Nondestructive and noncontact method for determining the spring constant of rectangular cantilevers.

Area of Science:

• Nanoscience and Nanotechnology
• Materials Science
• Experimental Physics

Background:

• Atomic Force Microscopy (AFM) is a crucial tool for nanoscale imaging and force measurements.
• Accurate calibration of AFM cantilever spring constants is essential for reliable quantitative measurements.
• Existing added-mass methods often require complex micromanipulation and can leave residues.

Purpose of the Study:

• To present an experimental setup for an extended added-mass method for AFM cantilever calibration.
• To introduce a novel, nearly contactless calibration technique using water microdrops.
• To validate the accuracy of the proposed method against established techniques.

Main Methods:

• Utilizing a commercial inkjet dispenser to generate highly reproducible water microdrops.
• Applying water microdrops to AFM cantilevers as a known, evaporative mass.
• Investigating two variants: varying microdrop size and varying microdrop position along the cantilever.
• Performing numerical simulations for the variant with constant microdrop size and varying position.

Main Results:

• Water microdrops provide highly reproducible masses for calibration.
• The method allows for nearly contactless deposition and removal of mass (evaporation).
• Measured spring constants using this method are comparable to those obtained by the thermal noise method.
• Demonstrated accuracy across six different AFM cantilevers.

Conclusions:

• The water microdrop method offers an efficient, accurate, and nearly contactless approach for AFM cantilever calibration.
• This technique overcomes limitations of traditional added-mass methods, such as mechanical manipulation and residue.
• The proposed method is a viable and reliable extension to existing cantilever calibration techniques.