Imaging stability in force-feedback high-speed atomic force microscopy.

Area of Science:

• Surface science
• Microscopy techniques
• Biophysics

Background:

• Atomic Force Microscopy (AFM) is crucial for nanoscale imaging.
• High-speed AFM (HSAFM) enables dynamic surface studies.
• Force-feedback mechanisms enhance imaging stability and resolution.

Purpose of the Study:

• To investigate the stability of force-feedback HSAFM across different sample types and applied forces.
• To understand the influence of surface properties and imaging parameters on HSAFM stability.
• To evaluate HSAFM performance for imaging soft biological samples.

Main Methods:

• Force-feedback HSAFM was employed to image soft hydrocarbon films, hard grating surfaces, and Escherichia coli biofilms.
• Imaging was performed at various applied forces, including positive and negative values.
• The effect of imaging rate on stability was assessed for biological samples.

Main Results:

• HSAFM exhibited instability with negative applied forces on soft hydrocarbon films, attributed to contact/noncontact regime transitions.
• Imaging stability improved significantly on cleaned, hydrophilic grating surfaces due to higher adhesion.
• Force-feedback HSAFM demonstrated reproducible imaging of E. coli biofilms within a force deviation of ~0.5 nN at imaging rates up to 0.2s/frame.

Conclusions:

• Force-feedback HSAFM stability is sensitive to applied force and surface characteristics.
• Hydrophilic surfaces and increased tip-surface adhesion enhance imaging stability.
• HSAFM is a stable and reliable technique for imaging soft, adhesive biological samples at various imaging speeds.