Microscale ratchet structured surfaces were coated with nanoparticles, which resulted in anisotropic behavior of superparamagnetic microdroplet by magnetic field actuation. This ratchet structure enables superparamagnetic microdroplets to generate the anisotropic behavior through the alternative external magnetic field. A tuning behavior was revealed by changing the height of ratchet, the numbers of superparamagnetic nanoparticles, and the size of microdroplets. It is significant to understand the wetting properties on superhydrophobic surfaces with anisotropic
structure.
