Doctoral School

Reading date: 22/04/2024

• AZIZIAN, POOYA: MICROFLUIDICS FOR BIOSENSING WITH ADDITIVE MANUFACTURING:SIMULATION MODEL AND FABRICATION
  
  Author: AZIZIAN, POOYA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN MECHANICAL, FLUIDS AND AEROSPACE ENGINEERING
  Department: Department of Mechanical Engineering (EM)
  Mode: Article-based thesis
  Deposit date: 26/03/2024
  Reading date: 22/04/2024
  Reading time: 09:00
  Reading place: Sala de Conferències del TR1 de Campus UPC Terrassa.
  Thesis director: CASALS TERRE, JASMINA | CABOT CANYELLES, JOAN MARC | ORTEGA NOVILLO, ADRIAN | RICART CAMPOS, JORDI
  Committee:
       PRESIDENT: BENITO LÓPEZ, FERNANDO
       SECRETARI: RODRÍGUEZ VILLARREAL, ÁNGELES IVÓN
       VOCAL: BORTOLOTTI, CARLO AUGUSTO
  Thesis abstract: Over the last decade, biosensing has been moving towards the miniaturized and cost-effective point-of-care (POC) testing. Even though microfluidics is becoming a key enabling technology for POC testing, the need for robust peripheral equipment has been a notable limiting factor in extending its prevalence. By manipulating microchannels' geometry and surface properties, capillary-driven microfluidics can control fluids spontaneously, reducing the need for external instrumentation. This advantage is becoming more accessible, considering that additive manufacturing technologies are reaching a high level of maturity that allows cost-effective and rapid fabrication of three-dimensional (3D) features down to the sub-millimeter scale. Therefore, capillary-driven microfluidics are achieving higher technological readiness.A key component within the field of capillary-driven microfluidics is the capillary valve. The capillary valve can automatically stop and actuate fluid flows depending on the molecular interactions between the liquid and the microchannel surfaces. However, a major concern for these valves is the presence of unwanted diffusion and mixing during the valve function, leading to cross-contamination between reagents or even with the sample. This thesis studied different methods in the literature to stop and actuate the flow as the two main stages of these valves. Then, passing over the state-of-the-art, a novel 3D diffusion-free capillary valve was developed: the ¿-valve. This valve incorporates an air gap between solutions to eliminate diffusion between them. Based on the valve's distinctive configuration, the capillarity of the microfluidic circuit displaces the air gap at a predefined time to actuate without producing bubbles into the circuit. The proposed valve's design and study were performed via numerical simulation and experimental assays, while 3D printing (3DP) was employed to fabricate the microfluidic devices.The ¿-valve's functionality, single and in array, was proven and compared with the conventional capillary valves. Then, it was applied to the precise control of reagents for biosensing, demonstrated by two different competitive immunoassays via (i) the subsequent washing step for the lateral flow assay of cortisol, and (ii) the valve array for the sequential delivery of sample and three reagents to detect benzodiazepine quantitatively. The sensitivity was enhanced by avoiding the reagent diffusive premixing when using the ¿-valve by approximately 40%. As a result, the proposed capillary valve is a promising capillary component for conducting automated immunoassays at POC.In conclusion, the novel capillary valve addresses a current biosensing sensitivity issue coming from reagent diffusive premixing, and together with other disruptive capillary-driven circuit components, paves the way for truly packing lab-on-a-chip without requiring a lab around the chip. In this regard, the next generation of capillary-driven microfluidic devices will be promising tools offering (i) miniaturized features needing fewer samples and reagents, (ii) non-costly POC testing without peripheral instrumentation, (iii) automated, preprogrammed, and easy-to-use for non-expert users, as well as (iv) sensitive, precise and reliable based on novel 3D designs employing surface properties. This is owing to the recent advancements in microfabrication based on additive manufacturing extending 3D forming freedom.
  

