J.A. Plaza

Barcelona Microelectronics Institute, Barcino, Catalonia, Spain

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Publications (90)100.47 Total impact

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    ABSTRACT: This paper reports and compares the implementation of magnetic variable optical attenuators (M-VOA) by two fabrication strategies. In the first case, a two-layer structure containing a non-doped polydimethylsiloxane (PDMS) layer on a magnetic PDMS (M-PDMS) layer is fabricated by soft lithography (SLT). M-PDMS is obtained by doping PDMS with different ferrofluid (FF) volumes. The second technology consists of selectively dispense FF microdroplets using the inkjet printing technique (IJP) on a non-doped, non-cured PDMS structure, previously defined by SLT. In this second case, FF volumes are encapsulated inside the polymer matrix. The optical and mechanical properties of structures fabricated using both strategies and containing similar ferrofluid amounts are compared.
    Sensors and Actuators A Physical 08/2014; · 1.84 Impact Factor
  • Human Reproduction. 01/2013; 28:i2-i3.
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    ABSTRACT: This paper reports the implementation of magnetic variable optical attenuators (M-VOA) by soft lithography (SLT) and using polydimethylsiloxane (PDMS) as constituent material. Two different fabrication protocols are used and compared. In the first case, a two-layer structure containing a clean PDMS layer on a magnetic PDMS (M-PDMS) layer is fabricated by SLT. M-PDMS is obtained by doping clean PDMS with different ferrofluid (FF) amounts. The second protocol consists of selectively dispensing droplets of FF by the inkjet printing technique (IPT) on a clean and non-cured PDMS structure previously defined by SLT. The optical and mechanical properties of structures fabricated using both protocols and containing similar ferrofluid amounts are compared.
    Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International Conference on; 01/2013
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    ABSTRACT: The low number of oocytes collected from unstimulated donors by ovum pick-up means that embryos produced from each female have to be cultured in very small groups. Because embryo quality and development rates are reduced in individual and small group culture, several methods to culture embryos individually but sharing the same medium have been designed. However, these systems prevent embryo movements, interfering with paracrine factors transmission and gradient changes. Here, we present an alternative in vitro culture method to allow the co-culture of embryos from different origins, without movement restriction and preserving their pedigree, by labelling the zygotes with polysilicon barcodes attached to the outer surface of the zona pellucida (ZP). Barcodes (10×6×1µm) with 8 rectangular bits of binary codification (256 possible combinations), which can be read under a standard inverted microscope, were fabricated using silicon microtechnologies. To provide the barcodes with a ZP-binding capacity, they were biofunctionalized by self-assembled monolayers with the wheat germ agglutinin (WGA) lectin, which recognizes specific saccharides highly abundant in the ZP of most mammalian species. As a proof of concept, the culture method was tested on bovine zygotes produced from slaughterhouse-derived cow oocytes matured and fertilized in vitro. Using a mouth-controlled pipette, presumptive zygotes were individually rolled over WGA-biofunctionalized barcodes (8 barcodes/embryo) previously placed at the bottom of a drop of manipulation media. Four different barcodes, each one with a different codification, were used to encode 25 embryos (6-7 embryos/barcode codification), which were then cultured together in the same drop of medium. Day 7 (D7) and Day 8 (D8) blastocyst, and barcode retention rates were assessed. In addition, D7 expanded blastocysts were vitrified by the cryotop method and post-warming survival was determined as re-expansion rate at 24h in culture. Finally, the quality of D8 blastocysts was assessed by differential staining and counting of inner cell mass (ICM) and trophectoderm (TE) cells. In all the experiments, a control group without barcodes was cultured and vitrified-warmed. Data were analyzed by chi-square and Mann-Whitney tests. The presence of barcodes attached to the ZP did not affect in vitro embryo development (D8 blastocysts: 29.7% control n=309, 36.2% encoded n=315), post-warming survival (86.4% control n=66, 80.5% encoded n=82), or blastocyst quality (IMC/TE: 22.1±1.4/64.5±5.7 control n=18, 22.2±1.7/64.1±6.1 encoded n=23). The labelling system was effective until D8 of culture, as all the embryos maintained barcodes attached (4±1.8 barcodes/embryo) and could be identified, even after undergoing vitrification and warming. In conclusion, identification of co-cultured embryos by biofunctionalized barcodes attached to the ZP is feasible and will allow to culture embryos from different donors in the same drop, keeping the benefits of collective culture.
    Reproduction Fertility and Development 12/2012; 25(1):218-9. · 2.58 Impact Factor
