In this diploma work, organic electrochemical transistors based on PEDOT:PSS have been studied, focusing on the influence of the geometry and physical dimensions on the transistor characteristics. The geometrical parameters studied are the area ratio between the gate and channel, the channel width and the channel length. Each parameter has been varied in five steps with each step containing three identical transistors. Results concerning the geometrical influence of the linear region resistance, the saturation current (density) and the on/off ratio are presented and discussed. Also, empirical curve-fits of the geometrical influence on the linear region resistance and the saturation current have been performed. In addition, tentative results of the locus of the saturation current versus saturation voltage for specific transistors have been obtained.

<p>In this diploma work, organic electrochemical transistors based on PEDOT:PSS have been studied, focusing on the influence of the geometry and physical dimensions on the transistor characteristics. The geometrical parameters studied are the area ratio between the gate and channel, the channel width and the channel length. Each parameter has been varied in five steps with each step containing three identical transistors. Results concerning the geometrical influence of the linear region resistance, the saturation current (density) and the on/off ratio are presented and discussed. Also, empirical curve-fits of the geometrical influence on the linear region resistance and the saturation current have been performed. In addition, tentative results of the locus of the saturation current versus saturation voltage for specific transistors have been obtained.</p>

<p dir="ltr">Efficiently identifying commercial and improvised explosives is a crucial prerequisite for disarming and disposing of these dangerous materials. In conjunction with traditional techniques (e.g., ion mobility spectrometry and mass spectrometry), electrochemical sensors can function as low-form factor and inexpensive options to quickly identify chemical threats. In particular, organic electrochemical transistors (OECTs) have many attractive properties, and they have become viable options for biosensing. OECTs employ a simple geometry consisting of a conducting polymer active layer and an electrolyte controlled by a gate electrode. In turn, this provides a means for the solution-phase detection in short times. Here, the OECT architecture was extended to the challenge of explosive trace detection. These sensors were adapted to detect several families of explosives (i.e., acid-salts, nitroaromatics, nitroamines, nitrate-esters, and peroxides). Many of these sensors incorporated molecularly imprinted polymers (MIPs) to improve chemical selectivity. These MIPs were shown to introduce size exclusive properties to the OECTs, which can be leveraged to detect acid salts explosives. MIPs that were complementary to nitrated explosives (nitroaromatics, nitroamines, and nitrate-esters) also were prepared. These MIPs can adsorb their respective explosive decreasing their polymer porosity and ion-transport. Finally, a stand-alone OECT design was applied to detect peroxide-based explosives. These explosives were decomposed to hydrogen peroxide intermediates. The evolved hydrogen peroxide was then identified as it was electro-oxidized at the gate electrode. After establishing the viability of the discussed techniques, two new directions for designing OECT sensors were proposed. Finally, these two outlooks were combined as a potential strategy for directly detecting peroxide-based explosives. While only a small subset of explosives was considered, the strategies applied were not unique to these specific targets. Indeed, these OECTs detecting principles could be applied to a broader scope of explosives detection as well as novel chemical sensing horizons.</p>

