Abstract:

This dissertation presents theoretical and experimental investigations into the dynamical behavior of Micro electromechanical systems (MEMS) resonators and their exploitation for filtering, sensing, and logic applications. The dissertation is divided into two major parts:  MEMS coupled structures and MEMS dynamic logic devices. 

First, a theoretical and experimental investigation on both electrostatically and mechanically coupled resonator is presented. Static and dynamic analysis of weakly electrostatically coupled silicon microbeams, and strongly mechanically coupled polyimide microbeams is presented. The static analysis focuses on revealing pull-in characteristics, while the dynamic analysis focuses on the frequency response of the system and its exploitation for potential applications in filtering and amplification. Next, the phenomenon of mode localization is explored theoretically and experimentally on both electrostatically and mechanically weakly coupled resonators. Eigenvalue analysis and dynamic response of the coupled system under different external perturbations is investigated. It is observed, that the exploitation of mode localization depends on the fact that which resonator of the coupled system is under direct excitation, which resonator’s stiffness is perturbed, and which resonator is used to record the output results. These understandings will potentially help improve the performance of MEMS mode-localized sensors.

Finally, three techniques to realize cascadable MEMS logic devices are presented. MEMS logic device vibrates at two steady states; a high on-resonance state (1) and a low off-resonance state (0). First, a MEMS logic device capable of performing the AND/NAND logic gate and a tri-state logic gate using mixed-frequency excitation is presented that works on the concept of activation (1) and deactivation (0) of combination resonances due to the mixing of two or more input signals. Second, exploitation of subharmonic resonance under an AC only excitation to perform AND logic operation is presented. Finally, another MEMS logic device working on the principle of activation (1) and deactivation (0) of second resonant mode of a clamped-clamped microbeam is presented. This device is capable of performing OR, XOR and NOT gate. Experimental demonstration of the cascadability is shown for this case cascading and OR and NOT gate to perform a universal NOR logic gate.

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• CONTACTEmmanuelle Sougrat

​Abstract:  Removal of water vapor from humid streams is an energy-intensive process used widely in industry. Effective dehumidification has the potential to significantly reduce energy consumption and the overall cost of a process stream. Membrane-based separations, particularly dehumidification, are an emerging technology that can change the landscape of global energy usage because they have a small footprint, they are easy to scale up, to implement and to operate. The focus of this thesis is to evaluate new directions for the development and use of materials for membrane-based dehumidification processes. It will show advances in the synthesis of new copolymers, a surprising boost in performance with the addition of 2-D materials, propose the use of polybenzimidazole for challenging dehumidification applications, and show how by tuning the nanostructure of a commercially available block copolymer (BCP) it is possible to increase the performance.

The design of novel amphiphilic ternary copolymers comprising P(AN-r-PEGMA-r-DMAEMA) allowed selective removal of water vapors from gaseous streams; the effect of varying PEGMA chain length on membrane performance was studied. The membranes showed an excellent performance when the content of the PEGMA segment was 2.9 mol% with a chain length of 950-Da.

In the mixed-matrix approach, the inclusion of graphene oxide (GO) nanosheets in a different copolymer enhanced the membrane performance by creating selective tortuous pathways for inert gases. The well-distributed GO nanosheets in the defect-free composite membranes resulted in an 8 fold increase in water vapor/N2 selectivity compared to neat membranes.

Thirdly, dense polybenzimidazole membranes showed good water vapor permeability, and the addition of TiO2-based fillers with varying chemistry and geometry enhanced the performance of PBI membranes.

Lastly, the effect of tuning the morphology of commercially available BCP on dehumidification was demonstrated successfully. The self-assembled morphology formed with cylindrical hydrophobic cores, and the hydrophilic coronas, formed ion-rich highways for fast water vapor transport. Water vapor permeability improved up to 6-fold with the nanostructure modulation more than any membrane reported in the literature.
In summary, the work reported in this dissertation has the potential to lay a framework towards tailor-made next-generation membranes aimed for water vapor removal in various dehumidification applications.

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• CONTACTLinda J. Sapolu
• EMAILLinda.Sapolu@kaust.edu.sa

Abstract:​ Humanity faces existential threats: climate warming, overpopulation, rampant pollution and decline of all high-quality resources. However, almost all world governments are pushing continuation of business as usual, albeit by “greener” means. Commendable behavior of a few individuals has almost zero effect on the resource-wasting societies. The 11.1 terawatts of continuous power from oil and coal cannot be replaced with photovoltaics (PV) within a reasonable time; a transition to wind turbines is even less probable. Even if humanity devoted 35 million barrels of oil per day (Mbopd) to the solar PV transition, it still would take 51 years. Devoting 1 billion tons of coal per year would make this transition happen in 128 years. Currently we do not have 35 Mbopd and 1 billion tons of coal to spare for decades. In fact, without investing 14 trillion USD over the next 20 years, world oil production might drop to 20 Mbopd, less than I chose to devote each year for 51 years to the very large size (VLS) PV arrays.

