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Polymeric materials have seen increasing use as microfluidic device substrates due to their low cost and the simplicity of templated fabrication procedures. I showed that poly(methyl methacrylate) (PMMA) microdevices could be enclosed in a boiling water bath, which allowed the seal to form more quickly than in conventional approaches, and enabled microchannels to remain hydrated throughout the bonding process. Microchip capillary electrophoresis (µ-CE) devices were fabricated using water-based enclosure, and a mixture of fluorescently labeled amino acids was separated in 30 s in these microchips. To create more robust capillary electrophoresis (CE) microdevices with improved separation performance, phase-changing sacrificial materials were developed for solvent bonding of polymer microchips. Devices were fabricated by filling channels in embossed PMMA with a heated liquid that formed a solid sacrificial layer at room temperature. The sacrificial material prevented the bonding solvent and softened PMMA from filling the channels. Once the sealing step was finished, the sacrificial layer was melted and removed, leaving enclosed microchannels. These solvent-welded devices withstood internal pressures >2,200 psi, and 300 CE runs were performed on a single microchip without any loss of separation performance. Furthermore, CE separations of peptides and amino acids were completed in ~10 s, with peak efficiencies of 43,000 theoretical plates. Electric field gradient focusing (EFGF), which uses a combination of pressure-driven flow and an electric field gradient to separate charged species according to their electrophoretic mobilities, was explored for protein analysis. Capillary-based EFGF devices were characterized; mixtures of four proteins were resolved, band focusing dynamics were studied, and analytes were enriched 10,000-fold. EFGF was miniaturized further to a microfluidic platform. Phase-changing sacrificial layers were employed to interface an electric field gradient enabling semi-permeable copolymer with microchannels. Because of decreased channel dimensions, EFGF microchips produced narrower bands and yielded threefold higher resolution compared with capillary-based devices. Beyond providing improved performance for polymer-based µ-CE and EFGF, the advances in microchip fabrication technology presented here should be applicable broadly in interfacing microfluidics with hydrogel structures, for example in sample pretreatment.

This thesis encompasses a feasibility study of using low-cost materials to manufacture microfluidic chips that can perform the same functions as chips manufactured using traditional methods within an acceptable range of efficiency of chips created with more exotic methods and materials. The major parts of the project are the selection and characterization of the fabrication methods for creating the channels for fluid flow, the methods for sealing the channels to create a usable chip and the electrophoretic separations of carboxylated microspheres of different potentials. In this work we seek to answer the question if laser-etched PMMA microfluidic chips are comparable in functionality to microfluidic chips created with PDMS or glass. In the process of answering this question we will touch on FEA modeling, characterization of the manufacturing process and multiple prototype designs while keeping within the low-cost theme. The purpose of capillary electrophoresis is to separate proteins based on their inherent electric charge. Capillary electrophoresis is a standard chip design used in the microfluidics world to prove a new fabrication method or chip material before branching out to other experiments because it is a fairly simple and robust design. Common problems associated with the manufacturing methods and materials were taken into account such as electroosmotic flow and chip sealing. CZE designs from literature were referenced to create a chip that would separate carboxylated microbeads with reasonable resolution. Wire electrodes were affixed to the chip to induce electric fields for the electrophoresis experiments. The goal of this thesis is to prove the manufacturing methods and attain results within 70% of literature standards.

The global market for waterborne coatings will continue to grow because alternative solventborne coatings emit environmentally hazardous volatile organic compounds (VOCs). However, most waterborne coatings are softer than solventborne crosslinked thermoset coatings because they feature thermoplastic polymer dispersions. To overcome these challenges, in this thesis we suggest a novel crosslinkable aqueous dispersion system that incorporates epoxy and amine particles into poly(methyl methacrylate) (PMMA); the particles will react when water (the solvent) evaporates, offering a potential one-component (1K) reactive system. Emulsion polymerization was used to synthesize the particles with the help of surfactants. Epoxy and amine particles were successfully incorporated during the synthesis of PMMA and formed a two-component (2K) aqueous dispersion. In this process, a non-ionic surfactant, Triton X405 (TX405), was used to prevent interactions with the amine particles. Nuclear magnetic resonance (NMR) was used to determine the actual incorporation ratios of epoxy and amine and we found an epoxy incorporation plateau. Dynamic light scattering (DLS) was used to determine the particle size distributions and a uniform distribution was observed. The pendulum test and the pencil test were used for coating hardness, which surpassed currently marketed waterborne coatings. The resulting aqueous dispersions could be cured under facile conditions, i.e., in air and at low temperatures. An increase in Tg was observed after crosslinking. Different mechanical properties were observed when the coatings were cured at different temperatures, 25°C, 70°C, and 100°C. These results suggest that we have successfully formed crosslinked coatings that contain our epoxy and amine incorporated particles, with mechanical properties comparable to the traditional solventborne coatings.

