The electrification of transportation is gradually becoming more prominent as it is more efficient and sustainable than conventional transportation alternatives found today. At the centre of this growth is battery testing and research, as they are the primary energy storage devices used to power electric vehicles. With the growing complexity of battery systems, testing and monitoring their performance relies on highly specialized and precise equipment. Furthermore, the use of battery models helps researchers improve their research while reducing the time and costs involved in testing. As such, accurate battery modelling is a critical component in predicting how a battery will behave in specific applications and under various conditions. In this research, a lithium-ion cell is tested extensively, and its performance is characterized across a wide range of operating conditions including temperature, current rates and state of charge (SOC) values. An equivalent circuit model for impedance modelling is proposed, which utilizes constant phase elements represented in the time domain to improve fitting accuracy. This is done concurrently with the development of a state of the art, fully automated battery test system which is showcased throughout the course of the research. In addition to this, an analysis is conducted on the low frequency impedance data used during research, as well as its effect on model accuracy. To provide significance behind the results and relevance to real-world applications, all of the impedance modelling is experimentally validated using temporal drive cycle data. This research was able to demonstrate that the use of a ZARC element can improve the mid-frequency fitting of impedance data relative to a conventionally used modelling approach. It also showcases how the use of low frequency electrochemical impedance spectroscopy (EIS) data can negatively impact the accuracy of impedance modelling. / Thesis / Master of Applied Science (MASc)

The focus of this dissertation research involves surface charge manipulation of functionalized monolayers. Application of potential to acid or base terminated organic films immobilized on electrodes results in the ionization of the terminal groups. The ionization of these groups using applied potential provides conditions favorable the control of polyelectrolyte deposition to the monolayer surface. Research is presented that asserts that the interfacial pH of acid or base terminated monolayers responds to applied potential as a result of the accumulation of phosphate counterions to the monolayer-solution interface. Results obtained from applied potential modulation of surface charge endeavors strongly suggest that manipulation of terminal group ionization with applied potential “turns on“ or “turns off“ the charge of the monolayer. Switching on the surface charge of functionalized monolayers using applied potential yields conditions that make it possible for the promotion or inhibition of electrostatic attachment of polyelectrolyte to the monolayer surface. Electrostatic interactions between immobilized polyelectrolytes and redox probes result in changes in electron transfer that can be monitored with electrochemical impedance measurements. Impedance measurements provide a qualitative assessment of the degree of potential-driven polyelectrolyte self assembly. The electrostatic interactions between the redox probe in solution and the terminal region of monolayers directly affects the extent of charge-transfer between the electrode and the redox probe in solution. For this reason, impedance measurements are able to provide an indication of whether or not potential drives to electrostatic deposition to the terminal region of a functionalized monolayer. Unlike impedance measurements, quartz crystal microbalance measurements provide quantitative mass assessments that confirm polyelectrolyte deposition of inhibition under the direction of applied potential. Application of appropriate potentials is shown to induce variations in the electrostatic interactions between redox probes in solution and terminal groups of monolayers. Variations in the electrostatic interactions between the modified electrode and the redox probe modulate electron transfer that produces varying current. Since scanning electrochemical microscopy (SECM) relies on modulation of feedback current underneath a ten-micrometer platinum tip, SECM provides a means for monitoring of potential-driven surface charge modulation. Experiments presented in this dissertation will show that in addition to monitoring the effect of applied potential on the charge of ionizable surface groups, SECM can also be used to selectively deposit a polyelectrolyte to the surface of a carboxylic acid terminated monolayer. The SECM tip was rastered over the surface of a functionalized monolayer in the form of a simple pattern while the electrode was immersed in a dilute polyelectrolyte solution. As the SECM tip was moved and potential stepped more positive than the PZC, ionization was confined ionization to one spot encouraging localized ionic self assembly. / Ph. D.

