No abstract

Abstract:This paper presents an analysis of the self-assembly of millimeter-sized, rectangular-shaped parts floating on a molten solder-air interface under a rotating external magnetic field. For part at the millimeter scale, gravitational effects may not be negligible compared to interfacial surface energy, resulting in a non-spontaneous self-assembly process. A rotating magnetic field produces a torque which rotates the magnetized parts into their specific in-plane orientations, and are then fixed in these orientations by the surface tension of the molten solder. A theoretical model for estimating the magnetic torque is developed. Experiments are carried out on glass substrates with patterned copper foil. Rectangular binding sites are the only hydrophilic areas on the substrate. By a simple coating process, molten solder wets only the binding sites on the substrate. Parts with orientation angles up to 90°can be rotated and translated to align with the binding sites by the magnetic torque and surface tension.