J.A. Plaza

Barcelona Microelectronics Institute, Barcino, Catalonia, Spain

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Publications (128)278.93 Total impact

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    ABSTRACT: 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 cell-internalizable 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 μm2. 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 multi-functional. Hence, and as a proof of concept, two different proteins, Wheat Germ Agglutinin (WGA) and Concanavalin (ConA), were 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. Eventually, two different dyes (Oregon Green® 488 and BODIPY® 581/591) were used to bi-functionalize each surface of the multi-material chip in order to demonstrate that functional chips can also be internalized in living cells. These devices have a promising future as intracellular functional platforms for biosensing, drug delivery and diagnosis.
    Sensors and Actuators B Chemical 03/2015; 209:212-224. DOI:10.1016/j.snb.2014.11.077 · 3.84 Impact Factor
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    ABSTRACT: We present a study for the development of flexible microfilters based on sealing microstructured poly(dimethylsiloxane) (PDMS) to different functionalized thermoplastic films [polyimide (PI), polyethylene naphthalate (PEN), and polyethylene terephthalate (PET)]. The microfilter was manufactured by soft-lithography and replica molding and then combined with plasma activation and chemical treatment using 3-(aminopropyl)triethoxysilane (APTES). To demonstrate the functionality of the PDMS microfilters, poly(lactic-co-glycolic acid) (PLGA) microparticles (MPS) were filtered through the microfluidic device based on the three thermoplastic films. Subsequently, the mixing capabilities of a passive PDMS micromixer was observed with the injection of polymeric MPS (fluorescent and nonfluorescent) as fluidic mixers are not generally effective at mixing particles. On mixing nonfluorescent MPS (∼<10–30 µm in diameter) a mixing performance of 13.3% at 5 mm was observed. Therefore, a PDMS microfiltering device was integrated with a PDMS micromixer using a simple and cost effective home-made polymeric connector for filtration at a size sorting of 11 µm. The results exhibit that the combination of the two microfluidic devices can be achieved with size sorting and mixing of MPS with an improved mixing performance of 62.5% at 3 mm. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42088.
    Journal of Applied Polymer Science 03/2015; DOI:10.1002/app.42088 · 1.64 Impact Factor
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    ABSTRACT: The adhesion of small silicon chips to cells has many potential applications as direct interconnection of the cells to the external world can be accomplished. Hence, although some typical applications of silicon nanowires integrated in microsystems are focused on achieving a Cell-on-a-Chip strategy, we are interested in obtaining Chip-on-a-Cell systems. This paper reports the design, technological development and characterization of polysilicon barcodes featuring silicon nanowires as nanoscale attachment to identify and track living mouse embryos during their in vitro development. Chips are attached to the outer surface of the Zona Pellucida, the cover that surrounds oocytes and embryos, to avoid the direct contact between the chip and the embryo cell membrane. Two attachment methodologies, Rolling and Pushpin, which allow two entirely different levels of applied forces to attach the chips to living embryos, are evaluated. The former consists of rolling the mouse embryos over one barcode with the silicon nanowires facing upwards, while in the latter the barcode is pushed against the embryo with a micropipette. The effect on in vitro embryo development and the retention rate related to the calculated applied forces are stated. Field emission scanning electron microscopy inspection, which allowed a high resolution imaging, also confirms the physical attachment of the nanowires with some of them piercing or wrapped by the Zona Pellucida and revealed extraordinary bent silicon nanowires.
    Lab on a Chip 01/2015; 15(6). DOI:10.1039/C4LC01299B · 5.75 Impact Factor
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    ABSTRACT: Magnetically-actuable, polymer-based variable optical attenuators (VOA) are presented in this paper. The design comprises a cantilever which also plays the role of a waveguide and the input/output alignment elements for simple alignment, yet still rendering an efficient coupling. Magnetic properties have been conferred to these micro-opto-electromechanical systems (MOEMS) by implementing two different strategies: in the first case, a magnetic sensitive stimuli material (M-SSM) is obtained by a combination of polydimethylsiloxane (PDMS) and ferrofluid (FF) in ratios between 14.9 wt % and 29.9 wt %. An M-SSM strip under the waveguide-cantilever, defined with soft lithography (SLT), provides the required actuation capability. In the second