title: Chemotaxis of artificial microswimmers in active density waves.
abstract: Living microorganisms are capable of a tactic response to external stimuli by swimming toward or away from the stimulus source; they do so by adapting their tactic signal transduction pathways to the environment. Their self-motility thus allows them to swim against a traveling tactic wave, whereas a simple fore-rear asymmetry argument would suggest the opposite. Their biomimetic counterpart, the artificial microswimmers, also propel themselves by harvesting kinetic energy from an active medium, but, in contrast, lack the adaptive capacity. Here we investigate the transport of artificial swimmers subject to traveling active waves and show, by means of analytical and numerical methods, that self-propelled particles can actually diffuse in either direction with respect to the wave, depending on its speed and waveform. Moreover, chiral swimmers, which move along spiraling trajectories, may diffuse preferably in a direction perpendicular to the active wave. Such a variety of tactic responses is explained by the modulation of the swimmer's diffusion inside traveling active pulses.
authors: Institut für Physik, University of Augsburg, D-86159, Germany.
authors: Alexander
authors: A
authors: Geiseler
authors: Institut für Physik, University of Augsburg, D-86159, Germany.|Nanosystems Initiative Munich, Schellingstraße 4, D-80799 München, Germany.|Department of Physics, National University of Singapore, 117551 Singapore, Republic of Singapore.
authors: Peter
authors: P
authors: Hänggi
authors: Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China.|Dipartimento di Fisica, Università di Camerino, I-62032 Camerino, Italy.
authors: Fabio
authors: F
authors: Marchesoni
authors: Institut für Physik, University of Augsburg, D-86159, Germany.
authors: Colm
authors: C
authors: Mulhern
authors: Department of Physics, Loughborough University, Loughborough, LE11 3TU, United Kingdom.
authors: Sergey
authors: S
authors: Savel'ev