“…One recent advance in this area is the fabrication of composite particles made of a nonmagnetic material such as a hydrogel or elastomer within which magnetic nanoparticle (MNP) assemblies are embedded. − Such magnetically responsive composites could find diverse applications such as actuators, − microbots, − magnetorheological fluids, magnetically controllable colloidal crystals, , and biological manipulation. − While the assembly behavior of magnetic nanoparticles in bulk systems or large domains has been reported in multiple studies, ,,,,, an emerging question is how magnetically responsive particles assemble in confined microdomains. In such cases, the patterns formed by the assembled particles not only depend on the strength of the magnetic field, but also on topological constraints such as geometry of the confining environment and the particle packing. − Normally, in the absence of field interactions, hard particles can transition from a disordered fluid into an ordered crystal or other organized structures due to the spatial confinement. , In those cases, confinement mediates the entropy effects to determine the final structures of the assemblies.…”