• RIVET FERNÁNDEZ, IVÁN: Computational Multiscale Analysis for Additive Manufacturing
  
  Author: RIVET FERNÁNDEZ, IVÁN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CIVIL ENGINEERING
  Department: (DECA)
  Mode: Article-based thesis
  Deposit date: 18/03/2024
  Reading date: 22/04/2024
  Reading time: 11:00
  Reading place: Sala de Seminarios O.C. Zienkiewicz del Centro Internacional de Métodos Numéricos en Ingeniería - CIMNE Campus Nord de la UPC, Edifici C1 - 2a Planta, 08034 Barcelona
  Thesis director: CERVERA RUIZ, LUIS MIGUEL | DIALAMI SHABANKAREH, NARGES
  Committee:
       PRESIDENT: AURICCHIO, FERDINANDO
       SECRETARI: CAICEDO SILVA, MANUEL ALEJANDRO
       VOCAL: DOMINGO-ESPIN, MIQUEL
  Thesis abstract: This thesis aims towards the understanding and optimization of Additive Manufacturing (AM) components through the application of accurate computational multiscale simulations. The research is guided by three primary objectives: (1) the development of a multiscale orthotropic material model tailored for Fused Filament Fabrication (FFF) components, (2) the formulation of an optimization strategy to enhance the mechanical performance of FFF parts, and (3) the comprehensive characterization and modeling of their failure mechanisms.To address the first objective, a printing pattern-based orthotropic material model in the framework of multiscale analysis is constructed. This model accounts for the intricate interactions occurring at both filament and component scales in FFF, offering a nuanced representation of the material's behavior. By bridging these scales, the model ensures a comprehensive understanding of the mechanical response of FFF parts, enabling accurate predictions of their performance and failure modes.The second objective focuses on the optimization of the mechanical performance of FFF components. Leveraging the developed multiscale material model, an optimization strategy based on a novel statistics-based algorithm and an orthotropic failure criterion is formulated. The computational domain generation strategy is also tackled, analyzing different approaches and taking advantage of an Adaptive Mesh Refinement (AMR) technique to reduce the computational cost of the simulations. The developed methodology is fully embedded into the AM workflow.The final objective involves the characterization and modeling of the different failure mechanisms present in FFF parts. The different failure modes exhibited by FFF components are identified for each printing pattern present in the component, and a Mechanism-Based (MB) damage criterion is developed to model their stiffness degradation. In addition, an MB cracking model that accounts for the orthotropic brittleness of FFF parts is presented and validated against experimental tests.The central motivation driving this thesis is to alleviate the dependency on costly experimental procedures for characterizing and/or predicting the mechanical behavior of FFF components by performing high-precision and inexpensive multiscale simulations. The outcomes of this study aim to improve the current Design for Additive Manufacturing (DfAM) guidelines.
  

• UDAONDO GUERRERO, CARLOS: Analysis of Q factor degradation mechanisms in BAW resonators
  
  Author: UDAONDO GUERRERO, CARLOS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 22/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: COLLADO GOMEZ, JUAN CARLOS | MATEU MATEU, JORDI
  Committee:
       PRESIDENT NO PRESENCIAL: AIGNER, ROBERT
       SECRETARI: VALENZUELA GONZALEZ, JOSE LUIS
       VOCAL NO PRESENCIAL: VILLANUEVA TORRIJO, LUIS GUILLERMO
  Thesis abstract: The emergence of smartphones not only changed the way people uses its phone for, but it also changed the traffic amount that networks need to carry, increasing the demand of higher data rates. The overall result was the appearance of 4G networks, and nowadays, the current development of 5G, implying the need for more frequency bands, and the application of new techniques such as Carrier Aggregation (CA), MIMO antennas, and so on. All these market driven necessities suppose a great challenge for the radiofrequency (RF) industry, which have been facing the necessity of miniaturization and band coexistence on its devices since the beginning of mobile communications.Microwave filters based on Bulk Acoustic Wave (BAW) resonators, have been able to this day to overcome these limitations. These devices consist in a thin piezoelectric layer comprised by two metal electrodes, and an acoustic confinement method, which can be simply made of air or a Bragg reflector. The use of electroacoustic technology enables to reduce the filter size up to five orders of magnitude, allowing the integration of multiple filters in handsets. This thesis focuses on modelling some of different physical phenomena at the resonator level that affect the performance of the filters.The first part of this thesis is the one regarding the spurious response of BAW resonators. This response is originated by acoustic waves traveling in the lateral dimension of the resonator. These waves couple electromechanically, degrading the filter response. BAW filters have been capable of overcoming this limitation suppressing them by the use of different electrode geometries (Apodization), or by surrounding the electrode by a decreased, or increased frame (Border Ring). The nature of these waves is studied through the thesis and several equivalent models are proposed in order to accurately predict them, helping to the design of the correspondent suppression structures. One of this thesis contributions regarding the lateral spurious resonances, consists in making use of a modified Mason model to determine the origin of the additional spurious resonances generated by the Border Ring. These resonances can be attributed to an acoustic mode, different from the fundamental, propagating across the resonator stack. By adding nonlinear sources to that model, the second harmonic (H2) emissions and the impact of the spurious resonances in them, is also studied.Finally, a new equivalent model based in the Transmission Line Matrix (TLM) method is proposed for the acoustic cavity of a BAW resonator. This new approach is able to model resonators with different electrode geometries, in a much faster way than traditionally used methods like the Finite Elements Method (FEM). In addition, by determining different propagation regions, it can be used to model both the apodization and the Border Ring at the same time.The second family of contributions are the ones regarding to the thermoelastic behavior of the BAW resonators. A solid heats up when compressed and vice versa. In a harmonic oscillation, when heat is able to flow through the solid regions, this flow from hotter to colder regions generates a relaxation of the acoustic wave. This is the thermoelastic damping. A thermo-electro-mechanical Mason model is used for quantifying this source of losses on BAW resonators. The model is compared with experimental data taken at cryogenic temperatures and an analysis of losses of the broadband spurious resonances of the Bragg reflector has been performed.
  

