The dissertation presented here describes two research projects that may, at first glance, seem unrelated. Their unifying principle is the measurement of electrical impedance for the detection and analysis of biological materials. Impedance measurements have long been employed and studied in scientific fields, and the dissertation begins with a summary of historical methodology, applications, and terminology. Utilizing impedance measurements for microscopic imaging is the driving motivation for Scanning Impedance Imaging (SII). This technique manifests the distribution of electrical impedance inside biological tissues and is described after the dissertation's introduction. SII can provide micron-scale imaging resolution by scanning a shielded microprobe over a sample placed on a conducting plane. A known voltage is applied to the microprobe and the sample immersed in a conductive aqueous medium. Both the probe height and the shield spacing were evaluated and optimized and two hardware configurations were developed to implement image scanning. A combined value ρh (resistivity × height) was used to represent impedance for heterogeneous samples. Experiments on photosensitive polymers, a butterfly wing, an oxide coated silicon wafer and cancer cells were performed and impedance images obtained. Impedance measurements for sensitive detection are demonstrated using a microchip capable of capillary electrophoresis separations. The chip was built using exclusively thin film deposition techniques, fully compatible with microelectronics batch processing. Standard photolithography provided control of the spacing between impedance measurement electrodes used in and overall channel geometry. The chip's performance was tested using concentrations of sodium chloride and calcium chloride ranging from 1 µM to 1 mM in a 5 mM MES/His buffer. Separations were performed by applying different voltages to reservoirs positioned at the four fluid channel openings. Impedance detection was performed by applying a small AC voltage (1 Vrms, 250 kHz) to the insulated electrodes positioned inside the fluid channels. Electropherograms were obtained and signal-to-noise ratio (S/N) was calculated. Measurements indicated that the trend of S/N as a function of molar concentrations was consistent with bulk conductivity tests and the chip's detection limit was below 1 µM for both sodium and calcium cations.

Microfluidics is a continually growing field covering a wide range of applications, such as cellular analysis, biomarker quantification, and drug discovery; but in spite of this, the field of microfluidics remains predominately academic. New materials are pivotal in providing tailored properties to improve device integration and decrease prototype turnaround times. In biosensing, nonspecific adsorption in microfluidic systems can deplete target molecules in solution and prevent analytes, especially those at low concentrations, from reaching the detector. Polyethylene glycol diacrylate (PEGDA) mixed with photoinitiator forms, on exposure to ultraviolet (UV) radiation, a polymer with inherent resistance to nonspecific adsorption. Optimization of the polymerized PEGDA (poly-PEGDA) formula imbues this material with some of the same properties, including optical clarity, water stability, and low background fluorescence, that makes polydimethylsiloxane (PDMS) a widely used material for microfluidics. Poly-PEGDA demonstrates less nonspecific adsorption than PDMS over a range of concentrations of flowing fluorescently tagged bovine serum albumin solutions, and poly-PEGDA has greater resistance to permeation by small hydrophobic molecules than PDMS. Poly-PEGDA also exhibits long-term (hour scale) resistance to nonspecific adsorption compared to PDMS when exposed to a low (1 μg/mL) concentration of a model adsorptive protein. Electrophoretic separations of amino acids and proteins resulted in symmetrical peaks and theoretical plate counts as high as 4 × 105/m. Pneumatically actuated, non-elastomeric membrane valves fabricated from poly-PEGDA have been characterized for temporal response, valve closure, and long-term durability. A ∼100 ms valve opening time and a ∼20 ms closure time offer valve operation as fast as 8 Hz with potential for further improvement. Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance. After initial fabrication, the fluid pressure required to open a closed circular valve is ∼50 kPa higher than the control pressure holding the valve closed. However, after ∼1000 actuations to reconfigure polymer chains and increase elasticity in the membrane, the fluid pressure required to open a valve becomes the same as the control pressure holding the valve closed. After these initial conditioning actuations, poly-PEGDA valves show considerable robustness with no change in effective operation after 115,000 actuations.Often, localized areas of surface functionalization are desired in biosensing, necessitating site-specific derivatization. Integration of poly-PEGDA with different substrates, such as glass, silicon, or electrode-patterned materials, allows for broad application in biosensing and microfluidic devices. Deposition of 3-(trimethoxysilyl) propyl methacrylate or (3-acryloxypropyl) dimethylmethoxysilane onto these substrates makes bonding to poly-PEGDA possible under UV exposure. Primary deposition of (3-acryloxypropyl) dimethylmethoxysilane, followed by photolithographic patterning, allows for silane removal through HF surface etching in the exposed areas and subsequent deposition of 3 aminopropyldiisopropylethoxysilane on the etched regions. Fluorescent probes are used to evaluate surface attachment methods. Primary attachment via reaction of Alexa Fluor 488 TFP ester to the patterned aminosilane demonstrates excellent fluorescent signal. Initial results with glutaraldehyde were demonstrated but require more optimization before this method for secondary attachment is viable. Fabrication of 3D printed microfluidic devices with integrated membrane-based valves is performed with a low-cost, commercially available stereolithographic 3D printer and a custom PEGDA resin formulation tailored for low non-specific protein adsorption. Horizontal microfluidic channels with designed rectangular cross sectional dimensions as small as 350 µm wide and 250 µm tall are printed with 100% yield, as are cylindrical vertical microfluidic channels with 350 µm designed (210 µm actual) diameters. Valves are fabricated with a membrane consisting of a single build layer. The fluid pressure required to open a closed valve is the same as the control pressure holding the valve closed. 3D printed valves are successfully demonstrated for up to 800 actuations. Poly-PEGDA is a versatile material for microfluidic applications ranging from electrophoretic separations, valve implementation, and heterogeneous material integration. Further improvements in PEGDA resin formulation, in combination with a UV source 3D printer, will provide poly-PEGDA devices that are not only rapidly fabricated (<40 min per device), but that also include pumps and valves and are usable with a variety of detection methods, such as laser-induced fluorescence and immunoassays, for broad application in biosensing.

This work presents the development of 3D printed microfluidic devices and their application to microchip analysis. Initial work was focused on the development of the printer resin as well as the development of the general rules for resolution that can be achieved with stereolithographic 3D printing. The next stage of this work involved the characterization of the printer with a variety of interior and exterior resolution features. I found that the minimum positive and negative feature sizes were about 20 μm in either case. Additionally, micropillar arrays were printed with pillar diameters as small as 16 μm. To demonstrate one possible application of these small resolution features I created microfluidic bead traps capable of capturing 25 μm polystyrene particles as a step toward capturing cells. A second application which I pioneered was the creation of devices for microchip electrophoresis. I separated 3 preterm birth biomarkers with good resolution (2.1) and efficiency (3600 plates), comparable to what has been achieved in conventionally fabricated devices. Lastly, I have applied some of the unique capabilities of our 3D printer to a variety of other device applications through collaborative projects. I have created microchips with a natural masking monolith polymerization window, spiral electrodes for capacitively coupled contactless conductivity detection, and a removable electrode insert chip. This work demonstrates the ability to 3D print microfluidic structures and their application to a variety of analyses.

No description available.

No description available.

No description available.

