Non-equilibrium self-assembly processes of complex dipolar colloids

This work investigates the influence of induced dipolar interactions on the non-equilibrium structure formation in quasi-two dimensional colloidal systems. On the one hand, theoretical models for certain experimentally realized systems are developed and investigated by means of Brownian Dynamics Simulations. To estimate phase transitions, basic density functional theory methods are applied. On the other hand, also generic models are developed with the aim to unveil the underlying mechanisms of structure formation and particle aggregation. The experimental systems motivating this work correspond to two prototype non-equilibrium processes, which are lane formation and diffusion limited aggregation. In the case of lane formation it is Janus particles in AC electric fields which are considered. These particles form either chain-like aggregates or yield a self-propulsion mechanism, depending on the field frequency. The investigation of an explicitly dipolar model shows chain formation as well as lane formation in the self-propulsion regime. Additionally, a generic system is considered, which allows for the first time to make a connection between lane formation and spinodal decomposition. Furthermore, this is the first study on lane formation in systems with attractive particle interactions. The second part of this work investigates the field directed assembly of colloidal particles in the diffusion limited aggregation regime. Again, two model systems are developed and investigated. First, experimentally observed structures are analyzed and compared to results from extensive computer simulations. To this end, a new method for structure analysis is introduced and applied. Experiments were performed by Dr. B. Bharti at North Carolina State University and analyzed by myself. The theoretical considerations allow, in contrast to experiments, to investigate the dependency of the aggregation behavior on the particle density. Additionally, a second model system, aiming on the generic features of particle aggregation is investigated. Here, special attention is paid on the diffusion limited aggregation. The latter is an extensively studied non-equilibrium process, which is extended by new features, namely the influence of field induced dipolar interactions.

Author dc:creator

• Kogler, Florian

Advisor dc:contributor.advisor

• Klapp, Sabine H. L.

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-5070

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/5395