Reading date: 23/04/2024

• ALBUQUERQUE PORTELLA, FELIPE: A paradigm shift of HPC for geosciences: a novel HPC service model for geosciences applications
  
  Author: ALBUQUERQUE PORTELLA, FELIPE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTER ARCHITECTURE
  Department: (DAC)
  Mode: Normal
  Deposit date: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: BERRAL GARCÍA, JOSEP LLUÍS | CARRERA PÉREZ, DAVID
  Committee:
       PRESIDENT: FONTOURA DE GUSMAO CERQUEIRA, RENATO
       SECRETARI: TOUS LIESA, RUBÉN
       VOCAL: DE MORAES, RAFAEL JESUS
  Thesis abstract: The Oil and Gas (O&G) industry ranks prominently among the leading commercial users of powerful supercomputers worldwide, as indicated by global High-Performance Computing (HPC) ranking lists, such as TOP500 and Green500. Geoscience applications, particularly flow and geomechanical simulators, pose demanding workloads for HPC in adressing complex engineering challenges in the O&G industry, together with seismic processing. The rise of hybrid on-demand and cloud HPC environments presents new challenges to end users. Beyond expertise in their fields, users must navigate the intricacies of computer architecture to select the optimal hardware and parallelization option. They also need to consider the business model decisions of the cloud providers, such as managing spot instances, selecting different cloud regions, or even different cloud providers.Furthermore, users struggle with the complexities of configuring their own geoscience software due to the multitude of tunable numerical parameters. Default values may not be optimal for specific reservoir models, requiring geoscientists¿ expertise in both the physics and mathematics behind the simulators and in computer science. A deep understanding of application performance is challenging, as it can vary based on input parameters. Many users end up relying on default configurations or decisions by system administrators for geoscience software, missing opportunities to optimize speed and cost-effectiveness.This thesis aims to shift the paradigm in utilizing HPC for geoscience by entrusting computer architecture decisions to domain-aware optimization algorithms. Such an approach not only enhances usability for the end user, but can also translate into substantial reductions in both time and cost. These algorithms could lead to better utilization of on-premises supercomputers and cost optimization of cloud resources. We evaluate the feasibility of this approach through the contributions of three algorithms. The first algorithm of this work was named TunaOil, which is a novel methodology that uses previous reservoir simulation executions to train an oracle that proposes near-optimal numerical parameters for subsequent simulations within a History Matching (HM) workflow. This allows the simulation parameters to be adjusted without additional executions, saving valuable time. Experiments show that the contribution of this algorithm is an improvement of up to 31% in the overall runtime of the HM workflow.The second algorithm, named MScheduler, is a metascheduler framework designed for reservoir simulations in the cloud. It effi-ciently executes SLURM jobs by utilizing spot Virtual Machines (VMs) to minimize costs and ensure job completion even in the event of VM termination. Key contributions include a novel methodology for reservoir simulation checkpointing, a cost-based scheduler, and an analysis of the strategy using real production jobs. MScheduler significantly reduces financial costs with a slight increase in makespan. On average, it reduces monetary costs by up to 32%, with only an 8% increase in the makespan compared on-demand executions. In the best case, the monetary savings reach 66%, with a 19% increase in makespan.The third algorithm utilizes Machine Learning (ML) algorithms in job schedulers to predict execution times of reservoir job, improving cluster resource efficiency. The developed model classifies the duration time interval of SLURM reservoir simulation jobs with an accuracy of more than 70%, exceeding the standard performance described in the job scheduling literature, thus contributing to improved scheduling decisions.Together, these algorithms mark a paradigm shift in HPC utilization for geoscience applications. They liberate end users from complex computer architecture choices, contributing to improved decision-making and significant time and cost benefits.
  

