R.J. Sheridan, I. Saito, L.C. Brinson
Duke University,
United States
Keywords: nanoindentation, dataset, viscoelastic, metrology
Summary:
Our recent publication[1] identifying the limits of resolution for AFM nanoindentation measurement near a rigid substrate required particular care in selecting material, processing, and indentation conditions[2, 3] to produce our findings. This included minimizing rate-dependent effects from the force curves to avoid biasing the material property estimates. A side-effect of this was the realization that we had tight, reproducible control over the effective relaxation time of the material and the indentation rate of the probe, such that the fine details of viscoelastic behavior of the material could be explored. In this presentation, we discuss the new, expanded dataset that grew out of the work, including several variations of thiol-ene network chemistry to manipulate surface energy, rubbery modulus, and other measurables. Because these materials have robust structure-property relationships, we can confidently present macroscopic-scale measurements of viscoelastic spectrum, surface energy, and IR spectroscopy as representative of the material under test by AFM. And, thanks to the fast data collection rate of modern pulsed-force mode, we have many consistent examples of indentations at each condition to help distinguish signal from noise. We will make this robust corpus of real indentation measurements available publicly in the hope of advancing the theory of viscoelastic indentation, but we will also share our own preliminary findings drawn by the application of interpretable machine learning algorithms for dimensionality reduction. 1. Saito I, Sheridan RJ, Zauscher S, Brinson LC (2024) Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body. Macromolecules, https://doi.org/10.1021/acs.macromol.4c01993 2. Sheridan RJ, Collinson DW, Brinson LC (2020) Vanishing Cantilever Calibration Error with Magic Ratio Atomic Force Microscopy. Advanced Theory and Simulations, 3(8):2000090. https://doi.org/10.1002/adts.202000090 3. Collinson DW, Sheridan RJ, Palmeri MJ, Brinson LC (2021) Best practices and recommendations for accurate nanomechanical characterization of heterogeneous polymer systems with atomic force microscopy. Progress in Polymer Science, 119:101420. https://doi.org/10.1016/j.progpolymsci.2021.101420