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Martin-Becerra D.,Institute Microelectronica Of Madrid Imm | Martin-Becerra D.,International Iberian Nanotechnology Laboratory | Gonzalez-Diaz J.B.,Institute Microelectronica Of Madrid Imm | Temnov V.V.,Massachusetts Institute of Technology | And 7 more authors.
Applied Physics Letters | Year: 2010

The deposition of a dielectric overlayer on top of Au/Co/Au multilayer films can significantly enhance the magnetic field induced modulation of the surface plasmon polariton (SPP) wave vector. This enhancement is analyzed as a function of the thickness of the dielectric overlayer and the associated SPP electromagnetic field confinement and redistribution. The decrease in SPP propagation distance is taken into account by analyzing an adequate figure of merit. © 2010 American Institute of Physics.


Papaioannou E.T.,Uppsala University | Kapaklis V.,Uppsala University | Patoka P.,Helmholtz Center Berlin | Giersig M.,Free University of Berlin | And 5 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The magneto-optic and magnetic properties of hexagonal arrays of holes in optically thin iron films are presented. We analyze their dependence on the hole radius and compare the results to a continuous iron film of the same thickness. We observe a large enhancement of the magneto-optic Kerr rotation with respect to that of the continuous film, at frequencies where surface-plasmon excitations are expected. The spectral position of the Kerr maxima can be tuned by the size and the distance between the holes. Additional simulations are in very good agreement with the experiment and thus confirm the effect of the surface plasmons on the Kerr rotation. The altering of the magnetic properties by the hole array is also visible in the hysteretic behavior of the sample where a significant hardening is observed. © 2010 The American Physical Society.


Calzado-Martin A.,Institute Microelectronica Of Madrid Imm | Encinar M.,Institute Microelectronica Of Madrid Imm | Tamayo J.,Institute Microelectronica Of Madrid Imm | Calleja M.,Institute Microelectronica Of Madrid Imm | San Paulo A.,Institute Microelectronica Of Madrid Imm
ACS Nano | Year: 2016

We study the correlation between cytoskeleton organization and stiffness of three epithelial breast cancer cells lines with different degrees of malignancy: MCF-10A (healthy), MCF-7 (tumorigenic/noninvasive), and MDA-MB-231 (tumorigenic/invasive). Peak-force modulation atomic force microscopy is used for high-resolution topography and stiffness imaging of actin filaments within living cells. In healthy cells, local stiffness is maximum where filamentous actin is organized as well-aligned stress fibers, resulting in apparent Young's modulus values up to 1 order of magnitude larger than those in regions where these structures are not observed, but these organized actin fibers are barely observed in tumorigenic cells. We further investigate cytoskeleton conformation in the three cell lines by immunofluorescence confocal microscopy. The combination of both techniques determines that actin stress fibers are present at apical regions of healthy cells, while in tumorigenic cells they appear only at basal regions, where they cannot contribute to stiffness as probed by atomic force microscopy. These results substantiate that actin stress fibers provide a dominant contribution to stiffness in healthy cells, while the elasticity of tumorigenic cells appears not predominantly determined by these structures. We also discuss the effects of the high-frequency indentations inherent to peak-force atomic force microscopy for the identification of mechanical cancer biomarkers. Whereas conventional low loading rate indentations (1 Hz) result in slightly differentiated average stiffness for each cell line, in high-frequency measurements (250 Hz) healthy cells are clearly discernible from both tumorigenic cells with an enhanced stiffness ratio; however, the two cancerous cell lines produced indistinguishable results. © 2016 American Chemical Society.


Sansa M.,Institute Microelectronica Of Barcelona Imb Cnm | Fernandez-Regulez M.,Institute Microelectronica Of Barcelona Imb Cnm | Llobet J.,Institute Microelectronica Of Barcelona Imb Cnm | San Paulo A.,Institute Microelectronica Of Barcelona Imb Cnm | And 2 more authors.
Nature Communications | Year: 2014

Highly sensitive conversion of motion into readable electrical signals is a crucial and challenging issue for nanomechanical resonators. Efficient transduction is particularly difficult to realize in devices of low dimensionality, such as beam resonators based on carbon nanotubes or silicon nanowires, where mechanical vibrations combine very high frequencies with miniscule amplitudes. Here we describe an enhanced piezoresistive transduction mechanism based on the asymmetry of the beam shape at rest. We show that this mechanism enables highly sensitive linear detection of the vibration of low-resistivity silicon beams without the need of exceptionally large piezoresistive coefficients. The general application of this effect is demonstrated by detecting multiple-order modes of silicon nanowire resonators made by either top-down or bottom-up fabrication methods. These results reveal a promising approach for practical applications of the simplest mechanical resonators, facilitating its manufacturability by very large-scale integration technologies. © 2014 Macmillan Publishers Limited. All rights reserved.


PubMed | Institute Microelectronica Of Madrid Imm
Type: Journal Article | Journal: ACS nano | Year: 2016

We study the correlation between cytoskeleton organization and stiffness of three epithelial breast cancer cells lines with different degrees of malignancy: MCF-10A (healthy), MCF-7 (tumorigenic/noninvasive), and MDA-MB-231 (tumorigenic/invasive). Peak-force modulation atomic force microscopy is used for high-resolution topography and stiffness imaging of actin filaments within living cells. In healthy cells, local stiffness is maximum where filamentous actin is organized as well-aligned stress fibers, resulting in apparent Youngs modulus values up to 1 order of magnitude larger than those in regions where these structures are not observed, but these organized actin fibers are barely observed in tumorigenic cells. We further investigate cytoskeleton conformation in the three cell lines by immunofluorescence confocal microscopy. The combination of both techniques determines that actin stress fibers are present at apical regions of healthy cells, while in tumorigenic cells they appear only at basal regions, where they cannot contribute to stiffness as probed by atomic force microscopy. These results substantiate that actin stress fibers provide a dominant contribution to stiffness in healthy cells, while the elasticity of tumorigenic cells appears not predominantly determined by these structures. We also discuss the effects of the high-frequency indentations inherent to peak-force atomic force microscopy for the identification of mechanical cancer biomarkers. Whereas conventional low loading rate indentations (1 Hz) result in slightly differentiated average stiffness for each cell line, in high-frequency measurements (250 Hz) healthy cells are clearly discernible from both tumorigenic cells with an enhanced stiffness ratio; however, the two cancerous cell lines produced indistinguishable results.

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