E. Cavalletti | Searcharxiv

arXiv2026

Decoupling Structure and Elasticity in Colloidal Gels Under Isotropic Compression

We exploit the controlled drying of millimeter-sized gel beads to investigate isotropic compression of colloidal fractal gels. Using a custom dynamic light scattering setup, we demonstrate that stresses imposed by drying on the bead surface propagate homogeneously throughout the gel volume, inducing plastic rearrangements. We find that the Young modulus and yield stress of the gels increase monotonically with the instantaneous colloid volume fraction, $\phi$, exhibiting a mechanical response that depends solely on $\phi$, regardless of the drying history. In striking contrast, small-angle X-ray scattering reveals that the gel microstructure retains a strong memory of its initial state, depending on both $\varphi$ and the entire compression pathway. Our findings challenge the prevailing paradigm of a one-to-one relationship between microstructure and elasticity in colloidal fractal gels, opening new avenues for independent control over the structural and mechanical properties of soft materials.

cond-mat.soft↗

arXiv2025

Synthesis of spherical mesoporous silica beads with tunable size, stiffness and porosity

We present an innovative template-free water-based sol-gel method to produce uniform mesoporous silica beads of millimeter size, which have tunable size, stiffness and porosity, and could be used for adsorption applications. Our protocol exploits an in-situ enzymatic reaction to produce spherical beads of hydrogel from a charge-stabilized suspension of silica nanoparticles confined in a millimetric drop suspended in a non-miscible oil. Once the gelation step is complete, the spherical bead of gel is cleaned from oil and deposited onto a hydrophobic surface and let dry. Separating the gelation to the drying steps ensures a spatially uniform gel and allows us to perform a solvent exchange before drying. For all beads, we observe a crack-free drying process leading to the formation of stiff quasi-spherical beads with diameter in the range 1 to 5 mm and Young modulus in the range $(0.1-2)$ GPa and narrow pore size distribution, centered around $10$ to $25$ nm depending on the experimental conditions. Finally, to demonstrate the potentiality of these materials, we graft on the bead surface aminosilane molecules, and quantify their CO$_2$ adsorption efficiency. Overall, the production method we have developed is simple, readily adaptable, and offers promising materials for adsorption, storage, catalysis and chromatography.

cond-mat.soft↗