• HÖSCHELE, JONATAN: A strontium quantum-gas microscope
  
  Author: HÖSCHELE, JONATAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 25/03/2024
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: TARRUELL PELLEGRIN, LETICIA
  Committee:
       PRESIDENT: SCHRECK, FLORIAN EBERHARD
       SECRETARI: DE RIEDMATTEN, HUGUES
       VOCAL: WEITENBERG, CHRISTOF
  Thesis abstract: The development of quantum-gas microscopes has revolutionized the field of quantum simulation with ultracold atoms. More specifically, their ability of direct observation and manipulation of degenerate quantum gases in optical lattices on a single particle level has brought novel ways of probing and engineering quantum degenerate many-body systems. So far, most of these setups have focused on alkali atoms. Combining quantum-gas microscopy with the properties of alkaline-earth atoms such as strontium gives rise to exciting research directions. In this thesis, we report on the design and construction of a strontium quantum-gas microscope. The findings in this thesis can be divided into three parts.In the first part, we focus on the accumulation of atoms in the science cell and develop a scheme to enhance the atom number in magneto-optical traps of strontium atoms operating on the 461-nm transition. This scheme resonantly populates a short-lived reservoir state, partially shielding the atomic cloud from losses in the cooling cycle. We demonstrate a factor of 2 enhancement in the atom number for the bosonic isotopes Sr-88 and Sr-84, and the fermionic isotope Sr-87, showing the efficient capture of these isotopes in our experiment. Our scheme can be readily implemented in the majority of strontium experiments, given that the shielding transition at 689 nm is commonly used for further cooling. In our case, the shielding scheme facilitates the generation of Bose-Einstein condensates.The second part of the thesis reports on the generation of degenerate quantum gases of Sr-84 with up to 200000 atoms. After summarizing the required cooling steps, we study the formation of Bose-Einstein condensates during evaporative cooling in our experiment. Analyzing the evolution of the horizontal and vertical size of our quantum-degenerate clouds in free fall leads to the characteristic asymmetric expansion, which we compare to theory for our experimental parameters. We also show the generation of smaller Bose-Einstein condensates of less than 20000 atoms with the help of a light-sheet potential. With this highly-anisotropic confinement we can consider our Bose-Einstein condensates two-dimensional for atom numbers of the order of 1000.In the third part we demonstrate site-resolved imaging of a Sr-84 bosonic quantum gas in a Hubbard-regime optical lattice potential. We confine the quantum gas by a two-dimensional optical lattice and the aforementioned light-sheet potential, both operating at strontium's clock-magic wavelength. A high-NA imaging objective enables single-atom and single-site resolved fluorescence imaging by scattering photons on strontium's broad 461-nm transition, while performing efficient attractive Sisyphus cooling of the atoms on a narrower transition at 689 nm. We reconstruct the atomic occupation of the lattice sites from the fluorescence images, obtaining imaging fidelities above 94%. Finally, we realize a Sr-84 superfluid in the Bose-Hubbard regime and observe its characteristic interference pattern after free expansion in the light sheet with single-atom resolution. Our strontium quantum-gas microscope provides a new platform to study dissipative Hubbard models and cooperative effects in atom-light interaction at the microscopic level. Moreover, the ability to capture also the fermionic isotope Sr-87 paves the way to generate degenerate Fermi gases with SU(N) symmetry and study SU(N) quantum magnetism.