Uncertainty quantification in nanomechanical measurements using the atomic force microscope.

Area of Science:

• Materials Science
• Nanotechnology
• Metrology

Background:

• Accurate characterization of nanomaterials is essential for developing reliable nanoengineered products.
• Atomic Force Microscopy (AFM) is a key technique for measuring properties at the nanoscale.
• Uncertainty quantification (UQ) is often overlooked in AFM measurements, hindering material reliability.

Purpose of the Study:

• To present a framework for quantifying uncertainty in nanomechanical properties measured by AFM.
• To identify and assess the main sources of uncertainty in AFM-based material property measurements.
• To demonstrate the framework using cellulose nanocrystals (CNCs).

Main Methods:

• Development of a general framework for uncertainty quantification in AFM measurements.
• Application of the framework to measure the transverse elastic modulus of cellulose nanocrystals (CNCs).
• Analysis of uncertainty contributions from photodiode sensitivity, cantilever stiffness, and Z-piezo calibration.

Main Results:

• A framework for UQ in AFM-based nanomechanical property measurements was established.
• The transverse elastic modulus of CNCs was quantified with a mean of 8.1 GPa and a 95% confidence interval of 2.7-20 GPa.
• Systematic errors, particularly photodiode sensitivity calibration, were identified as dominant uncertainty sources, not measurement replicates.

Conclusions:

• The developed framework enables rigorous uncertainty quantification for AFM measurements.
• Photodiode sensitivity calibration is a critical factor influencing uncertainty in AFM nanomechanical measurements.
• This work provides a pathway to minimize and quantify uncertainty in AFM analysis of diverse nanomaterials.