A design method for out-of-plane structures by multi-step magnetic self-assembly

We provide the design method of multi-step magnetic self-assembly using ferromagnetic-hinged structures. The process uses the magnetostatic torque generated by an external magnetic field perpendicular to the substrate to lift hinged structures. Hinged structure is composed of a rigid plate connected by elastic hinges to one side of a substrate. If hinged structures are raised in sequential order, it is possible to assemble like Japanese "origami" complex three-dimensional structures. In our previous study, we found that a dimensionless factor that depends on its shape determines the sensitivity of the hinged microstructures to a magnetic field. This factor can be used as a criterion in designing a process for sequential batch self-assembly, because the factor indicates the differences in the sensitivity. In this study, we designed multi-step sequential assembly by using the dimensionless factor. Four-step sequential batch assembly was demonstrated using this method. This method will be useful for optical systems, which consist of many complex three-dimensional structures.