This dissertation describes the impact of defects on monolayer properties for self-assembled monolayers (SAMs) created by interfacial patterning methods. When forming a two-dimensional interfacial pattern with n-alkanethiols on gold, the desired electrochemical properties are those of a homogeneous, solution adsorbed monolayer. However, even well-ordered SAMs contain a small degree of defects, especially at domain boundaries where two nucleating domains converge. Patterning a surface creates user-defined domain boundaries within the monolayer, potentially having a significant impact on the properties of the interface. This dissertation investigates the effect that user-created domain boundaries have on the properties of a monolayer, as studied by electrochemical impedance spectroscopy. Two patterning methods are investigated for creating user-defined domain boundaries: the soft lithography method of contact printing and site-selective reductive desorption. The electrochemical properties of homogeneous contact printed monolayers are measured and compared to those of monolayers prepared by solution adsorption. The contact printed monolayers are found to have dramatically different impedance behavior from the solution prepared monolayers, consistent with the contact printed monolayers having greater defect density. In addition, these studies show that the overall defect density depends on the concentration of the solutions used for contact printing. In this work, simple patterns are created by contact printing a pattern onto the substrate and then backfilling the remaining gold substrate by solution adsorption. Backfilling with the same alkanethiol used to create the pattern generates a homogeneous monolayer; however, it is found that the contact printed/backfilled monolayer has an impedance intermediate between the homogeneous contact printed and the homogeneous solution adsorbed monolayer. This result suggests that the backfilling process also saturates the pinhole defects associated with the contact printed areas. In addition to exploring defects that arise from contact printing, simple patterns with user-defined defects, created by site-selective reductive desorption (SSRD), were also investigated. Following the backfill step, the impedance behavior of the SSRD produced patterns was similar to that of the impedance of the initial pattern before backfilling. This important result implies that the domain boundaries play the most important role in defining the overall impedance of the patterned interface. / Ph. D.

The main objective of the research in this dissertation is to take advantage of unique materials, innovative designs, novel microfabrication techniques, and specialized characterization tools to develop a set of BioMEMS devices and systems further validated with electrical, interface, geometric, and multiphysics models to address unique biological problems emanating from ethical treatment of animals in drug discovery, biological translation, decentralization and personalization of healthcare. This set of devices is designed to interface with multi-sized biological constructs such as 3D cellular networks, viruses, and proteins. The first objective explored a 3D printing-based microfabrication technology to create 2.5D/3D microelectrodes to interface with cellular constructs such as tissues and organoids. Investigations were carried out on how surface roughness and printing parameters play a critical role in the electrical response of the system for in-vitro applications. Three different metallization strategies were investigated and modeled in order to define novel self-insulated 2.5 and 3D microelectrodes. The second objective centered around virus and microparticle detection using a novel combination of microfluidics and Wi-Fi optical detection. Microfluidics were created designing a multilayered system and processing various polymeric materials. The optical system was able to detect and wirelessly transmit information about the presence of viruses including COVID-19 Delta strain and microparticles in the 5 to 10 microns size. The last objective of the dissertation presented the microfabrication of a BioMEMS platform for electrophysiological characterization of Actin protein (smallest entity within the size spectrum). This platform combined interdigitated electrodes, PDMS soft lithography, and impedance and interface modeling to better understand Actin protein dynamics in bundles. This dissertation proposes innovative ideas to the current state of the art for emerging paradigms in the medical technology field involving rapid sensing and manipulating biological entities at various size scales: (proteins, DNA/RNA), (pathogens, virus), and (organoids, spheroids, assembloids).

