Bead Capture on Magnetic Sensors in a Microfluidic System

Østerberg, Frederik Westergaard; Dalslet, Bjarke Thomas; Damsgaard, Christian Danvad; Freitas, Susana Vaz; Freitas, P. P.; Hansen, Mikkel Fougt

doi:10.1109/jsen.2009.2021122

Cited by 18 publications

(12 citation statements)

References 16 publications

(19 reference statements)

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“…Importantly, the strongly bound layer of nanoparticles provides a rudimentary demonstration of the sensing platform, which is one of the ultimate goals of our research. 22–24 …”

Section: Resultsmentioning

confidence: 99%

Cubic Silica-Coated and Amine-Functionalized FeCo Nanoparticles with High Saturation Magnetization

et al. 2013

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By systematically varying the reaction parameters in a liquid-phase reduction reaction, large FeCo nanocubes with tunable body diagonal lengths of 175, 350, and 450 nm were synthesized. The nanocubes were initially stabilized with poly(vinyl pyrrolidone) (PVP) and then coated with a relatively thin layer of silica (~55 nm thick), which allowed them to retain their cubic shape. The magnetization curves showed that the PVP-stabilized nanocubes exhibited a high saturation magnetization of 167 ± 4 emu/g. The saturation magnetization, however, decreased upon coating with silica to 146 ± 13 emu/g for the particles with 350 and 450 nm FeCo cores and 48 ± 1 emu/g for the particles with 175 nm FeCo cores. The silica-coated FeCo nanocubes were then functionalized with 3-(aminopropyl)-trimethoxysilane (APTMS), and a layer of surface-bound nanoparticle was generated by exposing the resultant amine-functionalized nanocubes to self-assembled monolayers (SAMs) on gold terminated with carboxylic-acid groups.

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“…Importantly, the strongly bound layer of nanoparticles provides a rudimentary demonstration of the sensing platform, which is one of the ultimate goals of our research. 22–24 …”

Section: Resultsmentioning

confidence: 99%

Cubic Silica-Coated and Amine-Functionalized FeCo Nanoparticles with High Saturation Magnetization

et al. 2013

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“…The first observations of the beads being magnetized by the self-field by use of the out-of-phase second-harmonic lock-in signal were presented by Dalslet et al 19 and Østerberg et al 22 However, the lack of detailed information on the bead distribution prevents a comparison between the calculations and the experimental results. Thus, by lock-in technique it is possible to separate the effect of a dc magnetic field from that of the self-field and it is noted that the latter response, with the presented assumptions, is directly proportional to the response from the beads without any offset.…”

Section: ͑33͒mentioning

confidence: 99%

Theoretical study of in-plane response of magnetic field sensor to magnetic beads magnetized by the sensor self-field

Hansen

Damsgaard

Dalslet

et al. 2010

Journal of Applied Physics

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We present a theoretical study of the spatially averaged in-plane magnetic field on square and rectangular magnetic field sensors from a single magnetic bead, a monolayer of magnetic beads, and a half-space filled with magnetic beads being magnetized by the magnetic self-field due to the applied bias current through the sensor. The analysis of the single bead response shows that beads always contribute positively to the average magnetic field as opposed to the case for an applied homogeneous magnetic field where the sign of the signal depends on the bead position. General expressions and analytical approximations are derived for the sensor response to beads as function of the bead distribution, the bias current, the geometry and size of the sensor, and the bead characteristics. Consequences for the sensor design are exemplified and it is described how the contribution from the self-field experimentally can be separated from that due to static magnetic fields.

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“…For biosensing applications, magnetic sensors are exposed [7,[9][10][11][12] or integrated into microfluidic systems [8,[13][14][15]. Magnetic beads and nanoparticles are dropped on the exposed sensor and the signal is measured.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Sensor-Based Detection of Picoliter Volumes of Magnetic Nanoparticle Droplets in a Microfluidic Chip

Jeong¹,

Eu²,

Kim³

et al. 2012

Journal of Magnetics

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We have designed, fabricated and tested an integrated microfluidic chip with a Planar Hall Effect (PHE) sensor. The sensor was constructed by sequentially sputtering Ta/NiFe/Cu/NiFe/IrMn/Ta onto glass. The microfluidic channel was fabricated with poly(dimethylsiloxane) (PDMS) using soft lithography. Magnetic nanoparticles suspended in hexadecane were used as ferrofluid, of which the saturation magnetisation was 3.4 emu/cc. Droplets of ferrofluid were generated in a T-junction of a microfluidic channel after hydrophilic modification of the PDMS. The size and interval of the droplets were regulated by pressure on the ferrofluid channel inlet. The PHE sensor detected the flowing droplets of ferrofluid, as expected from simulation results. The shape of the signal was dependent on both the distance of the magnetic droplet from the sensor and the droplet length. The sensor was able to detect a magnetic moment of 2 × 10 −10 emu at a distance of 10 µm. This study provides an enhanced understanding of the magnetic parameters of ferrofluid in a microfluidic channel using a PHE sensor and will be used for a sample inlet module inside of integrated magnetic lab-on-a-chip systems for the analysis of biomolecules.

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Bead Capture on Magnetic Sensors in a Microfluidic System

Cited by 18 publications

References 16 publications

Cubic Silica-Coated and Amine-Functionalized FeCo Nanoparticles with High Saturation Magnetization

Cubic Silica-Coated and Amine-Functionalized FeCo Nanoparticles with High Saturation Magnetization

Theoretical study of in-plane response of magnetic field sensor to magnetic beads magnetized by the sensor self-field

Magnetic Sensor-Based Detection of Picoliter Volumes of Magnetic Nanoparticle Droplets in a Microfluidic Chip

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