Organic electrochemical transistors (OECTs) based on Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) are a benchmark system in organic bioelectronics. In particular, the superior mechanical properties and the ionic-electronic transduction yield excellent potential for the field of implantable or wearable sensing technology. However, depletion-mode operation PEDOT:PSS-based OECTs cause high static power dissipation in electronic circuits, limiting their application in electronic systems. Hence, having control over the threshold voltage is of utmost technological importance. Here, PEDOT:PSS-based dual-gate OECTs with solid-state electrolyte where the threshold voltage is seamlessly adjustable during operation are demonstrated. It is shown that the degree of threshold voltage tuning linearly depends on the gate capacitance, which is a straightforward approach for circuit designers to adjust the threshold voltage only by the device dimensions. The PEDOT:PSS-based dual-gate OECTs show excellent device performance and can be pushed to accumulation-mode operation, resulting in a simplified and relaxed design of complementary inverters.

Organic electronics has evolved into a well-established research field thanks to major progresses in material sciences during recent decades. More attention was paid to this research field when “the discovery and development of conductive polymers” was awarded the Nobel Prize in Chemistry in 2000. Electronic devices that rely on tailor-made material functionalities, the ability of solution processing and low-cost manufacturing on flexible substrates by traditional printing techniques are among the key features in organic electronics. The common theme while exploring organic electronics, and the focus of this thesis, is that (semi-)conducting polymers serve as active materials to define the principle of operation in devices. This thesis reviews two kinds of organic electronic devices. The first part describes electrochemical devices based on conducting polymers. Active matrix addressed displays that are printed on flexible substrates have been obtained by arranging electrochemical smart pixels, based on the combination of electrochemical transistors and electrochromic display cells, into cross-point matrices. The resulting polymer-based active-matrix displays are operated at low voltages and the same active material is used in the electrochemical transistors as well as in the electrochromic display cells, simply by employing the opto-electronic properties of the material. In addition to this first part, a switchable optical polarizer based on electrochromism in a stretch-aligned conducting polymer is described. The second part reports switchable charge traps in polymer diodes. Here, a device based on a solid-state blend of a conjugated polymer and a photochromic molecule has been demonstrated. The solid state blend, sandwiched between two electrodes, provide a polymer diode that allows reversible current modulation between two different charge transport mechanisms via externally triggered switching of the charge trap density.

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.

As the Worlds energy demand is increasing we need more of our energy to be generated from resources that affect the climate as little as possible. Solar power could be the solution if there were solar panels with a less energy demanding production than the established silicon based solar modules. Printable organic solar cells will enable a cheap production process, thus they are mainly made out of polymers in solution. However, to be able to decrease the total cost of the solar modules the commonly used indium tin oxide (ITO) for the transparent electrode needs to be replaced by a less expensive material. If the cheap, high conductive and transparent polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) could replace ITO the cost of organic solar modules would significantly decrease. For PEDOT:PSS to be able to replace ITO there are requirements that have to be met. The transparent electrode needs to be apart from transparent, highly conductive, have a low contact resistance to the other materials in the organic solar cell and be printable. In this study it has been shown that the PEDOT:PSS film with Zonyl and Diethylene Glycol (DEG) as an secondary dopant, is capable of laminating to thin films made out of PEDOT:PSS, metal or a polymer fullerene blend. The contact resistances between two PEDOT:PSS films and PEDOT:PSS film and a metal film proved to be low. When laminating to a metal film an interlayer of Silver Nano Wires (AgNW) was needed to achieve a low contact resistance.

