Smart-Phone Based Magnetic Levitation for Measuring Densities.
Smart-Phone Based Magnetic Levitation for Measuring Densities.
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DOI：
10.1371/journal.pone.0134400
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Tasoglu S
中科院分区：
文献类型：
--
作者：
Knowlton S;Yu CH;Jain N;Ghiran IC;Tasoglu S
磁悬浮是一种利用磁场将物体悬浮在液体中的技术，是一项强大而通用的技术。我们开发了一种与智能手机兼容的紧凑型磁悬浮平台来分离微小物体，并根据样品的悬浮高度来估计样品的密度。3D打印附件被机械地安装在智能手机现有的摄像头单元上。可以是球形或不规则形状的微小物体悬浮在顺磁介质中，加载到微毛细管中，然后将其插入两个永久磁铁之间。微对象在微毛细管中以平衡高度悬浮和限制，该平衡高度取决于它们的体积质量密度(导致朝向微毛细管边缘的浮力)和相对于悬浮介质的磁化率(导致朝向微毛细管中心的磁力)。智能手机相机通过放置在样品和相机镜头盖之间的额外镜头捕捉漂浮的微型物体的放大图像。然后，一个定制开发的Android应用程序分析这些图像，以确定悬浮高度并估计密度。使用这个平台，我们能够分离不同密度的微球，并将它们的悬浮高度校准到已知密度，从而开发出一种精确和准确的密度估计技术。我们还对该平台的磁场、光学成像能力以及随时间变化的热状态进行了表征。
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.