Jose Plaza - Academia.edu (original) (raw)

Papers by Jose Plaza

IEEE Transactions on Nanotechnology, 2015

This work presents a sensor composed of a differential arrangement of coils capable of measuring ... more This work presents a sensor composed of a differential arrangement of coils capable of measuring nanometric metallic film thickness. Experimental results achieved aluminium thickness measurements as low as 20 nm with a sensitivity of 3.8 mV/nm. This makes this sensor a flexible, nondestructive and cheap alternative for metallic thickness measurement down to nanometric scale.

2009 Spanish Conference on Electron Devices, 2009

This paper shows the technology development of microneedles electrodes for living cell applicatio... more This paper shows the technology development of microneedles electrodes for living cell applications. The study (6) (b)

SPIE Proceedings, 2007

Deflection of a microcantilever caused by any kind of biochemical reaction occurring on its surfa... more Deflection of a microcantilever caused by any kind of biochemical reaction occurring on its surface can be detected with subangstrom resolution if an appropriate detection technique is exploited. This kind of transducers has become widely used in biological research since a few years ago. Usually, for the readout of the nanomechanical response of the micro beams to bio-specific interactions, a technique similar to one used in the atomic force microscopy is employed. The optical read-out method has some disadvantages, such as low degree of integration and difficulties in work with arrays of cantilevers. In the technique presented in this work the cantilever itself is an optical waveguide butt-coupled with another one. The device is fabricated as an array of 20 waveguide cantilever channels which allows for higher integration level. The analysis of the capabilities of the device, the problems associated with the design and the fabrication of the device, the choice of the material and the technology for the fabrication of very flat cantilevers have been successfully addressed. The characterisation of the device was done, showing that the resolution of the device is comparable with the one using the optical lever read-out. Results of the simulations and experimental data on the optical cantilevers coated with an absorbent material will be presented. The choice of the appropriate thickness of the absorbent material on the cantilever surface allows for acceptable losses, for single mode behaviour and adjustment of the initial displacement of the cantilever.

Sensors and Actuators A: Physical, 2010

A system of two solid microlenses with uncoupled optical properties is presented. This structure ... more A system of two solid microlenses with uncoupled optical properties is presented. This structure has been designed in order to have one lens as a reference, while the other one can be mechanically tuneable. The reference lens presents a diameter of 2 m and it is placed in the optical axis of the mechanically tuneable lens, which has a diameter of 10 m. The proposed microoptical structure has been fabricated in poly(dimethilsiloxane) (PDMS) merging deep reactive ion etching, SU-8 and soft lithography, with a low-cost (mass-production), simple and highly repetitive technology. This device was numerically simulated prior to its fabrication, to optimize its design and improve its behaviour. In addition, an optical characterization of the fabricated devices was carried out. Both simulation and experimental results shows a good agreement, under mechanical actuation behaviour of the reference lens is invariable, while the tuneable lens become an elliptic lens and the interval of Sturm can be observed. These results provide a proof of concept of the proposed devices and validate both the design and the fabrication technology.

Journal of Micromechanics and Microengineering, 2004

In the last decade research in chips for DNA amplification through the polymerase chain reaction ... more In the last decade research in chips for DNA amplification through the polymerase chain reaction (PCR) has been relatively abundant, but has taken very diverse approaches, leaving little common ground for a straightforward comparison of results. Here we report the development of a line of PCR chips that is fully compatible with complementary-metal-oxidesemiconductor (CMOS) technology and its revealing use as a general platform to test and compare a wide range of experimental parameters involved in PCR-chip design and operation. Peltier-heated and polysilicon thin-film driven PCR chips have been produced and directly compared in terms of efficiency, speed and power consumption, showing that thin-film systems run faster and more efficiently than Peltier-based ones, but yield inferior PCR products. Serpentine-like chamber designs have also been compared with standard rectangular designs and with the here reported rhomboidal chamber shape, showing that serpentine-like chambers do not have detrimental effects in PCR efficiency when using non-flow-through schemes, and that chamber design has a strong impact on sample insertion/extraction yields. With an accurate temperature control (±0.2 • C) we have optimized reaction kinetics to yield sound PCR amplifications of 25 µl mixtures in 20 min and 24.4 s cycle times, confirming that a titrated amount of bovine albumin serum (BSA, 2.5 µg µl −1) is essential to counteract polymerase adsorption at chip walls. The reported use of a CMOS-compatible technological process paves the way for an easy adaption to foundry requirements and for a scalable integration of electro-optic detection and control circuitry.

