Institute of Electrical Engineering

Lausanne, Switzerland

Institute of Electrical Engineering

Lausanne, Switzerland
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Wilczynski W.,Institute of Electrical Engineering
Journal of Magnetism and Magnetic Materials | Year: 2010

The paper is aimed at modelling dynamic hysteresis loops of high silicon steel. Hysteresis loops are described with the modified Jiles-Atherton approach. The dynamic effects due to eddy currents are taken into account by the introduction of components of effective field related to loss components in Bertotti's model. A satisfactory agreement between the measured and the modelled dynamic hysteresis loops as well as derived quantities is obtained for those values of peak flux density and frequency, which are of interest from industrial point of view. © 2009 Elsevier B.V. All rights reserved.


Angulo-Vinuesa X.,CSIC - Institute of Optics | Martin-Lopez S.,CSIC - Institute of Optics | Nuno J.,CSIC - Institute of Optics | Corredera P.,CSIC - Institute of Optics | And 3 more authors.
Journal of Lightwave Technology | Year: 2012

Raman assistance in distributed sensors based on Brillouin optical time-domain analysis can significantly extend the measurement distance. In this paper, we have developed a 2 m resolution long-range Brillouin distributed sensor that reaches 100 km using first-order Raman assistance. The estimated uncertainty in temperature discrimination is 1.2 °C, even for the position of worst contrast. The parameters used in the experiment are supported by a simple analytical model of the required values, considering the main limitations of the setup. © 2012 IEEE.


News Article | November 1, 2016
Site: physicsworld.com

The atomic force microscope (AFM) has played an essential role in 2D materials research since it was used to confirm the first isolation of graphene. Today’s AFMs are even more powerful, with higher spatial resolution, faster imaging rates, greater environmental control and enhanced modes for mapping physical properties. They can image crystal lattice structure as well as nanoscale morphology, and sense local electrical, mechanical and functional response in more ways than ever before. In this webinar we explore the latest AFM tools that enable higher resolution, sensitivity and more quantitative results for analysing 2D materials. We present results from measurements of a variety of 2D materials for device manufacturing, energy storage and optoelectronics including: Finally, we discuss how AFM can now be used to accurately determine the thickness of single or multiple layers of a 2D material. This challenges the misconception that AFM cannot be used to precisely measure the thickness of 2D materials. Presenter: Prof. Andras Kis, EPFL, STI-IEL-LANES Andras Kis is currently an associate professor at the École Polytechnique Fédérale de Lausanne (EPFL), School of Engineering (STI), Institute of Electrical Engineering (IEL) with a research focus in developing 2D materials. His group demonstrated the first transistor based on a 2D semiconductor. He has more than 16 years of AFM experience, including 63 peer-reviewed papers, more than 50 invited talks at scientific meetings and participation in organization committees for numerous 2D materials and graphene conferences. He has also been the editor-in-chief for Nature partner journal 2D Materials and Applications. Prof. Kis received his PhD from EPFL and did his postdoc at the University of California Berkeley, Zettl Laboratory. Presenter: Keith Jones, Oxford Instruments Asylum Research Keith Jones is currently an application scientist at Oxford Instruments Asylum Research (12 years). He has more than 18 years of SPM experience specializing in nanoelectrical characterization. He was instrumental in developing and applying electrical AFM techniques such as dopant profiling and scanning microwave impedance microscopy. Mr Jones is also a co-inventor on a patent for scanning impedance microscopy. He has co-authored 34 published papers. He received his MS in physics at Virginia Commonwealth University.


Feng J.,Institute of Bioengineering | Liu K.,Institute of Bioengineering | Bulushev R.D.,Institute of Bioengineering | Khlybov S.,Institute of Bioengineering | And 3 more authors.
Nature Nanotechnology | Year: 2015

The size of the sensing region in solid-state nanopores is determined by the size of the pore and the thickness of the pore membrane, so ultrathin membranes such as graphene and single-layer molybdenum disulphide could potentially offer the necessary spatial resolution for nanopore DNA sequencing. However, the fast translocation speeds (3,000-50,000ntms-1) of DNA molecules moving across such membranes limit their usability. Here, we show that a viscosity gradient system based on room-temperature ionic liquids can be used to control the dynamics of DNA translocation through MoS 2 nanopores. The approach can be used to statistically detect all four types of nucleotide, which are identified according to current signatures recorded during their transient residence in the narrow orifice of the atomically thin MoS 2 nanopore. Our technique, which exploits the high viscosity of room-temperature ionic liquids, provides optimal single nucleotide translocation speeds for DNA sequencing, while maintaining a signal-to-noise ratio higher than 10. © 2015 Macmillan Publishers Limited. All rights reserved.


Husale B.S.,Institute of Bioengineering | Sahoo S.,Institute of Electrical Engineering | Radenovic A.,Institute of Bioengineering | Traversi F.,Institute of Bioengineering | And 2 more authors.
Langmuir | Year: 2010

We used AFM to investigate the interaction of polyelectrolytes such as ssDNA and dsDNA molecules with graphene as a substrate. Graphene is an appropriate substrate due to its planarity, relatively large surfaces that are detectable via an optical microscope, and straightforward identification of the number of layers. We observe that in the absence of the screening ions deposited ssDNA will bind only to the graphene and not to the SiO 2 substrate, confirming that the binding energy is mainly due to the π-π stacking interaction. Furthermore, deposited ssDNA will map the graphene underlying structure. We also quantify the π-π stacking interaction by correlating the amount of deposited DNA with the graphene layer thickness. Our findings agree with reported electrostatic force microscopy (EFM) measurements. Finally, we inspected the suitability of using a graphene as a substrate for DNA origami-based nanostructures. © 2010 American Chemical Society.


