Mechanical and microstructural characterization of 3D printed ceramic electrolyte

Nowadays, 3D printing(3DP)is leading a revolution of the processing technique, thanks to its versatility in the manufacture of complex geometries and having the ability to manufacture complex parts in one step,reducing both the manufacturing time and costs.With this technology, the aim is to bring science and society closer together, with the ultimate goal of developing new devices that are more efficient than the current ones in order to produce clean energy,since the fuel used is derived from hydrogen in contact with air to produce energy and water vapour.Specifically, in the field of energy and in particular by using this advanced methodology to 3DPsolid oxide fuel cells is growing during the last decade.Therefore, in this sense, the solid oxide fuel cells (SOFCs) avoids the generation of greenhouse gases, such as CO2, which is the ultimate global purpose to face the present worldwide climate crisis.The purpose of this Master’s thesis is the combination of these two fields, focusing on the electrolyte 3DPof SOFC, with the main objective to obtain the final material with microstructural and mechanical properties similar to those obtained by traditional techniques.To carry out this study, two different geometries have been chosen, tubular and cylindrical, where the proportions of the printing material, processing conditions, etc. have been modified in order to achieve materials with a relative density higher than 96%, compared to traditional techniques, and mechanical properties similar to the materials produced by traditional routes, in this case, by using cold isostatic press (CIP). Within this context, the microstructural and mechanical properties have been determined by means of advanced characterization techniques, like: field emission scanning electron microscopy, nanoindentation, etc. Subsequently, the methodology of preliminary micro-compression of cylindrical and/or tubular fuel cells was determined.To sum up, a density greater than 98% has been obtained with a hardness and elastic modulus of the 3DP electrolytes similar than those processed by using the conventional manufacturing techniques

Microwell arrays with nanoholes

A device for conducting parallel analysis or manipulation of multiple cells or biomolecules is disclosed. In one embodiment, the device comprises a silicon chip with a microwell, and at least one membrane suspended at the bottom opening of the microwell. The suspended portion of the membrane defines a nanohole that provides access to the material on the other side of the membrane

3D Printed Microfluidic Devices

3D printing has revolutionized the microfabrication prototyping workflow over the past few years. With the recent improvements in 3D printing technologies, highly complex microfluidic devices can be fabricated via single-step, rapid, and cost-effective protocols as a promising alternative to the time consuming, costly and sophisticated traditional cleanroom fabrication. Microfluidic devices have enabled a wide range of biochemical and clinical applications, such as cancer screening, micro-physiological system engineering, high-throughput drug testing, and point-of-care diagnostics. Using 3D printing fabrication technologies, alteration of the design features is significantly easier than traditional fabrication, enabling agile iterative design and facilitating rapid prototyping. This can make microfluidic technology more accessible to researchers in various fields and accelerates innovation in the field of microfluidics. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in 3D printing and its use for various biochemical and biomedical applications

Microwell Arrays for Studying Many Individual Cells

"Laboratory-on-a-chip" devices that enable the simultaneous culturing and interrogation of many individual living cells have been invented. Each such device includes a silicon nitride-coated silicon chip containing an array of micromachined wells sized so that each well can contain one cell in contact or proximity with a patch clamp or other suitable single-cell-interrogating device. At the bottom of each well is a hole, typically 0.5 m wide, that connects the well with one of many channels in a microfluidic network formed in a layer of poly(dimethylsiloxane) on the underside of the chip. The microfluidic network makes it possible to address wells (and, thus, cells) individually to supply them with selected biochemicals. The microfluidic channels also provide electrical contact to the bottoms of the wells

Cooperation, Fair Trade, and the Development of Organic Coffee Growing in Chiapas (1980-2015)

