Effect of Wetting and Dewetting Dynamics on Atomic Force Microscopy Measurements

Area of Science:

• Computational physics
• Nanotechnology
• Surface science

Background:

• Atomic force microscopy (AFM) relies on understanding tip-substrate interactions.
• Liquid bridges and meniscus dynamics are crucial in AFM measurements and nanolithography.

Purpose of the Study:

• To validate and demonstrate the efficacy of the multibody dissipative particle dynamics (MDPD) model for simulating water bridge dynamics.
• To analyze the behavior of liquid bridges under various AFM tip configurations and operating conditions.

Main Methods:

• Utilized the multibody dissipative particle dynamics (MDPD) model to simulate water bridge formation and dynamics.
• Validated the MDPD model against literature data for contact angles and liquid bridge behavior.
• Conducted parametric studies on AFM tip geometry and operating conditions, including static and dynamic cases.

Main Results:

• Identified a critical capillary number of approximately 0.001 for dynamic force changes.
• Successfully predicted capillary force hysteresis during AFM tip approach and retraction.
• Achieved excellent agreement between MDPD predictions and theoretical results for water bridge breakup distance.
• Demonstrated good agreement with experimental data for capillary force transitions in multibody AFM tips.

Conclusions:

• The validated MDPD model accurately captures liquid bridge dynamics, including meniscus behavior and capillary forces.
• The MDPD model serves as a powerful tool for meniscus manipulation technologies like dip-pen nanolithography.
• This model facilitates the study of dynamic AFM tip interactions with liquid bridges, such as in tapping mode.