Yes / Rapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25300号 / 工博第5259号 / 新制||工||2001(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 准教授 松井 敏明 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Philosophiae Doctor - PhD / Electroanalytical and optical properties of nanoscale materials are very important for biosensing applications as well as for understanding the unique one-dimensional carrier transport mechanism. One-dimensional semiconductor nanomaterials such as semiconductor quantum dots are extremely attractive for designing high-density protein arrays. Because of their high surfaceto-volume ratio, electro-catalytic activity as well as good biocompatibility and novel electron transport properties make them highly attractive materials for ultra-sensitive detection of biological macromolecules via bio-electronic or bio-optic devices. A genosensor or gene based biosensor is an analytical device that employs immobilized deoxyribonucleic acid (DNA) probes as the recognition element and measures specific binding processes such as the formation of deoxyribonucleic acid-deoxyribonucleic acid (DNA-DNA), deoxyribonucleic acid- ribonucleic acid (DNA-RNA) hybrids, or the interactions between proteins or ligand molecules with DNA at the sensor surface.In this thesis, I present four binary and two ternary-electrochemically and optically modulated selenide and telluride quantum dots, all synthesised at room temperature in aqueous media. Cationic gallium (Ga3+) synthesized in form of hydrated gallium perchlorate salt[Ga(ClO4)3.6H2O] from the reaction of hot perchloric acid and gallium metal was used to tailor the optical and electrochemical properties of the selenide and telluride quantum dots. The synthesized cationic gallium also allowed successful synthesis of novel water soluble and biocompatible capped gallium selenide nanocrystals and gallium telluride quantum dots. Cyclic voltammetric studies inferred that presence of gallium in a ZnSe-3MPA quantum dot lattice improved its conductivity and significantly increased the electron transfer rate in ZnTe-3MPA.Utraviolet-visible (UV-vis) studies showed that incorporation of gallium into a ZnSe-3MPA lattice resulted in a blue shift in the absorption edge of ZnSe-3MPA from 350 nm to 325 nm accompanied by decrease in particle size. An amphiphilic bifunctional molecule, 3-Mercaptopropionic acid (3-MPA) was used as a capping agent for all quantum dots. It was found that 3-MPA fully solubilised the quantum dots, made them stable, biocompatible, non agglomerated and improved their electron transfer kinetics when immobilized on gold electrodes.Retention of the capping agent on the quantum dot surface was confirmed by Fourier transform infrared spectroscopy (FTIR) which gave scissor type bending vibrations of C-H groups in the region 1365 cm-1 to 1475 cm-1, stretching vibrations of C=O at 1640 cm-1, symmetric and asymmetric vibrations of the C-H in the region 2850 cm-1 to 3000 cm-1 as well as stretching vibrations of –O-H group at 3435 cm-1. The particle size and level of non-agglomeration of the quantum dots was studied by high resolution transmission electron microscopy (HRTEM). The optical properties of the quantum dots were studied using UV-vis and fluorescence spectroscopic techniques.Quantum dot/nanocrystal modified gold electrodes were prepared by immersing thoroughly cleaned electrodes in the quantum dot/nanocrystal solution, in dark conditions for specific periods of time. The electrochemical properties of the modified electrodes were characterized by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance and spectroscopy (EIS). Six sensing platforms were then prepared using quantum dot/nanocrystal, one of which was used for detection of dopamine while the rest were used for detection of a DNA sequence related to 5-enolpyruvylshikimate-3-phosphate synthase, a common vector gene in glyphosate resistant transgenic plants.The first sensing platform, consisting of ZnSe-3MPA modified gold electrode (Au|ZnSe-3MPA) gave rise to a novel method of detecting dopamine in presence of excess uric acid and ascorbic acid. Using a potential window of 0 to 400 mV, the ZnSe-3MPA masked the potential for oxidation of uric and ascorbic acids, allowing detection of dopamine with a detection limit of 2.43 x 10-10 M (for SWV) and 5.65 x 10-10 M (for steady state amperometry), all in presence of excess uric acid (>6500 higher) and ascorbic acid (>16,000 times higher). The detection limit obtained in this sensor was much lower than the concentration of dopamine in human blood(1.31 x 10-9 M), a property that makes this sensor a potential device for detection of levels of dopamine in human blood.The other sensing platforms were prepared by bioconjugation of amine-terminated 20 base oligonucleotide probe DNA (NH2-5′-CCC ACC GGT CCT TCA TGT TC-3′) onto quantum dot modified electrodes with the aid of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The prepared DNA electrodes were electrostatically hybridized with different sequences which included 5′-GAA CAT GAA GGA CCG GTG GG-3′ (complementary target), 5′-CATAGTTGCAGCTGCCACTG-3′ (non complementary target) and 5′-GATCATGAAGCACCGGAGGG-3′ (3-base mismatched target).The hybridization events were monitored using differential pulse voltammetry (DPV) and SWV by monitoring the guanine oxidation signal or using EIS by monitoring changes in the charge transfer resistance. The quantum dot genosensors were characterized by low detection limits (in the nanomolar range), long linear range (40 - 150 nM) and were able to discriminate among complementary, non-complementary and 3-base mismatched target sequences.