In present day Mexico, Chiapas is the state that produces the greatest amount of coffee, with both the highest number of producers and the largest cultivated area. A significant part of this production is organic coffee. Organic coffee growing emerged as an important alternative for small producers who previously devoted themselves to the production and commercialization of conventional coffee but found it increasingly difficult to make a living. The expansion of the cultivation of organic coffee was closely related to the processes of peasant mobilization that started in the 1970s when the agricultural model of the Green Revolution went into crisis. This article analyzes the expansion of organic coffee growing in Chiapas and its connection with the process of the collective organization of small coffee producers in cooperatives. In these cooperatives, an alternative model of production was established based on the peasants' traditional knowledge. We argue that the development of organic coffee growing was strongly linked to the long tradition of community life, communal management of land and natural resources, and collective action. We also underline the resilience of the peasants' traditional farming systems and their contribution to a more sustainable and environmentally respectful agriculture

Tunable Resins with PDMS-like Elastic Modulus for Stereolithographic 3D-printing of Multimaterial Microfluidic Actuators

Stereolithographic 3D-printing (SLA) permits facile fabrication of high-precision microfluidic and lab-on-a-chip devices. SLA photopolymers often yield parts with low mechanical compliancy in sharp contrast to elastomers such as poly (dimethyl siloxane) (PDMS). On the other hand, SLA-printable elastomers with soft mechanical properties do not fulfill the distinct requirements for a highly manufacturable resin in microfluidics (e.g., high-resolution printability, transparency, low-viscosity). These limitations restrict our ability to SLA-print efficient microfluidic actuators containing dynamic, movable elements. Here we introduce low-viscous photopolymer resins based on a tunable blend of poly(ethylene glycol) diacrylate (PEGDA, Mw~258) and poly (ethylene glycol methyl ether) methacrylate (PEGMEMA, Mw~300) monomers. In these blends, which we term PEGDA-co-PEGMEMA, tuning the PEGMEMA-to-PEGDA ratio alters the elastic modulus of the printed plastics by ~400-fold, reaching that of PDMS. Through the addition of PEGMEMA, moreover, PEGDA-co-PEGMEMA retains desirable properties of highly manufacturable PEGDA such as low viscosity, solvent compatibility, cytocompatibility and low drug absorptivity. With PEGDA-co-PEGMEMA, we SLA-printed drastically enhanced fluidic actuators including microvalves, micropumps, and microregulators with a hybrid structure containing a flexible PEGDA-co-PEGMEMA membrane within a rigid PEGDA housing

Modeling long term Enhanced in situ Biodenitrification and induced heterogeneity in column experiments under different feeding strategies

Enhanced In situ Biodenitrification (EIB) is a capable technology for nitrate removal in subsurface water resources. Optimizing the performance of EIB implies devising an appropriate feeding strategy involving two design parameters: carbon injection frequency and C:N ratio of the organic substrate nitrate mixture. Here we model data on the spatial and temporal evolution of nitrate (up to 1.2 mM), organic carbon (ethanol), and biomass measured during a 342 day-long laboratory column experiment (published in Vidal-Gavilan et al., 2014). Effective porosity was 3% lower and dispersivity had a sevenfold increase at the end of the experiment as compared to those at the beginning. These changes in transport parameters were attributed to the development of a biofilm. A reactive transport model explored the EIB performance in response to daily and weekly feeding strategies. The latter resulted in significant temporal variation in nitrate and ethanol concentrations at the outlet of the column. On the contrary, a daily feeding strategy resulted in quite stable and low concentrations at the outlet and complete denitrification. At intermediate times (six months of experiment), it was possible to reduce the carbon load and consequently the C:N ratio (from 2.5 to 1), partly because biomass decay acted as endogenous carbon to respiration, keeping the denitrification rates, and partly due to the induced dispersivity caused by the well developed biofilm, resulting in enhancement of mixing between the ethanol and nitrate and the corresponding improvement of denitrification rates. The inclusion of a dual-domain model improved the fit at the last days of the experiment as well as in the tracer test performed at day 342, demonstrating a potential transition to anomalous transport that may be caused by the development of biofilm. This modeling work is a step forward to devising optimal injection conditions and substrate rates to enhance EIB performance by minimizing the overall supply of electron donor, and thus the cost of the remediation strategy.Peer ReviewedPostprint (author's final draft

