46 research outputs found
Impact of Planar and Vertical Organic Field‐Effect Transistors on Flexible Electronics
No full text: The development of flexible and conformable devices, whose performance can be maintained while being continuously deformed, provides a significant step towards the realization of next-generation wearable and e-textiles applications. Organic field-effect transistors (OFETs) are particularly interesting for flexible and lightweight products, because of their low-temperature solution processability, and the mechanical flexibility of organic materials that endows OFETs the natural compatibility with plastic and biodegradable substrates. Here, an in-depth review of two competing flexible OFET technologies, planar and vertical OFETs (POFETs and VOFETs, respectively) is provided. The electrical, mechanical, and physical properties of POFETs and VOFETs are critically discussed, with a focus on four pivotal applications (integrated logic circuits, light-emitting devices, memories, and sensors). It is pointed out that the flexible function of the relatively newer VOFET technology, along with its perspective on advancing the applicability of flexible POFETs, has not been reviewed so far, and the direct comparison regarding the performance of POFET- and VOFET-based flexible applications is most likely absent. With discussions spanning printed and wearable electronics, materials science, biotechnology, and environmental monitoring, this contribution is a clear stimulus to researchers working in these fields to engage towards the plentiful possibilities that POFETs and VOFETs offer to flexible electronics. This article is protected by copyright. All rights reserved
Advanced Neuromorphic Applications Enabled by Synaptic Ion-Gating Vertical Transistors
No full textAbstract Bioinspired synaptic devices have shown great potential in artificial intelligence and neuromorphic electronics. Low energy consumption, multi‐modal sensing and recording, and multifunctional integration are critical aspects limiting their applications. Recently, a new synaptic device architecture, the ion‐gating vertical transistor (IGVT), has been successfully realized and timely applied to perform brain‐like perception, such as artificial vision, touch, taste, and hearing. In this short time, IGVTs have already achieved faster data processing speeds and more promising memory capabilities than many conventional neuromorphic devices, even while operating at lower voltages and consuming less power. This work focuses on the cutting‐edge progress of IGVT technology, from outstanding fabrication strategies to the design and realization of low‐voltage multi‐sensing IGVTs for artificial‐synapse applications. The fundamental concepts of artificial synaptic IGVTs, such as signal processing, transduction, plasticity, and multi‐stimulus perception are discussed comprehensively. The contribution draws special attention to the development and optimization of multi‐modal flexible sensor technologies and presents a roadmap for future high‐end theoretical and experimental advancements in neuromorphic research that are mostly achievable by the synaptic IGVTs
Improvement of poly(3-hexylthiophene-2,5-diyl) electron mobility through complete elimination of regioregularity defects
No full textThe improvement of electron transport in polymer semiconductors is highly desirable for realizing robust, large-area and low-cost organic integrated circuits. This work investigates the effect of regioregularity on the intrinsic hole and electron transport characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) using current-voltage (I-V) measurements in metal/polymer/metal sandwich structures. Through a direct comparison between 93% regioregular P3HT (EG-P3HT) and 100% regioregular defect-free poly(3-hexylthiophene-2,5-diyl) (DF-P3HT), it is found that the elimination of regioregularity defects improves the electron mobility of DF-P3HT (1.05 × 10-7 cm2 V-1 s-1) by three orders of magnitude compared to the 93% regioregular EG-P3HT sample (1.82 × 10-10 cm2 V-1 s-1). Quantum chemical calculations indicate that the improvement of electron mobility in DF-P3HT can be associated to the lower degree of disorder in these samples that tends to increase the transfer angle between the lowest unoccupied molecular orbitals of adjacent chains. At the same time, the lower dipole moments produced by the defect-free polymer molecules also appears to play an important role in decreasing the susceptibility of charge transport to environment-induced electron traps. The obtained results provide a strong evidence that the elimination of regioregularity defects is an effective technique to improve electron transport and restore the symmetry between hole and electron mobility in P3HT as well as other thiophene-based polymers
