  In this article we explore the dynamics of a Brownian particle in a
feedback-free dynamic thermophoretic trap. The trap contains a focused laser
beam heating a circular gold structure locally and creating a repulsive thermal
potential for a Brownian particle. In order to confine a particle the heating
beam is steered along the circumference of the gold structure leading to a
non-trivial motion of the particle. We theoretically find a stability condition
by switching to a rotating frame, where the laser beam is at rest. Particle
trajectories and stable points are calculated as a function of the laser
rotations frequency and are experimentally confirmed. Additionally, the effect
of Brownian motion is considered. The present study complements the dynamic
thermophoretic trapping with a theoretical basis and will enhance the
applicability in micro- and nanofluidic devices.