case, specific volumes of FF are dispensed at the end of the cantilever tip (outside the waveguide) by means of inkjet printing (IJP), obtaining the required magnetic response while holding the optical transparency of the waveguide-cantilever. In the absence of a magnetic field, the waveguide-cantilever is aligned with the output fiber optics and thus the intrinsic optical losses can be obtained. Numerical simulations, validated experimentally, have shown that, for any cantilever length, the VOAs defined by IJP present lower intrinsic optical losses than their SLT counterparts. Under an applied magnetic field (Bapp), both VOA configurations experience a misalignment between the waveguide-cantilever and the output fiber optics. Thus, the proposed VOAs modulate the output power as a function of the cantilever displacement, which is proportional to Bapp. The experimental results for the three different waveguide-cantilever lengths and six different FF concentrations (three per technology) show maximum deflections of 220 µm at 29.9 wt % of FF for VOASLT and 250 µm at 22.3 wt % FF for VOAIJP, at 0.57 kG for both. These deflections provide maximum actuation losses of 16.1 dB and 18.9 dB for the VOASLT and VOAIJP, respectively.
    Journal of Micromechanics and Microengineering 12/2014; 24(12). DOI:10.1088/0960-1317/24/12/125008 · 1.73 Impact Factor
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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; 215. DOI:10.1016/j.sna.2014.01.021 · 1.94 Impact Factor
  • Atherosclerosis 08/2014; 235(2):e227. DOI:10.1016/j.atherosclerosis.2014.05.675 · 3.97 Impact Factor
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    ABSTRACT: The low number of oocytes collected from unstimulated donors by ovum pick-up means that embryos produced from each individual female have to be cultured individually or in very small groups. However, it has been demonstrated that single-embryo culture is less efficient than embryo culture in groups. To overcome this limitation, we developed a direct embryo-tagging system, which allows the collective culture of embryos from different origins whilst preserving their pedigree. Presumptive bovine zygotes were tagged with eight wheat-germ agglutinin biofunctionalised polysilicon barcodes attached to the outer surface of the zona pellucida (ZP). Four different barcodes were used to encode groups of 20-25 embryos, which were then cultured in the same drop. Cleavage, Day-7 and Day-8 blastocysts and barcode retention rates were assessed. In addition, Day-7 blastocysts were vitrified and warmed. Barcode attachment to the ZP of bovine embryos affected neither in vitro embryo development nor post-warming survival of the tagged embryos. All the embryos maintained barcodes attached until Day 8 of culture (3.63±0.37 barcodes per embryo) and could be identified. In conclusion, identification of embryos by barcodes attached to the ZP is feasible and will allow the culture of embryos from different donors in the same drop.
    Reproduction Fertility and Development 06/2014; 26(5):645-52. DOI:10.1071/RD13066 · 2.58 Impact Factor
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    ABSTRACT: This work presents a polydimethylsiloxane (PDMS) system (named microbridle) monolithically integrating optical (microlenses, air mirrors etc.) and mechanical elements (cantilever) for the real time monitoring of dilatation and contraction events in small resistance arteries. Structural (response to intraluminal pressure changes) and functional properties (response to vasoactive substances) of mesenteric arteries were determined with the microbridle structure and compared to those obtained with conventional myograph systems. Both systems provide comparable data although microbridles were found advantageous in terms of precision, resolution (below the μm) and reliability for the poor contrast between sample and surrounding medium that impede reliable myography recordings.
    2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS); 01/2014
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    ABSTRACT: 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.
    Colloids and surfaces B: Biointerfaces 12/2013; 116C:104-113. DOI:10.1016/j.colsurfb.2013.12.053 · 4.29 Impact Factor
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    ABSTRACT: 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)? 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. 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. Fresh immature and mature fertilization-failed oocytes (n = 21) and cryopreserved day 1 embryos produced by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) (n = 205) were donated by patients (n = 76) undergoing ARTs. In vitro development rates, embryo quality and post-vitrification survival were compared between tagged (n = 106) and non-tagged (control) embryos (n = 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. 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 time-lapse monitoring. Injected oocytes were parthenogenetically activated using ionomycin and 6-dimethylaminopurine. 