Manipulation and sorting of magnetic particles by a magnetic force microscope on a microfluidic magnetic trap platform

Abstract

We have integrated a microfluidic magnetic trap platform with an external magnetic force microscope (MFM) cantilever. The MFM cantilever tip serves as a magnetorobotic arm that provides a translatable local magnetic field gradient to capture and move magnetic particles with nanometer precision. The MFM electronics have been programmed to sort an initially random distribution of particles by moving them within an array of magnetic trapping elements. We measured the maximum velocity at which the particles can be translated to be 2.2mm∕s±0.1mm∕s, which can potentially permit a sorting rate of approximately 5500particles∕min. We determined a magnetic force of 35.3±2.0pN acting on a 1μm diameter particle by measuring the hydrodynamic drag force necessary to free the particle. Release of the particles from the MFM tip is made possible by a nitride membrane that separates the arm and magnetic trap elements from the particle solution. This platform has potential applications for magnetic-based sorting, manipulation, and probing of biological molecules in a constant-displacement or a constant-force mode.

Transport and selective chaining of bidisperse particles in a travelling wave potential

“…Recent years have witnessed an increasing interest in developing novel techniques which make use of uniform magnetic field modulated by a periodic substrate in order to induce the controlled motion of colloidal microspheres in water [1,2,3,4,5,6,7,8]. In contrast to optical or electric field micromanipulation, magnetic fields have the advantages that they neither alter the fluid medium nor affect biological systems, although their use is limited to polarizable particles [9,10].…”

Protein‐Functionalized Synthetic Antiferromagnetic Nanoparticles for Biomolecule Detection and Magnetic Manipulation

“…This sample is mainly composed of monodis-persed nanoparticles, as seen from SEM (see the Supporting Information, Figure S2). These A594s-SAF 12 clearly responded by translating along the external magnetic field gradient direction. Disturbance by Brownian motion was apparent with the "jiggling" of the particle tracks.…”

“…The simplicity and success of this approach, evidenced by the biochemical specificity and the magnetic-fluorescence multifunctionality demonstrated herein, suggest that SAFs can serve as better labels for applications that include magnetic separation, manipulation, biomolecule detection, and magnetic lab-on-a-chip devices. [9][10][11][12][13][14][15][16] High-moment, zero-remanence SAFs are trapezoidal disks with multilayer structures. [7] The essential magnetic feature of each SAF is two ferromagnetic layers separated by a nonmagnetic spacer layer.…”

Confinement of single macromolecules in free solution using a hydrodynamic trap

“…However, confinement and fine-scale manipulation of macromolecules and nanoparticles remains a significant challenge. Currently, particle trapping methods based on acoustic [1][2][3][4] , electrokinetic [5][6][7][8][9][10][11][12][13][14][15] , magnetic [16][17][18] , and optical [19][20][21][22][23][24][25][26][27][28] fields are utilized, but these methods are limited to trapping particles with specific material properties and bulky micron-scale dimensions. [29][30][31] Recently, we developed a new flow-based confinement method that enables 2-D manipulation of single micro and nanoscale particles suspended in aqueous solution.…”