to electronics and industrial, giving us unrivalled knowledge and experience – knowledge and experience that makes us the go-to experts in nanopositioning.
Contact our technical sales team to learn more.