The larger, boulder-like particles may break down due to impact fractures below T g which, as with the previously described samples, generates high numbers of smaller particles of similar form. The smaller particles with high AR and low solidity could be the result of a secondary mechanism, for example wear or abrasion. These are possibly generated above T g which is plausible as the heating due to friction will be localized to a thin region at the surface, from which wear-generated MPs are produced. These heated regions may allow the formation of rolls and which tear, forming highly tortuous particles, which are measured by their low solidity. The pronounced bimodality is what likely leads to the significant under-reporting of the smaller particles by the LD measurement. It can be seen that the LD data does identify a peak and trough at the same location as the OM measurement, however, it does not measure any particles smaller than 13 µm, which are evidenced in both SEM and OM. To demonstrate how such engineered MPs can be used in a research context, we devised a simple identification experiment using µ-Raman microscopy: Analysing an environmental roadside sample we anticipated it would contain a detectable amount of MPs. In absence of a prepared automatic search algorithm, we manually screened the material for traces of µ-Raman signals of polymers by taking Raman spectra of each particles, but could not identify any MPs (fig. ). This method has been demonstrated previously, but was unsuccessful here, likely due to the high amount of matrix material, including silicates and bio-material. Thus, we spiked our environmental matrix with a small amount of the tire rubber composite (fig. and) and subsequently analyzed both of these samples using µ-Raman. The cryo-milled tire MPs were easily identifiable in the spiked sample, especially with the aid of the purely tire particle images and spectra. By collecting Raman spectra from the added MPs, we could calibrate the illumination to the optimum conditions to identify tire particles. Furthermore, visual differences between the MPs and the other matter could be observed and used to identify environmental particles, showcasing that the here prepared materials and their characterization are likely to become invaluable for different method developments.