Influència del context geològic i hidrogeològic en l'eficiència energètica dels sistemes geotèrmics de molt baixa entalpia

L'elevat consum energètic de les societats actuals, així com la impossibilitat de sostenir-lo a llarg termini implica la cerca de noves fonts d'energia. D'aquesta manera, en el camp de la climatització residencial, l'energia geotèrmica de molt baixa entalpia es posiciona com una alternativa als recursos energètics actuals. Així, els primers metres de subsòl presenten una temperatura adequada per al seu aprofitament calorífic, mitjançant els sistemes geotèrmics de bomba de calor. Si bé a nivell energètic, són sistemes, intrínsecament, molt eficients, el seu rendiment pot patir importants variacions davant dels canvis en les condicions del medi geològic i hidrogeològic. Especialment, els col·lectors de calor verticals, treballen, amb freqüència, en el si de les formacions hidrogeològiques. En aquest sentit, els canvis del nivell hidràulic i de la temperatura de l'aigua de l'aqüífer es manifesten amb variacions de la conductivitat tèrmica equivalent i del flux subterrani d'aigua, que alhora, aquestes, es tradueixen en alteracions del flux subterrani de calor. Davant d'aquest fet, l'avaluació quantitativa de l'efecte d'aquestes fluctuacions que es presenta en aquest treball mostra petites variacions del nivell hidràulic i de la temperatura de l'aigua comporten canvis molt notables en l'eficiència dels sistemes verticals de bomba de calor geotèrmica.El importante consumo energético de las sociedades actuales, así como la imposibilidad de sostenerlo a largo plazo conlleva la búsqueda de nuevas fuentes de energía. De este modo, en el campo de la climatización residencial, la energía geotérmica de muy baja entalpia se desvela como una alternativa a los recursos energéticos actuales. Así los primeros metros de subsuelo presentan una temperatura adecuada para su aprovechamiento calorífico, mediante los sistemas geotérmicos de bomba de calor. Si bien a nivel energético, son sistemas, intrínsecamente, muy eficientes, su rendimiento tan privilegiado puede sufrir variaciones importantes frente los cambios de las condiciones del medio geológico e hidrogeológico. Especialmente los colectores verticales de calor trabajan, con frecuencia, dentro de formaciones hidrogeológicas. En este sentido los cambios del nivel hidráulico y de la temperatura del agua del acuífero se manifiestan con variaciones de la conductividad térmica equivalente y del flujo subterráneo de agua, que al mismo tiempo, estas se traducen en alteraciones del flujo subterráneo de calor. En frente de tal hecho, la evaluación cuantitativa del efecto de las fluctuaciones citadas, que se presenta en el presente trabajo muestra que pequeñas variaciones de nivel hidráulico y de la temperatura del agua inducen cambios muy notables en la eficiencia de los sistemas verticales de bomba de calor geotérmica.The high energy consumption of current populations and the impossibility of keeping it on the time involve the search for new energy sources. In this way, low enthalpy geothermal energy is revealed as a good alternative to cooling and heating houses. Thus, the first meters of subsoil have a suitable temperature for a thermal use by geothermal heat pump systems. If these systems are, inherently, very efficient, this performance so privileged may suffer significant changes caused by geological and hydrogeological alterations. Especially, vertical heat collectors, often work on hydrogeological formations. So, the changes at hydraulic level and at aquifer temperature, implies thermal conductivity and underground water flow variations, and these, at the same time, induce alterations on the underground heat flow. The quantitative effect evaluation of those fluctuations, which is presented in this paper shows that small variations in hydraulic level and water temperature induce notable changes in the efficiency of pump systems, vertical geothermal heat.Nota: Aquest document conté originàriament altre material i/o programari només consultable a la Biblioteca de Ciència i Tecnologia