Tilted Magnetic Levitation Enables Measurement of the Complete Range of Densities of Materials with Low Magnetic Permeability

Abstract

Magnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic field gradient provides a simple method to measure the density of small samples of solids or liquids. One major limitation of this method, thus far, has been an inability to measure or manipulate materials outside of a narrow range of densities (0.8 g/cm 3 <  < 2.3 g/cm 3 ) that are close in density to the suspending, aqueous medium. This paper explores a simple method-"tilted MagLev"-to increase the range of densities that can be levitated magnetically. Tilting the MagLev device relative to the gravitational vector enables the magnetic force to be decreased (relative to the magnetic force) along the axis of measurement. This approach enables many practical measurements over the entire range of densities observed in matter at ambient conditions-from air bubbles ( ≈ 0) to osmium and iridium ( ≈ 23 g/cm 3 ). The ability to levitate, simultaneously, objects with a broad range of different densities provides an operationally simple method that may find application to forensic science (e.g., for identifying the composition of miscellaneous objects or powders), industrial manufacturing (e.g., for quality control of parts), or resource-limited settings (e.g., for identifying and separating small particles of metals and alloys). INTRODUCTIONMagnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic field gradient provides a simple method to measure density. [1][2][3][4] Based the balance of gravitational and magnetic forces, this method has four important capabilities and types of applications that make it attractive for use in a variety of settings. i) MagLev offers the ability to resolve small differences in the densities of samples (e.g., pastes, gels, heterogeneous solids, small particles, crystal polymorphs) 1,2,4-7 with physical properties that make them difficult or impossible to analyze by other instruments (e.g., density gradient columns, pycnometers, oscillating-tube densometers). 8 ii) MagLev can be used for complex, shape-based tasks, such as noncontact, three-dimensional self-assembly, 9,10 orientation control 11 , and quality control 12 of a wide variety of polymeric components. iii) MagLev can be used to perform a range of important, density-based bioanalyses. [13][14][15][16][17] iv) The simplicityof-use, portability, and low cost of MagLev make it particularly attractive for use in resource-limited settings (e.g., schools, mines, archeological sites, field operations, and laboratories in the developing countries).Despite these advantages, one major limitation, thus far, has been an inability to measure or manipulate materials outside of

Analysis of Powders Containing Illicit Drugs Using Magnetic Levitation

“…Sodium carbonate (2.54 gcm À3 ) [34] and talc (2.84 gcm À3 ) [35] are the only diluents that are routinely encountered by law enforcement that did not levitate because their densities fell outside of the allowable range.W ehave,in other work, demonstrated methods for levitation of objects with densities much higher than these. [36] Thed ensities of compounds determined by MagLev largely agree with values reported in the literature (Supporting Information, Table S4), which were measured by XRD and calculated from the dimensions and occupancyofthe unit cells,o rb yg as pycnometry.O ur density measurements deviated from literature values by less than 20.2 %. We recorded the largest differences for the hydrochlorides of methamphetamine (20.1 %), levamisole (10.7 %), procaine (6.0 %), cocaine (5.6 %), and diltiazem (4.8 %).…”

Design and evaluation of quantitative MRI phantoms to mimic the simultaneous presence of fat, iron, and fibrosis in the liver

“…After pouring into the beaker, the mixing of MRI biomarker modulators and water‐agar solution was performed using a hand‐held homogenizer (Model D1000; Dot Scientific, Burton, MI) for a duration of 30 seconds, to obtain a homogeneous emulsion with smaller fat droplets. Immediately after homogenization, the mixture in the beaker was poured into high‐density polyethylene 43 vials (volume = 25 mL and diameter = 20 mm). The mixed materials in the vials were left overnight so the gel could form before subsequent imaging experiments.…”

Magnetic Levitation in Chemistry, Materials Science, and Biochemistry

“…This capability leads to applications of MagLev in density-based separations. [20,22,101,123,41,42,93,[95][96][97][98]100] MagLev also provides au nique environment in which diamagnetic objects can be levitated and manipulated, without contacting the walls of the container,f or 3D assembly.T his capability,inconjunction with densitybased levitation, opens unexplored domains of research, and enables new applications of MagLev in emerging areas such as advanced manufacturing, quality control, and 3D self-assembly of both hard and soft, fragile components. [21,135À139]…”