De nos jours, efficacité et précision des diagnostics médicaux sont des éléments essentiels pour la prévention en termes de santé et permettre une prise en charge rapide des maladies des patients. Les récentes innovations technologiques, particulièrement dans les domaines de la microélectronique et des sciences des matériaux ont permis le développement de nouvelles plateformes personnalisées de diagnostics portatifs. Les matériaux électroniques organiques qui ont déjà par le passé démontré leur potentiel en étant intégrés dans des produits de grande consommation tels que les écrans de smartphones ou encore les cellules solaires montrent un fort potentiel pour une intégration dans des dispositifs biomédicaux. En effet, de par leurs natures et leurs propriétés physiques et chimiques, ils peuvent être à la fois en contact avec les milieux biologiques et constituer l’interface entre les éléments biologiques à l’étude, et les dispositifs électroniques. L’objectif de mes travaux de thèse et d’étudier et évaluer les performances des matériaux organiques électroniques intégrés dans des dispositifs biomédicaux en étudiant leurs interactions avec des milieux biologiques et par l’utilisation et l’optimisation de ces dispositifs permettre la détection de métabolites tel que le glucose ou lactate par exemple. Pendant ma thèse, j’ai notamment créé une plateforme de diagnostics combinant à la fois microfluidique et électronique organique permettant la multi détection de métabolites présents dans des fluides corporels humains, j’ai également conçu des capteurs intégrant des transistors organiques au sein des circuits électroniques classiques afin de détecter la présence des cellules tumorales. D’autres applications biologiques ont également été envisagées telles que la détection d’acides nucléiques par l’utilisation d’une approche simple de biofonctionnalisation. Bien que l’objectif ma thèse était de de créer des capteurs biomédicaux en utilisant une approche in vitro, il pourrait être également possible d’intégrer ces dispositifs « in vivo » ou encore dans des e-textiles. / Rapid and early diagnosis of disease plays a major role in preventative healthcare. Undoubtedly, technological evolutions, particularly in microelectronics and materials science, have made the hitherto utopian scenario of portable, point-of-care personalized diagnostics a reality. Organic electronic materials, having already demonstrated a significant technological maturity with the development of high tech products such as displays for smartphones or portable solar cells, have emerged as especially promising candidates for biomedical applications. Their soft and fuzzy nature allows for an almost seamless interface with the biological milieu rendering these materials ideally capable of bridging the gap between electronics and biology. The aim of this thesis is to explore and validate the capabilities of organic electronic materials and devices in real-world biological sensing applications focusing on metabolite sensing, by combining both the right materials and device engineering. We show proof-of-concept studies including microfluidic integrated organic electronic platforms for multiple metabolite detection in bodily fluids, as well as more complex organic transistor circuits for detection in tumor cell cultures. We finally show the versatility of organic electronic materials and devices by demonstrating other sensing strategies such as nucleic acid detection using a simple biofunctionalization approach. Although the focus is on in vitro metabolite monitoring, the findings generated throughout this work can be extended to a variety of other sensing strategies as well as to applications including on body (wearable) or even in vivo sensing.

<p>Electrochemical Transistor(ECT) was reported by David Nilsson in 2002. Later,its dimensios were specified and a SPICE model was developed.</p><p>The main purpose of this diploma work is to check the performance of electrochemical transistors in amplifier circuits. Simple amplifier circuits were simulated using SPICE model of ECT. Lateral and Vertical structures of electrochemical transistors were patterned on orgacon sheet(provided by AGFA),with various electrolytes(EG010,MS-HEC & MS-L). Characteric curves and time responses of these transistors were studied and then were then used as an active component in single amplifier circuits. Screen printed ECT's were also checked with the best available electrolyte. Behaviour of self made and screen printed ECT's were compared on the basis of on-off ratio,slew rate,frequency response and gain. Screen printed transistors showed promising results having less deterioration with time  but  till  an  an  input  signal  frequency  of  2Hz  only. Mismatch with simulation results and Shockley's equation were other findings after data analysis.</p><p><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot.jpg" /><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot-1.jpg" /></p>

Electrochemical Transistor(ECT) was reported by David Nilsson in 2002. Later,its dimensios were specified and a SPICE model was developed. The main purpose of this diploma work is to check the performance of electrochemical transistors in amplifier circuits. Simple amplifier circuits were simulated using SPICE model of ECT. Lateral and Vertical structures of electrochemical transistors were patterned on orgacon sheet(provided by AGFA),with various electrolytes(EG010,MS-HEC &amp; MS-L). Characteric curves and time responses of these transistors were studied and then were then used as an active component in single amplifier circuits. Screen printed ECT's were also checked with the best available electrolyte. Behaviour of self made and screen printed ECT's were compared on the basis of on-off ratio,slew rate,frequency response and gain. Screen printed transistors showed promising results having less deterioration with time  but  till  an  an  input  signal  frequency  of  2Hz  only. Mismatch with simulation results and Shockley's equation were other findings after data analysis. <img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot.jpg" /><img src="file:///C:/DOCUME%7E1/zia/LOCALS%7E1/Temp/moz-screenshot-1.jpg" />

