Active and Passive Motion in Complex pH‐Fields

We create pH landscapes of increasing spatial complexity by placing ion exchange resin beads different types and sizes in a closed cell featuring negatively charged bottom substrate. thus extend previous measurements chemically homogeneous background to investigations structured backgrounds, which evolve time. determine local gradients photometry study the resulting solvent flows along substrate tracking passive tracer particles. Analytical modelling dispersion chemicals is possible for situations with dominantly diffusive transport. then release phoretic swimmers differently shaped fields their motion selected examples. Catalytic Janus assembled wake mobile source form modular swimmer showing noise-dominated trajectory. For standard cargo, we identify well-defined reproducible swimming trajectory at around single sources. These include deflection swing-by maneuvers, trapping escape, as well circular orbits. More complicated paths result from combining multiple Finally, address swimmer-swimmer interactions superposition own fields. Our findings clearly demonstrate high potential environments steering. They can further be rationalized simple heuristic model considering interplay on length time scales its influence speed, orientation emerging propulsion direction. In view vast range combinations, our has remain preliminary. anticipate, however, that it will aid general understanding transport experiments pH-driven systems other phoresis also help design novel useful strategies directed micro-scale.