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Printed Biosensor Based on Organic Electrochemical Transistor
Omasta, Lukáš ; Mikula, Milan (referee) ; Boušek, Jaroslav (referee) ; Salyk, Ota (advisor)
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.
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Microelectrode arrays for mioelectronic
Bráblíková, Aneta ; Vala, Martin (referee) ; Salyk, Ota (advisor)
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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Study of electrical and dielectric properties of ionic liquids
Mitáčková, Martina ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
This bachelor thesis is focused on the study of electrical and dielectric properties of ionic liquids. Two types of OECT substrates with different semiconductor channel lengths made of PEDOT:PSS were used to measure these properties. The dielectric properties were measured by impedance spectroscopy, where the dependence of the impedance value and its phase angle on the voltage frequency was measured. It was found from V-A characteristics, that the best closing of semiconductor layer occurs at a positive UGD voltage. The switching speeds of different ionic liquids were compared for this voltage.
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Study of possibilities of increasing the biocompatibility of organic semiconductor surfaces
Malečková, Romana ; Šafaříková, Eva (referee) ; Vala, Martin (advisor)
This bachelor thesis deals with the possibility of biocompatibilization of organic semiconducting polymer PEDOT:PSS using RGD peptide for the construction of biosensors. Samples were prepared and compared where the RGD peptide was bound directly, as well as samples with a peptide bound via crosslinker molecule sulfo-SANPAH. Whether the RGD peptide was bound to the substrate was determined by the method of measuring the contact angle of liquids with subsequent calculation of surface energy. The results were further verified by elemental analysis, infrared spectrometry and Raman spectroscopy.
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Development of a sensing platform for the study of physiological functions of living cells
Marková, Aneta ; Víteček, Jan (referee) ; Vala, Martin (advisor)
The aim was to develop a sensing platform on the base of organic electrochemical transistor (OECT). The focus was on the preparation of proper electrode system and on optimalization of properties of thin layer of organic semiconductor. As a base, commercial glass substrates with integrated indium-tin oxide electrodes were chosen. Thin layers were prepared from organic semiconductor poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) by spin-coating. Four formulations of material were studied. Layers with different thickness were prepared and the dependence of transconductance on the thickness of the layer and ratio of width and length was observed. The degradation of electrode system was solved by galvanic plating with gold. Attention was also paid to modifications to PEDOT: PSS. It has been found that the optimal layer thickness for use in sensors is approximately 150 nm. By reducing the series resistance by using a silver paste, the transconductance of 23 mS was obtained for the Ink 2, for the Ink 3 the transconductance was 44 mS. Sensoric platforms with these transconductances can be used for detection of physiological functions of electrogenic cells, e.g. cardiomyocytes.
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Study of perovskite solar cells degradation
Hrbková, Silvie ; Novák, Vítězslav (referee) ; Vala, Martin (advisor)
This thesis studies the degradation of perovskite photovoltaic cells placed in atmospheres of different moisture. Samples with inverse structure: ITO/ PEDOT:PSS/ CH3NH3PbI3–XClX / PC70BM/ Ca/ Al were prepared. Electrical characteristics were measured for 2 months and similar degradation trend was observed for all the samples. Perovskite cell efficiency PCE decreased to 20 % of the initial value in t80= 46±3 days in laboratory, t80=23±1$ days in nitrogen atmosphere and t80=25,7±0,6 dní days in dry atmosphere. For the initial 27 days of the experiment, a faster degradation linked with the decrease of ISC, FF and VOC was observed. After this period, the value of FF has stabilised at 0,777±0,009 % and the value of VOC at 0,70±0,02 % of their original value (in the laboratory atmosphere). Additional fall of PCE resulted only from the decrease of ISC and was slower than in the initial period. From the results acquired, it has emerged that during the experiment, the cell encapsulation provided a sufficient barrier against outer moisture. Residual moisture present in the sctructure, was labeled as the source of the degradation. The moisture is believed to enter with the hygroscopic material PEDOT:PSS during the samples preparation procedure. During the degradation, absorption measurements of photovoltaic cells were executed. The absorption spectra didn't change. That indicates, that the decrease of ISC is not caused by the reduction of light absorption. The thesis also studied the degradation of perovskite solar cells under illumination. The samples were exposed to UV radiation for 55,5 hours. The PCE time of decrease to 20 % of the initial value was t80 = 6±2 days. It was revealed, that UV radiation significantly accelerates the decrease of ISC.
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Optimization of printing of organic electronic devices printing for bioelectronics
Bráblíková, Aneta ; Hrabal, Michal (referee) ; Salyk, Ota (advisor)
This bachelor thesis is focused on optimization of printing of organic electronic devices printing for bioelectronics. The main goal of this bachelor thesis is a series of experiments devised to optimize semiconductive structures of PEDOT (semiconductive polymer) and description of the process used in the preparation of organic electrochemical transistors for biosensor by screen printing technology. The research focused on application of bioelectronics, printing technologies, conductive inks suitable for the preparation of OECTs (organic electrochemical tranzistors) and rheological properties of materials. Main conditions tested in the experimental part were temperature, stirring and additon of DMSO (dimethylsulfoxide) into a printing pasted. The evaluated parameters of materials were basic viscoelastic characteristics. At the ent of the thesis have been successfully designed the series of transistors to monitor cell cultures.
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Optimalization of printing methods of organic semiconducting layers preparation
Ehlich, Jiří ; Vala, Martin (referee) ; Salyk, Ota (advisor)
Electrophysiological biosensors enables a novel way to measure electrical activity of biological structures both in-vitro and in-vivo and represents valuable alternative to current cellular activity measuring methods. Within this work we will be focusing on development of organic semiconductor (PEDOT:PSS) based Organic Electrochemical Transistors (OECTs) and optimization of material printing methods used in their development. These transistors are meant to be able to transfer electrochemical signals within the cell membrane to electrical signal. Such sensors should be used for cytotoxicity testing of chemicals and potential drugs on cardiomyocytes. Main benefits of OECTs are in their higher sensitivity thanks to their ability to locally amplify electric signals, better noise-signal ratio and outstanding biocompatibility. Their development is undemanding and inexpensive due material printing methods and materials processable at room temperatures.
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Organic electronics for biosensors
Netočný, Martin ; Vala, Martin (referee) ; Salyk, Ota (advisor)
In the first part are discussed the organic thin-film transistors and their possible use for chemical and biological sensors. Middle section discusses the electrical properties of OECT device in steady-state and transient behaviour and potential use of OECT for cell monitoring. The final experimental part deals with influence of temperature, aging, electrolyte environment and geometry on the function of OECT device.
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Study of electrical and dielectric properties of ionic liquids
Maráčková, Lucie ; Nešpůrek, Stanislav (referee) ; Zmeškal, Oldřich (advisor)
This bachelor´s thesis is focused on a study of electrical and dielectric properties of ionic liquids in the form of solution and thin layers. The values of breakdown voltage have been determined from current-voltage characteristics in solutions. Frequency dependencies have been also observed and used for calculation of values of parallel conductivity and capacity of ionic liquid. It was found that solutions is contained by model with one parallel combination of conductivity and capacity. Thin layers have been created by mixing up PEDOT:PSS with two ionic liquids: 1-butyl-3- methylimidazolium trifluoromethanesulfonate and 1-ethyl-3-methylimidazolium tetrafluoroborate. These layers have created electrochemical battery as is evident from current-voltage characteristics. Frequency dependencies are more complex, a model contained two or respectively three parallel conductivities and capacities which have been influenced by PEDOT:PSS and by ionic liquids characteristics.
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