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    ABSTRACT: This paper describes a technique that uses applied force to dice anodically bonded silicon–glass wafers with high yields. The chips are suspended to the wafer by anchors; when pressure is applied to a chip, stress concentrates at the narrow anchors, which then fracture and release the chip from the wafer. Anchor fracturing has been used to dice crystalline and non-crystalline materials but its application to dicing constructs of various materials has remained challenging because of the disparity with which fractures propagate in different materials and in their interfaces. The technique we present here makes it possible to fracture composite materials (silicon and glass anodically bonded) by eliminating any material interface from the fracturing regions—i.e. the anchors. The approach was tested using two types of anchors fabricated in anodically bonded silicon–glass wafers: in one type, the silicon–glass interface expanded most of the anchor (coincident anchors) but such an interface was inexistent in the other type (non-coincident anchors). The study determined dicing yields—i.e. percentage of chips not damaged by the fracture of the anchors—of ~40% and 100% for test structures with coincident and non-coincident anchors, respectively. The presence of a silicon–glass interface in the suspending anchors often resulted in fractures propagating away from the anchors, and ultimately in damage to the suspended chips. This technique provides an inexpensive, robust and simple alternative to currently available dicing methods for the glass–silicon wafer pairs frequently used in wafer-level packaging of MEMS.
    Journal of Micromechanics and Microengineering 01/2012; 22(2):025023. · 1.79 Impact Factor
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    ABSTRACT: We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials.
    Nanotechnology 11/2011; 22(50):505301. · 3.84 Impact Factor
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    ABSTRACT: In this work, two types of polycrystalline silicon (polysilicon) microparticles were modified with specific ligands in order to be selectively attached to chemical residues located at the plasma membrane and thus to be applied to study individual cells in culture. Two different functionalization approaches based on adsorption and covalent attachment were assayed. A comparative study of the efficiency of the ligand immobilization and stability of the modified particle in the culture medium was carried out using the selected ligands labeled with a fluorophore. Cylindrical microparticles (nonencoded microparticles) and shape-encoded microparticles (bar codes) were used with the aim of demonstrating the nondependence of the particle size and shape on the efficiency of the immobilization protocol. Fluorescence imaging and statistical analysis of the recorded fluorescence intensity showed that the covalent attachment of the ligand to the surface of the microparticle, previously modified with an aldehyde-terminated silane, gave the best results. As a proof of concept, Vero cells in culture were labeled with the covalently modified bar codes and successfully tracked for up to 1 week without observing any alteration in the viability of the cells. Bar code numbers could be easily read by eye using a bright-field optical microscope. It is anticipated that such modified microparticles could be feasible platforms for the introduction of other analytical functions of interest in single-cell monitoring and cell sorting in automatic analysis systems.
    Langmuir 06/2011; 27(13):8302-8. · 4.38 Impact Factor
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    ABSTRACT: This paper focuses on the design and experimental test of a null-offset differential electromagnetic sensor characterized by simplicity, flexibility and low cost. This sensor consists of two planar excitation coils, which generate magnetic field and a planar acquisition coil, which senses the sample material. The differential configuration of the sensor improves signal conditioning and reduces the common-mode noise. We present analytical and numerical (simulation) studies of the working principle. Experiments were performed to test the ability of the sensor to detect non-invasively: (i) the presence of metallic samples and (ii) the variations of glucose in human blood.
    Sensors and Actuators A Physical 11/2010; · 1.84 Impact Factor
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    ABSTRACT: The dynamic properties of membranes have been object of many researches since they can be used as sensor heads in different devices. Some methods have been proposed to solve the problem of determining the resonance frequencies and their dependence on the stress caused by forces applied on the membrane surface. The problem of the vibrating rectangular membrane under a stress caused by a uniform in-plane force is well known. However, the resonance frequency behaviour when the force is out-of-plane instead of in-plane, is not so well understood and documented. A gradiometer which uses a silicon square membrane with a magnet fixed on it as a sensor head has been developed in a previous work. This device reports a quadratic dependence of the frequency on the out-of-plane magnetic force. In this work, simulations to obtain the dependence of the frequency of the fundamental flexural mode on the stress have been performed. It has been studied the influence of in-plane and out-of-plane forces applied to the membrane. As expected, a square root dependence has been found for in-plane forces. Nevertheless, the problem is more complex when out-of plane forces are considered. Out-of-plane forces gives rise to an initial quadratic dependence which turns into a square root dependence from a certain stress value. The quadratic range increases and the rate of change of the frequency decreases as the surface of the magnet fixed on the membrane increases. The study has addressed these problems and both, experimental and simulated results have been compared and a good agreement between experimental and simulated results has been found Comment: 14 pages, 10 figures
