A photopatternable superparamagnetic nanocomposite: Material characterization and fabrication of microstructures

Abstract

A superparamagnetic nanocomposite obtained by dispersing superparamagnetic magnetite nanoparticles in the epoxy SU-8 is used to fabricate microstructures by photolithography. The dispersion of the nanoparticles and the level of agglomerations are analyzed by optical microscopy, TEM (transmission electron microscope), SAXS (small-angle X-ray scattering), XDC (X-ray disc centrifuge) and XRD (X-ray diffraction). Two different phosphate-based dispersing agents are compared. In order to obtain a high-quality nanocomposite, the influence of particle concentration 1-10 vol.% (4-32 wt.%) on composite fabrication steps such as spin coating and UV exposure are systematically analyzed. Features with narrow widths (down to 1.3 m) are obtained for composites with 5 vol.% particle concentration. Mechanical, magnetic and wetting properties of the nanocomposites are characterized. These nanocomposites exhibit superparamagnetic properties with a saturation magnetization up to 27.9 kA m −1 for10 vol.%. All nanocomposites show no differences in surface polarity with respect to pure SU-8, and exhibit a moderate hydrophobic behavior (advancing dynamic contact angles approximately 81 • ). Microcantilevers with particle concentrations of 0-5 vol.% were successfully fabricated and were used to determine the dynamic Young's modulus of the composite. A slight increase of the Young's modulus with increased particle concentration from 4.1 GPa (pure SU-8) up to 5.1 GPa (for 5 vol.%) was observed.

Magnetic micropillar sensors for force sensing

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“…Examples are nanocomposite materials, which combine the advantages of polymers like flexibility, elasticity, chemical resistance or biocompatibility with the unique properties of nanoparticles. Magnetic nanocomposites have been introduced before using superparamagnetic particles [7]. However, these particles require a high magnetic field for magnetization, which increases the power consumption and limits the possibility of integration and miniaturization.…”

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“…Examples are nanocomposite materials, which combine the advantages of polymers like flexibility, elasticity, chemical resistance or biocompatibility with the unique properties of additives [9][10][11]. Magnetic nanocomposites have been introduced before using superparamagnetic particles [12,13]. Unlike these particles that require a high magnetic field for magnetization, which increases the power consumption and limits the possibility of integration and miniaturization, iron nanowires (NWs) have a high magnetization at remanence, due to the strong shape anisotropy, and they can be easily fabricated with a cost effective process.…”

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“…Examples are nanocomposite materials, which combine the advantages of polymers like flexibility, elasticity, chemical resistance or biocompatibility with the unique properties of additives [6][7][8]. Magnetic nanocomposites have been introduced before using superparamagnetic particles [9,10]. Unlike these particles that require a high magnetic field for magnetization, which increases the power consumption and limits the possibility of integration and miniaturization, iron nanowires (NWs) have a high magnetization at remanence due to the strong shape anisotropy, and they can be easily fabricated with a cost effective process.…”