Advancing the application of atomic force microscopy (AFM) to the characterization and quantification of geological material properties

Atomic force microscopy (AFM) has been widely used in materials science and chemistry research since it was invented in the 1980s. It is a relatively new tool for geosciences and is very powerful for micro- and nano-scale surface characterization with a resolution down to atomic scale. One of the major advantages of this microscopy technique is that it can perform continuous non-destructive measurements on a sample surface. Surface studies provide important structural information for geological materials, especially in energy geosciences. In this review, recent applications of AFM in energy geosciences are critically reviewed, including surface topography, mechanical properties, surface dynamics, and state-of-the-art AFM-based infrared spectroscopy (AFM-IR) and the AFM-Raman technique. AFM imaging enables the mapping and recording of surface information and enhances the understanding of morphology and mechanical properties of geological materials, and is especially useful for those displaying a strong heterogeneity. This review aims to demonstrate the accessibility, versatility, limitations, and promising developments of AFM techniques in energy geoscience. We highlight the major advantages and disadvantages of AFM analysis of geological materials and highlight where factors can cause potential deviations between different experimental results. We further highlight where we believe are the most promising potential uses of AFM. It is foreseen that with the improvement of experimental processes and hardware, AFM will provide indispensable information on surface characterization in a wide range of geological studies.