A combinação de célula eletroquímica (EC) com a entrada do equipamento de eletroforese capilar (CE), apesar de recente, tem permitido realizar determinação de ânions radicais; pré-concentração eletroquímica de metais pesados, seguida de redissolução, separação e detecção; bem como monitorar produtos carregados formados por oxidação eletrocatalítica de espécies neutras, como álcoois primários e glicerol. Empregando o sistema EC-CE-C4D desenvolvido pelo grupo, a determinação simultânea de cátions, ânions (no contra fluxo) e espécies neutras (detectadas após derivatização eletroquímica) foi demonstrada pela primeira vez, tendo o antisséptico bucal (Listerine® Tartar Control) como amostra real. Embora constante e reprodutível, a conversão dos álcoois primários nos respectivos carboxilatos apresentou rendimento relativamente baixo, ~16%, nas condições anteriormente adotadas, 1,6 V vs. Ag/AgClKCl 3M empregando eletrodo de platina em meio ácido (HNO3 5 mmol L-1 / HCl 1 mmol L-1). Dessa maneira, avaliou-se a oxidação de álcoois primários de cadeia normal (C2 &#8722; C5) sobre diferentes materiais de eletrodo (ouro e platina) em diferentes meios (ácido, neutro e alcalino). Os carboxilatos gerados foram monitorados injetando uma alíquota da amostra derivatizada no capilar (50 &#181;m d.i., 45 cm de comprimento e 20 cm efetivo) aplicando 5 kPa durante 5 s, e durante as separações, 30 kV foi aplicado entre as extremidades do capilar preenchido com Tris 30 mmol L-1 / HCl 10 mmol L-1 usado como BGE. Os resultados obtidos com o sistema EC-CE-C4D apontaram maior conversão dos álcoois nos respectivos ácidos carboxílicos em meio ácido, tanto em ouro quanto em platina. Adicionalmente, em eletrodo de ouro a formação dos carboxilatos apresentou certa seletividade não observada sobre platina, favorecendo a conversão dos álcoois de cadeia menor. Noutra vertente, buscando atender as necessidades atuais por metodologias que possibilitem monitorar a eletrooxidação do glicerol em reatores eletroquímicos, desenvolveu-se um método que permitiu determinar simultaneamente o glicerol e alguns de seus possíveis produtos de oxidação neutros, como gliceraldeído e dihidroxiacetona, explorando a formação de complexo carregado com borato (presente no BGE composto por H3BO3 60 mmol L-1 / LiOH 30 mmol L-1), além dos produtos ionizáveis (ácidos carboxílicos) que são comumente analisados por CE. O equipamento de CE utilizado, munido de dois detectores C4D, também permitiu avaliar a interação de alguns ácidos carboxílicos com os modificadores de EOF, Polybrene® e CTAB, empregando MES 30 mmol L-1 / His 30 mmol L-1 como BGE. Seguindo a atual tendência à miniaturização de sistemas analíticos, avaliou-se a possibilidade de construir um sistema EC-CE-C4D miniaturizado. Para isso, um novo método para fabricação de microdispositivos em vidro, baseado em ablação a laser de CO2 assistida por parafina, como alternativa aos dispendiosos métodos de corrosão por via úmida foi desenvolvido. Os dispositivos obtidos por esse método apresentaram canais de perfil semicircular, e as dimensões puderam ser controladas variando a potência e/ou a velocidade de ablação do laser. Contudo, pelos desafios ainda encontrados para se construir um sistema EC-CE-C4D completo em substrato de vidro por ablação a laser de CO2, optou-se por iniciar a miniaturização do sistema EC-CE-C4D com um sistema híbrido em que se aproveita as características mais bem definidas e favoráveis dos tubos capilares de sílica fundida usados em CE convencional. Esse sistema permitiu a determinação quantitativa de metanol na presença de alta concentração de etanol, possibilitando, numa primeira aplicação, realizar o monitoramento da quantidade de metanol e etanol nas frações iniciais coletada durante o processo de destilação fracionada na produção de uísque de milho (moonshine) feito em laboratório. Visto a maior seletividade para conversão dos álcoois de cadeia menor obtidas em eletrodo de ouro e meio ácido, esse foi escolhido para a presente aplicação. As condições que apresentaram melhores resultados no sistema híbrido EC-CE-C4D abrangeram diluição de 100 vezes da amostra em HNO3 2 mmol L-1, eletrooxidação a 1,4 V vs. Ag durante 60 s, injeção eletrocinética no capilar mediante aplicação de 3 kV durante 4 s, e a separação dos carboxilatos realizada aplicando 3 kV entre as extremidades do capilar (50 &#181;m d.i., 15 cm de comprimento com 12 cm efetivo), preenchido com CHES 10 mmol L-1 / NaOH 5 mmol L-1, usado como BGE. A análise das primeiras frações destiladas da \"labmade moonshine\" apresentou um aumento na concentração de etanol (variando de ~80 % a ~100 %) e simultâneo decréscimo da concentração de metanol (variando de 4 % a ~0,1 %). Em suma, avançou-se tanto no leque de aplicações da derivatização eletroquímica hifenizada com a eletroforese capilar como na miniaturização da instrumentação