Using Magnetic Levitation for Three Dimensional Self‐Assembly

The development of practical strategies for the assembly of objects into 3D arrays is an unsolved problem. This paper describes the use of magnetic levitation (MagLev) to guide the self-assembly of millimeterto centimeter-scale dia magnetic objects, which we call “components”, each programmed by shape and distribution of density, into 3D assemblies and structures in a paramagnetic fl uid medium positioned in the magnetic fi eld gradient generated by NdFeB magnets. When the components are not in contact, their equilibrium confi guration depends on the balance of magnetic and gravitational forces they experience. This technique provides a convenient method to position components in 3D without mechanical contact; we demonstrate its unique capabilities using components with optical functions, and with components that form ordered, assembled structures when transferred into contact with solid supports. Most functional devices are assembled from components (by either humans or machines) and connected mechanically. The ability to carry out any part of these processes automatically, or even to preposition or preorient the components reliably, would simplify them. Self-assembly is a useful technique for generating ordered assemblies, [ 1–3 ] and although there are exceptions, it has been most highly developed when the components are all the same, and when there is a (quasi) 2D template (e.g., surface) to guide the process. [ 3–5 ] We and others have demonstrated self-assembly across a range of sizes, [ 6–14 ] and have also generated self-assembled functional structures, [ 3 , 15–25 ]