Rotational force test method for determination of particle adhesion—from a simplified model to realistic dusts

The deposition of dust particles on surfaces can be problematic for many applications, both industrial (e.g., semi-conductor manufacturing) and outdoor (e.g., solar power generation). A new test procedure was developed to evaluate particle–surface interactions and particle removal by rotating planar surfaces that are homogenously covered by dust deposits. The spatial change of the particle removing centrifugal forces, combined with large-area optical microscopy and image analysis with respect to particle sizes, allows for a statistical determination of particle removal forces. Within this study, we investigate how results from the “rotational force test method” (RFT) can be interpreted for natural dust deposits. Based on a simplified static force- and moment-balance approach of spherical particles on flat surfaces, necessary model modifications are discussed to approach natural dusts. The theoretical considerations are validated by RFT results for different dust types, including PMMA spheres, quasi-mono-disperse calcite particles, and Middle East Test Dust, which are comparable to natural dust deposits. The experimentally obtained values for adhesion forces of natural dust particles agree well with theoretical considerations and with other studies from the literature using different techniques. The developed metrology is widely applicable since only a commercial spin coater and an optical microscope are required. It can be used to determine dust-type dependent adhesion forces for coated and uncoated surfaces and specified environmental conditions.