Journal of Lightwave Technology, 2006

This study presents a novel generic multipurpose probe based on an array of 20 waveguide channels... more This study presents a novel generic multipurpose probe based on an array of 20 waveguide channels with microcantilevers acting as optical waveguides operated in the visible range. The principle of operation is based on the sensitivity of energy transfer between two butt-coupled waveguides to their misalignment with respect to each other. The technique can be considered an alternative to the known methods used for the readout of the nanomechanical response of microcantilevers to the external force exerted on them. The cantilever displacement can be detected with a resolution of 18 fm/ √ Hz. The limit is generally defined by the shot noise of a conventional photodetector used for the readout of the output signal. Real-time parallel monitoring of several channels can be realized. In contrast to devices based on the atomic force microscope detection principle, no preliminary alignment or adjustment, except for light coupling, is required. The detection of the cantilever deflection at subnanometer range was demonstrated experimentally.

Human Reproduction, 2013

study question: Is the attachment of biofunctionalized polysilicon barcodes to the outer surface ... more study question: Is the attachment of biofunctionalized polysilicon barcodes to the outer surface of the zona pellucida an effective approach for the direct tagging and identification of human oocytes and embryos during assisted reproduction technologies (ARTs)? summary answer: The direct tagging system based on lectin-biofunctionalized polysilicon barcodes of micrometric dimensions is simple, safe and highly efficient, allowing the identification of human oocytes and embryos during the various procedures typically conducted during an assisted reproduction cycle. what is known already: Measures to prevent mismatching errors (mix-ups) of the reproductive samples are currently in place in fertility clinics, but none of them are totally effective and several mix-up cases have been reported worldwide. Using a mouse model, our group has previously developed an effective direct embryo tagging system which does not interfere with the in vitro and in vivo development of the tagged embryos. This system has now been tested in human oocytes and embryos. study design, size, duration: Fresh immature and mature fertilization-failed oocytes (n ¼ 21) and cryopreserved day 1 embryos produced by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) (n ¼ 205) were donated by patients (n ¼ 76) undergoing ARTs. In vitro development rates, embryo quality and post-vitrification survival were compared between tagged (n ¼ 106) and non-tagged (control) embryos (n ¼ 99). Barcode retention and identification rates were also calculated, both for embryos and for oocytes subjected to a simulated ICSI and parthenogenetic activation. Experiments were conducted from January 2012 to January 2013. participants/materials, setting, methods: Barcodes were fabricated in polysilicon and biofunctionalizated with wheat germ agglutinin lectin. Embryos were tagged with 10 barcodes and cultured in vitro until the blastocyst stage, when they were either differentially stained with propidium iodide and Hoechst or vitrified using the Cryotop method. Embryo quality was also analyzed by embryo grading and timelapse monitoring. Injected oocytes were parthenogenetically activated using ionomycin and 6-dimethylaminopurine. main results and the role of chance: Blastocyst development rates of tagged (27/58) and non-tagged embryos (24/51) were equivalent, and no significant differences in the timing of key morphokinetic parameters and the number of inner cell mass cells were detected between the two groups (tagged: 24.7 + 2.5; non-tagged: 22.3 + 1.9), indicating that preimplantation embryo potential and quality are not affected by the barcodes. Similarly, re-expansion rates of vitrified-warmed tagged (19/21) and non-tagged (16/19) blastocysts were similar. Global identification rates of 96.9 and 89.5% were obtained in fresh (mean barcode retention: 9.22 + 0.13) and vitrified-warmed (mean barcode retention: 7.79 + 0.35) tagged embryos, respectively, when simulating an automatic barcode reading process, though these rates were increased to 100% just by rotating the embryos during barcode reading. Only one of the oocytes lost one barcode during intracytoplasmic injection (100% identification rate) and all oocytes retained all the barcodes after parthenogenetic activation.

Biomedical Microdevices, 2010

Microchips can be fabricated, using semiconductor technologies, at microscopic level to be introd... more Microchips can be fabricated, using semiconductor technologies, at microscopic level to be introduced into living cells for monitoring of intracellular parameters at a single cell level. As a first step towards intracellular chips development, silicon and polysilicon microparticles of controlled shape and dimensions were fabricated and introduced into human macrophages and mouse embryos by phagocytosis and microinjection, respectively. Microparticles showed to be non-cytotoxic for macrophages and were found to be localized mainly inside early endosomes, in tight association with endosomal membrane, and more rarely in acidic compartments. Embryos with microinjected microparticles developed normally to the blastocyst stage, confirming the non-cytotoxic effect of the particles. In view of these results silicon and polysilicon microparticles can serve as the frame for future intracellular chips development and this technology opens the possibility of real complex devices to be used as sensors or actuators inside living cells.

