Logarithmic decrease of adhesion force with lateral dynamic revealed by an AFM cantilever at different humidities

ABSTRACT

Adhesion forces between a tipless cantilever and an Au film were determined to investigate the influence of lateral velocity by recording force curves with an atomic force microscope at 20%–90% relative humidities. The sample was moved laterally, forth and back, with a frequency of 0.001–100 Hz and scan distances of 0.8, 8, and 80 μm to achieve a velocity ranging over 7 orders of magnitude. Experimental results show that at low lateral velocities (between 1.6 nm/s and 1–10 μm/s), the adhesion force either increases or decreases or remains stable with the lateral velocity without a certain characteristic trend. However, after a critical velocity, the adhesion force decreases logarithmically with the lateral velocity (between 1–10 and 16,000 μm/s). The decreasing magnitude can be as large as 97.3% of the maximum adhesion force. This decrease is well-explained by the contact time dependence of water bridges formed by capillary condensation.

KEYWORDS:

• Adhesion by physical adsorption
• atomic force microscope
• capillary condensation
• coatings
• pull-off force
• sliding velocity

Funding

This work was supported by the National Natural Science Foundation of China (Grant Nos. 51505250, 51635009 and 51575190) and China Postdoctoral Science Foundation (Grant Nos. 2015M570088 and 2016T90088).

Supplementary materials

Supplemental data for this article can be accessed on the publisher’s website.

Movie S1; Glove box to adjust relative humidity; Detail of the cantilever; Force–displacement curves; Mean adhesion force at different RHs.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant Nos. 51505250, 51635009 and 51575190) and China Postdoctoral Science Foundation (Grant Nos. 2015M570088 and 2016T90088).