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Martinez-Martin D.,Autonomous University of Madrid | Herruzo E.T.,CSIC - National Center of Microelectronics | Dietz C.,CSIC - National Center of Microelectronics | Gomez-Herrero J.,Autonomous University of Madrid | Garcia R.,CSIC - National Center of Microelectronics
Physical Review Letters | Year: 2011

Mapping of the protein structural flexibility with sub-2-nm spatial resolution in liquid is achieved by combining bimodal excitation and frequency modulation force microscopy. The excitation of two cantilever eigenmodes in dynamic force microscopy enables the separation between topography and flexibility mapping. We have measured variations of the elastic modulus in a single antibody pentamer from 8 to 18 MPa when the probe is moved from the end of the protein arm to the central protrusion. Bimodal dynamic force microscopy enables us to perform the measurements under very small repulsive loads (30-40 pN). © 2011 American Physical Society.

Lopez-Polin G.,Autonomous University of Madrid | Gomez-Navarro C.,Autonomous University of Madrid | Parente V.,CSIC - Institute of Materials Science | Guinea F.,CSIC - Institute of Materials Science | And 3 more authors.
Nature Physics | Year: 2015

The extraordinary strength, stiffness and lightness of graphene have generated great expectations of its application in flexible electronics and as a mechanical reinforcement agent. However, the presence of lattice defects, unavoidable in sheets obtained by scalable routes, might degrade its mechanical properties. Here we report a systematic study on the elastic modulus and strength of graphene with a controlled density of defects. Counter-intuitively, the in-plane Youngâ €™ s modulus increases with increasing defect density up to almost twice the initial value for a vacancy content of â 1/40.2%. For a higher density of vacancies, the elastic modulus decreases with defect inclusions. The initial increase in Youngâ €™ s modulus is explained in terms of a dependence of the elastic coefficients on the momentum of flexural modes predicted for two-dimensional membranes. In contrast, the fracture strength decreases with defect density according to standard fracture continuum models. These quantitative structure-property relationships, measured in atmospheric conditions, are of fundamental and technological relevance and provide guidance for applications in which graphene mechanics represents a disruptive improvement. © 2014 Macmillan Publishers Limited. All rights reserved.

Chiesa M.,CSIC - National Center of Microelectronics | Garcia R.,CSIC - National Center of Microelectronics
Applied Physics Letters | Year: 2010

We have measured the surface potential and the space charge generated during the first stages of atomic force microscopy field-induced oxidation. Space charge densities are about 1017 cm-3 for oxidation times below 10 ms. In a dry atmosphere, the surface potential is negative. However, in humid air the surface potential could be either positive or negative. This effect is attributed to a screening effect of the water molecules. These results explain and support the use of local oxidation patterns as templates for building molecular architectures. They also establish the space charge build up as an intrinsic feature in local oxidation experiments. © 2010 American Institute of Physics.

Tamayo J.,CSIC - National Center of Microelectronics | Kosaka P.M.,CSIC - National Center of Microelectronics | Ruz J.J.,CSIC - National Center of Microelectronics | San Paulo A.,CSIC - National Center of Microelectronics | Calleja M.,CSIC - National Center of Microelectronics
Chemical Society Reviews | Year: 2013

The advances in micro- and nanofabrication technologies enable the preparation of increasingly smaller mechanical transducers capable of detecting the forces, motion, mechanical properties and masses that emerge in biomolecular interactions and fundamental biological processes. Thus, biosensors based on nanomechanical systems have gained considerable relevance in the last decade. This review provides insight into the mechanical phenomena that occur in suspended mechanical structures when either biological adsorption or interactions take place on their surface. This review guides the reader through the parameters that change as a consequence of biomolecular adsorption: mass, surface stress, effective Young's modulus and viscoelasticity. The mathematical background needed to correctly interpret the output signals from nanomechanical biosensors is also outlined here. Other practical issues reviewed are the immobilization of biomolecular receptors on the surface of nanomechanical systems and methods to attain that in large arrays of sensors. We then describe some relevant realizations of biosensor devices based on nanomechanical systems that harness some of the mechanical effects cited above. We finally discuss the intrinsic detection limits of the devices and the limitation that arises from non-specific adsorption. © 2013 The Royal Society of Chemistry.

Martinez R.V.,CSIC - National Center of Microelectronics | Martinez J.,CSIC - National Center of Microelectronics | Garcia R.,CSIC - National Center of Microelectronics
Nanotechnology | Year: 2010

We report a top-down process for the fabrication of single-crystalline silicon nanowire circuits and devices. Local oxidation nanolithography is applied to define very narrow oxide masks on top of a silicon-on-insulator substrate. In a plasma etching, the nano-oxide mask generates a nanowire with a rectangular section. The nanowire width coincides with the lateral size of the mask. In this way, uniform and well-defined transistors with channel widths in the 10-20nm range have been fabricated. The nanowires can be positioned with sub-100nm lateral accuracy. The transistors exhibit an on/off current ratio of 105. The atomic force microscope nanolithography offers full control of the nanowire's shape from straight to circular or a combination of them. It also enables the integration of several nanowires within the same circuit. The nanowire transistors have been applied to detect immunological processes. © 2010 IOP Publishing Ltd.

