Correction of height-fluctuation-induced systematic errors in polymers by AFM-based nanomechanical measurements. (January 2021) - Mao, Lu
Abstract: AFM-based nanomechanical measurements are powerful tools for the characterization of polymer composites. However, a flat surface of the samples is usually required, which restricts the wide applications of nanomechanical measurements. In this work, the height-fluctuation induced systematic errors were investigated taking polystyrene beads as the model sample. Corrections were further made based on the assumption that the components of force and deformation parallel to the sample surface can be approximately ignored. Results show the deviations of force and deformation due to height-fluctuations can be well corrected by the proposed method. Moreover, the reliability of the corrected force curves was further verified in the calculation of the mechanical properties. Young's moduli value without height-gradient dependency can be obtained by applying both Johson-Kendall-Roberts (JKR) model and Derjaguin-Muller-Toporov (DMT) model. The correction method proposed in this work can broaden the applications of AFM-based nanomechanical measurements on polymers without strict restrictions on the surface flatness. Highlights: Systematic errors occur when measuring samples with height-fluctuations along the direction of the cantilever beam. Systematic errors are more obvious when the value of cantilever deflections is close to the piezoscanner displacement. The correction works well by considering the sample surface height-gradients and the sitting angle of the probes. Reliable nanomechanical measurements can be done by analyzing the corrected force curves using both JKR and DMT models.