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Lateral flow biosensors are analytical devices that detect biomaterials with physicochemical signals, such as optical signals. Unlike other biosensors, lateral flow biosensors are based on porous membranes, which use capillary force to transport biomaterials spontaneously. However, lateral flow biosensors are fabricated in batch mode, which means that membranes need to be cut from the rolls, pretreated, and assembled using a step-by-step process. Thus, there is a need for a more efficient manufacturing process. This thesis aims to accelerate the fabrication process by developing a method wherein the whole device is printed directly, including the printable substrates, as well as by developing a clog-free process for depositing expensive reagents. These novel printable porous media were developed using printing inks that contained various pigments and polymer binders. To this end, candidate formulations were screened from nine hundred inks formulations via wicking experiments. The results of these tests showed that the most promising formulations were based on calcium carbonates and latex polymers. This formulation was then used to develop printable porous media that can easily be printed into complex patterns, with changeable wicking speeds within each pattern. In addition, a bio- colorimetric assay of alkaline phosphates conducted on these porous media showed strong color signals that were comparable to the traditional membrane-based lateral flow strips. Clog-free printing processes were investigated by using a piezoelectric inkjet printer to print silica sols and six nanoparticle inks. The results of these tests showed that the vibration of the piezoelectric layer and the deposition of particles on the printhead surfaces induced clogging issues. Over time, the silica sols formed multilayer deposits on the print head surface, which subsequently detached due to the vibration of the piezoelectric layer. Consequently, these large sheets of silica clogged the nozzles during printing. This clogging issue was eliminated by adjusting the pH value of the silica sol inks to 3.1. The hydrophobic cationic polystyrene nanoparticles form a sub-monolayer on the printhead surface, which causes air entrainment and promotes air bubble adhesion into the interior of the print head surface when the piezoelectric layer deforms. Thus, alternate surface chemistries for the print head and ink particle surfaces may be required in order to print hydrophobic ink materials. Overall, this enhanced understanding of these clogging mechanisms helps to explain why printer performance varies when different particles are used. / Thesis / Doctor of Philosophy (PhD) / Many devices in our day-to-day lives incorporate lateral flow biosensors, for example, home pregnancy test kits. These tests allow users to obtain results within 30 minutes by simply applying a few droplets of urine onto a test strip. However, these biosensors are largely manufactured using manual processes: workers cut strips (also called substrates) from sheets, deposit reagents onto the strips, and then assemble the pretreated strips into devices. As such, these processes are time consuming and less productive. To accelerate the manufacturing process, we developed printable porous substrates and a clog-free printing process for depositing expensive reagents onto the substrates. Novel porous media can be flexibly printed into complex patterns using pigment- based inks. Moreover, the use of different pigments within the designed patterns enables these porous media to control wicking velocity. In addition to printable porous substrates, the research in this thesis shows that the manufacturing process can be improved by using piezoelectric inkjet printers. The use of these printers not only allows the expensive reagents to be precisely deposited onto the substrates, but it also offers a more cost-effective method of doing so. Finally, in order to ensure the printing process remained clog-free, we systematically investigated clogging mechanisms by printing with different polymers and nanoparticles.

