The Nanoscale World

PeakForce Tapping vs. "jump" mode

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Bruker Employee
BrukerApplications posted on Thu, Mar 25 2010 12:43 PM

Isn't PeakForce Tapping the same as "jump" mode or Pulsed Force Mode?

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Top 25 Contributor
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Suggested by Bede Pittenger

Peak Force Tapping has similarity to "jumping mode" and "pulse force' mode; as well as differences.

Similarities: Both peak force tapping (PFT) and jumping mode acquire the entire force curve at each measurement point or pixel; cantilever operates below its resonance frequency; they can use any lever of user's choice;

Difference: The level of force control in pulse force mode and jumping mode is in the nN range, or slightly lower and both mode runs slow. The level of force control in PFT can be single digit of pN even with conventional fluid tapping level; the imaging speed is similar to tapping mode; Further more, the full range of nanomechanical properties (modulus-based on DMT model, adhesion, deformation-hardness, energy dissipation) are calculated at real time. We also allow user to capture data and analyze these properties offline using their own analysis models.

The reason we are able to achieve such fine force control and high imaging efficiency is attributed to state of art AFM and the control algorithm. The biggest challenge of the force control in fluid is parasitic deflection due to viscous force and system non-linearity (the deflection variation when the tip is not interacting with the sample). PFT performs system ID, analyze parasitic deflection and removes them at each control point. As a result the control is purely the physical interaction force which can be two orders of magnitude better than other technologies, including tapping mode. The feedback maintains a constant peak force for each tap (ranging from single digit of pN to uN, depending on the lever used and force demanded by the sample). We have demonstrate high resolution imaging with OmpG membrane where the force control accuracy need to be better than 50 pN.

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