# Micromechanical Characterization of Diatom Frustules of Multiple Origin
## 4 Results and Discussion
### Young's Modulus Determination  
Upon analyzing the curves and incorporating the Hertz model with considerations for the tip geometry, [PERSON]'s moduli were determined for each species and categorized according to the load application zone. These results are presented in Table 3, revealing  
Figure 8: Contrast of force-displacement curves obtained by AFM on frustules or their derivatives [23; 51; 55].  
Figure 7: Block contrast of force-displacement curves for different species.  
that the species from Mexico exhibit the lowest modulus values, the Colombian species display the highest, and the Peruvian species demonstrate the most consistent behavior. This pattern is akin to the concentration of force-displacement curves observed in Figure 7.  
In terms of the average value of Young's modulus, the lowest magnitudes are recognized in the Mexican species, both in the outer edge (148 MPa) and the Radial striae (219 MPa), which is consistent with the blocks of the \"force-deformation\" curves of Figure 7 that is, the most significant deformations are observed. The Modulus values of the Peruvian species are the most regular, with the lowest coefficient of variability (Cv) of the three species (<38%): its average value (496 MPa) is higher than that of the Mexican species but lower than that of the Colombian species. Although the Colombian species reports the maximum modulus values, 626 MPa (ringleist) and 574 MPa (cylinder walls), it also exhibits low magnitudes that derive in the most evident dispersion of the three samples (Cv > 68%).  
Figure 2 shows the sillification level of the frustules (EDS tests in SEM). For the Colombian sample, an average percentage of contents greater than 36.75% are identified,  
\begin{table}
\begin{tabular}{c c c c c} \hline \multicolumn{2}{c}{**Colombian Species**} & \multicolumn{2}{c}{**Mexican Species**} & \multicolumn{2}{c}{**Peruvian Species**} \\ \hline
**Axial Load** & **Lateral Load** & **Outer Edge Load** & **Radial Striae Load** & **Sternum Load** \\ (Ringleist) & **(Cylinder Walls)** & **Outer Edge Load** & **Radial Striae Load** & **Sternum Load** \\ \hline
596.76 & 638.97 & 181.90 & 219.40 & 586.19 \\
320.91 & 94.66 & 330.60 & 193.48 & 292.03 \\
1150.00 & 211.75 & 165.80 & 357.23 & 325.94 \\  
while the Mexican and Peruvian species report average values of 27% and 17%, respectively. A relationship between the high modulus values of the Colombian species and its Silica content is evidenced.  
Figure 9 is a schematic representation of the frustules studied in this research. Their characteristic shapes are highlighted again: cylindrical, plate-shaped, and elongated for the Colombian, Mexican, and Peruvian species. This figure exposes the load application points (where it was physically possible) and the elastic moduli obtained.  
Multiple frustules were analyzed in each species, and the graphic representation corresponded to the superposition of data obtained from the different fossils.  
Figure 9 shows that the Colombian frustules Moduli's extreme values (upper and lower peak) are more representative on the lateral faces compared to those obtained in the circular cross-section (ringleist).  
In the Mexican species, peak values were obtained in the middle section (over the striae) and the outer ring (outer edge). However, these records are not homogeneous or representative of the entire area; they are specific measurements.  
The Peruvian fossil reveals module values that are less dispersed in order of magnitude, which can be understood by the pieces' smaller dimensions (geometric width).  
The homogeneity in the results of the Peruvian species is highlighted again; its narrower geometry and lower pore density imply less mechanical variability. It is worth highlighting the geometric differences between the Peruvian and the other two species. In the case of the Colombian species, when applying axial load on the ringleist, higher module values were identified towards the center of the frustule.  
Figure 9: Cont.