Stefano Caimi

Last Name

Caimi

First Name

Stefano

ORCID

0000-0003-3898-559X

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Publications1 - 6 of 6

Preparation of perfusive chromatographic materials via shear-induced reactive gelation
Cingolani, Alberto; Baur, Daniel; Caimi, Stefano; et al. (2018)
Journal of Chromatography A
Aggregation of stable colloidal dispersion under short high-shear microfluidic conditions
Lu, Jichang; Caimi, Stefano; Erfle, Peer; et al. (2019)
Chemical Engineering Journal
Recovery of mineral oil from underground electrical cables
Caimi, Stefano; Colombo, Claudio; Ferrari, Raffaele; et al. (2019)
International Journal of Environmental Research and Public Health
To remove the mineral oil impregnating the insulating paper present in old, disconnected, underground electrical cables, which represents a threat to the environment, two approaches are investigated at laboratory (1 m) and pilot (10 m) scales. The first one involves in situ polymerization to clog the inner channel of the cables and to enable the washing of the outer paper region impregnated by the oil by axial flow of a displacing fluid (water). The second approach leaves the inner channel open and employs repeated cycles of pressurization and rest to displace the oil contained in the paper by radially pushing the water from the inner channel into the outer layers. The pressurization and rest times were optimized to obtain the highest oil extraction rate. While the first approach showed limitations in terms of required pressures and operating time, which increase with the length of the cables, the second one was effective at removing 97% of the oil impregnating the paper layers within 25 cycles. Even more relevant, this second solution, in contrast to the first one, can be easily scaled up as it does not depend on the length of the cable, and was successfully tested on a 10 m cable, showing 98% oil recovery.
Effect of SiO2 Nanoparticles on the Performance of PVdF-HFP/Ionic Liquid Separator for Lithium-Ion Batteries
Caimi, Stefano; Klaue, Antoine; Wu, Hua; et al. (2018)
Nanomaterials
Safety concerns related to the use of potentially explosive, liquid organic electrolytes in commercial high-power lithium-ion batteries are constantly rising. One promising alternative is to use thermally stable ionic liquids (ILs) as conductive media, which are however, limited by low ionic conductivity at room temperature. This can be improved by adding ﬁllers, such as silica or alumina nanoparticles (NPs), in the polymer matrix that hosts the IL. To maximize the effect of such NPs, theyhavetobeuniformlydispersedinthematrixwhilekeepingtheirsizeassmallaspossible. Inthis work, starting from a water dispersion of silica NPs, we present a novel method to incorporate silica NPs at the nanoscale level (<200 nm) into PVdF-HFP polymer clusters, which are then blended with the IL solution and hot-pressed to form separators suitable for battery applications. The effect of different amounts of silica in the polymer matrix on the ionic conductivity and cyclability of the separator is investigated. A membrane containing 10 wt.% of silica (with respect to the polymer) was shown to maximize the performance of the separator, with a room temperature ionic conductivity of of 1.22 mS cm−1. The assembled half-coin cell with LiFePO4 and Li as the cathode and the anode exhibited a capacity retention of more than 80% at a current density of 2C and 60◦C.
Mechanical phase inversion of Pickering emulsions via metastable wetting of rough colloids
Zanini, Michele; Cingolani, Alberto; Hsu, Chiao-Peng; et al. (2019)
Soft Matter
The possibility to invert emulsions from oil-in-water to water-in-oil (or vice versa) in a closed system, i.e. without any formulation change, remains an open fundamental challenge with many opportunities for industrial applications. Here, we propose a mechanism that exploits particle surface roughness to induce metastable wetting and obtain mechanically-responsive Pickering emulsions. We postulate that the phase inversion is driven by an in situ switch of the particle wettability from metastable positions at the interface following the input of controlled mechanical energy. Oil-in-water emulsions can be prepared at low energy using mildly hydrophobic rough colloids, which are dispersed in water and weakly pinned at the interface, and switched to water-in-oil emulsions by a second emulsification at higher energy, which triggers the relaxation of the particle contact angle. The same principle is demonstrated for the complementary emulsions using mildly hydrophilic colloids initially dispersed in oil. Our experiments and simulations support that the delicate interplay between particle surface design during synthesis and the energy of the emulsification process can encode a kinetic pathway for the phase inversion. Both organic and inorganic nanoparticles can be used, allowing for the future implementation of our strategy in a broad range of smart industrial formulations.
A hydrophobic low-complexity region regulates aggregation of the yeast pyruvate kinase Cdc19 into amyloid-like aggregatesin vitro
Grignaschi, Erica; Cereghetti, Gea; Grigolato, Fulvio; et al. (2018)
Journal of Biological Chemistry
Cells form stress granules (SGs) upon stress stimuli to protect sensitive proteins and RNA from degradation. In the yeast Saccharomyces cerevisiae, specific stresses such as nutrient starvation and heat-shock trigger recruitment of the yeast pyruvate kinase Cdc19 into SGs. This RNA-binding protein was shown to form amyloid-like aggregates that are physiologically reversible and essential for cell cycle restart after stress. Cellular Cdc19 exists in an equilibrium between a homotetramer and monomer state. Here, we show that Cdc19 aggregation in vitro is governed by protein quaternary structure, and we investigate the physical–chemical basis of Cdc19's assembly properties. Equilibrium shift toward the monomer state exposes a hydrophobic low-complexity region (LCR), which is prone to induce intermolecular interactions with surrounding proteins. We further demonstrate that hydrophobic/hydrophilic interfaces can trigger Cdc19 aggregation in vitro. Moreover, we performed in vitro biophysical analyses to compare Cdc19 aggregates with fibrils produced by two known dysfunctional amyloidogenic peptides. We show that the Cdc19 aggregates share several structural features with pathological amyloids formed by human insulin and the Alzheimer's disease–associated Aβ42 peptide, particularly secondary β-sheet structure, thermodynamic stability, and staining by the thioflavin T dye. However, Cdc19 aggregates could not seed aggregation. These results indicate that Cdc19 adopts an amyloid-like structure in vitro that is regulated by the exposure of a hydrophobic LCR in its monomeric form. Together, our results highlight striking structural similarities between functional and dysfunctional amyloids and reveal the crucial role of hydrophobic/hydrophilic interfaces in regulating Cdc19 aggregation.

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Stefano Caimi

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