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Resonance curves of NSC18 cantilever. Frequency sweep curve taken in liquid exhibits (a) forest of peaks using acoustic excitation and (b) a single peak using magnetic excitation. (c) Similar to acoustic excitation, the forest of peaks can also be observed in the liquid movement recorded by an external laser and a segmented photodiode. Convolution of the magnetic excitation and fluid movement is also shown in (a).
Comparison of the (a) shaker piezo movement in dry cell and (b) fluid movement using NSC18/Co–Cr cantilever. To record the piezo movement, we pushed the tip against a hard surface and excited the shaker piezo with similar voltage as used in liquid. Importantly, most peaks appearing in the fluid movement are also present in the spectrum of the shaker piezo movement taken in the dry cell. Consequently, the forest of peaks phenomenon originates from the shaker piezo.
(a) Simulated amplitude-distance curves and (b) maximal tip-sample repulsive forces. Simulation data: cantilever spring constant was , undamped resonance frequency was , while drive frequencies were (solid line), (dashed line), and (dotted line). Free amplitude was set to in each simulation. Young’s modulus of the sample was for the simulation. (c) To illustrate the proposed drive frequency adjustment procedure, experimental amplitude-distance curves are shown using acoustic excitation. During the experiments, we used NSC-36 silicon cantilevers from MikroMasch having a nominal spring constant of .
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