Arrays of gold microelectrodes made from split integrated circuit chips

A simple and inexpensive way to fabricate arrays of gold microelectrodes is proposed. Integrated circuit chips are sawed through their middle, normal to the longest axis, leading to destruction of the silicon circuit and rupture of the gold wires that interconnect it with the external terminals. Polishing the resulting rough surface converts the tips of the wires embedded in the chip halves into arrays of gold microdisks of about 25 mu m diameter. The number of active microelectrodes (MEs), of an array depends on the number of pins in the chip, n, being typically (n/2)-4. These MEs can be used individually or externally interconnected in any combination. X-ray images of the chips and micrographs of the resulting surface of the polished arrays have revealed variable distances between neighbor MEs, which are, however, larger than 10 times the radius of the disks. This feature of the MEs prevents diffusional cross-talk between electrodes. The use of these microdisk electrodes for analytical purposes exhibits sigmoidal voltammograms, and chronoamperometric experiments confirm the nonlinear i vs. t(1/2) plots, typical for processes where radial diffusion prevails. Satisfactory uniformity was observed for the response of each electrode of an array, indicating similarity of geometry and disk areas. The potentialities of these MEs were demonstrated by the determination of cadmium at ppb levels using square wave voltammetry with preconcentration. Due to the relative ease with which these MEs can be manufactured and their good performance in (chemical) analysis, wide applications in electrochemistry and electroanalysis is envisioned.

Flow-through cell based on an array of gold microelectrodes obtained from modified integrated circuit chips

The construction of a flow-through cell incorporating an array of gold microelectrodes is described and its application to flow injection analysis with amperometric detection is presented, Simple modification of almost any conventional integrated circuit chip, used as an inexpensive source of pre-assembled gold micro-wires, leads to the rapid and successful preparation of arrays of 8-48 elements, the polymeric encapsulation material from the top face of the chip is removed by abrasion until the gold micro-mires (used to interconnect the silicon circuit to the external contact pins of the chip) are disrupted and their transversal (elliptical) sections become exposed. Once polished, the flat and smooth top surface of the gold microelectrode-array chip (MEAC) is provided with a spacer and fitted under pressure against an acrylic block with the reference and auxiliary electrodes, to form the electrochemical (thin-layer) flow cell, while the contact pins are plugged into a standard IC socket, This design ensures autonomous electric contact with each electrode and allows fast dismantling for polishing or substitution, the performance of flow cells with MEACs was investigated utilizing the technique of reverse pulse amperometry without oxygen removal, A method was established for the determination of the copper concentration in sugar cane spirit, regulated by law for beverages, Samples from industrial producers and small-scale (alembic) brewers were compared, With a 24 MEAC, a detection limit of 30 mu g I-l of copper (4.7 x 10(-7) mol l(-1) of Cu-II for 100 mu l injections) was calculated, Routine operation was established at a frequency of 60-90 determinations per hour, Intercomparison with atomic absorption spectrometric determinations resulted in excellent agreement.

Properties of individual YBCO layers in a two-layered design for energy-efficient digital data cables

We are developing two-layered Yttrium Barium Copper Oxide (YBCO) thin film structures for energy efficient data links for superconducting electronics and present the results of their property measurements. High temperature superconductors (HTS) are advantageous for the implementation of energy-efficient cables interconnecting low temperature superconductor-based circuits and other cryogenic electronics circuits at higher temperature stages. The advantages of the HTS cables come from their low loss and low dispersion properties, allowing ballistic transfer of low power signals with very high bandwidth, low heat conduction and negligible inter-line crosstalk. The microstrip line cable geometry for typical materials is a two-layered film, in which the two superconducting layers are separated by an insulation layer with a minimized permittivity. We have made a proof of concept design of two YBCO films grown by pulsed laser deposition and then assembled into a sandwich with uniform insulating interlayer of tens of micrometers thick. We report on results obtained from such systems assembled in different ways. Structural and electromagnetic properties have been examined on individual films and on the corresponding sandwich composite. © 2013 IEEE.

Reconfiguração de alimentadores em sistemas de distribuição usando a metaheurística GRASP

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Algoritmo GRASP especializado aplicado ao problema de reconfiguração de alimentadores em sistemas de distribuição radial

Pós-graduação em Engenharia Elétrica - FEIS

Sistema silvipastoril com Myracrodruon urundeuva Fr. All. como alternativa de sustentabilidade

Pós-graduação em Agronomia - FEIS

Análise do 'LA''CR'O IND.3' dopado com 'SR' e 'CO',preparados via reação de combustão, utilizando difração de raios X com aplicação do método de Rietveld

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ecologia da paisagem para avaliação da idoneidade de redes ecológicas, como subsídio para o planejamento territorial

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Experimentação e educação ambiental: contribuições metodológicas

During the last centuries, the human being have been considered the center of the universe. The man believed that nature was at his disposal. Appropriated their processes, their cycles changed, redefined their spaces. Today, when faced with an environmental crisis which threatens the planet life, including the human life, the Science Education can contribute to a reconstruction of man-nature relationship in other terms. The transformation of teaching practices in the school environment, to be reflective, it is still a process that challenges the vast majority of teachers. As has been indicated by Guerra (2004), among others, the traditional teaching of content delivery is still very strong and certainly more deeply embedded in ideas and activities of the teachers who focus on environmental education. With it, a theory and pedagogical discourses in critical-reflexive actions is still a major obstacle. Therefore, new proposals for education and continuing education activities need to be formulated and presented based on the characteristics and needs breathing. Therefore propose changes in the way of teaching, where there is more room for a theory and praxis alone or with a only scientific truth. The scenery of society requires that knowledge is constructed to interconnect all disciplines, joining theory and practice so we can understand the whole and their relations in an integrated manner. It was proposed here a way to build a school and applying theoretical and practical activities involving experimental and seeking to meet the principles of Environmental Education for the training of citizens aware and critical. At the same time cares to use textbooks very rich in its pedagogical character that are present in schools and often are, forgotten and unused by teachers. From this way, I chose to Experimentoteca, ...(Complete abstract click electronic access below)

O papel das redes de transformação no processo de inovação: estudos de caso sobre a descoberta e a comercialização da inovação

Innovation is widely recognized as important. In addition, in this context, innovation networks have gained importance in academic studies, since an organization alone, does not always have access to all necessary resources. Gobbo Junior and Olsson (2010) proposed a model of network innovation whereby the transformation networks would be the linking structures between exploration and exploitation networks. In this context, this paper presents two case studies of innovation networks, aiming to increase the understanding on transformation networks. The objective was to understand how they interconnect exploration and exploitation networks; the main actors present in this interface; and to evaluate whether these actors can act as agents, to accelerate the innovation process. It was possible to verify how the transformation networks interconnect exploration and exploitation, and identify the practices and their main actors.