Validation of an Atomistic Field Theory for Contact Electrification Using a MEMS Load Cell

Abstract

Abstract This work depicts an experimental method for the validation of an Atomistic Field Theory (AFT) model for contact electrification of dielectrics. The AFT model is used to simulate the effects of Triboelectric Nanogenerators (TENGs) for energy harvesting. Recently, the AFT model has shown that contact electrification can be described by the induced surface dipoles when two dissimilar materials are brought into close contact assuming that the crystal lattices are free of defects, no residual strain in the materials is present and that the experiment is performed in vacuum. These simulations have been used to predict the induced contact potential between MgO and BaTiO3. To validate the AFT model, a set of quasi-static experiments will be conducted to test two different operating modes of TENGs, which can be mirrored in the simulations. The first experiment is a micro-scale pull-in/pull-off test in which a pad of single crystal Si (SCSi) will be brought into and out of contact with a dielectric substrate (thermally grown SiO2). The second experiment will mimic the TENG during sliding operation. A SCSi microcantilever will be brought into contact with the dielectric surface and displaced in sliding mode. These experiments will be conducted using a custom, reusable MEMS load cell and an electrometer to monitor the interaction forces and induced charge on the surfaces. To obtain the required displacement resolution of the load cell, a high-speed Michelson interferometer will be used. This allows for higher load cell stiffness to accommodate for surface adhesion effects. The load cell will be calibrated using the well-known technique of hanging masses from the load cell. The relative distance between the interacting surfaces in both experiments will be controlled by a piezo stage with 1 nm resolution. Results from these experiments are to be compared to the AFT model results.