Industries (food, beverage, petrochemical, etc.) normally use various gravitational separation echniques in their processes. Such separation processes often suffer from the deposition of undesirable material on the active surfaces of the process equipment, e.g. a high-speed separator or decanter, causing a slew of problems with the process or product quality. To restore operational efficiencies, additional cleaning steps using both water and chemicals are required, making the process more expensive and less environmentally friendly. Other than operating time and concentration of the process fluid there are several factors such as surface nature, surface roughness, type of material, surface charge, etc which influence the fouling deposition of surfaces. Fouling on the surfaces can grow following different mechanisms. The goal of this research work is to learn more about the nature of foulant interactions with stainless steel surfaces and eventually design some antifouling methodology. It is too difficult to study foulingfor all kinds of solutions and industries, so we tried to investigate the organic deposition in dairy and brewery industries by using lab-scale synthesized milk and beer solutions, For quantitative and statistical examination of these characteristics, several experimental approaches (FTIR, percent weight change, surface roughness, surface energy) were used. It was confirmed that fouling grows on the surfaces in a non-linear fashion irrespective of the time and concentration of the solution. The fouling of surfaces can be improved by producing more hydrophilic surfaces or by reducing surface roughness. Steric hindrance, electrostatic charge, and water barrier or hydration layer theories can be used to modify the surface nature and hence the fouling deposition. For antifouling purposes, PMMA (organic) and tungsten oxide (inorganic) coatings were employed. The PMMA was deposited using a dip-coating technique using (6%,10%, and 12%) PMMA solution, and the tungsten oxide coating was carried out by using a standard two electrode electrochemical system under different voltage (3.5V and 4.5V) and time (5min, 10 min, and 20 min) conditions. The coatings were characterized by using different techniques and their antifouling effects were studied in model milk and model beer solutions / Vid industriella processer (livsmedel, petrokemisk etc.) används ofta olika tekniker för separation med hjälp av gravitation. Sådana separationsprocesser drabbas ofta av oönskade beläggningar och påväxt på processutrustningens aktiva ytor så som t.ex. i en separator eller en dekanter, vilket orsakar problem med processen eller produktkvaliteten. För att återställa driftseffektivitet krävs särskilda rengöringssteg med både vatten och kemikalier vilket gör processen dyrare och mindre miljövänlig. Förutom drifttid och processvätskans sammansättning finns det flera faktorer såsom ytbeskaffenhet, ytjämnhet, materialtyp, ytladdning m.m. som påverkar mängden oönskade beläggningar på ytor. Föroreningarna på ytor kan tillväxa med olika mekanismer. Målet med detta forskningsarbete är att studera interaktionen mellan olika former av påväxt och ytan på rostfritt stål och senare utforma metoder för att förhindra bildandet av sådana oönskade beläggningar. Det är en stor utmaning att studera olika typer av påväxt för alla typer av flöden och industrier. I studien undersöktes organisk påväxt inom mejeri- och bryggeriindustrin genom att använda syntetiserade mjölk- och ölprodukter i laboratorieskala, för kvantitativa och statistiska undersökningar av dessa egenskaper. Flera olika experimentella metoder användes (FTIR, viktförändring, ytjämnhet, ytenergi). Det bekräftades att tillväxten på ytorna var olinjärt oavsett tid och lösningens koncentration. Bildandet och tillväxt av oönskade beläggningar kan minskas med hjälp av mera hydrofila ytor eller genom att minska ytans ojämnhet. Steriska hinder, elektrostatisk laddning och vattenbarriär eller hydratiseringsskal kan användas för att modifiera ytan och därmed fördröja bildandet av oönskade beläggningar. För att förhindra påväxt belades ytan med PMMA (organisk) och volframoxid (oorganisk). PMMA deponerades genom en doppbeläggningsteknik med användning av (6%, 10% och 12%) PMMA-lösning och volframoxidbeläggningen utfördes med ett elektrokemiskt tvåelektrodssystem med olika spänningar (3,5V och 4,5V) och tider (5min, 10min och 20min). Ytbeläggningarna karakteriserades genom att använda olika tekniker och deras förmåga att förhindra snabb påväxt studerades i modellösningar av mjölk och öl.

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