Electrokinetic Phenomena in Colloidal Systems: Experimental and Numerical Investigations of Electrophoresis and Diffusiophoresis
Notice bibliographique
Résumé
Transport and manipulation of particles and droplets are of significant interest in various fields, including biology, separation systems, and reaction engineering. In this regard, electrokinetic phenomena such as electrophoresis (EP) and diffusiophoresis (DP) have been widely adopted. EP involves the motion of particles or droplets under the influence of an external electric field, whereas DP refers to the spontaneous motion of colloids driven by a bulk concentration gradient of dissolved solute in the liquid phase. Improving the flexibility and controllability of colloidal EP and DP is crucial for a more widespread application in analytical, biomedical and other applications due to their inherent complexity. The objective of this thesis is to explore the effect of EP and DP on manipulation of droplets and particles in microscale systems. A combination of experimental and numerical techniques are employed to investigate these phenomena. The first system examines how amphoteric surfactants, having a specific structure carrying both positive and negative groups, affect the electrokinetic velocity of droplets in an external electric field. This type of surfactant alter their charge under the influence of changing pH, which allows them to impact the surface charge of droplets, which can be applied to gain control over the droplet movement through pH switching. The second system involves a numerical study of the EP of droplets containing mobile ions, considering both variable and constant permittivity within the EDL surrounding the droplets, which is relevant for systems of oil droplets that contain free charges. The third system examines the DP of porous and non-porous particles in electrolytes with different compositions, laying the groundwork for increased control of particle movement with applications in catalysis and load-carrying colloids. The first experimental study demonstrated that the electrokinetic velocity of oil-in water emulsion droplets stabilized by an amphoteric surfactant can be effectively controlled by changing the pH from acidic to alka- line under an external electric field. At the isoelectric pH of the surfactant monomers, varying the surfactant concentration altered the direction of droplet motion due to the competing effects of EP and electroosmotic flow (EOF) along the channel wall. Numerical simulations for EP of droplets containing mobile ions showed a significant reduction in the droplet EP velocity when variable permittivity was considered within the outer EDL. Additionally, decreasing the viscosity ratio of oil to electrolyte resulted in reduced droplet velocity due to the formation of a vortex around the droplet. It was also found that with constant permittivity in the outer EDL, variations in κaouter had a more significant effect on droplet EP velocity than changes in κainner. The third study, focusing on the experimental DP of porous and non-porous particles, demonstrated that electrolyte composition has a substantial impact on the particle DP behavior. The findings indicated that particle motion direction was governed by the interaction between double layer polarization (DLP), EOF and EP. Overall, this thesis advances the understanding of particle and droplet manipulation using electrokinetic phenomena, specifically through electric fields and concentration gradients. The study offers new insights into droplet EP, demonstrating its potential for designing separation strategies based on pH variations, which is particularly relevant in systems with natural pH gradients like the human body. It also has practical applications in soil remediation, where controlling droplet movement through pH gradients can be beneficial. The research on EP of droplets with mobile ions is helpful for improving water and waste treatment processes, such as lubricant removal from processing streams. These findings are also significant for manipulating biological colloids, especially for nanocarriers like liposomes or nanocapsules that encapsulate ions. Additionally, the investigation into the DP behavior of porous particles provides knowledge for advancing separation technologies and targeted drug delivery systems. By elucidating these mechanisms, the research paves the way for optimizing particle and droplet transport efficiencies, thereby enhancing the effectiveness and precision of various biomedical and environmental processes.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».