Calibration of T-shaped atomic force microscope cantilevers using the thermal noise method

Area of Science:

• Atomic Force Microscopy (AFM)
• Nanoscale Science
• Materials Science

Background:

• Atomic force microscopy (AFM) uses tip-sample interaction forces for nanoscale material property analysis.
• T-shaped cantilevers in Torsional-Harmonic AFM measure rapid force changes via torsional deflections.
• Conventional thermal noise calibration is difficult for T-shaped cantilevers due to coupled flexural and torsional deflections.

Purpose of the Study:

• To develop a robust thermal noise-based calibration method for T-shaped AFM cantilevers.
• To overcome challenges in determining deflection sensitivities caused by mechanical mode coupling.
• To enable accurate nanoscale force measurements using T-shaped cantilevers.

Main Methods:

• Simultaneous analysis of flexural and torsional thermal noise spectra.
• Integration of deflection signals from force-distance curves.
• Computer-aided calculations to account for flexural-torsional mode coupling.
• Validation of calibration robustness against laser spot position and cantilever orientation.

Main Results:

• Successfully calibrated T-shaped AFM cantilevers using an adapted thermal noise method.
• Demonstrated robustness and reliability of the calibration technique through various tests.
• Achieved consistent quantitative force measurements validated against protein unfolding forces.

Conclusions:

• The presented method provides accurate calibration for T-shaped AFM cantilevers.
• This technique enhances the reliability of nanoscale force measurements in AFM.
• It enables precise characterization of material properties at the nanoscale.