    08/2010;
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    ABSTRACT: 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 μm and it is placed in the optical axis of the mechanically tuneable lens, which has a diameter of 10 μm. 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.
    Sensors and Actuators A: Physical. 08/2010;
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    ABSTRACT: Design, fabrication and testing of a novel micromachined “quasi-digital” microflow regulator for integrated microfluidic systems. Operation relies on the use of a permanent magnet which interacts with an electrodeposited layer of Co–Ni on an array of V-shaped cantilever beams under a constant pressure. Each valve actuates as an on–off fluidic switch, opening or closing its corresponding microchannel. The flow can be adjusted to a set of different values (digital) by changing the position of the magnet. The microflow regulator has been designed, fabricated and experimentally tested showing a flow variation of 211% at a pressure of 160mbar.
    Sensors and Actuators A Physical 07/2010; 162(1):107-115. · 1.84 Impact Factor
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    ABSTRACT: A novel, versatile and robust technology to manufacture transparent micropipettes, suitable for biological applications, is presented here. Up to three deep reactive ion etchings have been included in the manufacturing process, providing highly controlled geometry of reservoirs, connection cavities and inlet ports. Etching processes have been used for the definition of chip and reservoir and for nozzle release. Additionally, special design considerations have been developed to facilitate micro-to-macro fluidic connections. Implementation of anodic bonding to seal a glass substrate to the fluidic structure etched on Si, allowed observation of the flow inside the reservoir. Flow tests have been conducted by filling channels with different fluids. Flow was observed under an optical microscope, both during capillary filling and also during pumping. Dispensing has been demonstrated by functionalizing the surface of an AFM cantilever. Mechanical tests performed by piercing live mouse cells with FIB-sharpened micropipettes suggest the design is sturdy for biological piercing applications.
    Journal of Micromechanics and Microengineering 09/2009; 19(10):105013. · 1.79 Impact Factor
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    ABSTRACT: Packaging technologies are a great issue in MEMS/NEMS fabrication. Moreover, silicon to glass anodic bonding is a common boding technique for MEMS/NEMS packaging. Hence, dicing the wafer into individual devices is a real challenge for fragile structures. This investigation shows an extension of the manual cleaving dicing for bonded silicon/glass wafers. The designed structure with no coincident anchors between silicon and glass avoids that the fracture expands toward the interior of the device during manual cleaving. Highest stresses are localized on the anchors, causing the fracture in those points. This method was experimentally tested to dice anodically bonded silicon-glass wafers.
    Procedia Chemistry. 09/2009; 1(1):68-71.
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    ABSTRACT: Microworld barcoding has become a promising tool for cell biology. Individual and subpopulation cell tracking is of great interest to evaluate cell behaviour. Nowadays, many micrometer and even nanometer size silicon structures can be fabricated using microelectronics techniques. In this work we report for first time the development of 3D barcodes based on silicon substrate. The proposed silicon micromachining technology based on deep reactive ion etching (DRIE) allows to obtain micrometer-sized cylindrical structures with vertical etch profile that defines a bit = 1 and non-vertical etch profile that defines a bit = 0. Although this technology will allow more than 15 bits representation, only 4–8 bits are necessary for cell labelling. The results of this work show that DRIE has become a versatile technique to produce high aspect 3D biocompatible silicon-based barcodes structures for cell studies.
    Sensors and Actuators B: Chemical. 09/2009;
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    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.
    Sensor Letters 07/2009; 7(4):563-570. · 0.52 Impact Factor