Nitrocellulose is currently the most common porous material used in commercially available lateral flow assays. It is, however, unsafe to manufacture and time consuming to incorporate into multi-component assay devices. Precipitated calcium carbonate is a material produced from naturally occurring lime that can be suspended in a binder and extruded onto a surface. This extruded suspension forms a porous coating through which a solution can be wicked. The physical characteristics of three different types of calcium carbonate types were investigated to determine differences that may yield better lateral flow. The capillary flow rate through the coating was found to be largely affected by the calcium carbonate type used, the binder concentration and whether any post-printing treatment was applied, specifically heating the print. Calcium carbonate has a high specific surface area, which results in a high protein binding capacity. To prevent protein binding, pre-treating calcium carbonate particles prior to forming the suspension in a binder was attempted. Pre-treatment with bovine serum albumin, casein or methoxy-PEG phosphate did not show prevention of protein binding. Furthermore, by treating the calcium carbonate particles with a protein before suspension formulation, the wicking rate after printing was found to be diminished. / Thesis / Master of Applied Science (MASc)

Nutrient accumulation in vegetable crops is declining. New varieties, selected for high yield, may be subject to a dilution effect of nutrient concentration. Alternatively, soil fertility may be to blame. Here, we investigate how nitrogen fertilization can enhance or suppress calcium and potassium content in two lettuce varieties already known to accumulate high or low amounts of these nutrients. Effects of varying the ammonium:nitrate ratio and effects of calcium carbonate buffering on plant growth by mass and on uptake and accumulation of potassium and calcium in two lettuce (Lactuca sativa L.) cultivars, Two Star and Red Deer Tongue, were investigated in three greenhouse hydroponic experiments in which ammonium supplied none, 6%, 12%, 25%, 50%, 75% or all of the nitrogen. Ammonium, supplied as the sole nitrogen source (15 mM), was toxic under buffered or unbuffered conditions. It limited growth and concentrations of potassium and calcium in lettuce leaves. Proportions of ammonium-N greater than 50% of total N nutrition severely curtailed growth and nutrient accumulation for both cultivars. For both cultivars, optima for all three variables occurred in treatments that contained less than 50% NH4+-N in the total N supply. Application of calcium carbonate buffer did not result in improved maxima for growth and shoot potassium or shoot calcium concentrations compared to the best responses in unbuffered solutions. However, supplying calcium carbonate buffer did raise the minima for growth and shoot potassium and shoot calcium concentration. Both cultivars in buffered solutions compared to unbuffered solutions had significantly greater values for growth and for shoot potassium or shoot calcium concentration in treatments that contained 50% ammonium-N or greater in the total N supply. Although buffering relieved symptoms of ammonium toxicity, it did not eliminate symptoms, confirming the work of other researchers that ammonium toxicity is not due solely to acidification of the root-zone and that buffering has an effect on the capacity of plants to tolerate ammonium nutrition. Supplying nitrogen with ammonium:nitrate ratios in which nitrate predominates enhances yield and accumulation of calcium and potassium in lettuce. Two Star, the modern variety, is more ammonium-sensitive than Red Deer Tongue, the heirloom variety, if calcium carbonate buffering is not provided.

Organisms have evolved a remarkable ability to mineralize complex skeletons and functional biomaterials. These structures are nucleated and grown in close associaiton with macromolecular assemblages of proteins and polysaccharides that are implicated in regulating all stagees of mineralization. Because of this intimate association of organic with inorgaic components, many studies have investigated the effects of particular organic species on mineral morphology, phase, and growth rate. However, the diversity and species-specific nature of the organic assemblages associated with biominerals across a wide variety of taxa, has limited our understanding of how organisms use biomolecules to regulate skeletal formation. It is clear that a mechanistic picture of biomolecular controls on mineralization requires molecular-level investigations of the interplay between organic and inorganic components at all stages of crystallizaiton. This dissertation presents the findings from theoretical and experimental studies of the physical mechanisms that underlie biomolecule controls on mineral formation. Molecular dynamics simulations probe the effects of acidic molecules on the hydration of alkaline earth cations. After first calculating baseline hydration properties for magnesium, calcium, strontium, and barium, I determine the effects of carboxylate-containing molecules on cation hydration state as well as the kinetics and thermodynamics of water exchange. Experimental work utilizes self-assembled monolayers as proxies for matrix macromolecules in order to understand their effects on CaCO3 nucleation kinetics and thermodynamics. Estimates of nucleation rates and barriers are made from optical microscopy data and correlated with measurements of crystal – substrate rupture force from dynamic force microscopy. These investigations show that an important function of biomolecules in directing mineralization lies in their ability to modulate cation hydration. Both chemical functionality and molecular conformation are influential in regulating the kinetics and thermodynamics of mineral nucleation, and these effects may be predicted by the strength of interaction between organic and inorganic components. These findings contribute to a mechanistic understanding of how organic matrices act to regulate biomineral formation. They demonstrate a plausible physical basis for how carboxyl-rich biomolecules accelerate the kinetics of biomineral growth and suggest roles for organic species in the nucleation and pre-nucleation stages of mineralization. / Ph. D.

Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less building hot water systems. Scaling can cause energy inefficiencies, flow reduction, pressure loss, and erosion corrosion damage. Consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to ameliorate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work critically evaluated previous testing efforts and revealed limitations in terms of reproducibility and a need to measure all key aspects of scale deposition including quantity, location, aesthetic and other issues. A Standardized Scaling Test Protocol (SSTP) was conceived and vetted to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model premise plumbing system, while using a synthesized test water that could provide reproducible results in any laboratory. This synthetic water and methodology was able to produce significant scaling in a model hot water system within the targeted 5-day experimental time frame. The average amount of scale recovered for the triplicate control tests (with no scale reduction device) was 25.1 grams of calcium carbonate with a 95% confidence interval of 20.3-29.8 grams of calcium carbonate. The approach also worked in recreating scaling in natural waters and was used to verify the performance of a wide array of scale reduction technologies including cation exchange softeners, electrochemical deionization, physical magnets or electric field generators, media induced precipitation, sacrificial media (phosphate), and sacrificial media (citric acid). While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally clogging leaks in pipes and extending the lifetime of aging infrastructure. Corrosion inhibitors, mainly phosphates, have been increasingly dosed (up to 3.0 mg/L as PO4) into water to inhibit the corrosion of lead and copper pipelines in potable water systems since the advent of the Lead and Copper Rule (LCR) in 1991 by US Environmental Protection Agency (EPA). Phosphate corrosion inhibitors are now used at over 50% of water utilities in the United States and they can affect calcium carbonate scaling kinetics. In bench-scale experiments, the critical concentrations of phosphates that could inhibit leak repair over the short-term in one water tested were: tripolyphosphate (0.05 mg/L as P) < hexametaphosphate (0.1 mg/L) < orthophosphate (0.3 mg/L). The results prove that dosing of phosphates for corrosion control will also affect the kinetics and likelihood of calcium carbonate precipitation, with both beneficial and adverse consequences for pipes and consumers. Specifically, increased use of inhibitors for corrosion control is expected to reduce the likelihood of all calcium carbonate scaling problems while reducing the likelihood of autogenous pipe leak repair. In Providence, RI the dosing of orthophosphate at relatively high pH to control a lead corrosion problem, caused formation of a white precipitate, consumer reports of white water, clogging of aerators and loss of the added soluble phosphate corrosion control inhibitor due to precipitation. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that at doses below 2 mg/L as PO4, precipitation did not occur in water at pH 10.4 even when the water was heated to 48°C. However, if the water was dosed above 2 mg/L as PO4 precipitation occurred within 5 minutes, and once pre-existing particles were formed precipitation tended to continue even at much lower phosphate doses. Virtually all of the phosphate precipitated within 4 hours at the upper range of 60°C that is commonly found in water heaters. Thus, dosing of phosphate can actually increase scaling problems in some circumstances. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. The SSTP and practical experience showed that the vast majority of scaling occurred in the water heater. Therefore, a simplified bench-scale test consisting of a heating element in a small volume of water could be used to focus on the most sensitive aspect of scaling. A 3-hour bench-scale test was developed to quickly examine scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This approach was used to evaluate aspects of scaling in water heaters for the following illustrative examples: (1) scale impacts of combined phosphate corrosion inhibitor addition and partial water softening at centralized treatment plants, (2) role of silica concentration in scaling propensity and deposit durability, (3) effects of phosphate addition on scaling in a water known to cause erosion corrosion pipe damage. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems. Dosing of phosphate corrosion control inhibitors can increase scaling from calcium phosphate, decrease scaling of calcium carbonate, and in other cases will have little or no effect on scaling. Both calcium carbonate and calcium phosphate can contribute to scaling as controlled by pH, temperature, hardness, phosphate dose, and other circumstances. The standardized bench and pilot scale approaches developed herein, can serve as a basis for building knowledge reproducibly in any modern laboratory. These methods can also be used to verify performance claims for a wide range of scale reduction technologies, test treatments that could be applied at centralized treatment plants, and optimize water heater design dependent on water