I have a tuning fork sensor with a probe tip that would be used in atomic force microscopy. Am I correct that the quartz tuning fork's resonance frequency increases with a repulsive force on it and decreases with an attractive force on it?

I have attached a gif that I made describing the process:

Force-dependent resonance frequency. No force refers to free-space.

Here is a picture of a force v. distance plot that I found online: https://i.sstatic.net/2gka7.jpg Distance-dependent force Does my gif seem correct?


1 Answer 1


You are correct. "Tapping Mode" is a form of AFM that raster scans a vibrating tip across a surface that minimizes the potential damage to the surface that normal AFM scanning might produce. The tip is vibrated at its resonant frequency.

A nice overview can be found here.

A mathematical analysis of the Tapping Mode, including shifts in resonance frequency, using simple harmonic models can be found here.

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    $\begingroup$ Thank you for the help. I am still a bit confused on why a repulsive force increases the resonator's resonance frequency, but I have posted this in a new question. $\endgroup$ Commented Mar 2, 2021 at 3:13

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