There is a great demand for low-cost disposable sensors in a variety of markets, such as the food chainand health care. No assay is performed more than that of glucose and approximately 85 % of the entirebiosensor market accounts for glucose biosensors. Each year, 6 billion glucose assays are performed andthe majority of them are based on electrochemical detection. Organic electrochemical transistors(OECTs) have favorable properties in terms of low operating voltages and have previously been used asbase for electrochemical detection of glucose. A low-cost disposable biosensor can be achieved by theuse of high throughput printing techniques. Up until now, no printable biosensors based on organic electrochemicaltransistors have been developed. In this thesis a printable miniaturized prototype for a glucose biosensor based on an OECT with a platinizedgate electrode has been designed, developed and evaluated. The biosensor has been functionalizedwith the enzyme glucose oxidase. Different platinum deposition techniques have been used to depositplatinum onto the printed carbon gate electrode: electrodeposition, platinum nanoparticle solutiondeposited either by inkjet printing or pipetting and thermal evaporation. The gate electrodes were characterized with cyclic voltammetry in hydrogen peroxide, ferricyanide andglucose. The characterizations revealed no significant differences between the different deposition techniques.However, with gate electrodes produced by printed carbon followed by electrodeposition ofplatinum it was possible to sense glucose in a concentration in the range of the values for diabetic persons.Thus, the electrodes are a promising option as gate electrodes in a glucose biosensor based on anOECT. The characteristics of the OECT revealed that the responses resembled a transistor.

