Quentin Brosseau, Florencio Usabiaga, Enkeleida Lushi and Yang Wu report in Physical Review Letters exploring the behavior of micron-scale autophoretic Janus (Au/Pt) rods, with various (Au/Pt) length ratios, swimming near a wall in an imposed background flow. They find that the ability of the Au/Pt rods to robustly orient and move upstream, i.e., to rheotax, depends strongly on the Au/Pt ratio, which is easily tunable in synthesis. Link to the article here.