Template-Free Ultrafast Directed Self-Assembly Using Biaxial Toggled Magnetic Fields

Speeding up the directed self-assembly of functional nanomaterials is a rapidly advancing area of research. Traditional self-assembly methods can be slow and limited by kinetic barriers. In this study, we demonstrate that the process can be dramatically accelerated for magnetic colloids when biaxial toggled magnetic fields (BTFs) are used. In this field configuration, a transversal pulsed magnetic field is superimposed perpendicular to the primary toggled magnetic field, facilitating faster phase separation in a model magnetic colloid. This approach offers enhanced control over aggregation dynamics by adjusting the field's frequency and intensity and does not require any physical templates. Beyond structure control, the aggregation kinetics can also be precisely tuned. Within the context of magnetic materials, this method enables the formation of diverse and tunable structures such as chains, columns, depercolated aggregates, and percolating bands. BTFs further promote the formation of highly crystalline domains, enhancing the properties of the resulting self-assembled materials. While this technique is specifically tailored for magnetic systems, its versatility makes it relevant for the design and fabrication of functional nanomaterials. The ability to tune aggregation kinetics and achieve a range of structures may be beneficial for applications in photonics, electronics, and biomedicine.