analítica para EC-CE-C4D, favorecendo a disseminação dessa poderosa combinação de três técnicas eletroquímicas. / The direct couple of electrochemical cell (EC) with the inlet of the capillary electrophoresis (CE) equipment, recently demonstrated, has allowed the determination of radical anions; to perform electrochemical preconcentration of traces of heavy metals, followed by stripping, injection, separation and detection; and the generation of charged species by electrochemical oxidation of neutral molecules, e.g. primary alcohols and glycerol. Employing the EC-CE-C4D system developed by our group, the simultaneous determination of cations, anions (in the counter EOF mode) and neutral species (after electrochemical derivatization) was demonstrated for the first time and a mouthwash (Listerine® Tartar Control) was used as a real sample. Although constant and reproducible, the conversion of primary alcohols into carboxylates had a low yield (~16%), under the adopted conditions, 1.6 V vs. Ag/AgClKCl 3M using platinum electrode in acid medium (5 mmol L-1 HNO3 / 1 mmol L-1 HCl). Thus, the yield of carboxylates was studied for the oxidation of alcohols (C2 &#8722; C5) on two electrode materials (gold and platinum) in different media (acid, neutral and alkaline). After the electrooxidation step an aliquot of the derivatized sample was automatically injected into the capillary (50 &#181;m i.d., 45 cm in length and 20 cm up to detector) by applying 5 kPa during 5 s. The separation was carried out applying 30 kV between the capillary ends previously filled with 30 mmol L-1 Tris / 10 mmol L-1 HCl BGE. Cyclic voltammograms show higher current density for alcohols oxidation in alkaline medium than in acid one both on gold and platinum electrodes. On the other hand the yields of carboxylic acids were higher in acidic medium. Besides that, only on gold electrode some selectivity for the carboxylate formation was observed favoring the conversion of the short chain alcohols. In order to meet the current needs for methodologies that allow the monitoring of the electrooxidation of glycerol in electrochemical reactors, a method was also developed that allowed the determination of glycerol and some of its possible neutral oxidation products, such as glyceraldehyde and dihydroxyacetone, by exploring the formation of borate complexes (provided in the BGE composed of 60 mmol L-1 H3BO3 / 30 mmol L-1 LiOH), together with ionizable ones like carboxylic acids. The employed CE equipment with two C4D detectors allowed the evaluation of the interaction between some carboxylic acids and the EOF modifiers, Polybrene® and CTAB, using 30 mmol L-1 MES / 30 mmol L-1 His as BGE. Aligned with a current trend of analytical instrumentation, the miniaturized EC-CE-C4D system was attempted. For that, a new method for manufacturing microdevices in glass, based on paraffin-assisted CO2 laser ablation, was developed as an alternative to costly wet-etching methods. The devices obtained by this method presented channels of semicircular profile and the dimensions could be controlled by varying the laser power and/or ablation velocity. Due to remaining challenges in the construction of a complete laser ablated EC-CE-C4D system on glass, a miniaturized system based on a hybrid approach is presented in the thesis, by taking advantage of the more defined and favorable characteristics of the well known fused silica capillary tubes used in CE. This system allowed the quantitative determination of methanol in the presence of high ethanol concentration by taking advantage of the higher yield of short-chain carboxylic acid formation on gold in acidic medium. The first application was the monitoring of the amount of methanol and ethanol in the initial fractions collected during the fractional distillation process in the production of corn whiskey (moonshine) made in the laboratory. The conditions that showed the best results with the hybrid EC-CE-C4D system included a 100-fold dilution of the sample in 2 mmol L-1 HNO3, electrooxidation at 1.4 V vs. Ag for 60 s, electrokinetic injection into the capillary by applying 3 kV for 4 s and separation of the carboxylates carried out under 3 kV between the ends of the capillary (50 &#181;m i.d., 15 cm in length and 12 cm up to detector) previously filled with 10 mmol L-1 CHES / 5 mmol L-1 NaOH, used as BGE. Analysis of the first distilled fractions of labmade moonshine showed an increase in ethanol concentration (ranging from ~ 80% to ~ 100%) and a simultaneous decrease in methanol concentration (ranging from 4% to ~ 0.1%). In short, both the range of applications of electrochemical derivatization hyphenated with capillary electrophoresis as well the miniaturization of analytical instrumentation for EC-CE-C4D were improved, favoring the dissemination of this powerful combination of three electrochemical techniques.

