# Micromechanical Characterization of Diatom Frustules of Multiple Origin
## 4 Results and Discussion
### Force--Deformation Curves  
The forces were applied at different points on the frustules, chosen based on the morphological characteristics of each species. In the Colombian sample, the main ring and the cylinder wall were targeted. For the Mexican sample, the forces were applied to the rim and the center of the plate. In the case of the Peruvian sample, due to the elongated shape of the particles, the forces were distributed between the edges and the center. Figure 5 illustrates the locations where the loads were applied. The force-displacement curves obtained for each of the species are shown in Figure 6.  
The curves obtained under the same conditions (species and area of application) were grouped and plotted to compare the results of the different samples. See Figure 7.  
In Figure 7, it is evident that the Mexican species exhibited the highest displacement values and the greatest dispersion, especially when the load was applied on the outer edge. Even when the force was applied to the inside of the radial striae, the displacement still exceeded that reported by the other species under any condition. On the other hand, the Peruvian species displayed the highest concentration and uniformity in displacement. The Colombian frustules showed similar displacement when a load was applied to the cylinder walls or to the ringleist. Interestingly, the maximum applied force values across the three species and different application points were consistent, ranging from 1.4 to 1.8 \(\times\) 10\({}^{-7}\) N.  
From Figure 7, it is possible to elucidate that the dispersion is more significant in terms of deformation than force. The uniformity of the results of the Peruvian species is outstanding and can be understood by the more straightforward geometric shape, with a smaller quantity and size of pores than in the other species; this is then associated with greater regularity in the fixation of silica, and in the way, the stresses are transmitted within a medium with fewer discontinuities. The Colombian species turns out to be quite porous, as much as the Mexican one. However, it registers better behavior in terms of deformations since the cylindrical shape gives it a space of continuity through which the stresses can be dissipated. On the contrary, the Mexican species exposes clear limits on the outer edges where stresses are concentrated. Figure 3 allows us to recognize that the mineralogical composition of the three species is similar, recording the presence of SiO\({}_{2}\) in all cases, particularly Tridymite and Cristobalite. The shape of the frustules and the organization of the silica spheres will then determine the differential behavior between species. This aspect invites the development of microscopic visualizations at higher levels, in which the organization of the mineral and its arrangement around pores or irregularities can be validated. Subsequently, to confirm the reliability of the results, the group of Force-Displacement curves (MEX_outer edge load) was compared with data from other researchers who had applied loads using AFM to diatoms, whether on the frustules, their organic coverings, or the substances they excrete. See Figure 8.  
Figure 5: Identification of species and load application points by means of AFM. (**a**) Colombia (Boyaca)_Aulacoseira Granulata_Centric monospecies, cylindrical; (**b**) Mexico (Jalisco)_Cyclostebhanos tholiformis_Centric monospecies, disc shape; (c) Peru (Ica)_Thalassionema nitzschioides_ Elongated, symmetrical shapes. Figure 6: Force-displacement curves obtained by AFM for different species. (**a**) Colombia Aulacoseira Granulata; (**b**) Cyclostephanos tholiformis; (**c**) Peru Thalassionea nitzschioides. Regarding Figure 8, the Force-Displacement profiles of the frustules examined in this study exhibit a higher degree of uniformity compared to those documented in previous research, wherein loads were applied to different species, either directly on the frustule or on the derived substances.