Unfortunately, such formulas can be inaccurate. For example, a significant component of the piezo excitation does not mechanically excite the cantilever, but rather transmits acoustic waves through the surrounding liquid, which in turn indirectly excites the cantilever. What's more, resonances of the piezo, chip and holder can obscure the true cantilever dynamics even in well designed liquid cells.

Now, by integrating an entire AFM with a scanning laser Doppler vibrometer, researchers at Purdue University, US, have developed a method to overcome these limitations. The vibrometer allowed the team to visualize the motion of the entire cantilever while the AFM is scanning in liquids (see the animation above).

Simple calibration procedure

Based on this data, the group has been able to develop an accurate mathematical model of the cantilever's motion in liquid when the base is excited by the piezoelectric crystal. The mathematical model shows that quantitative results are in fact possible with the acoustic excitation method.

A simple calibration procedure, which takes just five minutes or less, allows users to determine the necessary parameters. The result will enable researchers to obtain significantly more accurate quantitative results using their existing hardware.

Further information can be found in the journal Nanotechnology.