Heutzutage werden riesige Datenmengen zwischen Endgeräten und Cloud-Servern verschoben. Cloud-Computing war nach Bloomberg bereits für 1% des weltweiten Stromverbrauchs im Jahr 2021 verantwortlich. Darüber hinaus kann die monopolartige Speicherung personenbezogener Daten schwerwiegende Auswirkungen auf die Gesellschaften unserer Welt haben. Um persönlichen Datenschutz und einen nachhaltigen Energieverbrauch zu gewährleisten, bedarf es einer Datenverarbeitung direkt am Endgerät; bezeichnet als Edge Computing. In diesem Zuge wird die Nachfrage nach individuell gestalteten Edge-Geräten rapide ansteigen. Der neu entstehende Markt bietet der organischen elektrochemischen Elektronik eine große Chance, vor allem für bioelektronische Anwendungen; allerdings muss die Chipintegration verbessert werden. In dieser Arbeit habe ich elektrochemische organische Elektronik für die Integration in Computersysteme untersucht. Insbesondere habe ich einen festen, photostrukturierbaren Elektrolyten entwickelt, der die Integration von OECTs ohne Kreuzkommunikation zwischen Bauteilen ermöglicht. Die OECTs arbeiten bei Spannungen unter 1V und schalten mit einem großen An/Aus-Verhältnis von 5 Größenordnungen und einer Unterschwellenschwingung nahe des thermodynamischen Minimums von 60mV/Dekade. Darüber hinaus wurden bei der Untersuchung der Hysterese des Bauelements drei verschiedene Hystereseregime identifiziert. Anschließend untersuchte ich die Schaltdynamik des OECTs und demonstrierte ein Top-Gate-OECT mit einer maximalen Betriebsfrequenz von 1 kHz. Beim Versuch, die komplexe Wechselwirkung zwischen Ionen und Elektronen in integrierten OECTs zu verstehen, habe ich einen grundlegenden elektrochemischen Mechanismus identifiziert. Die Abhängigkeit dieses Mechanismus’ von der Gate-Größe und der Drain-Überlapplänge wurde aufgezeigt und dieses Wissen zur Optimierung elektrochemischer Inverter genutzt. Zur Darstellung von OECT-basierten Schaltungskomponenten habe ich verschiedene Halbleiter verwendet und entsprechende Inverter hergestellt. Schließlich wurde die Hysterese eines einzigen ambipolaren Inverters zur Demonstration eines dynamischen Klinkenschalters genutzt. Im Rahmen dieser Arbeit habe ich die OECT-Technologie von den Anfängen bis hin zu integrierten Schaltkreiskomponenten entwickelt. Ich glaube, dass diese Arbeit ein Startschuss für Wissenschaftler und Ingenieure sein wird, um die OECT-Technologie in der realen Welt des Edge Computing einzusetzen. / Nowadays, vast amounts of data are shuttled between end-user devices and cloud servers. This cloud computing paradigm was, according to Bloomberg, already responsible for 1% of the world’s electricity usage in 2021. Moreover, the monopoly-like storage of personal data can have a severe impact on the world’s societies. To guarantee data privacy and sustainable energy consumption in future, data computation directly at the end-user site is mandatory. This computing paradigm is called edge computing. Owing to the vast amount of end-user-specific applications, the demand for individually designed edge devices will rapidly increase. In this newly approaching market, organic electrochemical electronics offer a great opportunity, especially for bioelectronic applications; however, the integration into low-power-consuming systems has to be improved. In this work, I investigated electrochemical organic electronics for their integration into computational systems. In particular, I developed a solid photopatternable electrolyte that allows integrating organic electrochemical transistors (OECTs) without cross-talk between adjacent devices. The OECTs operate at voltages below 1 V, and exhibit a large on/off ratio of 5 orders of magnitude and a subthreshold-swing close to the thermodynamic minimum of 60mV/dec. Moreover, investigating the device’s hysteresis, three distinct hysteresis regimes were identified; the RC-time-dominated regime I, the retention time governed regime II, and the time-independent stable regime III. I then examined the OECT’s switching dynamics and, subsequently, demonstrated a top-gate device with a maximum operating frequency of 1 kHz. Trying to understand the complex interaction between ions and electrons in integrated OECTs, I disclosed a fundamental electrochemical mechanism and named it the electrochemical electrode coupling (EEC). The EEC’s dependence on gate size and drain overlap length was rigorously shown, and this knowledge was used to optimize electrochemical inverters. Yet, to exemplify OECT-based circuit components, I employed various semiconductors and fabricated five inverters, each with its unique advantage. Finally, the ambipolar inverter’s hysteresis was used to demonstrate a single-device dynamic latch, a basic in-memory computational element. In this thesis, I developed the OECT technology from an infancy stage to integrated circuit components. I believe that this work will be a starting signal for scientists and engineers to bring the OECT technology into real-world edge computing.

Conducting polymers entered the research field in late 70´s and efforts aimed at achieving printed electronics started a decade later. This thesis treats printable organic electrochemical transistors (OECT). Some conjugated polymers can be switched between a high conducting and a low conducting state in an electrochemical cell. In this thesis, the work carried out using poly(3,4-ethylenedioxythiophene) (PEDOT) as the active material in an electrochemical transistor is reported. The electrochemical transistors, presented, can be designed into a bi-stable and dynamic mode of operation. These transistors operates at voltages below 2V and current on/off ratios are typically 5000, but 105 have been reached. The transistor device can be built up from all-organic materials using common printing techniques such as with screen-printing. The bi-stable transistor can be combined with an electrochromic (EC) display cell to form a smart pixel circuit. Combining several of these smart pixels yield an actively addressed cross-point matrix display. From this an all-organic active matrix display printable on paper has been achieved. The OECT, combined with a resistor network was successfully used in inverter and logic circuits. One important feature of these organic electrochemical devices is that both ions and electrons are used as the charge (signal) carriers. This is of particular interest and importance for chemical sensors. By combining a proton-conducting electrolyte (Nafion®) that changes its conductivity upon exposure to humidity, a simple OECT humidity sensor was achieved. This proves the use of this OECT as the ion-to-electron transducer.

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.