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Advisor(s)
Abstract(s)
O principal objetivo deste trabalho consistiu no desenvolvimento de uma nova formulação para tintas
condutoras tendo por base o PEDOT:PSS e a preparação de camadas finas com elevada condutividade e
resistentes à água, que possam ser utilizadas em dispositivos elétricos com aplicações no campo da
bioeletrónica. Para tal, foi utilizado um composto oxetano, o 3-oxetanometanol, como aditivo em dispersões
aquosas de PEDOT:PSS. A partir da análise das propriedades relevantes das camadas finas preparadas em
substratos de vidro, pelas técnicas de espetroscopia de absorção UV-visível, medição da condutividade pelo
método de quatro pontos, microscopia de força atómica (AFM), espetroscopia de Raman, espetroscopia de
ressonância magnética nuclear, e medição do ângulo de contacto, foi possível demonstrar que as novas
formulações originaram filmes finos que apresentam uma maior resistência à água e condutividade muito
superior, em mais de duas ordens de grandeza (o valor máximo obtido foi de 596 S/cm), em relação a filmes
obtidos com a dispersão original de PEDOT:PSS. Adicionalmente, foi determinada a estrutura química básica
dos produtos reacionais formados a partir do oxetano nos filmes de PEDOT:PSS e propor uma explicação para
os aumentos de condutividade verificados. A aplicação das dispersões de PEDOT:PSS com 3-oxetanometanol
foi explorada por duas técnicas diferentes de deposição, spin-coating e impressão a jato de tinta com alta
resolução. Embora os trabalhos desenvolvidos na impressora de alta resolução tenham sido limitados por
alguns problemas técnicos da mesma, foi possível obter filmes com condutividade aumentada, depositados
em vidro, utilizando uma das formulações desenvolvidas, embora não se tenham obtido condutividades tão
altas como nos filmes preparados por spin-coating. Paralelamente ao estudo dos filmes finos em substratos de
vidro, as novas dispersões de PEDOT:PSS com 3-oxetanometanol foram depositadas em substratos flexíveis
de Poli(tereftalato de etileno) (PET), tendo-se obtido com condutividades da mesma ordem de grandeza que a
dos filmes depositados em vidro, embora os filmes fossem mais heterogéneos, em termos da sua espessura
ao longo do substrato. Por fim, foi explorada a aplicação de uma das novas formulações na produção de um transístor eletroquímico depositado em vidro, para operar com eletrólitos aquosos, utilizando-se para tal, uma impressora a jato de tinta de alta resolução. Apesar da estabilidade do desempenho dos dispositivos se ter revelado baixa, a caracterização dos transístores, com uma solução eletrolítica de KCl, demonstrou modulação da corrente, como desejado, demonstrando assim a potencial aplicação da formulação, como tinta condutora, em dispositivos elétricos que operam em meios aquosos.
The main objective of this work consisted of the development of a new formulation for conducting inks based on PEDOT:PSS and the preparation of thin layers exhibiting high conductivity and water resistance, which can be used in electronic devices with applications in the field of bioelectronics. To this end, an oxetane compound, 3-oxetanemethanol, is used as an additive in aqueous dispersions of PEDOT:PSS. From the analysis of the relevant properties of the thin layers prepared on glass substrates, by the techniques of UV-visible absorption spectroscopy, conductivity measurements by the four-point method, atomic force microscopy (AFM), Raman spectroscopy, nuclear magnetic resonance spectroscopy, and contact angle measurements, it was possible to demonstrate that the new formulations originated thin films that presented a better water resistance and much higher conductivity, by more than two orders of magnitude (the maximum value obtained was 596 S/cm), than the films obtained with the original PEDOT:PSS dispersion. In addition, it was determined the basic chemical structure of the reaction products formed from the oxetane compound in PEDOT:PSS films and an explanation for the observed increases in conductivities was proposed. The application of PEDOT:PSS dispersions with 3-oxetanemethanol was explored by two different deposition techniques, spin-coating and high-resolution inkjet printing. Although the work developed on the high-resolution printer was limited by some technical problems of the printer, it was possible to obtain films with improved conductivity deposited on glass, using one of the developed formulations, although the conductivities were not as high as in the films prepared by spin-coating. In parallel to the study of thin films on glass substrates, the new PEDOT:PSS mixtures with 3-oxetanemethanol were deposited on flexible Polyethylene terephthalate (PET) substrates, for which conductivities of the same order of magnitude as those of films deposited on glass were found, although the films were more heterogeneous, in terms of their thickness along the substrate. Finally, the application of one of the new formulations was explored in the production of an electrochemical transistor deposited on glass to operate with aqueous electrolytes, using a high-resolution inkjet printer. Although the stability of the device performance was low, the characterization of the transistors, with an electrolytic solution of KCl, demonstrated current modulation, as desired, thus demonstrating the potential application of the formulation, as a conductive ink, in electronic devices operating in aqueous media.
The main objective of this work consisted of the development of a new formulation for conducting inks based on PEDOT:PSS and the preparation of thin layers exhibiting high conductivity and water resistance, which can be used in electronic devices with applications in the field of bioelectronics. To this end, an oxetane compound, 3-oxetanemethanol, is used as an additive in aqueous dispersions of PEDOT:PSS. From the analysis of the relevant properties of the thin layers prepared on glass substrates, by the techniques of UV-visible absorption spectroscopy, conductivity measurements by the four-point method, atomic force microscopy (AFM), Raman spectroscopy, nuclear magnetic resonance spectroscopy, and contact angle measurements, it was possible to demonstrate that the new formulations originated thin films that presented a better water resistance and much higher conductivity, by more than two orders of magnitude (the maximum value obtained was 596 S/cm), than the films obtained with the original PEDOT:PSS dispersion. In addition, it was determined the basic chemical structure of the reaction products formed from the oxetane compound in PEDOT:PSS films and an explanation for the observed increases in conductivities was proposed. The application of PEDOT:PSS dispersions with 3-oxetanemethanol was explored by two different deposition techniques, spin-coating and high-resolution inkjet printing. Although the work developed on the high-resolution printer was limited by some technical problems of the printer, it was possible to obtain films with improved conductivity deposited on glass, using one of the developed formulations, although the conductivities were not as high as in the films prepared by spin-coating. In parallel to the study of thin films on glass substrates, the new PEDOT:PSS mixtures with 3-oxetanemethanol were deposited on flexible Polyethylene terephthalate (PET) substrates, for which conductivities of the same order of magnitude as those of films deposited on glass were found, although the films were more heterogeneous, in terms of their thickness along the substrate. Finally, the application of one of the new formulations was explored in the production of an electrochemical transistor deposited on glass to operate with aqueous electrolytes, using a high-resolution inkjet printer. Although the stability of the device performance was low, the characterization of the transistors, with an electrolytic solution of KCl, demonstrated current modulation, as desired, thus demonstrating the potential application of the formulation, as a conductive ink, in electronic devices operating in aqueous media.
Description
Trabalho final de Mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica
Keywords
Polímeros condutores PEDOT:PSS Oxetano Filmes finos Impressão a jato de tinta Transístor eletroquímico Conducting polymers PEDOT:PSS Oxetane Thin films Inkjet printing Electrochemical transistors
Citation
PRÍNCIPE, Cátia Alexandra Cordeiro - Desenvolvimento de novas formulações de tintas condutoras para aplicações em bioeletrónica. Lisboa: Instituto superior de Engenharia de Lisboa, 2022. Dissertação de Mestrado.