Ciencias Exactas y Ciencias de la Salud

Permanent URI for this collectionhttps://hdl.handle.net/11285/551014

Pertenecen a esta colección Tesis y Trabajos de grado de los Doctorados correspondientes a las Escuelas de Ingeniería y Ciencias así como a Medicina y Ciencias de la Salud.

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An integrated approach for additive manufacturing process planning: Selective Laser Melting
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Ramírez-Cedillo, Erick; 590430; 590430; 590430; Rodríguez, Ciro A.; Garcia Lopez, Erika; Sandoval, Jesús A.; López, Omar; Campus Monterrey; Campus Monterrey; Campus Monterrey; Siller, Hector R.; Ruiz-Huerta, Leopoldo
In many industrial applications, Laser Powder Bed Fusion Technology (LPBF) commercially well-known Selective laser melting (SLM) has been recognized for its flexibility in Net Shape Manufacturing. Where a feedstock is deposited and selectively fused with a thermal joining via laser power. In this work, an overview and integrated approach for the additive manufacturing process planning is presented. The unit process life cycle inventory (UPLCI) was used to discretize energy consumption and material losses for modeling the SLM process. A reusable perspective in terms of materials, parameters, and calculation tools to estimate the energy consumption and mass loss in practical evaluations of production lines is presented. Calculations of energy were obtained and classified as basic, idle, and active energy. Theoretical equations were also shown to relate the most important parameters of the process with its energy consumption. On the other hand, the optimization and characterization of parts for the processing parameters calibration in LPBF has been recently well studied in academia, but still under research in the industry, due to the early adoption of this technology in different companies and research centers. For this reason, a process planning workflow for the obtention of calibrated ranges of parameters for AISI 316L samples, and to understand the relationship between the improved parameters, the surface quality and part integrity with the microstructural characteristics. Two principal methods of characterization, (1) Nanoindentation and Electron backscatter diffraction (EBSD) and (2) non-contact profilometry by Focus Variation, were used to validate the influence of the overlap of the point distance (PD) and hatch distance (HD) in the fabrication process. In this study, hardness and the modulus of elasticity exhibited the highest values of 4.59 GPa and 229.7 GPa respectively in the parallel orientation to the build direction. The obtained hardness and modulus of elasticity were correlated with the different grain sizes and the resulting crystallographic orientation product of the thermal history of the process. Roughness (Ra) was improved with the selection of parameters and presented the lowest value of 5.433 μm. Finally, the microstructure was studied on the samples as the final assessment on the improved parameters where finer cellular/dendritic structures were found. At the end, a series of case studies were presented at the end to validate the use of these two-process planning methodology in the medical device applications.
Bidirectional AC electroosmotic pumping by hydrodynamic channeling using 2D and 3D photoresist-derived carbon microelectrodes
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Vázquez Piñón, Matias; 0000-0001-6407-4998; Martínez Chapa, Sergio Omar; Kulinsky, Lawrence; Madou, Marc; Pérez González, Víctor Hugo; Martínez López, José Israel; School of Engineering and Sciences; School of Engineering and Sciences; Campus Monterrey
In microfluidics, fluid movement is keystone for the correct operation of different system stages, including convective mixing, electrochemical sensing, and affinity bonding in immunoassays. Even though the most commonly developed microfluidic pumps are unidirectional, over the last decade, bidirectional approches have been developed to considerably improve the overall performance of microfluidic systems. Furthermore, the exploration of new approaches for bidirectional pumping allows the creation on fully integrated, stand-alone systems for applications including drug delivery, clinical analyses, cell culture, among many others. AC electroomosis is a suitable electrokinetic approach for fluid driving in microchannels. Opposite to commonly-used microfluidic pumping approaches, in AC electroosmosis no moving elements are required, and only a set of electrodes is used, thus fabrication of devices is remarkably simple and cost-effective as a standalone pump, or for integration with other microfluidic components. In this work we propose a hydrodynamic mechanism to reverse the flow in AC electroosmotic micropumps in order to attain bidirectional pumping. The flow reversal mechanism involves the channeling of the vortices generated by electroosmotic manners, by taking advantage of the microchannel geometrical properties; particularly, the microchannel height, which is closely related to the stimulating electrodes’ width and, in consequence, to the enclosed vortices’ size. We use the Carbon-MEMS fabrication process to develop two electrode architectures: asymmetric planar and high-aspect-ratio microposts. The carbonaceous material obtained from this process is characterized to validate the adecuate properties for electrokinetic applications, and the micropumps are then assembled by bonding a PDMS microchannel. The flow development by AC electroosmotic means is profoundly studied using a bidimensional finite element model comprehending the Poisson-Nernst-Plank-Navier-Stokes equation set to closely emulate the vortex formation on the electrodes surface. To explore the effect of electrode asymmetry ratio on the fluid velocity, we compare three asymmetry ratios for both, coplanar, and highaspect-ratio architectures. Experimental results are presented and a fluid velocity analysis is carried out for forward and reverse flows. An explanation of how flow reversal is achieved by hydrodynamic channeling is detailed, and experimental test analysis provides the conditions under flow reversal is produced, such as amplitude and frequency of the applied AC signal, and asymmetry ratio of electrodes. Furthermore, the effect of microposts on fluid velocity and flow reversal is thoroughly discussed. Hydrodynamic channeling using AC electroomosis is a new approach for bidirectional pumping, thus areas of opportinity are presented for future developments in this field, such as optimization of electrode asymmetry ratio, micropost spacing and microchannel height.