Dokument: Matrix-Mediated Interactions between Particulate Inclusions in Linearly Elastic and Viscoelastic Environments
| Titel: | Matrix-Mediated Interactions between Particulate Inclusions in Linearly Elastic and Viscoelastic Environments | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=49495 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20190510-133852-9 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Puljiz, Mate [Autor] | |||||||
| Dateien: |
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| Beitragende: | Priv.-Doz. Dr. Menzel, Andreas [Gutachter] [im Online-Personal- und -Vorlesungsverzeichnis LSF anzeigen] Prof. Dr. Löwen, Hartmut [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | A theoretical description of the interactions between finite-sized particles in linearly elastic or viscoelastic media is presented. Analogously to the famous Stokes flow around a rigid sphere in low-Reynolds-number hydrodynamics, the displacement field around a rigid spherical inclusion that is embedded in a continuous elastic environment can be analytically expressed in the framework of linear elasticity theory. The embedding medium is considered as isotropic, homogeneous, and infinitely extended. On this basis, ensembles of many spherical inclusions are addressed that are rigidly translated and rotated by external forces and torques, respectively. The external force and torque acting on each particle is transmitted to the surrounding medium and affects the other particles through the embedding material via local material distortions, leading to mediated interactions between the individual particles. Resulting effective interactions can formally be summarized by (mathematical) displaceability and rotateability matrices in analogy to the case of hydrodynamic mobility matrices describing interactions through incompressible fluid environments.
These mathematical expressions are determined via expansions in the inverse interparticle separation distances. Here, the interaction matrices were calculated up to (including) sixth inverse interparticle separation distance for a possibly compressible elastic medium. In the limit of incompressibility, the hydrodynamic mobility matrices are formally recovered. The theory was employed to quantify the experimentally observed interactions between rigid paramagnetic particles embedded in soft polymeric gels. When exposed to an external magnetic field, magnetic moments were induced in the particles. This resulted in magnetic interaction forces that displaced the particles from their initial equilibrium positions. Using the theory, the elastic shear moduli of the embedding polymeric gels, which were inaccessible to direct measurement, were extracted for several experimental samples. Very good agreement was found for the theoretically predicted and the measured particle displacements. In a further experiment, a reversible collapse of two paramagnetic particles into contact, starting from an initially well-separated state, was observed, if the (non-saturating) external field magnitude was large enough. Although the overall process is highly nonlinear, both with respect to the elastic and the magnetic effects, the theory could accurately determine the necessary field strength to initiate the collapse and furthermore qualitatively predict a hysteretic behavior for a magnetization-and-demagnetization cycle of the two-particle system. Finally, a dynamic theory for particulate inclusions in linearly viscoelastic environments is presented. Viscoelastic materials possess both viscous and elastic properties. The theory used to describe the viscoelastic media can be derived from a general continuum approach based on classical conservation laws and symmetry arguments. In analogy to what has been described above, the interactions between rigid inclusions in the viscoelastic media were characterized theoretically and evaluated for basic example situations. For instance, the behavior of active self-propelled microswimmers is briefly addressed in such viscoelastic surroundings. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Theoretische Physik | |||||||
| Dokument erstellt am: | 10.05.2019 | |||||||
| Dateien geändert am: | 10.05.2019 | |||||||
| Promotionsantrag am: | 25.01.2019 | |||||||
| Datum der Promotion: | 27.03.2019 |