Dutto F.,Institute of Bioengineering | Heiss M.,Institute of Materials | Lovera A.,Institute of Micro Engineering | Lopez-Sanchez O.,Institute of Electrical Engineering | And 2 more authors.
Nano Letters | Year: 2013

Geometrical effects in optical nanostructures on nanoscale can lead to interesting phenomena such as inhibition of spontaneous emission,1,2 high-reflecting omnidirectional mirrors, structures that exhibit low-loss-waveguiding,3 and light confinement.4,5 Here, we demonstrate a similar concept of exploiting the geometrical effects on nanoscale through precisely fabricating lithium niobate (LiNbO3) nanocones arrays devices. We show a strong second harmonic generation (SHG) enhancement, shape and arrangement dependent, up to 4 times bigger than the bulk one. These devices allow below diffraction limited observation, being perfect platforms for single molecule fluorescence microscopy6 or single cell endoscopy.7 Nanocones create a confined illumination volume, devoid from blinking and bleaching, which can excite molecules in nanocones proximity. Illumination volume can be increased by combining the SH enhancement effect with plasmon resonances, excited thanks to a gold plasmonic shell deposited around the nanostructures. This results in a local further enhancement of the SH signal up to 20 times. The global SH enhancement can be rationally designed and tuned through the means of simulations. © 2013 American Chemical Society.


Traversi F.,Institute of Bioengineering | Raillon C.,Institute of Bioengineering | Benameur S.M.,Institute of Electrical Engineering | Liu K.,Institute of Bioengineering | And 5 more authors.
Nature Nanotechnology | Year: 2013

Solid-state nanopores can act as single-molecule sensors and could potentially be used to rapidly sequence DNA molecules. However, nanopores are typically fabricated in insulating membranes that are as thick as 15 bases, which makes it difficult for the devices to read individual bases. Graphene is only 0.335 nm thick (equivalent to the spacing between two bases in a DNA chain) and could therefore provide a suitable membrane for sequencing applications. Here, we show that a solid-state nanopore can be integrated with a graphene nanoribbon transistor to create a sensor for DNA translocation. As DNA molecules move through the pore, the device can simultaneously measure drops in ionic current and changes in local voltage in the transistor, which can both be used to detect the molecules. We examine the correlation between these two signals and use the ionic current measurements as a real-time control of the graphene-based sensing device. © 2013 Macmillan Publishers Limited.


Liu K.,Institute of Bioengineering | Feng J.,Institute of Bioengineering | Kis A.,Institute of Electrical Engineering | Radenovic A.,Institute of Bioengineering
ACS Nano | Year: 2014

Atomically thin nanopore membranes are considered to be a promising approach to achieve single base resolution with the ultimate aim of rapid and cheap DNA sequencing. Molybdenum disulfide (MoS2) is newly emerging as a material complementary to graphene due to its semiconductive nature and other interesting physical properties that can enable a wide range of potential sensing and nanoelectronics applications. Here, we demonstrate that monolayer or few-layer thick exfoliated MoS2 with subnanometer thickness can be transferred and suspended on a predesigned location on the 20 nm thick SiN x membranes. Nanopores in MoS2 are further sculpted with variable sizes using a transmission electron microscope (TEM) to drill through suspended portions of the MoS2 membrane. Various types of double-stranded (ds) DNA with different lengths and conformations are translocated through such a novel architecture, showing improved sensitivity (signal-to-noise ratio >10) compared to the conventional silicon nitride (SiNx) nanopores with tens of nanometers thickness. Unlike graphene nanopores, no special surface treatment is needed to avoid hydrophobic interaction between DNA and the surface. Our results imply that MoS2 membranes with nanopore can complement graphene nanopore membranes and offer potentially better performance in transverse detection. © 2014 American Chemical Society.


Krajewski W.,Institute of Electrical Engineering
Progress in Electromagnetics Research | Year: 2011

The aim of this paper is to validate a proposed simplified boundary-integral approach (that is called here LEM&BEM) for the analysis of electric field in a live-line-working zone. A human body model of a simplified geometry that is applied to the electric field estimation around the live-line worker is also tested. Numerical results of a more accurate numerical approach, laboratory measurements as well as results of measurements taken on a real tower of HV overhead line are employed for this purpose. The numerical analysis of the electric field distribution in the hot-stick working zone on an anchor tower of 400 kV transmission line is presented to demonstrate the effectiveness of the numerical technique under consideration. The author's own software packages has been applied in computations.


Krajewski W.,Institute of Electrical Engineering
Progress In Electromagnetics Research M | Year: 2010

The paper deals with the analysis of the magnetic field distribution near the transition tower of an overhead-underground transmission line of 110kV. The current density induced in the human body due to this field is also estimated. A hybrid numerical technique combining both the boundary element method and the charge simulation method is employed for this purpose. This technique is implemented in the author's own software package dedicated to the analysis of electromagnetic exposure in the vicinity of power objects. A simplified numerical model of the human body of dimensions recommended by the IEC/EN standards is employed in computations. Obtained numerical results are related to the appropriate regulations regarding the human exposure to the electromagnetic fields.

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