Bioconjugate Chemistry, 2012

Cell tracking is an emergent area in nanobiotechnology, promising the study of individual cells o... more Cell tracking is an emergent area in nanobiotechnology, promising the study of individual cells or the identification of populations of cultured cells. In our approach, microtools designed for extracellular tagging are prepared, because using biofunctionalized polysilicon barcodes to tag cell membranes externally avoids the inconveniences of cell internalization. The crucial covalent biofunctionalization process determining the ultimate functionality was studied in order to find the optimum conditions to link a biomolecule to a polysilicon barcode surface using a self-assembled monolayer (SAM) as the connector. Specifically, a lectin (wheat germ agglutinin, WGA) was used because of its capacity to recognize some specific carbohydrates present on the surface of most mammalian cells. Self-assembled monolayers were prepared on polysilicon surfaces including aldehyde groups as terminal functions to study the suitability of their covalent chemical bonding to WGA. Some parameters, such as the polysilicon surface roughness or the concentration of WGA, proved to be crucial for successful biofunctionalization and bioactivity. The SAMs were characterized by contact angle measurements, time-of-flight secondary ion mass spectrometry (TOF-SIMS), laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS), and atomic force microscopy (AFM). The biofunctionalization step was also characterized by fluorescence microscopy and, in the case of barcodes, by adhesion experiments to the zona pellucida of mouse embryos. These experiments showed high barcode retention rates after 96 h of culture as well as high embryo viability to the blastocyst stage, indicating the robustness of the biofunctionalization and, therefore, the potential of these new microtools to be used for cell tagging.

Título: Dispositivo intracelular para el estudio de parámetros intracelulares en células, órganos... more Título: Dispositivo intracelular para el estudio de parámetros intracelulares en células, órganos y tejidos.

Applied Physics Letters, 2006

Employing higher oscillation modes of microcantilevers promises higher sensitivity when applied a... more Employing higher oscillation modes of microcantilevers promises higher sensitivity when applied as sensors, for example, for mass detection or in atomic force microscopy. Introducing a special cantilever geometry, we show that the relation between the resonance frequencies of the first and second resonance modes can be modified to separate them further or to bring them closer together. In atomic force microscopy the latter is of special interest as the photodiode of the beam deflection detection limits the accessible frequency range. Using finite element simulations, we optimized the design of the modified cantilever geometry for a maximum reduction of the frequency of the second oscillation mode with respect to the first mode. Cantilevers were fabricated by silicon micromachining and subsequently utilized in an ultrahigh vacuum Kelvin probe force microscope imaging the surface potential of C60 on graphite.

Lab on a Chip, 2015

We develop chip-on-a-cell barcodes featuring silicon nanowires as nanoscale attachment to label l... more We develop chip-on-a-cell barcodes featuring silicon nanowires as nanoscale attachment to label living mouse embryos.

Micromachined Devices and Components VI, 2000

Low-power micromachined structures for gas sensors with improved robustness. [Proceedings of SPIE... more Low-power micromachined structures for gas sensors with improved robustness. [Proceedings of SPIE 4176, 253 (2000)]. Isabel Gracia, Andreas Goetz, Jose A. Plaza, Carles Cane, Patrice Roetsch, Harald Boettner, Klaus Seibert. Abstract. ...

Sensors and Actuators B: Chemical, 2015

Increasingly, advances in microtechnologies are focused on obtaining new chips intended for appli... more Increasingly, advances in microtechnologies are focused on obtaining new chips intended for applications in fields such as nanomedicine and cell biology, taking advantage of the ability of microelectronics to manufacture devices with cell dimensions and a large variety of features. Here, we report a technology for the fabrication of multi-material chips, using polysilicon and gold as device layers, to be used as bi-functional cellinternalizable devices. In our case, one of the main technological challenges is to overcome the low adherence between these two materials, especially because of their small contact-area, only 9 µm 2. Thus, in order to circumvent this difficulty a chromium adherent-layer was deposited in between. After fabrication, the devices following this design can be successfully internalized inside living macrophages without affecting their viability. The advantage of having multiple material layers in one device is the potential to render multi-tasking chips, as once they are appropriately functionalized, we can provide the chip the ability of being bi-functional. Hence, and as a proof of concept, two different proteins, Wheat Germ Agglutinin (WGA) and Concanavalin (ConA), were 3 immobilized on the chip surface through self-assembled monolayers using orthogonal chemistry. The results of this work show a well-controlled fabrication, the bi-functional capabilities and no cell-toxicity of intracellular polysilicon-chromium-gold chips. These devices have a promising future as intracellular functional platforms for biosensing, drug delivery and diagnosis.

