Optimization of adhesion mode atomic force microscopy resolves individual molecules in topography and adhesion

Area of Science:

• Nanotechnology
• Surface Science
• Biophysics

Background:

• Atomic Force Microscopy (AFM) force sensors measure single molecular binding strengths using force-distance curves.
• Adhesion mode in AFM combines high-force sensitivity with spatial resolution but is limited by viscous drag in liquid.
• Current AFM techniques struggle with imaging speed and resolution in liquid environments.

Purpose of the Study:

• To enhance AFM adhesion mode for improved measurement speed and image quality in liquid.
• To achieve high-resolution imaging of individual molecules with AFM in liquid.
• To enable long-term tracking of single molecules using AFM.

Main Methods:

• Utilized an AFM equipped with a low-viscous drag cantilever to achieve pixel frequencies of 65 Hz.
• Implemented optimized filtering techniques and auto-zero circuitry to minimize height signal noise to 0.3 nm.
• Employed a thermally stabilized AFM system for enhanced stability during imaging.

Main Results:

• Achieved visualization of individual molecules on mica with image quality comparable to tapping mode.
• Demonstrated lateral resolution limited only by tip size in both topography and adhesion images.
• Enabled real-time tracking of individual molecules for over 30 minutes with small scan sizes (down to 60 x 60 nm2).

Conclusions:

• The enhanced AFM adhesion mode significantly improves imaging speed and resolution in liquid.
• This technique allows for detailed nanoscale imaging and long-term observation of molecular dynamics.
• The developed method offers a powerful tool for studying molecular interactions and structures at the nanoscale.