Creaming, diving and swimming microcapsules driven by chemical reactions
Experimental Condensed Matter Physics
Polymer Materials
Fluid Mechanics
Final Report Abstract
In this research project, we synthesized and investigated different types of swimming microcapsules. We studied their mechanisms of motion and developed several steering mechanisms. The motion of all presented types of micro-swimmers was affected by the variation of the concentration of the active substances, by changing the temperature or by influencing the propulsion reaction as, for instance, the process of cross-linking. The motion of the first type of swimmers was based on the formation of a surface tension gradient. These particles moved forming loops at the available surface area. This special swimming motion could be influenced by the chain length of fuel PEG and the cross-linking density of the alginate gels. Local temperature changes could be used to control the velocity and the position of these swimmers. The movement of the two other types of micro-swimmers was due to a backstroke of an evolving gas. One type used potassium permanganate as energy source. The movement of these particles was affected by the pH-values of the hydrogen peroxide solutions and the geometry of the micro-swimmers. Adding varying substances to the agarose had different effects. Especially the use of magnetic substances was interesting, because it allowed a magnetic guidance of these particles. As soon as more micro-swimmers were present, they formed big gas bubbles and gathered around them. The third type of swimmer consisted of platinized active charcoal, which catalyzed the decomposition of hydrogen peroxide. These particles moved forward until the fuel was consumed. They showed a periodical movement with phases of enhanced velocities disturbed by times of reduced speeds. For the propagation of these swimmers both phases, run and tumble, played a significant role. Although both backstroke swimmers consisted of the same gel material and used the same principle of motion, they showed different swimming motions. These discrepancies could be explained by the different elastic properties of the gels, the diverging chemical reactions and the effects of side products emerging over time.
Publications
- 11. Zsigmondy Colloquium of the German Colloid Society in Bielefeld, (2nd-3th March 2015). Synthesis and investigation of asymmetric, viscoelastic microswimmers with a propulsion mechanism based on chemical reactions
Monika Pella
- 116. Hauptversammlung der Deutschen Bunsengesellschaft für Physikalische Chemie in Kaiserslautern, (25th-27th May, 2017). Synthesis and characterization of self-propelled capsules inspired by a natural phenomenon
Ann-Kathrin Froin