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    ABSTRACT: Micromachining techniques are proposed to mass-manufacture innovative silicon oxide micropipettes and conventional boron-silicate pipettes with highly customized tips to address increasingly demanding cell handling procedures. Cell handling has become a crucial procedure in cell biology, especially in nuclear transfer, DNA injection, and in assisted reproductive techniques. Most pipette manufacturing procedures involve tedious artisanal methods prone to failure and with limited functionality. We expect high tip customization to have a large impact in current and future cell manipulation, paving the way for augmented functionality. Although proper biocompatibility assessments remain to be explored, initial pierced embryos are seen to continue their division procedure up to at least 24 hours. The continued cellular division is a good sign of biocompatibility. These results suggest that residual chemical agents or gallium ions injected during milling could be harmless to life development. We conclude that we have produced a novel technique combining microfabrication and Focus Ion Beam processes with great potential for industrial applications.
    Proc SPIE 05/2009;
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    ABSTRACT: Sharpened cantilevered nozzles were fabricated combining microsystem technologies and focused ion beam micromachining. Micronozzles consist of silicon chips with silicon oxide microchannels whose micronozzles were reshaped using Focused Ion Beam. Micronozzle body was defined by an aluminum sacrificial layer patterned over a silicon wafer. This layer was surrounded by a deposited silicon oxide structural layer. The chip is defined by a silicon deep reactive ion etching through the wafer. This process releases part of the metal line forming a cantilevered micronozzle. Sharp reshaped micronozzles were achieved by focused ion beam milling. Mechanical tests of silicon oxide nozzles still containing the aluminum sacrificial layer were performed by cell piercing. In some instances, zona pellucida and membrane were crossed without cell lysis, and micronozzles remained intact.
    Proc SPIE 02/2009; 7204:720407.
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    ABSTRACT: The optical and structural properties of poly(dimethylsiloxane) (PDMS) are considered to define disposable cantilever-based micooptoelectromechanical systems (MOEMS) by ways of soft lithography and with a high degree of monolithic integration. The very low Young's modulus of this material relaxes the dimensions' requirements, being then possible to define thick PDMS structures with a sensitivity comparable to nanometer scale silicon counterparts. Experimental results using a light-emitting diode working at 670 nm have determined the resonant frequencies of the proposed MOEMS and are in agreement with the numerical simulations done. Finally, when a 2-mu L droplet of ethanol (1.58 mg) is dispensed on the cantilever, relative losses rise to 25 dB, returning to its initial value when the droplet evaporates.
    IEEE Photonics Technology Letters 02/2009; · 2.04 Impact Factor
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    ABSTRACT: This paper shows the technology development of microneedles electrodes for living cell applications. The study includes the fabrication of cantilever electrodes to monitor individual cells. The technology is based on silicon micromachining by combining deep reactive ion etching and focused ion beam (FIB) nanomachining. Cell biology applications require micrometer size electrodes, smaller than living cells (~20 mum), and biocompatible materials. The metal electrode is fabricated in aluminum and passivated by silicon oxide. The opening of the tip electrode by FIB is also performed. Finally, the tip of the electrode is covered by a nanometer thick gold layer deposited by electroless to improved biocompatibility and electrochemical conductivity. The study also addresses questions concerning to the pre-treatment of the aluminum layer before gold deposition in other to improve the adherence and conductivity.
    01/2009;
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    ABSTRACT: In this paper it is shown the design and characterization of a differential electromagnetic sensor. In absence of the sample the output signal of the sensor is null. There will only be an output signal in the presence of a magnetic material or a conductive sample in which eddy currents are generated, producing an external magnetic field. This working principle is non invasive and improves greatly the possibilities for signal conditioning. The sensor has been tested with a copper sample and for detection of variations in the blood glucose concentration, showing high sensitivity and potentialities for other applications.
    Procedia Chemistry. 01/2009; 1(1):919-922.

Publication Stats

432 Citations
100.47 Total Impact Points

Institutions

  • 2006–2010
    • Barcelona Microelectronics Institute
      Barcino, Catalonia, Spain
  • 2008
    • San Diego Zoo
      San Diego, California, United States
    • Harvard University
      • Department of Chemistry and Chemical Biology
      Cambridge, MA, United States
  • 2007
    • Barcelona Media
      Barcino, Catalonia, Spain
  • 2002–2007
    • Institut Marqués, Spain, Barcelona
      Barcino, Catalonia, Spain
    • Fraunhofer Institute for Physical Measurement Techniques IPM
      Freiburg, Baden-Württemberg, Germany
    • University of Barcelona
      • Departament d'Electrònica
      Barcelona, Catalonia, Spain
  • 2004–2006
    • Technische Universität Braunschweig
      • Institut für Mikrotechnik
      Braunschweig, Lower Saxony, Germany
  • 1998–2006
    • Autonomous University of Barcelona
      Cerdanyola del Vallès, Catalonia, Spain