Sensors and Actuators A: Physical, 2008

This paper presents the design, fabrication and characterization of polymer microoptoelectromecha... more This paper presents the design, fabrication and characterization of polymer microoptoelectromechanical systems (MOEMS). An optical accelerometer and a variable optical attenuator (VOA) based on SU-8 are presented. Both devices consist on a quad-beam polymer structure and can be fabricated with a simple technology, requiring only two photolithographic steps. Self-alignment structures for fast and accurate fiber optic positioning have also been

Sensor Letters, 2009

ABSTRACT In this work a magnetic field gradiometer device has been developed. This device is not ... more ABSTRACT In this work a magnetic field gradiometer device has been developed. This device is not composed by two sensors separated a certain distance but by a single-sensor device which measures the real gradient value just at the point where it is wanted to be measured. The experimental set-up consists of a sensor head (a membrane with a fixed permanent magnet on it) vibrating at its resonance frequency, due to an alternating magnetic field gradient. Detection is performed using an optoelectronic method. Two different measurement techniques have been used: frequency measurements (the resonance frequency is measured for every external magnetic field gradient value) and amplitude measurements (the signal amplitude is measured without changing the resonance frequency obtained without an external magnetic field gradient applied). The mechanical stresses of the membrane are related with the dependence of both magnitudes (frequency and amplitude) on the external magnetic field gradient. The minimum and maximum value of the resonance frequency and signal amplitude respectively, correspond with magnetic forces equal to the magnet weight of the sensor head. This prototype shows a noise-limited sensitivity of 2 Gauss/m/√Hz at zero gradient. This device could be used also as a magnetic susceptometer.

Microelectronic Engineering, 2009

Colloids and Surfaces B: Biointerfaces, 2014

Self-assembled monolayers (SAMs) have been used for the preparation of functional microtools cons... more Self-assembled monolayers (SAMs) have been used for the preparation of functional microtools consisting of encoded polysilicon barcodes biofunctionalized with proteins of the lectin family. These hybrid microtools exploit the lectins ability for recognizing specific carbohydrates of the cell membrane to give an efficient system for cell tagging. This work describes how the control of the methodology for SAM formation on polysilicon surfaces followed by lectin immobilization has a crucial influence on the microtool biofunction. Several parameters (silanization time, silane molar concentration, type of solvent or deposition methodology) have been studied to establish optimal function. Furthermore, silanes incorporating different terminal groups, such as aldehyde, activated ester or epoxide groups were tested in order to analyze their chemical coupling with the biomolecules, as well as their influence on the biofunctionality of the immobilized protein. Two different lectins-wheat germ agglutinin (WGA) and phytohemagglutinin (PHA-L)-were immobilized, because they have different and specific cell recognition behaviour and exhibit different cell toxicity. In this way we can assess the effect of intrinsic bulk toxicity with that of the cell compatibility once immobilized as well as the importance of cell affinity. A variety of nanometrical techniques were used to characterize the active surfaces, and lectin immobilization was quantified using ultraviolet-visible absorption spectroscopy (UV-vis) and optical waveguide light mode spectroscopy (OWLS). Once the best protocol was found, WGA and PHA were immobilized on polysilicon coded barcodes, and these microtools showed excellent cell tagging on living mouse embryos when WGA was used.

Abstract: A novel micropipette fabrication technology has been successfully implemented, where im... more Abstract: A novel micropipette fabrication technology has been successfully implemented, where improved microsystem fabrication is enhanced by focused ion beam micro/nano machining. Micropipettes consist of silicon chips with polysilicon microchannels whose dispensing nozzles were reshaped in a variety of geometries. Reshaped micropippette nozzles were achieved by focused ion beam milling and can readily accommodate different applications. Functionalization tests successfully dispensed femtoliter droplets. Keywords: ...

Conference on Electron Devices, 2005 Spanish