## 3 Results
### Characterization of Diatomic Powders, Diatomite/Sodium Alginate Dispersions and Resultant Granules
Specifically, after drying, the shrinkage percentages were higher for the D04 to D16 granules (ranging from 59.6% to 45.0%) compared to those of granules derived from dispersions with higher solid contents (D40 to D44), which experienced lower shrinkage percentages (ranging from 25.8% to 4.6%). This phenomenon can be explained as follows: (1) Assuming a fixed tip dimension of 1 mm, we can consider a comparable volume of droplets (diatomite/sodium alginate dispersion) being detached from the capillary. (2) During the flow of the dispersion through the tip, the suspended SiO\({}_{2}\) particles were concentrated in the tip and were redistributed within the droplet as it is ejected. In particular, a significant concentration of particles tends to localize in the area/volume of the droplet that was lastly detached from the tip [63]. (3) With the increase in the diatomic content in the dispersion, more SiO\({}_{2}\) particles become bound to sodium alginate within the droplet. As a result, the area/volume occupied by these particles increases, leading to a decrease in the area/volume occupied by bound water within the droplet. (4) Eventually, the cross-linked alginate chains encapsulate the SiO\({}_{2}\) particles, following their distribution pattern within the droplet. It is suggested that, for low diatomic contents (D04 to D16), there were fewer binding sites between SiO\({}_{2}\) and sodium alginate, leading to the formation of more hydrogen bonds between sodium alginate and water. Likewise, the hydrophilicity of the SiO\({}_{2}\) particles in  
Figure 4: Representative porous diatomic granules (D44, D43, D12, and D04) obtained after each step in the processing route: (**a**) aging (CaCl\({}_{2}\) bath) and cleaning (DI water), (**b**) drying (80 \({}^{\circ}\)C, overnight), and (**c**) a heat treatment at 1200 \({}^{\circ}\)C for 1 h in air. (Additional images corresponding to porous diatomic granules between D08–D24 and D28–D40 are presented in Figures S2 and S3 in the Supplementary Materials). the formulated dispersions facilitated the formation of hydrogen bonds. Consequently, the volume of bound water present in the droplets was higher, resulting in lower viscosity compared to that of the D43 dispersion. For higher solid contents (D20 to D44), it is suggested that the binding interactions between SiO\({}_{2}\) and sodium alginate were stronger, increasing the structural stability (solid network) of the gel granule [51; 52; 61]. This also affected the shape of the granule, as the portion of solid matter (diatomic) interacting with the alginate chains was higher relative to the portion of bound water. As shown in Figure 1c, the drying process resulted in the evaporation of water from the gel granules composed of diatomic and cross-linked alginate, causing the structure to shrink. During the drying step, the bulk water trapped within the granules evaporated, leading to a closer packing of SiO\({}_{2}\) particles that were initially significantly saturated with water. This was followed by the invasion of air and the gradual emptying of pores [64; 65]. The cross-linked alginate network also shrank and collapsed [66] due to the aggregation of chain segments in the junction zones [34; 67]. Throughout the shrinkage process, the diatomic particles remained encapsulated in the polymer-like network of the cross-linked alginate, following the distribution pattern of SiO\({}_{2}\) particles within the droplet during the sodium alginate cross-linking process. Consequently, the shape of the heat-treated granules (Figure 5) closely resembled that of the dried granules, accompanied by decreased shrinkage values (D04: 18.45% to D44: 2.53%). After the heat treatment (Figure 1d), the diatomic particles bonded, forming a solid network with inter-particle pores. Figure 6 presents the sphericity of the diatomic-derived granules as a function of the mass of diatomic in the dispersions (Figure 6a) and the viscosity of the dispersions (Figure 6b).