Development of a Surface Forces Apparatus Featuring Ultrafast Non-resonant Imaging for Measuring Contact Electrification

The charging of surfaces via physical contact, known as contact electrification, is an off-equilibrium phenomenon that spans many lengthscales and can exhibit extreme energy focusing by conversion of diffuse mechanical energy into high energy x-rays. Due to the challenges of performing in-situ measurements of charge separation from buried interfaces, the fundamental mechanisms of contact electrification are still unknown. To make experimental advances in this field, we have developed a new multimodal platform that combines the angstrom precision of a surface forces apparatus with the interfacial access provided by a nonlinear optical measurement, i.e., second harmonic generation. Details of the instrument’s design and operation will be presented, which will include preliminary experimental results that tests how contact electrification is affected by monolayer-levels of surface absorbents.