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Fluid Imaging

Operating Principles

166 Dimension 3100 Manual Rev. D

damped. Instead, this step is used to ﬁnd an oscillating frequency speciﬁc to the ﬂuid and cantilever

holder where the cantilever can be driven into oscillation.

Enter the View > Sweep > Cantilever Tune menu to select a drive frequency. The optimal drive

frequency can depend upon sample, ﬂuid and ﬂuid volume inside the ﬂuid cell. Experiment to ﬁnd

the best drive frequency for speciﬁc imaging conditions. Two frequency ranges that are commonly

used are 16-19kHz and 8-12kHz; higher frequencies have also been used. Start with a Sweep width

of 20kHz. Users of TappingMode in air will notice that their is not a single well-deﬁned resonance,

but instead a large number of broad peaks. The peaks are resonances of the ﬂuid cell and ﬂuid, and

do not usually depend so much on the cantilever dimensions.

A typical Cantilever Tune screen is shown in Figure 10.5c. It is necessary to select a frequency

where there is some cantilever response, (i.e., near a peak), but experience suggests that it is best to

avoid the tops and sides of extremely sharp peaks. The best frequencies appear to be on the side of

a peak or in a shallow valley between peaks. Figure 10.5c shows a typical operating frequency that

produces good ﬂuid tapping images.

Figure 10.5c Typical Cantilever Tune Curve for Silicon Nitride Tip in Fluid

1. In the Feedback Controls panel, set Z Modulation to Enabled.

2. Select View > Sweep > Cantilever Tune, or click on the Cantilever Tune icon. The

initial Cantilever Tune panel appears with the Frequency Sweep (a plot of cantilever

response as a function of applied oscillation frequency) on the display monitor.

3. In the Cantilever Tune panel, set the Drive frequency parameter to 10kHz and the Sweep

width parameter to 20kHz.

4. Set the Drive amplitude to 200mV.

5. Zero the Amplitude setpoint.

6. Set the Amplitude limit to 2.5V.

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