A combinação de célula eletroquímica (EC) com a entrada do equipamento de eletroforese capilar (CE), apesar de recente, tem permitido realizar determinação de ânions radicais; pré-concentração eletroquímica de metais pesados, seguida de redissolução, separação e detecção; bem como monitorar produtos carregados formados por oxidação eletrocatalítica de espécies neutras, como álcoois primários e glicerol. Empregando o sistema EC-CE-C4D desenvolvido pelo grupo, a determinação simultânea de cátions, ânions (no contra fluxo) e espécies neutras (detectadas após derivatização eletroquímica) foi demonstrada pela primeira vez, tendo o antisséptico bucal (Listerine® Tartar Control) como amostra real. Embora constante e reprodutível, a conversão dos álcoois primários nos respectivos carboxilatos apresentou rendimento relativamente baixo, ~16%, nas condições anteriormente adotadas, 1,6 V vs. Ag/AgClKCl 3M empregando eletrodo de platina em meio ácido (HNO3 5 mmol L-1 / HCl 1 mmol L-1). Dessa maneira, avaliou-se a oxidação de álcoois primários de cadeia normal (C2 &#8722; C5) sobre diferentes materiais de eletrodo (ouro e platina) em diferentes meios (ácido, neutro e alcalino). Os carboxilatos gerados foram monitorados injetando uma alíquota da amostra derivatizada no capilar (50 &#181;m d.i., 45 cm de comprimento e 20 cm efetivo) aplicando 5 kPa durante 5 s, e durante as separações, 30 kV foi aplicado entre as extremidades do capilar preenchido com Tris 30 mmol L-1 / HCl 10 mmol L-1 usado como BGE. Os resultados obtidos com o sistema EC-CE-C4D apontaram maior conversão dos álcoois nos respectivos ácidos carboxílicos em meio ácido, tanto em ouro quanto em platina. Adicionalmente, em eletrodo de ouro a formação dos carboxilatos apresentou certa seletividade não observada sobre platina, favorecendo a conversão dos álcoois de cadeia menor. Noutra vertente, buscando atender as necessidades atuais por metodologias que possibilitem monitorar a eletrooxidação do glicerol em reatores eletroquímicos, desenvolveu-se um método que permitiu determinar simultaneamente o glicerol e alguns de seus possíveis produtos de oxidação neutros, como gliceraldeído e dihidroxiacetona, explorando a formação de complexo carregado com borato (presente no BGE composto por H3BO3 60 mmol L-1 / LiOH 30 mmol L-1), além dos produtos ionizáveis (ácidos carboxílicos) que são comumente analisados por CE. O equipamento de CE utilizado, munido de dois detectores C4D, também permitiu avaliar a interação de alguns ácidos carboxílicos com os modificadores de EOF, Polybrene® e CTAB, empregando MES 30 mmol L-1 / His 30 mmol L-1 como BGE. Seguindo a atual tendência à miniaturização de sistemas analíticos, avaliou-se a possibilidade de construir um sistema EC-CE-C4D miniaturizado. Para isso, um novo método para fabricação de microdispositivos em vidro, baseado em ablação a laser de CO2 assistida por parafina, como alternativa aos dispendiosos métodos de corrosão por via úmida foi desenvolvido. Os dispositivos obtidos por esse método apresentaram canais de perfil semicircular, e as dimensões puderam ser controladas variando a potência e/ou a velocidade de ablação do laser. Contudo, pelos desafios ainda encontrados para se construir um sistema EC-CE-C4D completo em substrato de vidro por ablação a laser de CO2, optou-se por iniciar a miniaturização do sistema EC-CE-C4D com um sistema híbrido em que se aproveita as características mais bem definidas e favoráveis dos tubos capilares de sílica fundida usados em CE convencional. Esse sistema permitiu a determinação quantitativa de metanol na presença de alta concentração de etanol, possibilitando, numa primeira aplicação, realizar o monitoramento da quantidade de metanol e etanol nas frações iniciais coletada durante o processo de destilação fracionada na produção de uísque de milho (moonshine) feito em laboratório. Visto a maior seletividade para conversão dos álcoois de cadeia menor obtidas em eletrodo de ouro e meio ácido, esse foi escolhido para a presente aplicação. As condições que apresentaram melhores resultados no sistema híbrido EC-CE-C4D abrangeram diluição de 100 vezes da amostra em HNO3 2 mmol L-1, eletrooxidação a 1,4 V vs. Ag durante 60 s, injeção