Experimental and Computational Issues Related to Adhesion, Friction and Wear of Surfaces Modified by Self-Assembled Monolayers K. M. Liechti Molecular self-assembled monolayers (SAMs) are used to minimize stiction, friction and wear in MEMs devices and control adhesion in composite materials and structures. Nano-mechanical models of adhesion, friction and wear require the properties of these SAMs. This talk examines the use of molecular dynamics and continuum analyses and a novel scanning probe microscope for this purpose. The talk will begin with a review of prior work on SAMs by leaders in the field. First we will examine hypotheses of the mechanisms of self-assembly along with models and detection of self-assembly, particularly in mixed or binary SAMs, where there is a strong interest in patterning for nano-fabrication. Next we will review experiments and analyses related to the mechanical and adhesive behaviour of SAMs. In essence this will deal with loading SAMs normal to the surface. This work has relevance to SAM durability in new lithography schemes that make repeated use of masks. A review of work related to shear loading or the frictional and wear behaviour of SAMs will finish up this section, which has obvious connection to the behaviour of MEMS devices. In all three areas, existing
experimental techniques will be reviewed and compared. This will lead
naturally to an identification of gaps and “show
stoppers”. Links will then be made to the current status of computational
techniques and the challenges of scale and timescale bridging. Methods
for linking atomistic and continuum analyses will be considered. Strategies
for hybrid experimental computational analyses will be suggested for
further discussion. The combination of experiments and analysis is crucial
for defining measures of verification and validation. Measures of importance
and relevance will be related to the three areas and their impact on
the use of SAMs in NEMS and MEMS devices. |