# Micromechanical Characterization of Diatom Frustules of Multiple Origin
## 2 State-of-the-Art
### Mechanical Strength of Diatom Frustules and Atomic Force Microscopy AFM
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Species** & **Young’s** & **Cantilever** & **Dimension** & **Spring** & **Remarks** & **Ref.** \\  & **Modulus** & **Tip** & & & **Constant** & **Remarks** & **Ref.** \\ \hline  & 15-30 GPa & & & & 294 N/m & Artificial freshwater culture. Tests & \\  & Central rib & & & Nominal radius 25 nm & developed on dry samples. & \\ _Naviculua_ & 40-100 GPa & & & Spherical indenter & 143 \(\pm\) 2 N/m & Preparation and visualization of & \\ _pelliculosa_ & Central rib & & & Outer radius 10 nm & samples by two methods (mechanical & \\  & 30-100 GPa & & & 24.4 N/m & transfer and surface growth with & \\  & Central node & & & & subsequent ethanol washing). & \\ \hline _Coscinidiscus_ & 1.7-15.61 GPa & & & Nominal radius 25 nm. & 132 N/m & Treatment with sulfuric acid to remove organic matter. & [10] \\  & & & & & organic matter. & [54] \\ \hline  & 0.25-0.75 MPa & & & & & \\  & 500 kPa & & & & & \\ _Phaedactyllum_ & ovoid-shaped & & & & & [57] \\ _tricormutum_ & valves & & & & & [51] \\  & 100 kPa other & & & & & [51] \\  & valve shapes. & & & & & \\ \hline  & 2-5 MPa & & & & & \\  & 43.7 MPa on silica & & & & & \\  & bands & & & & & \\ _Cylindrocean_ & 21.3 MPa between & & & & & \\ _colsterium_ & silica bands & & & & & \\  & 29.8 MPa mean & & & & & \\  & value in the valve & & & & & \\ \hline  & 0.25-9 MPa & Spherical & 2 μm & 4.5 N/m & Living cells in seawater. & \\  & 729 kPa & Spherical & 2 μm & 4.3 (\(\pm\)0.2) N/m & & mission nitride cantilevers. Living cell, & \\  & 729 kPa & Spherical & 2 μm & 4.3 (\(\pm\)0.2) N/m & & marginal ridge, cell division during & \\  & & & & & & incubation. & \\ _Lithodesmium_ & & & & & & \\ _undlatum_ & 737 kPa & Spherical & 2 μm & 4.3 (\(\pm\)0.2) N/m & Living cells, valve, and cell division & \\  & & & & & during incubation & \\  & 3.2 MPa & Spherical & 2 μm & 4.3 (\(\pm\)0.2) N/m & & Living cells, analyze, No cell division & \\  & & & & & & during incubation. & \\  & & & & & & Cells were cultured at 15 \({}^{\circ}\)C and & \\  & & & & & moderate light intensity. Tests carried & \\ _punctigen_ & 22.4 GPa & & & & & out in seawater environment. Loading & \\  & & & & & application with calibrated glass & \\ \hline _Cyclotella_ & & & & & & \\ _menghini_ & 7-25 GPa & & & & & \\  & & & & & with “Peak Force” contact method. & \\ \hline  & & & & & Central marine species. Clean diatom & \\ _Coscinidiscus_ & 1.1–10.6 GPa & Diamond & & & sample mounted on a glass sheet with & \\  & & Berkocvich & 20 nm & 42 N/m & an adhesive solution. Resonant & \\  & & & & frequency of 300 kHz in intermittent & \\  & & & & & contact. Pretreatment with nitric acid & \\  & & & & & and ethanol. & \\ \hline _Synedm_ & 13.7–18.6 GPa & Diamond & & & & & \\  & & & & & & adhesive solution. Resonant frequency & \\  & & & & & of 300 kHz in intermittent contact. & \\  & & & & & & Pretreatment with nitric acid and & \\  & & & & & ethanol & ethanol \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Young’s Modulus Register for different diatom species. (Young's Modulus values up to 500 kPa) than the components of a diatom that has not been silicified [20,57]. Indentation tests on diatom frustules of the _Coscinodiscus_ species by modifying the angles of incidence and the location point are reported by refs. [55,59]. The fossils' elastic modulus (E) and hardness (H) were calculated. The mechanical properties were defined mainly by the point of load application and not so much by the size of the frustule. The values ranged E: 0.59-2.77 GPa and H: 0.03-0.12 GPa in the center of the frustule. The reports obtained were complemented with simulations by the Finite Element Method, finding good agreement. Ref. [60] reports [PERSON]'s modulus values for different regions of diatom frustules (biogenic silica); thus, transapical rib (7-20 GPa), central rib (15-100 GPa), central nodule (30-100 GPa). Simultaneously, it reports values for synthetic silica between 66.3 and 74.8 GPa. The authors associate these values with the material's low density (2.2 g/cm\({}^{3}\)).