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The Scientific World Journal
Volume 2013 (2013), Article ID 748295, 6 pages
Research Article

Effect of Humidity and Hydrophobicity on the Tribological Properties of Self-Assembled Monolayers

Department of Chemical Engineering, Texas Tech University, 6th Street, Canton, Lubbock, TX 79409, USA

Received 6 March 2013; Accepted 10 April 2013

Academic Editors: X. Wang and C.-S. Wu

Copyright © 2013 Yen-Chih Liao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The tribological properties of two distinctive alkanethiol SAMs, 16-mercaptohexadecanoic acid (MHA) and 1-octadecanethiol (ODT), on gold substrates in various humidity conditions were examined by lateral force microscopy (LFM). The results suggest that hydrophobic ODT SAM is insensitive to humidity. The difference of lateral force signal is within ±10% regardless of humidity. The lateral force signal of hydrophilic MHA SAMs has a significant decrease in signal in humid environments. The influence of bulk water was also investigated by LFM. By imaging under water, the capillary force is eliminated on ODT SAMs, which leads to a lower lateral force. However, the lateral force image was reversed on MHA SAMs, which suggested that hydrophobic forces dominated in water.