Straining nanomembranes : InAs islands on compliant Si substrates and rolled-up metal microtubes for a SERS sensor with self-assembled monolayers
No full textOrientadores: Christoph Friedrich Deneke, Eduardo Granado Monteiro da SilvaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb WataghinResumo: Nanomembranas livres são definidas como filmes ultrafinos constituídos por metais, óxidos ou semicondutores, com espessuras nanométricas e vastas áreas superficiais. São obtidas em geral por um processo de subcorrosão seletiva de uma camada de sacrifício, cujo papel é liberá-las gradualmente, permitindo que o relaxamento da energia elástica nelas armazenada aconteça de maneira controlada, garantindo a integridade final das estruturas. Neste trabalho, nanomembranas livres de Si suportadas por um substrato de SOI foram utilizadas como substratos complacentes para o crescimento de ilhas de InAs em uma câmara de MBE. Além disso, nanomembranas metálicas tensionadas (Ag/Ti/Cr/Ag) foram utilizadas na obtenção de microtubos metálicos enrolados. Análises detalhadas da morfologia das amostras, das estruturas das ilhas e dos microtubos, do strain em ambos os sistemas e de suas possíveis aplicações foram realizadas. A microscopia eletrônica de varredura mostrou que as estruturas permaneceram íntegras após as deformações. A microscopia de força atômica revelou uma baixa densidade de ilhas no topo das nanomembranas de Si. Ademais, possibilitou o aperfeiçoamento de parâmetros superficiais das nanomembranas metálicas e o enrolamento de microtubos com diâmetros pré definidos, garantindo convergência com o modelo analítico. Técnicas de difração de raios X e modelagem por elementos finitos foram utilizadas para elucidar os estados de strain observados em ambas as estruturas. As simulações das curvaturas do substrato complacente de Si e do microtubo metálico sugeriram, respectivamente, um gradiente de strain dependente da posição lateral de cada ilha na nanomembrana e coeficientes de strain constantes nas nanomembranas de Ti e Cr. Finalmente, cálculos envolvendo elasticidade contínua sugeriram que para uma nanomembrana de Si com espessura adequada, o InAs pode transferir strain suficiente para possibilitar o crescimento epitaxial coerente. Ainda, medidas de espectroscopia Raman em moléculas auto organizadas de 1-octadecanethiol, adsorvidas em Ag e aprisionadas entre as paredes dos microtubos metálicos, sugeriram que tal sistema pode ser utilizado como um dispositivo SERS para self-assembled monolayersAbstract: Freestanding nanomembranes (NMs) are defined as metallic, semiconductor or oxide ultrathin films with nanometer thickness and macroscopic surface areas. In general, they are obtained by a process of selective underetching of a sacrificial layer, whose role is gradually release them, allowing relaxation of their stored elastic energy in a controlled way, ensuring integrity of the final structure. In this work, freestanding edge-supported Si nanomembranes are used as compliant substrate to the InAs growth on a SOI substrate in a MBE chamber. Furthermore, strained metallic nanomembranes (Ag / Ti / Cr / Ag) are used to obtain rolled-up metallic microtubes. A detailed analysis of sample morphology, InAs island and metallic microtube structure, strain on both systems and their possible applications is carried out. Scanning electron microscopy shows the structures stay intact during and after deformation. Atomic force microscopy reveals a lower island density on the top of the freestanding membranes. Moreover, it allowed optimizing the surface parameters of the strained metallic membranes, rolling-up tubes with pre-defined diameters and ensuring convergence with the proposed analytical model. X-ray diffraction and finite element modeling is used to elucidate the observed strain states in both structures. The bending simulations of compliant Si substrate and rolled up metallic microtube suggest, respectively, a lateral strain distribution depending on the island position on the freestanding membrane and a constant strain distribution on the Ti/Cr strained NMs. Finally, continuous elasticity calculations suggest that for a Si nanomembrane with adequate thickness, the InAs can transfer enough strain to enable coherent epitaxial growth. In addition, Raman spectroscopy measurements of 1-octadecanethiol self-assembled molecules adsorbed on an Ag nanomembrane and trapped between the microtube Ag walls suggest the system could be used as a SERS sensor for self-assembled monolayersMestradoFísicaMestre em Físic
Pushing On-Chip Photosensitivity Forward Using Edge-Driven Vertical Organic Phototransistors
