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Nanoscale Friction Switches: Friction Modulation of Monomolecular Assemblies Using External Electric Fields
Langmuir
  • Kanaga Karuppiah Kanaga Subramanian, Iowa State University
  • Yibo Zhou, Iowa State University
  • L. Keith Woo, Iowa State University
  • Sriram Sundararajan, Iowa State University
Document Type
Article
Publication Date
10-20-2009
DOI
10.1021/la901221g
Abstract
This paper presents experimental investigations to actively modulate the nanoscale friction properties of a self-assembled monolayer (SAM) assembly using an external electric field that drives conformational changes in the SAM. Such “friction switches” have widespread implications in interfacial energy control in micro/nanoscale devices. Friction response of a low-density mercaptocarboxylic acid SAM is evaluated using an atomic force microscope (AFM) in the presence of a DC bias applied between the sample and the AFM probe under a nitrogen (dry) environment. The low density allows reorientation of individual SAM molecules to accommodate the attractive force between the −COOH terminal group and a positively biased surface. This enables the surface to present a hydrophilic group or a hydrophobic backbone to the contacting AFM probe depending upon the direction of the field (bias). Synthesis and deposition of the low-density SAM (LD-SAM) is reported. Results from AFM experiments show an increased friction response (up to 300%) of the LD-SAM system in the presence of a positive bias compared to the friction response in the presence of a negative bias. The difference in the friction response is attributed to the change in the structural and crystalline order of the film in addition to the interfacial surface chemistry and composition presented upon application of the bias.
Comments

Reprinted with permission from Langmuir 25 (2009): 12114–12119, doi:10.1021/la901221g. Copyright 2009 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
Date Available
2014-03-10
File Format
application/pdf
Citation Information
Kanaga Karuppiah Kanaga Subramanian, Yibo Zhou, L. Keith Woo and Sriram Sundararajan. "Nanoscale Friction Switches: Friction Modulation of Monomolecular Assemblies Using External Electric Fields" Langmuir Vol. 25 Iss. 20 (2009) p. 12114 - 12119
Available at: http://works.bepress.com/l-woo/125/