Grâce à leurs excellentes propriétés mécaniques, électriques et chimiques, les dispositifs organiques électroniques à base de polymères conducteurs peuvent résoudre l’incompatibilité entre les modules électroniques rigides en silicone et les exigences des tissus mous qui constituent l’environnement biologique. Les avancées en matière de semiconducteurs organiques et en microélectronique ont donné naissance à la bioélectronique. Cette discipline emploie des capteurs à des fins diagnostiques, telles que la détection des métabolites ou la mesure d’un potentiel d’action neuronal, et des actionneurs à des fins thérapeutiques, comme l’application locale d’un traitement à l’intérieur même du corps, ou la stimulation cérébrale profonde afin de guérir un trouble neurologique. En bioélectronique, l’utilisation de matériaux organiques, tels que le polymère conducteur poly(3,4-éthylènedioxythiophène) polystyrène sulfonate de sodium (PEDOT:PSS) a permis de développer des composants électroniques biomédicaux de qualité exceptionnelle, comme par exemple le transistor organique électrochimique (OECT), qui ont été testés in vitro et in vivo. Ce manuscrit explique en détail la fabrication, la fonctionnalisation et la caractérisation du OECT à base de PEDOT:PSS. Afin de pouvoir intégrer ce capteur à des systèmes de mesure biomédicaux déjà établis, l’OECT est intégré à des circuits simples, tels qu’un amplificateur de tension ou un pont de Wheatstone. Ces circuits sont mis à l’épreuve de la pratique clinique, dans le cas de mesures électrocardiographiques, ou de détection de métabolites dans des cellules cancéreuses. Cela permet d’apprécier à la fois leur applicabilité, et leurs limites. / Due to their outstanding mechanical, electrical and chemical properties, organic electronic devices based on conducting polymers can bridge the gap between the rigid silicon based read-out electronics and the soft biological environment and will have a huge impact on the medical healthcare sector. The recent advances in the field of organic semiconductors and microelectronics gave rise to a new discipline termed bioelectronics. This discipline deals with sensors for diagnostic purposes, ranging from metabolite detection and DNA recognition all the way to single neuronal firing events, and actuators for therapeutic purposes, through for example active local drug delivery inside the body or deep brain stimulation to cure neurological disorder. The use of organic materials such as the conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) in the field of bioelectronics has brought about a variety of outstanding electronic biomedical devices, such as the organic electrochemical transistor (OECT), that have been implemented for both in vitro and in vivo applications. The present manuscript gives a detailed explanation of the fabrication, functionalization and characterization of OECTs based on PEDOT:PSS. To be able to intercept this sensor element with traditional biomedical recording systems, the OECT is implemented into simple circuit layouts such as a voltage amplifier or a Wheatstone bridge. These sensor circuits are then applied to real-life biomedical challenges, such as electrocardiographic recordings or metabolite detection in tumor cell cultures, to demonstrate their applicability as well as their limitations.

Organic electronic biosensors are developed as suitable devices that can transform electrochemical processes within the cell membrane into an electronic signal and enable to measure electrical activity of excitable cells and tissues both in vitro and in vivo and thus represent valuable alternative to current cell monitoring methods. In this work we focus on the fabrication of electrophysiological sensors based on organic semiconductors printed by the material printing method. Microelectrode arrays (MEAs) are active components of the device, which can monitore cellular activity and above that stimulating cells with electrical pulses. The proposed platform should be used for cytotoxicity of potential drugs especially on cardiac cells (cardiomyocytes). The experimental part focus on specific production processes of platforms, which were prepared in the laboraty with emphasis on biocompatibility and conductivity of device.

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In smart textiles, electrical conductivity is often required for several functions, especially contacting (electroding) and interconnecting. This thesis explores electrically conductive textile surfaces made by combining conventional textile coating methods with the intrinsically conductive polymer complex poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). PEDOT:PSS was used in textile coating formulations including polymer binder, ethylene glycol (EG) and rheology modifier. Shear viscometry was used to identify suitable viscosities of the formulations for each coating method. The coating methods were knife coating, pad coating and screen printing. The first part of the work studied the influence of composition of the coating formulation, the amount of coating and the film formation process on the surface resistivity and the surface appearance of knife-coated textiles. The electrical resistivity was largely affected by the amount of PEDOT:PSS in the coating and indicated percolation behaviour within the system. Addition of a high-boiling solvent, i.e. EG, decreased the surface resistivity with more than four orders of magnitude. Studies of tear strength and bending rigidity showed that textiles coated with formulations containing larger amounts of PEDOT:PSS and EG were softer, more ductile and stronger than those coated with formulations containing more binder. The coated textiles were found to be durable to abrasion and cyclic strain, as well as quite resilient to the harsh treatment of shear flexing. Washing increased the surface resistivity, but the samples remained conductive after five wash cycles. The second part of the work focused on using the coatings to transfer the voltage signal from piezoelectric textile fibres; the coatings were first applied using pad coating as the outer electrode on a woven sensor and then as screen-printed interconnections in a sensing glove based on stretchy, warp-knitted fabric. Sensor data from the glove was successfully used as input to a microcontroller running a robot gripper. These applications showed the viability of the concept and that the coatings could be made very flexible and integrated into the textile garment without substantial loss of the textile characteristics. The industrial feasibility of the approach was also verified through the variations of coating methods.

