Orientador: Neri Alves / Resumo: Nesta tese de doutorado são apresentados resultados a respeito da fabricação e caracterização de dois tipos de transístores com eletrólito no gate (EGTs, do inglês Electrolyte Gated Transistors): Transístores eletroquímicos orgânicos (OECTs, do inglês Organic Electrochemical Transistors) e transístores de dupla camada elétrica (EDLTs, do inglês Electric Double Layer Transistor). Os dispositivos foram produzidos utilizando inkjet printing e screen printing para imprimir soluções à base de polímeros como o poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), precursores de óxido de zinco e de nanopartículas de óxido zinco. Como eletrólito de gate foram utilizadas faixas auto sustentáveis de íon gel à base de celulose. Esse último foi desenvolvido por pesquisadores do CEMOP/CENIMAT e combina a alta mobilidade iônica dos eletrólitos líquidos com a plasticidade dos eletrólitos sólidos. Sua estrutura em gel possibilita que o material seja moldado ou cortado de acordo com a aplicação. Os ECTs foram fabricados em arquitetura planar sobre substrato de vidro ou de papel, onde foram impressos: PEDOT:PSS como semicondutor e carbono como eletrodos. Os resultados mostram uma forte dependência de parâmetros como: corrente no estado ligado (Ion), no estado desligado (Ioff), transcondutância, razão Ion/Ioff, morfologia da superfície do substrato e a rugosidade. Os EDLTs foram fabricados usando síntese de auto combustão e foto-ativação química para produzir dispositivos com baix... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: On this doctoral thesis is presented results of the manufacture and characterization of two types of Electrolyte-gated Transistors (EGTs): Organic Electrochemical Transistors (OECTs) and electric double-layer transistors (EDLTs). Devices were manufactured using inkjet printing and screen printing to print solutions based on polymers such as poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS), zinc oxide precursors and zinc oxide nanoparticles. Self-sustainable bands of cellulose-based ion gel were used as gate electrolyte. The last was developed by researchers from CEMOP/CENIMAT and combines the high ion mobility of liquid electrolytes with the plasticity of solid electrolytes. This gel structure allows this material to be shaped or cut according to the application. The ECTs were manufactured in planar architecture over glass or paper substrates, where they were printed: PEDOT: PSS as semiconductor and carbon as electrodes. The results presents a strong dependence on parameters such as: on-state current (Ion), off-state current (Ioff), transconductance, Ion/Ioff ratio, surface morphology of the substrate and roughness. The EDLTs were manufactured using auto-combustion synthesis and chemical photo-activation process to produce devices with low processing temperatures in a way to be used in flexible, plastic or paper substrates. These devices are based on nanoparticles of zinc oxide as a semiconductor channel, fully printed and with heat treatment below 200 oC.... (Complete abstract click electronic access below) / Doutor

Additive manufacturing technologies, including inkjet printing, have significantly transformed both research and industry, offering cost-effective and accessible solutions with innovative equipment capabilities. This study focuses on advancing p-type depletion and enhancement-mode poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) through molecular de-doping and rheological measurements, achieving a printing resolution of 30 μm. The versatility of these inks is demonstrated from three distinct perspectives. Firstly, the electrochemical stability of the enhancement-mode behavior opens new possibilities for low-power consumption, stable and sensitive platforms useful for detection of DopamineC and Ascorbic Acid at various concentrations. Secondly, we exemplify the democratization of in-house fabrication through fully printed, all-PEDOT:PSS, transparent, flexible, and bendable paper-based Organic Electrochemical Transistors (OECTs). This showcases the feasibility of employing inkjet printing to create functional electronic devices with ease. Lastly, we explore optimizations that enable deeper personalization by employing multiple material localizations and adjusting the electrical conductivity of OECTs. This engineering approach has resulted in the design of Organic Electrochemical Complementary Amplifiers (OECAs), we incorporated a second formulated enhancement-mode conducting polymer poly(benzimidazobenzophenanthroline) (BBL) as the n-type material to complement the PEDOT:PSS de-doped ink. These developments aim to foster global innovation, representing a significant leap forward in the field of organic electronics and in-house fabrication by complementing this engineering improvement from both fabrication and electrochemistry approaches.

The work presented in the thesis is about the evaluation of Organic Electrochemical Transistors (OECTs) for fast scan cyclic voltammetry (FSCV). FSCV is a method which has been used for real time dopamine sensing both in vivo and in vitro. The method is sensitive to noise and could therefore benefit from signal preamplification at the point of sensing, which could be achieved by incorporation of OECTs. In this study the OECTs are based on the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The gate consists of gold microelectrodes of different sizes to be used one at a time. When dopamine is reacted at the gate electrode, the redox state of the PEDOT:PSS OECT channel is modulated and the resulting change in drain current can be measured. The gate current, which contains the sensing information, is after filtering obtained by differentiating the channel potential with respect to time. The derived gate current is plotted in cyclic voltammogram for different dopamine concentrations and the amplitude of the oxidation/reduction peaks can be used to determine the dopamine concentration. In this thesis for the first time it is demonstrated that OECTs can be used for FSCV detection of dopamine. The results are discussed and an outlook on future work is given.