Investigation of mechanical interactions between the tips of two scanning near-field optical microscopes
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We describe a method to monitor the distance between two tips of a scanning near-field optical microscope setup. The interaction between the two tips, caused by shear forces and air pressure oscillations between the tips, makes each oscillating tip perform an additional oscillation at the frequency of the other tip. The interaction is detected by analyzing one of the tuning fork signals with a lock-in amplifier locked at the oscillation frequency of the other tuning fork. The resulting signal, called crosstalk, increases sharply only when the scanning tip comes into the immediate vicinity of the stationary one. This effect allows us to prevent the tips from colliding during scanning.
KeywordsScanning Line Tuning Fork Crosstalk Signal Acoustic Interaction Aerodynamic Interaction
We acknowledge the financial support from the German Research Foundation (DFG) and Jena School for Microbial Communication (JSMC).