Naslov
Beyond hard-walled spherical colloids

Autori
Kavre, Ivna

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Fakulteta za matematiko in fiziko

Mjesto
Ljubljana

Datum
23.09

Godina
2014

Stranica
159

Mentor
Babič, Dušan

Ključne riječi
photolithography; soft lithography; non-spherical magneto-responive microparticles; self-assembly; microgears; synchronization; hydrodynamic interactions

Sažetak
Two methods for fabrication of prism shaped microparticles are presented. The first is photolithography which allows the preparation of hard-walled microparticles while the second is a combination of photo- and soft lithography which enables the fabrication of non-magnetic and magnetic microparticles made out of an elastic polymer. Colloidal suspensions with such particles have been used in three different intriguing experimental blocks which deal with some of currently remarkable questions about self-assembly in colloidal suspensions under the influence of external fields, fabrication of active components in microfluidics and hydrodynamic synchronization of autonomously oscillating particles. Self-assembly experiments were performed with three and four armed magneto-responsive particles. The prismatic shape of those particles presents an additional degree of freedom leading to different and more complex assembly scenarios in the presence of an external rotating magnetic field. The magneto-responsive behavior of magnetic microparticles was demonstrated in an experiment with magnetic microgears subject to a rotating magnetic field of different strengths and frequencies. At low frequencies, the microgear follows the rotation of the field, while at frequencies above the critical the microgear rotation frequency decreases with increasing field frequency. Furthermore it was demonstrated that a magnetic microgear can transmit rotation to one or several non-magnetic microgears. Elliptically shaped colloidal particles in aqueous suspensions have been used in hydrodynamic synchronization experiments. When such particles are trapped by laser light they undergo an oscillatory motion and if they are placed close enough they can synchronize due to hydrodynamic interactions. The dependence of the oscillation frequency on the laser power was studied with one particle. Synchronization was studied in systems with two and few tens autonomously oscillating particles. The observed behavior was well explained with a phenomenological model.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA