WARF: P02343US

Heterodyne Feedback System for Scanning Force Microscopy


Daniel van der Weide, Bjoern Rosner

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a technique for down-converting the signal from high-frequency SFM probes so it can be sensed by standard detection electronics.
OVERVIEWScanning force microscopy (SFM) is a powerful technique for studying surfaces that resolves surface topology at the atomic scale. Most commonly, SFM uses a vibrating cantilever system carrying a probe tip that oscillates above the sample without contacting it directly. As the probe tip scans across the sample surface, changes in its vibration frequency, amplitude or phase are detected and used to produce a feedback signal that keeps the probe at a constant distance above the sample.

High-frequency SFM cantilevers, with resonance frequencies in the MHz range, not only minimize tip and sample damage, but can achieve less noisy scans in liquids. However, they also require expensive, custom feedback systems because standard feedback systems are limited to frequencies below 500 kHz.
THE INVENTIONNow, two UW-Madison radio engineers who are also experts in SFM technology have created a technique for down-converting the signal from high-frequency SFM probes so it can be sensed by standard detection electronics. The technique uses a heterodyne receiver to down-convert the signal, an approach that is well known in radio frequency engineering but has not been previously applied to measurement instrumentation.
  • Scanning force microscopes
  • Other microelectromechanical systems (MEMS)
  • Allows coupling of advanced high-frequency SFM probes to existing detection electronics, such as standard lock-in amplifiers, which are limited to frequencies below 500 kHz
  • Simple and inexpensive
  • Flexible -- allows use of a wide range of vibration frequencies and detection electronics
For More Information About the Inventors
Contact Information
For current licensing status, please contact Emily Bauer at or 608-960-9842.
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