Adhesion Behavior of a Grating at a Single Location by Using an AFM Flat Tip Under Different Conditions

Abstract

Adhesion forces were determined by recording force–displacement curves using a flat tip with an atomic force microscope. The outcomes show that the adhesion behavior at a single location depends largely on contact geometry, surface topography, instrumental parameters, and the environment. Moreover, these factors are mutually coupled with each other to determine the final adhesion force. A special surface structure will lead to special adhesion behaviors by repetitive measurements. The adhesion forces are grouped into several levels. In dry nitrogen (with charges removal), the adhesion force in each level first increases and then decreases slightly. In dry nitrogen and under ambient conditions, the adhesion force in different levels increases with measurement number, and jumps between different levels. The increasing trend was ascribed to the charge accumulation and the increased size of the capillary meniscus, respectively. The charges will increase only after contact and separation and have an additive effect. When the charges are saturated, the adhesion force becomes stable. Some special adhesion behaviors are also observed in the experiments. The fluctuation behaviors of adhesion in a single cluster under different conditions are different, which was attributed to the dominant force and the environment.

KEYWORDS:

• Atomic force microscope
• Contact electrification
• Dry adhesion
• Force–displacement curve
• Patterned surfaces