title: Noncontact orientation of objects in three-dimensional space using magnetic levitation.
abstract: This paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media.
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Anand Bala
authors.initials: AB
authors.lastname: Subramaniam
authors.affiliation: School of Engineering and Applied Science.
authors.forename: Dian
authors.initials: D
authors.lastname: Yang
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Hai-Dong
authors.initials: HD
authors.lastname: Yu
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Alex
authors.initials: A
authors.lastname: Nemiroski
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Simon
authors.initials: S
authors.lastname: Tricard
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Audrey K
authors.initials: AK
authors.lastname: Ellerbee
authors.affiliation: Department of Chemistry and Chemical Biology.
authors.forename: Siowling
authors.initials: S
authors.lastname: Soh
authors.affiliation: Department of Chemistry and Chemical Biology, Wyss Institute for Biologically Inspired Engineering, and The Kavli Institute for Bionano Science, Harvard University, Cambridge, MA 02138 gwhitesides@gmwgroup.harvard.edu.
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
keywords: colloidosomes; equilibrium; magneto-Archimedes levitation; self-assembly; soft robot