Environmental effects on adhesion forces

in nanosystem applications

 

J. Grobelny, N. Pradeep, D.-I. Kim, and Z. C. Ying

National Institute of Standards and Technology

Gaithersburg, Maryland 20899

Mentor: Robert F. Cook

 

Nanoscale adhesion forces have great effects in many technological and medical applications and knowledge of such forces is crucial in the design of many advanced nanodevices. Adhesion forces are composed of several contributing elements such as van der Waals force, electrostatic force, meniscus force and other interaction forces originating from the physics and chemistry of the surfaces.Pull-off forces between a gold sphere and flat gold substrate are studied using atomic force microscopy in different environments. Literature data exhibit various behaviors of pull-off force as a function of relative humidity and it is an open question whether the pull-off force measured in nitrogen atmosphere is free of a meniscus contribution. We observe that the pull-off force measured in vacuum is only a small fraction of that in ambient air or nitrogen atmosphere. In contrast, the snap-on force exhibits a weak environmental effect. Calculations to quantify the capillary condensation forces, including the effects of elastic deformation of the contacting bodies and of adsorption layers, reveal that the meniscus force is the dominant source of the observed difference in pull-off forces. Contrary to the popular belief, our experimental data show that nitrogen purge does not eliminate the meniscus contribution to the pull-off force completely.

 

Author Informations:

Name:††††††††††††††††††††††††† Jaroslaw Grobelny

Mentorís name:††††††††††† Robert F. Cook

Division:†††††††††††††††††††††† Ceramics, 852

Laboratory:††††††††††††††††† MSEL

Room/Building: B109/217

Mail Stop:††††††††††††††††††† 8526

Telephone #:†††††††††††††††† 301-975-6104

Fax #:†††††††††††††††††††††††††† 301-975-5334

Email:†††††††††††††† ††††††††††† jaroslaw.grobelny@nist.gov

Sigma Xi:††††††††††††††††††††† not a member

Category:†††††††††††††††††††† Materials