Smart-Phone Based Magnetic Levitation for Measuring Densities
#MMPMID26308615
Knowlton S
; Yu CH
; Jain N
; Ghiran IC
; Tasoglu S
PLoS One
2015[]; 10
(8
): e0134400
PMID26308615
show ga
Magnetic levitation, which uses a magnetic field to suspend objects in a fluid,
is a powerful and versatile technology. We develop a compact magnetic levitation
platform compatible with a smart-phone to separate micro-objects and estimate the
density of the sample based on its levitation height. A 3D printed attachment is
mechanically installed over the existing camera unit of a smart-phone.
Micro-objects, which may be either spherical or irregular in shape, are suspended
in a paramagnetic medium and loaded in a microcapillary tube which is then
inserted between two permanent magnets. The micro-objects are levitated and
confined in the microcapillary at an equilibrium height dependent on their
volumetric mass densities (causing a buoyancy force toward the edge of the
microcapillary) and magnetic susceptibilities (causing a magnetic force toward
the center of the microcapillary) relative to the suspending medium. The
smart-phone camera captures magnified images of the levitating micro-objects
through an additional lens positioned between the sample and the camera lens
cover. A custom-developed Android application then analyzes these images to
determine the levitation height and estimate the density. Using this platform, we
were able to separate microspheres with varying densities and calibrate their
levitation heights to known densities to develop a technique for precise and
accurate density estimation. We have also characterized the magnetic field, the
optical imaging capabilities, and the thermal state over time of this platform.
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