To
fully harness the potential of artificial active colloids, investigation
of their response to various external stimuli including external flow
is of great interest. Therefore, in this study, we perform experiments
on SiO2-Pt Janus particles suspended in an aqueous medium
in a capillary subjected to different shear flow rates. Particles
were propelled using varied H2O2 (fuel) concentrations.
For a particular propulsion speed, with increasing shear flow, a continuous
transition in the motion of active Janus particles (JPs) from the
usual random active motion to preferential movement along the vorticity
direction and then finally to migration along the flow was observed.
This transition was accompanied by a significant decline in in-plane
fluctuations of the particle trajectories. Another key observation
is that the activity of JPs produces a delay in shear-induced rolling,
which at moderate flow, allows the JPs to adopt a specific orientation,
facilitating their migration along the vorticity direction. At higher
flow rates, once shear flow overcomes the activity-induced resistance
and initiates rolling, the probability of JPs adopting such preferred
orientations reduces. Our analysis further revealed that these transitions
are governed by a nondimensional quantity λ, which compares
the relative strength of the shear-induced particle flow to the propulsion
speed.