Nanotribological characterization of perfluoroalkylphosphonate self-assembled monolayers deposited on aluminum-coated silicon substrates

Abstract

Aluminum-coated silicon substrates are commonly used for various micro/nanooptoelectromechanical systems (MOEMS/NOEMS) including Digital Micromirror Devices (DMD Ò ). For efficient and failure proof operation of these devices, ultra-thin lubricant films of self-assembled monolayers (SAMs) are increasingly being employed. Fluorinated molecules are known to exhibit low surface energy, adhesion, and friction, desirable for tribological applications. In this study, we investigate contact angle, surface energy, friction, adhesion, and wear properties of a perfluoroalkylphosphonate SAM and compare them with those of alkylphosphonate SAMs. The influence of relative humidity, temperature, and sliding velocity on the friction and adhesion behavior is studied. Failure mechanisms of SAMs are investigated by wear tests. These studies are expected to aid in the design and selection of proper lubricants for MOEMS/ NOEMS.

Biofouling: lessons from nature

“…Other coating examples include self-assembled monolayers (SAMs), which are desirable as they coat the surface with a molecularly thick biocompatible film. This is especially important for applications such as Biomedical Micro/Nano Electromechanical Systems (BioMEMS/NEMS) [35][36][37]146]. Figure 14 shows an orthopaedic hip implant covered with a biocompatible coating designed to control biofouling, wear rate and promote bone growth [147,148].…”

Nanotribology and nanomechanics in nano/biotechnology

“…Thus, the dewetting of liquid Z-15 film results in higher adhesive force and poorer lubrication performance. For lubrication of MEMS/NEMS, another effective approach involves the deposition of organized and dense molecular layers of long-chain molecules, referred to as SAMs, by chemical grafting of molecules (Bhushan et al 1995b(Bhushan et al , 2006b Si (100) Si (100) Z-15 (2005) and Bhushan et al (2006b) studied perfluorodecyltrichlorosilane (PFTS), n-octyldimethyl (dimethylamino) silane (ODMS; nZ7) and n-octadecylmethyl (dimethylamino) silane (ODDMS) (nZ17) vapour phase deposited on Si substrate, and decylphosphonate (DP), octadecylphosphonate (ODP) and perfluorodecylphosphonate (PFDP) on Al substrate (figure 8). Figure 9a presents the contact angle, adhesive force, friction force and coefficient of friction of two substrates and with various SAMs.…”

“…For wear performance studies, experiments were conducted on various films. Figure 9b shows the relationship between the decrease in surface height and the normal load for various SAMs and corresponding substrates (Kasai et al 2005;Tambe & Bhushan 2005;Bhushan et al 2006b). As shown in the figure, the SAMs exhibit a critical normal load beyond which point the surface height drastically decreases.…”

Modification of epoxy resin, silicon and glass surfaces with alkyl- or fluoroalkylsilanes for hydrophobic properties

“…For example, fluorinated silanes or fluoropolymers can be used for hydrophobization to obtain superhydrophobic lotus-like surfaces by using modification process based on chemical bath deposition (CBD) [10][11][12]. Moreover, fluorinated compounds can also influence the reduction in friction coefficient of modified surfaces [13]. Wettability of the solid surface is a unique property of the materials and strongly depends on both the surface energy and the surface roughness.…”