No full textDeveloping high-performance photosensors using prototype device architectures is essential to pushing forward developing and advancing next-generation optoelectronic applications. This work reports an organic phototransistor (OPT) with an ultra-short conducting channel (tens of nanometers) and outstanding photoelectric conversion efficiency. The OPT is based on a vertical organic field-effect transistor (VOFET) architecture, which utilizes a rolled-up metallic nanomembrane (NM) as the drain electrode and a photolithographically patterned (rectangular-shaped) perforated source electrode. These features expand the concept of conventional VOFETs as the former enables the incorporation of ultra-thin active layers and allows reliable control over gate-induced modulation of channel current. Using the engineering as abovementioned strategies, we focused on obtaining an improved device performance, studying their fundamental operating principle, and further investigating their application as photosensors. The optimized devices exhibited low operating voltages (<5 V) and enhanced on/off current ratio (∼105). The VOFET photoresponse was characterized by measuring the electrical characteristics in the dark and under illumination using three different monochromatic light colors. Under blue light, our devices demonstrated impressive photosensitivity (Pmax ≈ 105) and fast photoelectric conversion (steep light-induced threshold voltage shift), demonstrating that the rolled-up NM OPT shows excellent potential as a highly sensitive photodetector with low power consumption
Streptococcus agalactiae: caracterização fenotípica e genotípica de amostras isoladas de espermocultura
No full textStreptococcus agalactiae (“Group B Streptococcus”, GBS) inicialmente foi reconhecido como causador de mastite bovina e é um importante patógeno causador de infecções em humanos. A detecção de S. agalactiae em espermocultura de pacientes com prostatite bacteriana crônica gerou interesse, pois pouco se sabe da associação desse microrganismo com quadros de prostatite e epididimite. Por isso, o objetivo deste estudo foi caracterizar amostras de GBS, isoladas a partir de espécimes clínicos de espermoculturas por métodos fenotípicos e genotípicos. Este estudo incluiu 49 cepas de GBS, provenientes de sêmen, isoladas em um
laboratório particular, entre os anos de 2019 e 2022. Inicialmente foi realizada uma identificação presuntiva dos isolados pelos métodos de coloração de Gram, teste de fator CAMP e teste da hidrólise do hipurato de sódio. A confirmação da identificação foi realizada utilizando-se a técnica de MALDI-TOF. A determinação do tipo capsular foi realizada utilizando-se o método de aglutinação em látex, com auxílio do kit Immulex Strep-B (SSI Diagnóstica, Dinamarca) e a determinação do perfil de susceptibilidade aos antimicrobianos foi realizada através da técnica de disco-difusão, seguindo as recomendações do CLSI. Os genes envolvidos na produção dos pili PI-1, PI-2a e PI-2b foram detectados através da metodologia de PCR uniplex. Todas as amostras foram avaliadas quanto à capacidade de produção de biofilme em placas de poliestireno. As amostras de GBS se apresentaram como cocos gram positivos, CAMP positivas, capazes de hidrolisar o hipurato de sódio e com escores de confiabilidade (≥ 2,0) por MALDI-TOF. A distribuição dos tipos sorológicos entre as amostras
demonstrou predominância do sorotipo V (28,6%), seguido dos sorotipos Ia (22,4%), Ib (14,3%), IV (14,3%), III (10,2%) e II (4,1%). Três amostras foram não tipáveis (NT= 6%). Quanto ao perfil de susceptibilidade, todas as amostras foram sensíveis a penicilina e vancomicina, enquanto a resistência a tetraciclina, levofloxacina, eritromicina e clindamicina foi observada, respectivamente, em 81,6% 8,2%, 44,8% e 16,3% das amostras. Ainda, 4 amostras (8%) demonstraram multirresistência após apresentarem perfil de resistência a levofloxacina, eritromicina, clindamicina, tetraciclina e cloranfenicol. Todas as amostras apresentaram, ao menos um tipo dos pili avaliados, sendo o pilus mais prevalente o PI-2a (50%) e a combinação PI-1 + PI-2a a predominante (30%). Um total de 93,9% das amostras demonstrou a capacidade de formar biofilme, sendo que 55,1% foram consideradas fortes produtores. Esses resultados trazem subsídios importantes por se tratar de um trabalho com dados inéditos quanto a caracterização fenotípica e genotípica de amostras de GBS provenientes de esperma no Brasil. Além disso, os dados aqui reportados, como as altas taxas de resistência,
a multirresistência e a ampla distribuição de importantes estruturas de virulência entre as amostras analisadas, nos alertam para a necessidade de uma maior vigilância sobre as amostras de GBS nesse contexto em nossa região
Edge-driven nanomembrane-based vertical organic transistors showing a multi-sensing capability