chemistry. / Doctor of Philosophy / Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less hot water systems. In addition to scale build up within the hot water system, consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to mitigate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work evaluated previous testing efforts to determine limitations in their methodology. A Standardized Scaling Test Protocol (SSTP) was developed to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model home plumbing system, while using a test water that could provide reproducible results in any laboratory. The test water was able to produce significant scaling within a 5-day test period with reproducible results. While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally repairing leaks in pipes and extending the lifetime of aging plumbing systems. An increasing number of water treatment plants are adding corrosion inhibitors to water to prevent the corrosion of lead and copper pipelines. Small scale lab experiments were run to determine how effective this natural leak repair was when there were corrosion inhibitors in the water. The results showed that most corrosion inhibitors also prevented or delayed calcium carbonate precipitation which reduced the likelihood of pipe repair through clogging leaks. In Providence, RI the addition of a corrosion inhibitor caused a white precipitate to form in the water which led to consumer complaints of white water and clogging of aerators. This was due to the uniquely high pH of the water. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that there is a critical inhibitor dose, below which no precipitation occurred in the high pH water. However, if the water was dosed above this critical limit, precipitation occurred immediately and continued as time went on. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. A 3-hour bench-scale test was developed to quickly examine key aspects of scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems.

In this study, composite system was developed to enhance mechanical properties of plastic pallets. The potential of graphite nanoplatelets (GnP)/PP composites for the application in packaging was scrutinized by examining mechanical properties, thermal properties, flow properties, and morphology as a function of GnP loading and by comparison of two mixing methods: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Incorporation of the GnP into PP resulted in a significant enhancement in the mechanical strength (tensile, impact, and flexural strength) and thermal decomposition temperature compared to the neat PP specimen. The CPC process clearly shows good exfoliation and better distribution on the PP matrix compared to the PMC method based on morphological evaluation measured by SEM. The impact test at low temperature revealed that the composites made by the CPC process showed 64% higher impact strength than neat PP due to higher even-distribution of GnP molecules into the PP matrix. We attempted to discover the degree of dispersion of natural fiber (kenaf) and graphite nanoplatelets (GnP) into the polypropylene (PP) polymer matrix and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (graphite nanoplatelets (GnP)/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. The impact strength of composite samples, containing 1wt% of GnP and mCaCO3 nanoparticles, increased up to 64% compared to neat PP. Among all tested samples, the highest tensile strength was found at 1wt% of mCaCO3 nanoparticles regardless of the presence or absence of GnP addition. There was no significant difference in flexural strength regardless of any nano-filler addition. However, both the flexural modulus and Young's modulus increased significantly when 10wt% of mCaCO3 nanoparticles were added. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. It may be contributed by thermal degradation of polymeric structure by double heat processing. This study can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobile, where carbon-based nanomaterials are more affordable. / Doctor of Philosophy / Pallets are the basic structure of a unit load which allows handling and storage efficiency. The advantages of plastic pallets are durability, cleanliness, and performance reliability, However, those are expensive and have lower mechanical properties than that of wood, such as low strength, creeps and deformation. Therefore, hybrid composites were fabricated using various fillers, such as graphite nanoplatelets, kenaf fiber or calcium carbonate on polypropylene matrix to enhance mechanical properties for plastic pallets. In order to fabricate the composites, two methods were utilized and compared: physical melt compounding (PMC) and chemical pretreatment compounding (CPC) processes. Graphite nanoplatelets (GnP) reinforced polypropylene (PP) composites made by both PMC and CPC process showed significance in the mechanical process compared to the neat PP. Moreover, the CPC process showed better dispersion on the PP matrix resulting in higher impact strength in low temperature. Based on the first chapter, we attempted to focus on reducing weight and sustainability using natural fiber. At the same time, when two or more fillers are reinforced in a polymer matrix, I wondered if the