Magnetic characterization of micropatterned Nd–Fe–B hard magnetic films using scanning Hall probe microscopy

Kustov, Mikhail; Laczkowski, P.; Hykel, Danny; Hasselbach, K.; Dumas-Bouchiat, Frédéric; O'Brien, Daniel; Kauffmann, Paul; Гречишкин, Р. М.; Givord, D.; Reyne, Gilbert; Cugat, Orphée; Dempsey, Nora

doi:10.1063/1.3486513

Cited by 58 publications

(48 citation statements)

References 27 publications

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“…The entire wafer surface was covered with a trilayer of Ta(100 nm)/Fe(10 µm)/Ta(100 nm) deposited by triode sputtering at room temperature under a base pressure of 10 −6 mbar according to a procedure described elsewhere 30 . The role of the tantalum (Ta) is to protect the iron from oxidation.…”

Section: Methodsmentioning

confidence: 99%

Magneto-Active Substrates for Local Mechanical Stimulation of Living Cells

Coullomb

Bidan

Fratzl

et al. 2018

Biophysical Journal

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Cells are able to sense and react to their physical environment by translating a mechanical cue into an intracellular biochemical signal that triggers biological and mechanical responses. This process, called mechanotransduction, controls essential cellular functions such as proliferation and migration. The cellular response to an external mechanical stimulation has been investigated with various static and dynamic systems, so far limited to global deformations or to local stimulation through discrete substrates. To apply local and dynamic mechanical constraints at the single cell scale through a continuous surface, we have developed and modelled magneto-active substrates made of magnetic micro-pillars embedded in an elastomer. Constrained and unconstrained substrates are analysed to map surface stress resulting from the magnetic actuation of the micro-pillars and the adherent cells. These substrates have a rigidity in the range of cell matrices, and the magnetic micro-pillars generate local forces in the range of cellular forces, both in traction and compression. As an application, we followed the protrusive activity of cells subjected to dynamic stimulations. Our magneto-active substrates thus represent a new tool to study mechanotransduction in single cells, and complement existing techniques by exerting a local and dynamic stimulation, traction and compression, through a continuous soft substrate.Living cells have a sense of touch, which means that they are able to feel, respond and adapt to the mechanical properties of their environment. The process by which cells convert mechanical signals into biochemical signals is called mechanotransduction. Defects in the mechanotransduction pathways are implicated in numerous diseases ranging from atherosclerosis and osteoporosis to cancer progression and developmental disorders 1,2 . Since the 1990s, different static studies focused on mechanosensing have shown that cells can migrate along the rigidity gradient direction 3 and that stem cells can differentiate in vitro according to their substrate's stiffness 4 and geometry 5 . The interplay between a mechanical force and the reinforcement of cell adhesion has also been documented 6,7 . In their natural environment, cells face a complex and dynamic mechanical environment. Cyclic strain can induce reorientation of adherent cells and affect cell growth depending on the temporal and spatial properties of the mechanical stimulation [8][9][10][11] . The relevant timescales span from the milli-second for the stretching of mechanosensitive proteins, minutes for mechanotransduction signalling to hours for global morphological changes and even longer for adapting cell functions 12 . Taken together, previous works have shown that cells are sensitive to both the spatial and temporal signatures of mechanical stimuli. In order to study mechanotransduction, it is thus essential to stimulate cells with mechanical cues controlled both spatially and temporally.To address this topic, various methods have been proposed to exert experim...

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Section: Methodsmentioning

confidence: 99%

Magneto-Active Substrates for Local Mechanical Stimulation of Living Cells

Coullomb

Bidan

Fratzl

et al. 2018

Biophysical Journal

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“…where µ 0 is the vacuum permeability, V np is the volume of the object, M its magnetization and ∇H the gradient of magnetic field [8] . In the case of superparamagnetic particles, the magnetization is given by…”

Section: Magnetic Forcesmentioning

confidence: 99%

Autonomous magnetic devices for micro/nano particle handling

Zanini

Dumas-Bouchiat

2014

J3eA

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-This article describes a lab practical based on the fabrication of thick hard magnetic films, their patterning at the micro-scale, their integration into microfluidic systems and their use in particle capture and sorting. It combines both standard and recently developed microfabrication techniques in order to create autonomous, downscaled magnetic micro-systems which can produce high magnetic forces on micro-and nano-sized objects. The lab practical was designed for Master students, but can be used as an introductory course for higher-level students starting in the field.

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“…The flux density at the surface of these micro-patterned structures is maximal at the boundaries between oppositely magnetized domains. 21 …”

Section: B Micromagnet Fabricationmentioning

confidence: 99%

“…The permanent micromagnets integrated in the microfluidic device are capable of generating a high magnetic field gradient approaching 10 6 T/m at the magnetic film surface. 21 The miniMACS is a commercial system dedicated to high-gradient magnetic cell separation. Indeed, MS Columns contain an optimized matrix composed of ferromagnetic spheres, which concentrate the field lines when placed in the magnetic field of the MiniMACS Separator, thus inducing a high gradient within the column.…”

Section: B Jurkat Cell Enrichmentmentioning

confidence: 99%

“…Micro-patterning of such films, using topographic (lithography) 19 or thermo-magnetic (temperature control of magnetization reversal) 20 approaches, produces micron-sized permanent magnets characterized by stray magnetic field gradients as high as 10 6 T/m. 21 The flat surface of thermo-magnetically patterned films facilitates their integration into microfluidic devices, and they have been used to trap magnetic particles (SiO 2 and polystyrene particles containing magnetic nanoparticles) within such a device. 22 In this paper, we report the use of a microfluidic device containing integrated thermo-magnetically patterned NdFeB films for cell separation using immunomagnetic beads.…”

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confidence: 99%

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Microfluidic immunomagnetic cell separation using integrated permanent micromagnets

et al. 2013

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In this paper, we demonstrate the possibility to trap and sort labeled cells under flow conditions using a microfluidic device with an integrated flat micro-patterned hard magnetic film. The proposed technique is illustrated using a cell suspension containing a mixture of Jurkat cells and HEK (Human Embryonic Kidney) 293 cells. Prior to sorting experiments, the Jurkat cells were specifically labeled with immunomagnetic nanoparticles, while the HEK 293 cells were unlabeled. Droplet-based experiments demonstrated that the Jurkat cells were attracted to regions of maximum stray field flux density while the HEK 293 cells settled in random positions. When the mixture was passed through a polydimethylsiloxane (PDMS) microfluidic channel containing integrated micromagnets, the labeled Jurkat cells were selectively trapped under fluid flow, while the HEK cells were eluted towards the device outlet. Increasing the flow rate produced a second eluate much enriched in Jurkat cells, as revealed by flow cytometry. The separation efficiency of this biocompatible, compact micro-fluidic separation chamber was compared with that obtained using two commercial magnetic cell separation kits.

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Magnetic characterization of micropatterned Nd–Fe–B hard magnetic films using scanning Hall probe microscopy

Cited by 58 publications

References 27 publications

Magneto-Active Substrates for Local Mechanical Stimulation of Living Cells

Magneto-Active Substrates for Local Mechanical Stimulation of Living Cells

Autonomous magnetic devices for micro/nano particle handling

Microfluidic immunomagnetic cell separation using integrated permanent micromagnets

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