In response to the present and projected growth of the EV industry, the development of a large-scale, reliable and efficient lithium-ion battery recycling sector is vital to ensure circularity of the embedded valuable metals and ensure overall sustainability of the technology. One of the main recycling procedures under development is based on hydrometallurgy. As a pretreatment step before lithium-ion batteries can undergo this process, they have to be deactivated to prevent uncontrolled release of the contained electrical energy. This deactivation step is often performed by deep discharging batteries to 0.0 V, instead of the usual lower cut-off around 3.0 V. Usually, deep discharging is performed by connection to resistors or through submersion in a salt solution. However, due to the discharge current derating proportionally to the terminal voltage, this procedure can be quite slow, especially if considerable rebound voltages are to be prevented. This work explores the feasibility of a faster discharge procedure in terms of discharge speed, effectiveness, and safety. The proposed procedure entails deep discharging at constant current using a controllable load, followed by applying an external short-circuit immediately. The C-rate during constant current discharging is varied to study its effects. The short-circuit is applied at a terminal voltage of 0.0 V or 1.0 V. The safety of both process steps is assessed experimentally. The main safety risks that are reviewed are the temperature rise and subsequent risk of thermal runaway, as well as the risk of electrolyte leakage due to pressure increase and swelling. In the experimental work, two types of large format prismatic NMC811 cells are deep discharged starting from an SoC of 0%. The experiments are limited to single cells. It is found that an additional 4% of additional capacity is available in the deep discharging region for a stationary cell at 0% SoC. The risk of thermal runaway is assessed as low based on the temperature measurements and a literature review. To investigate the rise in pressure, the thickness of all cells are measured, and the in situ pressure is measured for three samples. The risk for electrolyte leakage is assessed as low. The rebound voltage and cell thickness are followed up to one week after the discharge procedure. After a short-circuit of 30 minutes, the rebound voltage of all cells is near 2.0 V, but a slightly longer short circuit duration would be necessary to reliably achieve this threshold. The total procedure time is much shorter than those of alternative discharge procedures, while still remaining safe. / Som svar på den nuvarande och förväntade tillväxten inom elbilsindustrin är utvecklingen av en storskalig, tillförlitlig och effektiv återvinningssektor för litiumjonbatterier avgörande för att säkerställa cirkularitet för de inbäddade värdefulla metallerna och säkerställa teknikens övergripande hållbarhet. En av de viktigaste återvinningsmetoderna som är under utveckling baseras på hydrometallurgi. Som ett förbehandlingssteg innan litiumjonbatterier kan genomgå denna process måste de avaktiveras för att förhindra okontrollerad frisättning av den elektriska energi som de innehåller. Detta deaktiveringssteg utförs ofta genom djupurladdning av batterierna till 0.0 V, istället för den vanliga lägre gränsen runt 3.0 V. Vanligtvis utförs djupurladdning genom anslutning till resistorer eller genom nedsänkning i en saltlösning. Eftersom urladdningsströmmen avtar proportionellt mot terminalspänningen kan denna procedur dock vara ganska långsam, särskilt om man vill förhindra stora återkopplingsspänningar. I detta arbete undersöks genomförbarheten av en snabbare urladdningsprocedur när det gäller urladdningshastighet, effektivitet och säkerhet. Det föreslagna förfarandet innebär djupurladdning vid konstant ström med en kontrollerbar belastning, följt av omedelbar applicering av en extern kortslutning. C-hastigheten under urladdning med konstant ström varieras för att studera dess effekter. Kortslutningen appliceras vid en terminalspänning på 0.0 V eller 1.0 V. Säkerheten för båda processtegen bedöms experimentellt. De huvudsakliga säkerhetsriskerna som granskas är temperaturökningen och den efterföljande risken för termisk rusning, samt risken för elektrolytläckage på grund av tryckökning och svullnad. I det experimentella arbetet djupurladdas två typer av prismatiska NMC811-celler i storformat från en SoC på 0%. Experimenten är begränsade till enstaka celler. Det visade sig att ytterligare 4% kapacitet finns tillgänglig i djupurladdningsområdet för en stationär cell vid 0% SoC. Risken för termisk urladdning bedöms som låg baserat på temperaturmätningarna och en litteraturgenomgång. För att undersöka tryckökningen mäts tjockleken på alla celler och in situ-trycket mäts för tre prover. Risken för elektrolytläckage bedöms som låg. Återkopplingsspänningen och cellernas tjocklek följs upp upp till en vecka efter urladdningsproceduren. Efter en kortslutning på 30 minuter är returspänningen för alla celler nära 2.0 V, men en något längre kortslutningstid skulle vara nödvändig för att tillförlitligt uppnå detta tröskelvärde. Den totala tiden för proceduren är mycket kortare än för alternativa urladdningsprocedurer, samtidigt som den fortfarande är säker.