No full textThe effective utilization of vertical organic transistors in high current density applications demands further reduction of channel length (given by the thickness of the organic semiconducting layer and typically reported in the 100 nm range) along with the optimization of the source electrode structure. Here we present a viable solution by applying rolled-up metallic nanomembranes as the drain-electrode (which enables the incorporation of few nanometer-thick semiconductor layers) and by lithographically patterning the source-electrode. Our vertical organic transistors operate at ultra-low voltages and demonstrate high current densities (~0.5 A cm-2) that are found to depend directly on the number of source edges, provided the source perforation gap is wider than 250 nm. We anticipate that further optimization of device structure can yield higher current densities (~10 A cm-2). The use of rolled-up drain-electrode also enables sensing of humidity and light which highlights the potential of these devices to advance next-generation sensing technologies
O diálogo dos derrotados: imagens dos guerrilheiros na obra de B. Kucinski
No full textEste artigo investiga de que maneira a obra literária de Bernardo Kucinski formaliza a figura do guerrilheiro que entrou em combate contra a Ditadura Militar Brasileira (1964-1985). Busca-se comparar a visão do autor com a de outros escritores sobre o tema e entender em que medida Kucinski aproxima-se e distancia-se da memória hegemônica que a sociedade civil possui em relação à oposição armada ao regime. This article investigates how the literary works of Bernardo Kucinski formalize the character of the guerrilla fighters who engaged in combat against the Brazilian Military Dictatorship (1964-1985). It seeks to compare the author\u27s vision with that of other writers on the subject and to understand to what extent Kucinski comes close and distances himself from the hegemonic memory that civil society has regarding armed opposition to the regimen
Reorganization Energy upon Controlled Intermolecular Charge‐Transfer Reactions in Monolithically Integrated Nanodevices
No full textIntermolecular electron-transfer reactions are key processes in physics, chemistry, and biology. The electron-transfer rates depend primarily on the system reorganization energy, that is, the energetic cost to rearrange each reactant and its surrounding environment when a charge is transferred. Despite the evident impact of electron-transfer reactions on charge-carrier hopping, well-controlled electronic transport measurements using monolithically integrated electrochemical devices have not successfully measured the reorganization energies to this date. Here, it is shown that self-rolling nanomembrane devices with strain-engineered mechanical properties, on-a-chip monolithic integration, and multi-environment operation features can overcome this challenge. The ongoing advances in nanomembrane-origami technology allow to manufacture the nCap, a nanocapacitor platform, to perform molecular-level charge transport characterization. Thereby, employing nCap, the copper-phthalocyanine (CuPc) reorganization energy is probed, ≈0.93 eV, from temperature-dependent measurements of CuPc nanometer-thick films. Supporting the experimental findings, density functional theory calculations provide the atomistic picture of the measured CuPc charge-transfer reaction. The experimental strategy demonstrated here is a consistent route towards determining the reorganization energy of a system formed by molecules monolithically integrated into electrochemical nanodevices
Tradução, adaptação cultural e propriedades psicométricas da Hurt Insult Threatened Scream para rastreio da violência doméstica contra idosos no Brasil
No full textINTRODUCTION: The scientific literature has shown limitations in the production of screening instruments for violence against the elderly in the Brazilian context. Currently, this type of study has been little approached in the Brazilian context, regarding the cross-cultural adaptation of instruments for the elderly population. HITS- Brazil is a brief screening tool for domestic violence against the elderly, which can be used in clinical and domicile contexts, aiming at establishing the risk of violence. This study, because it deals with the translation and adaptation and validation of an instrument that does not originate nor Brazilian validation, followed rigorous methodological criteria in order to guarantee wide reliability and later be applied and used by other researchers for screening of RV against the elderly. OBJECTIVE: This study aimed to translate, adapt and evaluate the psychometric properties (validity and reliability) of the Hurt Insult Threatened Scream (HITS) instrument for the screening of domestic violence against the elderly. METHOD: Study of translation, adaptation and validation. A total of 30 elderly people were recruited