Publication
Silicon dioxide is finding more and more applications in tribological systems thanks in part to the possibilities of micro-fabrication in large scales at high precision, and in part to its good mechanical properties. It has found a particular niche in the horological industry, being used in various wristwatch components. In industry applications, the primary challenge is to develop a tribosystem that allows constant and minimal friction for the micro-scale geometry and load conditions. A scientific approach is used to address the industry challenges. An overview of the state of the art reveals a gap in literature regarding tribological studies under watch-relevant micro-scale conditions. Thus, the devices and methods are developed that allow experimental studies under micro-scale conditions with precise geometric constraints. A detailed physical characterization of the tribocontact allows quantification of contact conditions using boundary element simulation. Tribological experiments demonstrate dependence of friction on contact area and on surface adsorption of contaminants. It also reveals a characteristic behavior of friction increase that consists of a time-dependent recoverable component, and a irrecoverable cumulative component. A simple mechanistic model is developed based on adsorption of contaminants and evolution of elastic deformation energy due to crack growth. The model is then assessed for its applicability to the experimental system. Ultimately, this study allows quantification of the trade-off between contact area and contact pressure in silicon dioxide systems given any surface topography, while also considering effects of contaminant adsorption.