This thesis is concerned with the study of morphology and properties of sub-micron thin Nafion® films. The motivation of the work arises from the need to characterize the 4 -10 nm thin ionomer films in the catalyst layer of polymer electrolyte fuel cell (PEFC). A protocol for the fabrication of self-assembled ultra-thin Nafion® films on planar substrates was successfully developed. Films of thickness ranging 4 nm-300 nm, determined by three different techniques - variable angle spectroscopy ellipsometry (VASE), atomic force microscope (AFM) and x-ray photo-electron spectroscopy (XPS), could be reproducibly generated on SiO2/Si wafer. The 4 nm thin film is one of the thinnest, continuous film of Nafion® ever reported. This is the first time that the structure/properties of such thin Nafion® film have been investigated. An interesting finding is the thickness-dependent structure and property of these films. Films with thickness <55 nm exhibited hydrophilic-free surface but thicker films (>55 nm) had hydrophobic surface. Similarly, sub-55 nm films had a lower and thickness-independent protonic conductivity compared to thicker films that exhibited thickness-dependent conductivity. Anomalously high water uptake (by quartz crystal microbalance) and swelling (by ellipsometry) of sub-55nm films indicate that low conductivity is not due to low water content However, differences in surface morphology were observed by the AFM phase contrast analysis. The lack of ionic domain was also observed in the thinner films (4-30 nm) from the grazing incidence small x-ray scattering (GISAXS) experiments. Thermal annealing over a range of temperature (110-160 oC) revealed a dramatic switching of the film surface from hydrophilic to hydrophobic was observed for sub-55 nm films with lower thickness film requiring higher annealing temperature. Bulk proton conductivity was significantly reduced after annealing for all films. An interesting finding was the regeneration of conductivity after to prolonged liquid water exposure and a corresponding switching back of the surface to hydrophilic. The thickness-dependent structure/property of ultra-thin Nafion® films is attributed to substrate induced confinement effect. Self-assembly of Nafion® on various substrates (SiO2, carbon, Pt and Au) was studied. The ionomer/substrate interaction and resulting film morphology followed a trend with respect to substrate surface energies and Nafion® dispersion compositions. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-09-29 12:36:19.05

Um dos principais problemas no emprego do biodiesel como combustível de automóveis é a corrosão que ele pode provocar nos motores, devido à facilidade com que pode degradar. A natureza corrosiva do biodiesel é relacionada com a presença de água, ácidos graxos livres, ions metálicos, impurezas, a incidência da luz, a temperatura e a presença de insaturações na cadeia de alquil ésteres. Na atualidade existem poucos trabalhos na literatura sobre a corrosão dos metais em contato com biodiesel e a maioria deles têm um enfoque mais qualitativo que quantitativo. O maior desafio para avaliar a corrosividade do biodiesel mediante técnicas eletroquímicas é sua baixa condutividade. A espectroscopia de impedância eletroquímica (EIE) é uma técnica sensível que tem sido empregada para estudar meios resistivos como o etanol, por muitos anos. No entanto, os experimentos são difíceis assim como a análise dos resultados, principalmente pelo desenvolvimento da queda ôhmica no meio, devido à alta resistividade do meio ao fluxo da corrente elétrica. Os microeletrodos têm sido empregados em várias pesquisas em eletroquímica e têm apresentado algumas vantagens com respeito aos eletrodos de tamanhos convencionais. O principal benefício é a redução da queda ôhmica em meios resistivos, devido às baixas correntes registradas. No presente trabalho foi avaliada a corrosão do cobre e do aço inoxidável, os quais se encontram presentes no circuito de combustível dos motores, quando entram em contato com o biodiesel obtido a partir do óleo de soja (B100) e etanol. A avaliação foi feita mediante técnicas eletroquímicas com auxilio