for the operational equivalence phase and 48 elderly people aged 65 to 80 years or more of both sexes were recruited, mean age for the two stages was 70.8 years taking into account the two groups. Data on sociodemographic variables, cognitive ability and HITS application were collected. For the analysis of the results we used the descriptive and inferential statistics, for the operational equivalence stage, the equivalence of the items that happened in five stages that evaluated the semantic, idiomatic, experimental and conceptual equivalences for the Brazilian context was evaluated. After this process the measurement equivalence stage was started, which sought to evaluate the validity and reliability of the 48 elderly subjects. RESULTS: The study complied with the five stages of HITS transcultural translation and adaptation process: translations, back translations, synthesis of translations, semantic, idiomatic, experiential and conceptual equivalence analysis by a committee of experts and pre-test in 30 elderly people, which was followed by adjustments of language and concepts, reaching the final form of the instrument, named HITS-Brazil. The values obtained through Cronbach's alpha coefficient showed acceptable results for all items (item 1: 0.80, item 2: 0, 75, item 3: 0,80 and item 4: 0,68). In the analysis of inter-examiner agreement we had good agreement for items 1 and 2 and low agreement for items 3 and 4 of the scale. We considered that the low agreement in items 3 and 4 would not negatively imply the overall coxtext of the scale, since we have a high reliability by the cronbach alpha. CONCLUSION: In its final version, HITS-Brazil obtained a high reliability index for the four items when its internal consistency was evaluated, indicating that the results are satisfactory.INTRODUÇÃO: A literatura científica tem mostrado limitações na produção de instrumentos de rastreio para violência contra o idoso no contexto brasileiro. Atualmente, esse tipo de estudo tem sido pouco abordado na realidade do contexto brasileiro, no que concerne à adaptação transcultural de instrumentos destinados a população idosa. A HITS- Brasil trata-se de um instrumento de rastreio breve da violência doméstica contra a pessoa idosa, que pode ser utilizado em contextos clínicos e domiciliares, objetivando a constatação do risco de violência. Este estudo por se tratar da tradução e adaptação e validação de um instrumento que não possui origem nem validação brasileira seguiu critérios metodológicos rigorosos no intuito de garantir ampla confiabilidade e posteriormente ser aplicado e utilizado por outros pesquisadores para rastreio de VD contra o idoso. OBJETIVO: Este estudo teve como objetivo traduzir, adaptar e avaliar as propriedades psicométricas (validade e confiabilidade) do instrumento Hurt Insult Threatened Scream (HITS) para o rastreio da violência doméstica contra idosos. MÉTODO: Estudo de tradução, adaptação e validação. Foram recrutados, de forma aleatória 30 idosos para a fase de equivalência operacional e 48 idosos com idade entre 65 a 80 anos ou mais de ambos os sexos, a média de idade para as duas etapas foi de 70,8 anos levando em consideração os dois grupos. Dados sobre variáveis sociodemografica, capacidade cognitiva e aplicação da HITS foram coletados. Para análise dos resultados foi utilizado a estatística descritiva e inferencial, para etapa da equivalência operacional foi avaliada a equivalência dos itens que aconteceu em cinco etapas que avaliou as equivalências semântica, idiomática, experimental e conceitual para o contexto brasileiro. Após esse processo foi dado início a etapa de equivalência de mensuração que buscou avaliar a validade e confiabilidade nos 48 idosos. RESULTADOS: O estudo cumpriu as cinco etapas do processo de tradução e adaptação transcultural da HITS, sendo elas: traduções, retrotraduções, síntese das traduções, análise da equivalência semântica, idiomática, experiencial e conceitual por um comitê de experts e pré-teste em 30 idosos, o qual foi seguido de ajustes da linguagem e conceitos, alcançando a forma final do instrumento, nomeado HITS-Brasil. Os valores obtidos através do Coeficiente do alfa de Cronbach mostraram resultados de aceitáveis para todos os itens (item 1: 0,80 ; item 2: 0, 75; item 3: 0,80 e item 4:0,68). Na análise da concordância interexaminador tivemos boa concordância para os itens 1 e 2 e baixa concordância pra os itens 3 e 4 da escala. Consideramos que a baixa concordância nos itens 3 e 4 não implicaria de forma negativa no coxtexto geral da escala, uma vez que temos uma alta confiabilidade pelo alfa de cronbach. CONCLUSÃO: Em sua versão final, a HITS-Brasil obteve índice de fidedignidade alto para os quatro itens quando avaliado a sua consistência interna, indicando que os resultados são satisfatórios