eletrocinética no capilar mediante aplicação de 3 kV durante 4 s, e a separação dos carboxilatos realizada aplicando 3 kV entre as extremidades do capilar (50 &#181;m d.i., 15 cm de comprimento com 12 cm efetivo), preenchido com CHES 10 mmol L-1 / NaOH 5 mmol L-1, usado como BGE. A análise das primeiras frações destiladas da \"labmade moonshine\" apresentou um aumento na concentração de etanol (variando de ~80 % a ~100 %) e simultâneo decréscimo da concentração de metanol (variando de 4 % a ~0,1 %). Em suma, avançou-se tanto no leque de aplicações da derivatização eletroquímica hifenizada com a eletroforese capilar como na miniaturização da instrumentação analítica para EC-CE-C4D, favorecendo a disseminação dessa poderosa combinação de três técnicas eletroquímicas. / The direct couple of electrochemical cell (EC) with the inlet of the capillary electrophoresis (CE) equipment, recently demonstrated, has allowed the determination of radical anions; to perform electrochemical preconcentration of traces of heavy metals, followed by stripping, injection, separation and detection; and the generation of charged species by electrochemical oxidation of neutral molecules, e.g. primary alcohols and glycerol. Employing the EC-CE-C4D system developed by our group, the simultaneous determination of cations, anions (in the counter EOF mode) and neutral species (after electrochemical derivatization) was demonstrated for the first time and a mouthwash (Listerine® Tartar Control) was used as a real sample. Although constant and reproducible, the conversion of primary alcohols into carboxylates had a low yield (~16%), under the adopted conditions, 1.6 V vs. Ag/AgClKCl 3M using platinum electrode in acid medium (5 mmol L-1 HNO3 / 1 mmol L-1 HCl). Thus, the yield of carboxylates was studied for the oxidation of alcohols (C2 &#8722; C5) on two electrode materials (gold and platinum) in different media (acid, neutral and alkaline). After the electrooxidation step an aliquot of the derivatized sample was automatically injected into the capillary (50 &#181;m i.d., 45 cm in length and 20 cm up to detector) by applying 5 kPa during 5 s. The separation was carried out applying 30 kV between the capillary ends previously filled with 30 mmol L-1 Tris / 10 mmol L-1 HCl BGE. Cyclic voltammograms show higher current density for alcohols oxidation in alkaline medium than in acid one both on gold and platinum electrodes. On the other hand the yields of carboxylic acids were higher in acidic medium. Besides that, only on gold electrode some selectivity for the carboxylate formation was observed favoring the conversion of the short chain alcohols. In order to meet the current needs for methodologies that allow the monitoring of the electrooxidation of glycerol in electrochemical reactors, a method was also developed that allowed the determination of glycerol and some of its possible neutral oxidation products, such as glyceraldehyde and dihydroxyacetone, by exploring the formation of borate complexes (provided in the BGE composed of 60 mmol L-1 H3BO3 / 30 mmol L-1 LiOH), together with ionizable ones like carboxylic acids. The employed CE equipment with two C4D detectors allowed the evaluation of the interaction between some carboxylic acids and the EOF modifiers, Polybrene® and CTAB, using 30 mmol L-1 MES / 30 mmol L-1 His as BGE. Aligned with a current trend of analytical instrumentation, the miniaturized EC-CE-C4D system was attempted. For that, a new method for manufacturing microdevices in glass, based on paraffin-assisted CO2 laser ablation, was developed as an alternative to costly wet-etching methods. The devices obtained by this method presented channels of semicircular profile and the dimensions could be controlled by varying the laser power and/or ablation velocity. Due to remaining challenges in the construction of a complete laser ablated EC-CE-C4D system on glass, a miniaturized system based on a hybrid approach is presented in the thesis, by taking advantage of the more defined and favorable characteristics of the well known fused silica capillary tubes used in CE. This system allowed the quantitative determination of methanol in the presence of high ethanol concentration by taking