In this paper, an application of the surface plasmon resonance (SPR) method to real-time and in-situ measurements of changes in adsorption film thickness, e.g., fatty acid adsorbed films, is presented. As discussed in the previous study, the high sensitivity and overall simplicity of its optical system make the SPR method advantageous for monitoring lubricant film thickness. In order to demonstrate the high sensitivity of the SPR method, in-situ and real-time adsorption film growth processes of stearic acid (additives) in hexadecane (base oil) were monitored using the Otto configuration. Based on a comparison between experimental and model calculation results, changes in the adsorption film thickness during a series of different contact tests were measured.
An In-situ Real-Time Optical Fiber Sensor Based on Surface Plasmon Resonance for Monitoring the Growth of TiO2 Thin Films
