Friction Force Obtained by FFM

Mate [6] first obtained the friction force signal as well as the normal load signal by modifying an AFM in 1987. The modified AFM was called FFM or LFM (lateral force microscopy). The friction force signal was obtained by detecting the tor- 

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The lateral force is obtained directly from the FFM. So the lateral force is needed to be quantitatively calibrated first and then the friction force can be calculated. As shown in Fig. 2, the lateral force can be expressed by 

There is a corresponding relationship between the lateral voltage (Vi) of four quadrant position detectors and the torsional angle. So can be obtained from Vy. 

The incident angle is a constant for this equipment, y = 15°. The torsional angle i, and the rotated angle a of the reflection ray are both infinitesimals. The formula can be simpli- 

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