Manipulating Superparamagnetic Microparticles with an Electromagnetic Needle

Abstract

organisms. The manipulation of superparamagnetic microparticles, in particular, has a wide range of applications, including magnetic logic; [13] sorting and trapping of magnetically tagged proteins, [14] cells, [15] and microorganisms; [16] microfluidic mixing; [17] magnetoresistive biosensing; [18] immunoassays; [19] and lab-on-a-tube devices. [20] In principle, the manipulation methods of these microparticles can be cate gorized into two groups: batch and individual particle manipulation. In batch manipulation, the magnetic field and field gradient originate from sources, such as external permanent magnet, [19] micropatterned current wires, [21,22] and microfabricated arrays of permanent magnets. [23] These systems are usually coupled with fluidic flows within fluidic chips. The microparticles are treated collectively as a lot with the manipulation strategies being mainly limited to trapping, separation (e.g., magnetic from nonmagnetic particles) or unidirectional transportation. [24] The individual particle manipulation, on the contrary, allows 1D, 2D, and 3D positioning, as well as possible orientation control of an individual magnetic microparticle. 1D transportation has been carried out by serpentine microcurrent lines [25] or by zig-zag Selective, precise, and high-throughput manipulation of individual superparamagnetic microparticles has profound applications in performing locationtailored in vitro biomedical studies. The current techniques for manipulation of microparticles allow only a single particle in the manipulation workspace, or simultaneous transportation of multiple microparticles in batches. In this work, a method based on a robotized electromagnetic needle for manipulation of individual superparamagnetic microparticles within a microparticle population is introduced. By automatically controlling the highly localized magnetic field of the needle, a single microparticle is selectively picked when its neighboring particle is few micrometers away. Supported by the nanometer resolution of the robotic positioner, particles are placed at sub-micrometer precision. This manipulation technique allows the creating of arbitrary patterns, sorting of microparticles based on size and morphology, and transporting of individual microparticles in 3D space. Therefore, this approach has the potential to enable more deterministic and quantitative microanalysis and microsynthesis using superparamagnetic microparticles.

Flexible Ferrofluids: Design and Applications

“…Much effort has been devoted to improving their behavior in extensive biomedical areas, including bioseparation, biosensor, medical imaging techniques, and therapy . For example, it is reported that after being bonded to specifically designed polymers or biological molecules and assembling into particular structures, the ability of ferromagnetic particles to capture and separate targets could be significantly improved, thus extremely enhancing the bioseparation and biosensing efficiency . In addition, by properly modifying their surface or using them to form magnetically responsive microspheres, the half‐life period could be noticeably elongated.…”

“…[33,172] For example, it is reported that after being bonded to specifically designed polymers or biological molecules and assembling into particular structures, the ability of ferromagnetic particles to capture and separate targets could be significantly improved, thus extremely enhancing the bioseparation [173][174][175] and biosensing efficiency. [18,[176][177][178] In addition, by properly modifying their surface or using them to form magnetically responsive microspheres, the half-life period could be noticeably elongated. Meanwhile, the uptake by macrophage cells could be greatly reduced and the accurate regional targeting could also be achieved, making the ferromagnetic particles applicable to MRI, [179,180] target drug delivery, [29,[181][182][183][184] and hyperthermia.…”

Automatic Noncontact Extraction and Independent Manipulation of Magnetic Particles Using Electromagnetic Needle

“…The particles manipulated by the EMN are subject to two different forces: i) the magnetic force, F m , which is a function of the distance between the particle and the needle tip, and ii) the drag force, F d , induced by motion in the fluid. These forces can be expressed as follows [36]:…”

“…The proposed method has been demonstrated in four cases: selective extraction, separation of two particles, independent manipulation of four particles and targeted delivery of two particles on two separate cells. This work is built upon our previous work on contact manipulation using electromagnetic needle [36].…”

Tunable and Magnetic Thiol–ene Micropillar Arrays

“…Local actuation of single pillars with aspect ratio of 6.6 by an electromagnetic needle [18] was used to determine the deflection and the responsiveness of the magnetic pillars immersed in water. The electromagnetic needle is oriented at ≈45° at a fixed distance from the pillar and the tip of the needle is leveled with the pillar edge.…”