Organické elektronické zariadenia sú vyvíjané ako vhodné riešenia senzorov pre bioelektroniku, a to najmä kvôli dobrej biokompatibilite organických polovodičov v nich použitých. Takzvané biosenzory dokážu premeniť elektrochemické procesy na elektronický signál. Matrica takýchto biosenzorov môže simultánne skenovať množstvo biologických vzoriek, alebo rôznych tkanív v živých systémoch. Aktívnou súčasťou zariadenia je organický elektrochemický tranzistor (OECT). V tejto práci je diskutovaný teoretický rámec fungovania takéhoto zariadenia, jeho elektrická charakterizácia, aplikácia v biosenzoroch na báze buniek, spôsoby výroby a aktuálnym stavom techniky v oblasti organickej elektroniky. Experimentálna časť obsahuje konkrétne výrobné postupy vývoja OECT zariadení, ktoré boli použité v našom laboratóriu. Hlavný dôraz sa kladie na schopnosť vyrobených zariadení detekovať reakciu a monitorovať stimuláciu elektrogenných buniek. Za týmto účelom boli vyvinuté matice mikroelektródových OECT zariadení založených na polovodivom polyméri PEDOT:PSS. Tieto boli vyrobené s využitím bežnými tlačiarenských techník (atramentová tlač a sieťotlač) spolu so štandardnými litografickými postupmi. Najnovšie nami vyvinuté zariadenia dosahujú najväčšieho zosílením signálu, g = 2,5 mS a časovú konštantu t = 0,15 s. Tieto zariadenia sú porovnateľné, často dokonca lepšie ako niektoré iné najmodernejšie a plne litograficky pripravené senzory.

