Coupling a voltage generator to an optical interferometer: outcomes from lubricant films subjected to varying electric field intensities

The study of electric field-responsive lubrication is gaining increasing attention in tribological research, driven by the pursuit for more adaptive and energy-efficient lubrication strategies. Understanding how electric stimuli affect lubricant behavior—particularly in terms of film formation—can pave the way for the development of smart lubrication technologies. In this study, we present an experimental setup that integrates a DC power supply with an optical interferometer to investigate the evolution of lubricant film thickness under varying electric field intensities. Such a system allows precise control of the electric potential across a ball-on-disc contact operating under rolling conditions, while film thickness is measured via optical interferometry.

As a case study, we explored the behavior of bio-based lubricants with electrorheological (ER) properties, consisting of castor oil dispersions with an organo-modified nanoclay (Cloisite 15A) at different concentrations. The results show a clear increase of film thickness upon voltage application (30 V), particularly at lower entrainment speeds, where lubricant films are typically thinner. This enhancement highlights the potential of ER lubricants to improve performance in low-speed regimes.