advantage of the higher yield of short-chain carboxylic acid formation on gold in acidic medium. The first application was the monitoring of the amount of methanol and ethanol in the initial fractions collected during the fractional distillation process in the production of corn whiskey (moonshine) made in the laboratory. The conditions that showed the best results with the hybrid EC-CE-C4D system included a 100-fold dilution of the sample in 2 mmol L-1 HNO3, electrooxidation at 1.4 V vs. Ag for 60 s, electrokinetic injection into the capillary by applying 3 kV for 4 s and separation of the carboxylates carried out under 3 kV between the ends of the capillary (50 &#181;m i.d., 15 cm in length and 12 cm up to detector) previously filled with 10 mmol L-1 CHES / 5 mmol L-1 NaOH, used as BGE. Analysis of the first distilled fractions of labmade moonshine showed an increase in ethanol concentration (ranging from ~ 80% to ~ 100%) and a simultaneous decrease in methanol concentration (ranging from 4% to ~ 0.1%). In short, both the range of applications of electrochemical derivatization hyphenated with capillary electrophoresis as well the miniaturization of analytical instrumentation for EC-CE-C4D were improved, favoring the dissemination of this powerful combination of three electrochemical techniques.

As technology advances with time, new devices are invented and old ones used in innovative ways. Microchips have been increasingly minimized to the point where they can now fit on a fingernail. When encased in a bio-friendly coating and equipped with the appropriate in- or output technology, new modes of natural digital interaction can be explored. This thesis studies how the general public perceives microchip implants as a digital interaction tool, as well as which features of microchip implants are important to them. Three different scenarios of implanted microchip use were created and used in eight semi-structured interviews. The results showed skepticism towards the technology due to worries about security and privacy, and a lack of knowledge of this technology. Benefits included keeping better track of health and making everyday actions easier, as well as excitement about this new technology.

Analysis of low-abundance components in small samples remains a challenge within bioanalytical chemistry, and new techniques for sample pretreatments followed by sensitive and informative detection are required. In this thesis, procedures for preconcentration and separation of proteins and peptides in open microchannels fabricated on silicon microchips are presented. Analyte electromigration was induced by applying a voltage along the channel length, and detection was performed either by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) within the open channel, or by sampling a nL fraction containing the preconcentrated analytes from the channel for subsequent nano-electrospray ionization- (nESI-) or MALDI-MS. Utilizing solvent evaporation from the open system during sample supply, sample volumes exceeding the 25-75 nL channel volume could be analyzed. For preconcentration/separation of components in the discrete channel volume a lid of inert fluorocarbon liquid was used for evaporation control. In Papers I and II, aqueous, carrier-free solutions of proteins and peptides were analyzed, and the method was successfully applied for fast and simple preconcentration of amyloid beta (Aβ) peptides, related to Alzheimer’s disease. The impact of possible impurities in the analysis of carrier-free solutions was investigated in Paper III with the 1D simulation software GENTRANS, and a method for open-channel isoelectric focusing in a tailor-made pH gradient was developed. The latter approach was used in Paper IV for preconcentration and purification of Aβ peptides after immunoprecipitation from cerebrospinal fluid and blood plasma, followed by MALDI-MS from a micropillar chip. Paper V includes simulations of an isotachophoretic strategy for selective enrichment of Aβ peptides. GENTRANS simulations were used to select the electrolyte composition, and 2D simulations in a geometry suitable for on-chip implementation were performed using COMSOL Multiphysics. / <p>QC 20160930</p>