1. Zielstellung der Arbeit war die Entwicklung von Musterkennungsmethoden zur automatischen Klassifizierung von Gasen. Um dieses Ziel zu erreichen, wurde die Reduktionsmethode Parameterabschätzung mittels Adaptive-Simulated-Annealing (ASA-PE) und eine Committee machine (CM) zur Klassifikation entwickelt. 2. Mittels PEDOT:PSS-Sensoren wurden mit Hilfe der Impedanzspektroskopie NH3 und NO2 in unterschiedlichen Konzentrationen gemessen. Die aufgenommenen Messdaten wurden durch die ASA-PE, die Komplexe Haupt-komponentenanalyse (CPCA) und die Discriminant analyses via Support Vector (SVDA) reduziert. 3. Der Vergleich der Merkmalsextraktionsmethoden zeigt: Die in dieser Arbeit neu entwickelte Methode ASA-PE liefert im Vergleich dazu ein sicheres Segmentierungs-Ergebnis. 4. Der Vergleich zwischen ASA-PE und ZView zeigt, dass die ASA-PE eine sichere Methode für die automatisierte Gasanalyse ist. Aber bei zweidimensionalen Merkmalen gibt es einen Bereich, in dem sich eine gemeinsame Häufung einstellt, welche zu einer Irritation in der Auswertung von CPCA und SVDA führen kann. Dieses Problem kann durch eine Erhöhung der Anzahl von Merkmalen gelöst werden. 5. Es wurden sechs die Klassifikationsmethoden: Abstandsgewichtete k-Nächste-Nachbarn-Klassifikation (DW-kNN), das mehrlagige Perzeptron (MLP), Support Vector Machine (SVM), CM, CM ohne MLP und CM mit Abstandskontrolle und AAi-Filter untersucht und miteinander verglichen. Um die Klassifikationsmethoden anzulernen wurden alle Merkmalsreduktions-ergebnisse der CPCA, SVDA und der ASA-PE in Trainings- und Testdaten eingeteilt. 6. Die Ergebnisse zeigen, dass die Kombination aus One-Against-All-SVM (OAA-SVM) und ASA-PE die besten Erkennungsraten liefert. Bei 200 Trainingsdatensätzen wird eine Erkennungsrate von bis zu 99.5% erzielt. Durch diese Kombination können jedoch nur 8 Typen ohne Identifikation von unbekannten Typen ermittelt werden. 7. Wenn das MLP aus CM entfernt wird, werden die Resultate von CM leicht verbessert. Mit Hilfe von 6-Sigma zeigt CM ohne MLP eine gute Erkennungsrate für unbekannte Gase und gleichzeitig bleibt die Erkennungsrate auf einem befriedigenden Niveau. 8. Die Streuung der ASA-PE führt zu einer schlechten Abgrenzung zwischen bekannten und unbekannten Gasen. Stattdessen zeigt die Kombination von CM ohne MLP und CPCA in diesem Fall eine gute Abgrenzung.:Abstract II Danksagung III Inhaltsverzeichnis IV Abkürzungen VII 1 Einführung 1.1 Einleitung 1.2 Entwicklungen bei Gassensoren 1.2.1 Fortschritte bei Material und Messmethode 1.2.2 Fortschritte bei Mustererkennungsmethoden 1.3 Motivation 1.4 Struktur der Arbeit 2 Verfahren zur Gasanalyse 2.1 Messverfahren 2.1.1 Impedanzspektroskopie als Detektionsmethode 2.1.1.1 Definition der Impedanz 2.1.1.2 Bauelemente des elektrischen Modells 2.1.2 Optische Verfahren 2.1.3 Elektrochemische Verfahren 2.2 Merkmalerkennung 2.2.1 Merkmalsreduktion 2.2.1.1 Komplexe Hauptkomponentenanalyse (Engl. Complex Principal Component Analysis) 2.2.1.2 Kernel-Diskriminanzanalyse mittels Support Vektoren (engl. kernel Discriminant Analysis via Support Vector) 2.2.2 Klassifikationsverfahren 2.2.2.1 Abstands-gewichtete k-Nächste-Nachbarn-Klassifikation (engl. Distance weighted k-Nearest-Neighbor-Algorithms, DW-kNN) 2.2.2.2 Mehrlagiges Perzeptron (MLP) 2.2.2.3 Support Vektor Maschine (SVM) 3 Eigene Mustererkennungsverfahren 3.1 Parameterschätzung mittels Adaptive-Simulated-Annealing (ASA-PE) 3.1.1 Allgemeines Impedanzspektroskopiemodell eines Gassensors 3.1.2 Parameterschätzung 3.1.3 Die Optimierungsverfahren 3.2 Committee machine 4 Anwendungsbeispiel 4.1 Experiment mit einem Gassensor aus PEDOT:PSS 4.1.1 Sensoraufbau und vereinfachtes Sensormodell 4.2 Experimentelle Ergebnisse 4.2.1 Messaufbau und Versuchsdurchführung 4.2.2 Vorbereitung zur Messung 4.2.3 Durchführung der Messung 4.2.4 Fehlerbetrachtung 4.2.5 Messergebnisse des Gassensors 4.3 Ergebnisse der Merkmalreduktion 4.3.1 CPCA und SVDA 4.3.2 Parameterschätzung mittels Adaptive-Simulated-Annealing (ASA-PE) 4.4 Ergebnisse der Klassifikationen 4.4.1 Ergebnisse der Gasbestimmung mittels Trainingssatz und Testsatz 4.4.1.1 DW-kNN 4.4.1.2 MLP 4.4.1.3 OAO-SVM 4.4.1.4 OAA-SVM 4.4.1.5 Committee machine 4.4.1.6 CM ohne MLP 4.4.1.7 CM mit AAi-Filter 4.4.2 Abhängigkeit der Klassifikationsergebnisse von der Anzahl der Trainingsdaten 5 Zusammenfassung und Ausblick 5.1 Zusammenfassung 5.2 Ausblick Abbildungsverzeichnis Formelverzeichnis Literaturverzeichnis