Munoz M.,CSIC - National Center of Microelectronics | Prieto J.L.,Technical University of Madrid
Nature Communications | Year: 2011

Nanofabrication has allowed the development of new concepts such as magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls on magnetic nanostripes. One of the issues that has to be solved before devices can meet the market demands is the stochastic behaviour of the domain wall movement in magnetic nanostripes. Here we show that the stochastic nature of the domain wall motion in permalloy nanostripes can be suppressed at very low fields (0.6-2.7 Oe). We also find different field regimes for this stochastic motion that match well with the domain wall propagation modes. The highest pinning probability is found around the precessional mode and, interestingly, it does not depend on the external field in this regime. These results constitute an experimental evidence of the intrinsic nature of the stochastic pinning of domain walls in soft magnetic nanostripes. © 2011 Macmillan Publishers Limited. All rights reserved.

Bratov A.,CSIC - National Center of Microelectronics | Abramova N.,CSIC - National Center of Microelectronics
Journal of Colloid and Interface Science | Year: 2013

A new device based on an interdigitated electrode array with electrode digits located at the bottom of microcapillaries is presented. Microcapillaries formed in silicon dioxide are 3μm wide, 4μm high and are open at the top, so that in contact with an electrolyte solution the AC current flows from one capillary to another and is significantly affected by changes in surface conductivity at the SiO2/electrolyte interface. The effect of charged polyelectrolyte layers electrostatically assembled on the sensor surface on the surface conductivity in solutions with different KCl concentration is presented. From measured impedance spectra polyelectrolyte adsorption curve is determined. The device is shown to be useful for real time adsorption kinetics monitoring. © 2013 Elsevier Inc.

Bausells J.,CSIC - National Center of Microelectronics
Microelectronic Engineering | Year: 2015

Microfabricated cantilevers have enabled a wide range of applications in scanning probe microscopies (SPM) and in high-sensitivity nanomechanical sensors. The use of piezoresistivity for self-sensing the cantilever motion is preferred to the standard optical readout for some applications, in view of the advantages that it offers in terms of miniaturization, operation in non-transparent liquid media and capability of simultaneously addressing arrays of devices. Although in principle piezoresistive cantilevers should have a lower resolution than their optical counterparts, current devices can achieve similar performances. This is because a large amount of work has been devoted in the past two decades to their development. This paper provides a short review of the field of piezoresistive cantilevers. We discuss the device performances for the measurement of forces or surface stresses in static operation, or masses in dynamic operation. We then describe the fabrication technologies and materials that are typically used to manufacture the cantilevers. Finally, the main applications in the domains of SPM and nanomechanical sensing are presented. © 2015 Elsevier B.V. All rights reserved.

Calleja M.,CSIC - National Center of Microelectronics | Kosaka P.M.,CSIC - National Center of Microelectronics | San Paulo A.,CSIC - National Center of Microelectronics | Tamayo J.,CSIC - National Center of Microelectronics
Nanoscale | Year: 2012

Nanomechanical biosensing relies on changes in the movement and deformation of micro- and nanoscale objects when they interact with biomolecules and other biological targets. This field of research has provided ever-increasing records in the sensitivity of label-free detection but it has not yet been established as a practical alternative for biological detection. We analyze here the latest advancements in the field, along with the challenges remaining for nanomechanical biosensors to become a commonly used tool in biology and biochemistry laboratories. © 2012 The Royal Society of Chemistry.

Martin J.,CSIC - National Center of Microelectronics | Martin-Gonzalez M.,CSIC - National Center of Microelectronics
Nanoscale | Year: 2012

Large area silicon nitride (SiN x) nanoporous surfaces are fabricated using poly(ether-ether-ketone) (PEEK) nanorod arrays as a template. The procedure involves manipulation of nanoporous anodic aluminum oxide (AAO) templates in order to form an ordered array of PEEK nanopillars with high temperature resistant characteristics. In this context, self-ordered AAO templates are infiltrated with PEEK melts via the "precursor film" method. Once the melts have been crystallized in the porous structure of AAO, the basis alumina layer is removed, yielding an ordered array of PEEK nanopillars. The resulting structure is a high temperature and chemical resistant polymeric nanomold, which can be utilized in the synthesis of nanoporous materials under aggressive conditions. Such conditions are high temperatures (up to 320°C), vacuum, or extreme pH. For example, SiN x nanopore arrays have been grown by plasma enhanced chemical vapor deposition at 300°C, which can be of interest as mold for nanoimprint lithography, due to its hardness and low surface energy. The SiN x nanopore array portrays the same characteristics as the original AAO template: 120 nm diameter pores and an interpore distance of 430 nm. Furthermore, the aspect ratio of the SiN x nanopores can be tuned by selecting an AAO template with appropriate conditions. The use of PEEK as a nanotemplate extends the applicability of polymeric nanopatterns into a temperature regime up to now not accessible and opens up the simple fabrication of novel nanoporous inorganic surfaces. This journal is © The Royal Society of Chemistry 2012.

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