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. Although the direct embryo tagging system developed is effective, it only allows the identification and traceability of oocytes destined for ICSI and embryos. Thus, the traceability of all reproductive samples (oocytes destined for IVF and sperm) is not yet ensured. The direct embryo tagging system developed here provides fertility clinics with a novel tool to reduce the risk of mix-ups in human ARTs. The system can also be useful in research studies that require the individual identification of oocytes or embryos and their individual tracking. This study was supported by the Sociedad Española de Fertilidad, the Spanish Ministry of Education and Science (TEC2011-29140-C03) and the Generalitat de Catalunya (2009SGR-00282 and 2009SGR-00158). The authors do not have any competing interests.
    Human Reproduction 11/2013; 29(1). DOI:10.1093/humrep/det409 · 4.59 Impact Factor
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    ABSTRACT: The ability to measure pressure changes inside different components of a living cell is important, because it offers an alternative way to study fundamental processes that involve cell deformation. Most current techniques such as pipette aspiration, optical interferometry or external pressure probes use either indirect measurement methods or approaches that can damage the cell membrane. Here we show that a silicon chip small enough to be internalized into a living cell can be used to detect pressure changes inside the cell. The chip, which consists of two membranes separated by a vacuum gap to form a Fabry-Pérot resonator, detects pressure changes that can be quantified from the intensity of the reflected light. Using this chip, we show that extracellular hydrostatic pressure is transmitted into HeLa cells and that these cells can endure hypo-osmotic stress without significantly increasing their intracellular hydrostatic pressure.
    Nature Nanotechnology 06/2013; DOI:10.1038/nnano.2013.118 · 33.27 Impact Factor
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    ABSTRACT: 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 cultured embryos? SUMMARY ANSWER: The results achieved provide a proof of concept for a direct embryo tagging system using biofunctionalized polysilicon barcodes, which could help to minimize the risk of mismatching errors (mix-ups) in human assisted reproduction technologies. WHAT IS KNOWN ALREADY: Even though the occurrence of mix-ups is rare, several cases have been reported in fertility clinics around the world. Measures to prevent the risk of mix-ups in human assisted reproduction technologies are therefore required. STUDY DESIGN, SIZE, DURATION: Mouse embryos were tagged with 10 barcodes and the effectiveness of the tagging system was tested during fresh in vitro culture (n=140) and after embryo cryopreservation (n = 84). Finally, the full-term development of tagged embryos was evaluated (n =105). PARTICIPANTS/MATERIALS, SETTING, METHODS: Mouse pronuclear embryos were individually rolled over wheat germ agglutinin-biofunctionalized polysilicon barcodes to distribute them uniformly around the ZONA PELLUCIDA surface. Embryo viability and retention of barcodes were determined during 96 h of culture. The identification of tagged embryos was performed every 24 h in an inverted microscope and without embryo manipulation to simulate an automatic reading procedure. Full-term development of the tagged embryos was assessed after their transfer to pseudo-pregnant females. To test the validity of the embryo tagging system after a cryopreservation process, tagged embryos were frozen at the 2-cell stage using a slow freezing protocol, and followed in culture for 72 h after thawing. MAIN RESULTS AND THE ROLE OF CHANCE: Neither the in vitro or in vivo development of tagged embryos was adversely affected. The tagging system also proved effective during an embryo cryopreservation process. Global identification rates higher than 96 and 92% in fresh and frozen-thawed tagged embryos, respectively, were obtained when simulating an automatic barcode reading system, although these rates could be increased to 100% by simply rotating the embryos during the reading process. LIMITATIONS, REASONS FOR CAUTION: The direct embryo tagging developed here has exclusively been tested in mouse embryos. Its effectiveness in other species, such as the human, is currently being tested. WIDER IMPLICATIONS OF THE FINDINGS: The direct embryo tagging system developed here, once tested in human embryos, could provide fertility clinics with a novel tool to reduce the risk of mix-ups in human assisted reproduction technologies. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by Spanish Ministry of Education and Science (TEC2011-29140-C03) and by the Generalitat de Catalunya (2009SGR-00282). The authors do not have any competing interest.
    Human Reproduction 03/2013; 28:1519-27. DOI:10.1093/humrep/det083 · 4.59 Impact Factor
  • Human Reproduction; 01/2013