dos microeletrodos clássicos e na forma de arranjos (de 25 m de diâmetro), sem adição de eletrólito suporte. Adicionalmente, os resultados foram correlacionados com as mudanças nas propriedades fisicoquímicas do biodiesel (viscosidade, teor de água, teor de acidez e estabilidade oxidativa) e com ensaios gravimétricos segundo a norma ASTM G31. Os ensaios de impedância eletroquímica com os microeletrodos clássicos e os arranjos de microeletrodos mostraram duas constantes de tempo e foi possível demostrar que a constante em altas frequências está relacionada com a qualidade do biodiesel, enquanto que a constante nas baixas frequências é uma resposta da interface metal-biodiesel. A viscosidade e o teor de umidade aumentaram com a degradação do biodiesel e a estabilidade oxidativa diminuiu na mesma proporção independentemente do metal que estava em contato com o biocombustível. A presença de defeitos nos arranjos de microeletrodos obtidos por fotolitografia é um problema importante e é preciso estar sempre atento para evitar resultados equivocados. A voltametria cíclica se mostrou como técnica quantitativa para caracterizar e controlar a área exposta dos microeletrodos simples e em arranjos. Finalmente se corroborou com os ensaios eletroquímicos, a maior velocidade de corrosão para o cobre obtida nos ensaios gravimétricos, comparada à do aço inoxidável. / One of the most relevant aspects related with the use of biodiesel in automobile motors is its corrosivity, due to its susceptibility to oxidation reactions. The corrosive nature of biodiesel is related with the presence of water, free fatty acids, metallic ions, impurities, incidence of light, temperature, as well as the insaturation degree of the main chain of the alkyl esters. Currently there are few works in literature about corrosion of metals in contact with biodiesel, and most of them have more a qualitative than a quantitative focus. The main issue for electrochemical studies in biodiesel is its low conductivity. Electrochemistry impedance spectroscopy (EIS) is a sensitive technique that has been used for studying resistive media like ethanol for many years. However the experiments are difficult and the results are complex to understand, mainly because of the ohmic drop developed in this media due to the inherent solution resistance to the flow of electrical current. Microelectrodes have been used in many researches in electrochemistry showing some advantages with respect to conventional electrodes. The principal benefit is the reduction of the ohmic drop in resistive media, due to its negligible value when small currents are registered. In this work corrosiveness of copper and stainless steel which are present in fuel circuit of an automobile motor was evaluated when they come in contact with biodiesel, obtained from soybean oil and ethanol (B100). The evaluation was made using classic microelectrodes and arrays of microelectrodes (25m diameter) without addition of supporting electrolyte. Aditionally the results were correlated with the changes in biodiesel physicochemical properties (viscosity, water content, acid number and oxidation stability) and weight loss tests according to ASTM G31. The electrochemical results with classic microeletrodes and arrays of microelectrodes showed two time constants and it was demonstrated that the time constant at high frequencies is related with biodiesel quality, while the time constant at low frequencies is due to the response of metal-biodiesel interface. The viscosity and water content increased with biodiesel degradation and oxidation stability decrease in the same proportion independently of the metal in contact with biofuel. The presence of defects in the microelectrodes arrays obtained by photolitography is an important issue and the researcher must be atempt to them to avoid equivocated results. Cyclic voltammetry has shown to be a useful technique to characterize and control the exposed are in microlectrodes and their arrays. Finally, the electrochemical measurements corroborate the higher corrosion rate for copper obtained from weight loss tests compaired to corrosion rate for stainless steel.