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Overview of the IAMS device separation principle. The target and nontarget particles are introduced at the sample inlet alongside a buffer stream. Next, both acoustic and magnetic target particles are acoustically separated. The target particles are then magnetically separated by a series of microfabricated ferromagnetic structures. As a result, the acoustic and magnetic targets are eluted through two independent outlets.
(a) Photograph of the assembled device, showing the acoustic and magnetic components and fluidic connections. (b) Cross-sectional schematic of the device, showing the relative locations of the magnets, micropatterned Ni and piezo, and the orientation of the acoustic field. (c) Schematic of the experimental setup. The sample containing acoustic target, magnetic target, and nontarget particles is loaded into inlet tubing and introduced alongside buffer solution into the IAMS device via dual programmable syringe pumps (PhD 2000, Harvard Apparatus, Holliston, MA). The microfabricated ferromagnetic structures within the device are magnetized by three neodymium iron boron permanent magnets. Acoustic resonances are excited by a single piezotransducer that is attached onto the back of the chip and driven by a function generator (33120A, Hewlett Packard, Palo Alto, CA) and custom-built amplifier based on an LT1210 op-amp (Linear Technology, Milpitas, CA). The separation process is observed via an inverted fluorescence microscope for monitoring during separation. The purities of the eluted fractions are analyzed via flow cytometry (FACSAria, BD Biosciences, San Jose, CA).
Simulation of acoustic and magnetic fields within the IAMS device (COMSOL Multiphysics, Comsol Inc., Los Angeles, CA). (a) Simulation of the long-range magnetic field from the external magnets shows that within the cross-section of the device. (b) Simulation of the short-range magnetic field due to a microfabricated Ni element. Contours show magnetic field gradient magnitude, arrows show gradient direction. (c) The acoustic resonance is locally disrupted by modulating the width of the microchannel. Longitudinal acoustic modes are indicated by the dashed lines.
(a) Separation of a mixture of acoustic target, magnetic target, and nonmagnetic nontarget, showing enrichment to very high purity starting from rare amount of each target. (b) Separation of a mixture of acoustic target, magnetic target, and magnetic nontarget, demonstrating that particles entering the magnetic outlet must respond to a combination of both separation forces.
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