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    ABSTRACT: Over the past few years, a growing interest on covalent bonding of polydimethylsiloxane (PDMS) microfluidic devices to thermoplastic films has developed due to reduced costs, biocompatibility, and flexibility. The silane reagent, 3-aminopropyltriethoxysilane (APTES) has been applied to create this bonding. Here, we report on the fabrication of replica PDMS micromixer devices from a silicon mold using soft lithography that is rapid, facile, and cost-effective to manufacture. After replica molding, the PDMS micromixer devices were bonded to the APTES-activated thermoplastic films of polyimide, polyethylene terephthalate, and polyethylene naphthalate. Characterization of these thermoplastic surfaces was analyzed by contact angle measurement, surface free energy, and X-ray photoelectron spectroscopy. To demonstrate the functionality of this technology, we have analyzed the PDMS micromixers by a peel test, nonleakages, and mixing with the injection of inks, a surfactant, and varying pH solutions. To our knowledge, this is the first reported example in literature of the PDMS–APTES–thermoplastic films preparation that integrates a complex micromixer device. Here, we have established that the hydrophobicity of both sealed polymers required alteration in order for dispersion of a polar liquid in the mixing loops. The application of a polar solvent before injection can remedy this ill effect formulating a hydrophilic micromixer. These preliminary results demonstrate the feasibility of the fabrication technology, bonding technique, and application of the micromixer that, once optimized, can eventually integrate more components to formulate a lab-on-a-chip with the fabrication of gold microelectrodes for biological analysis of blood or plasma. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
    Journal of Polymer Science Part A Polymer Chemistry 01/2013; 51(1):59-70. DOI:10.1002/pola.26387 · 3.54 Impact Factor
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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
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    ABSTRACT: 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 to it, 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 bio-activity. 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.
    Bioconjugate Chemistry 11/2012; 23:2392-2402. DOI:10.1021/bc3004205 · 4.82 Impact Factor
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    ABSTRACT: Prussian-blue analogues (PBA) are a family of molecule-based magnetic compounds of general formula AxMy[M’(CN)6]z, whose magnetic properties can be tuned by an external stimulus. This tunability makes PBA good candidates for their integration into new electronic or spintronic devices. As a previous step to accomplish this integration, PBA need to be deposited onto surfaces in controllable ways and if possible into specific positions on the surface. Even though the study of PBA has traditionally been limited to bulk, lately they have also been processed as nanoparticles (NPs). Here an efficient approach is presented for the accurate deposition and organization of PBA-NPs of different sizes (from ∼6 to ∼25 nm) over silicon surfaces. The approach used in this work, relies on a combination of surface functionalization with local oxidation nanolithography (LON) and uses electrostatic interactions between PBA-NPs and a charged self-assembled monolayer patterned on specific parts of the silicon surface. By using atomic force microscopy (AFM), magnetometry, infrared spectroscopy (IR) and auger electron spectroscopy (AES) we show that the deposition process does not affect NPs properties. In addition, we present a study on the evolution of AFM nanolithographed SiO2 patterns under sonication.
    Advanced Functional Materials 09/2012; 22(17). DOI:10.1002/adfm.201200067 · 10.44 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. DOI:10.1088/0960-1317/22/2/025023 · 1.73 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. DOI:10.1088/0957-4484/22/50/505301 · 3.67 Impact Factor

Publication Stats

870 Citations
278.93 Total Impact Points

Institutions

  • 2006–2015
    • Barcelona Microelectronics Institute
      Barcino, Catalonia, Spain
    • Technische Universität Braunschweig
      • Institut für Mikrotechnik
      Braunschweig, Lower Saxony, Germany
  • 2006–2013
    • Institut Marqués, Spain, Barcelona
      Barcino, Catalonia, Spain
  • 1998–2010
    • Autonomous University of Barcelona
      Cerdanyola del Vallès, Catalonia, Spain
  • 1997–2008
    • Spanish National Research Council
      • National Microelectronics Center
      Madrid, Madrid, Spain
  • 2007
    • Polytechnic University of Catalonia
      • Department of Mechanical Engineering (EM)
      Barcino, Catalonia, Spain
  • 2005
    • Barcelona Science Park
      Barcino, Catalonia, Spain
  • 2003
    • University of Barcelona
      Barcino, Catalonia, Spain
  • 2002
    • Fraunhofer Institute for Physical Measurement Techniques IPM
      Freiburg, Baden-Württemberg, Germany