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Felix Kümmel: „Shape dependence of active Brownian swimmers”
Universität Stuttgart

Felix Kümmel(1), Ivo Buttinoni(1), Giovanni Volpe(3) & Clemens Bechinger(2)
1 2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
2 Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
3 Bilkent University, Department of Physics, 06800 Çankaya, Ankara, Turkey

Active Brownian particles are capable of taking up energy from their environment and converting it into directed motion; examples range from chemotactic cells and bacteria to artificial micro-swimmers. We recently introduced [1] a self-chemophoretic propulsion mechanism based on a local chemical gradient being created around metal-capped Janus particles suspended in a critical binary mixture. Due to the illumination with a defocused laser beam, the particle’s metal cap is heated over the critical temperature, which leads to a local demixing of the fluid and to a local chemical gradient being responsible for the propulsion. Here, we focus on the swimming behavior of particles with different shapes and analyze the characteristics of their trajectories. In case of quadratic swimmers we find their motion to be similar to spherical Janus-particles. The motion of L-particles and rods is characterized by an additional torque, which results in circular trajectories. In particular, for L-shaped particles with two different chiralities, the circle’s orientation is determined by their chirality. When such particles come close to a straight wall, there are two different kinds of interaction: stable sliding along the wall and reflection. Furthermore, a fluorescent dye is used to visualize the demixing-zone around the diverse swimmers for further understanding the origin of the chemophoretic motion and the torque.


  1. Volpe, G., I. Buttinoni, et al. (2011). "Microswimmers in patterned environments." Soft Matter 7(19): 8810-8815.