order in which the fillers were added could affect properties. Kenaf fiber and GnP were reinforced in the PP matrix through the CPC process to discover the degree of dispersion of fillers and the effect of filler-adding sequence on physical and mechanical properties. Tensile strength of the composites was increased up to 25%. In the case of Young's modulus, composites showed a 56% enhancement compared to the control. However, the impact strength decreased as a result of the increased brittleness when kenaf fiber was added. Another study investigated the effects of hybrid filler systems (GnP/commercially available modified calcium carbonate (mCaCO3) nanoparticles) on mechanical and physical properties of polypropylene nanocomposites with three variables, filler loading amount, the number of compounding processes, and the compounding order of two different fillers. This study was concentrating on the impact strength based on the result that the material adding sequence affects the mechanical strength when manufacturing the hybrid composites. The hybrid composite system on GnP/mCaCO3/PP resulted in enhancement of impact strength, tensile strength, flexural modulus and Young's modulus. The number of compounding processes did not affect any strength, and the single compounding process was found to be more effective than the double compounding process. Enhancement of impact strength in low temperature, and effect of filler-adding sequence on mechanical properties in hybrid composite system can be able to provide a solution for value-added high-end products in various industries such as application in logistics, aerospace or electric automobiles, where carbon-based nanomaterials are more affordable.

The formation of calcium carbonate (CaCO3) (i.e. scale) in potable water systems has long been a concern in water treatment and distribution. A literature review reveals that CaCO3 scaling issues are re-emerging due to climate change, temperature increases in hot water systems and lower use of scaling and corrosion inhibitors. Moreover, we have gathered insights that suggest CaCO3 coatings can be beneficial and stop pipeline leaks via self-repair or clogging. Ironically, the actions we are taking to increase the lifespan of distribution systems (i.e. adding corrosion inhibitors) might have worsened leaks and pipe lifespans due to interference with self-repair. The increasing occurrence of scaling coupled with gaps in knowledge over CaCO3 formation in water systems make revisiting this topic timely. The concept of autogenous repair by clogging with inert particles was examined using silica and alumina. Small 250 m diameter pinhole leaks were simulated in bench-scale water recirculation systems. Silica and alumina particles were added to solutions ranging from high to low ionic strength to determine the impact of water quality on leak repair. Size distribution and zeta potential of the particles were measured. Silica particles were practically unchanged by the different solution chemistries while the size and zeta potential of alumina particles varied. The rate of clogging with silica particles was not impacted by water chemistry. Alumina particles with a positive charge clogged 100% of the leaks while negatively charged alumina could not clog 100%. Very small alumina particles (4.1 m) stayed suspended but were unable to clog leaks. / Master of Science

The influence of calcium carbonate on the properties of four non-plastic lime-stabilized soils was studied. The four soils span a range in mica content and sand content. It was found that carbonate generally increased unconfined compressive strength and secant modulus of elasticity when included as part of the lime stabilizing agent. This effect was most pronounced with soils with a large sand content and low mioa content. A calcium hydroxide-calcium carbonate weight ratio of 3 to 1 was most effective for the case where six percent additive was used. It is hypothesized that the presence of carbonate enhances pozzolanic activity in lime-stabilized non-plastic soils by increasing the solubility of siliceous minerals at high pH levels. / Master of Science

Yes / Fouling on heat transfer surfaces due to scale formation is the most concerned item in thermal desalination industry. Here, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms in the fouling phenomena with more relaxation of the assumptions such as the density of the fouling layer and salinity of the recycle brine. While calcium sulphate might precipitate at very high temperature, only the crystallization of calcium carbonate and magnesium hydroxide are considered in this work. Though the model is applied in a 24 stages brine recycle MSF plant, only the heat recovery section (21 stages) is considered under this study. The effect of flow velocity and surface temperature are investigated. By including both diffusion and reaction mechanism in the fouling model, the results of the fouling prediction model are in good agreement with most recent studies in the literature. The deposition of magnesium hydroxide increases with the increase in surface temperature and flow velocity while calcium carbonate deposition increases with the increase in the surface temperature and decreases with the increase in the flow velocity.