Since all other means have been exhausted, we must limit and reverse population growth and consume much less of everything. Otherwise, we will continue to commit suicide as a species, while denying the truth. 

Bio: Tadeusz (Tad) Patzek is Director of the Ali I Al‐Naimi Petroleum Engineering Research Center and Professor of Petroleum and Chemical Engineering at the King Abdullah University of Science and Technology (KAUST) in the Kingdom of Saudi Arabia. Until December 2014, he was the Lois K. and Richard D. Folger Leadership Professor and Chairman of the Petroleum and Geosystems Engineering Department at The University of Texas at Austin. He also held the Cockrell Family Regents Chair #11. Between 1990 and 2008, he was a Professor of Geoengineering at the University of California, Berkeley. Prior to joining Berkeley, he was a Senior Reservoir Engineer at Shell Western E&P in Bakersfield, CA (1989‐1990), and a Senior Research Scientist at the venerable Shell Development Bellaire Research Center (BRC) in Houston, TX. (1983‐1989). 

Patzek is also a Presidential Full Professor in Poland (highest honor) and a Distinguished Member of the SPE. By education, he is a chemical process engineer and a physicist trained in catalysis and computational fluid mechanics. In 1983, at BRC, UT professors Larry Lake and Gary Pope introduced Patzek to petroleum engineering, and his life was never the same. 

Patzek has engaged in the studies of complex systems, focusing on the human factors in ultra‐ deepwater offshore operations. He briefed Congress on the BP Deepwater Horizon well disaster in the Gulf, and was a frequent guest on NPR, ABC, BBC, CNN, and CBS programs. In January 2011, Patzek became a member of the Ocean Energy Safety Advisory Committee for the Department of Interior's Bureau of Safety and Environmental Enforcement (BSEE). He co‐ wrote a popular book with a famous historian, Joseph Tainter, "Drilling Down: The Gulf Debacle and our Energy Dilemma."

In 2014, Patzek and his colleagues, Prof. Michael Marder and Mr. Frank Male, received the Cozzarelli Prize from the National Academy of Sciences for the best paper in engineering in 2013, "Gas production in the Barnett Shale obeys a simple scaling law."

Since 2003, Patzek has engaged in the studies of sustainability, and industrial agricultural and agrofuel systems, all viewed through the lens of ecology and irreversible thermodynamics. Patzek’s papers in this domain are among his most cited and most important. In 2007, Patzek participated in the OECD ministerial meetings in Paris that coped with the new biofuel mandates established in the US. In 2006 and 2007, Patzek and his son Lucas argued in vain against the irreversible damage of the tropical ecosystems in Indonesia, Malaysia, equatorial Africa and Brazil.

For the last 7 years, Patzek has maintained a blog about the environment, ecology, energy, complexity and human activities with 370,000 unique readers.  

Patzek coauthored some 300 papers and reports, and wrote five other books, one of which is submitted for publication.

​Abstract:  Polymers with intrinsic microporosity (PIMs) showed the potential to provide highly permeable and highly selective membranes for gas separation applications with the ability to fine-tune their properties for better performance. The concept of microporosity was extended to the polyimides by using kinked, contorted and stable structures to obtain high gas performance combined with excellent solution-processability, high thermal stability, and a unique platform for a wide range of possible modifications and tunability. Thus, studying the structure-property relationships is a critical key to develop advanced materials that can replace the commercially available membranes like cellulose acetate and Matrimid. Importantly, in the microporous polyimides (PIM-PIs) system, varying the type of the side chains appended to the diamines or dianhydrides impacts polymeric membrane properties, and in turn, gas separation performance.

In this dissertation, we have examined the effect of ring substitutes, incorporated into novel polyimides backbones, on polymer properties and gas separation performance. The choice of side group can induce subtle changes in material properties and molecular interactions between the polymeric chains and affect the pore-size distribution, chain packing and yielding distinct combination between gas permeability and permselectivity.

We have shown that the effect of tertiary amine groups, in polyimide structures, on the CO2 solubility is marginal but it can control the chain packing.  However, introducing bromine groups on the polymer backbone can boost the O2 permeability and O2/N2 selectivity and perform better than the commercially available membranes. BCBr4-SBIDA demonstrated the same O2/N2 selectivity relative to cellulose acetate but approximately 10-fold higher gas permeability. Combining high selectivity with good permeability was achieved by a newly designed carboxyl-functionalized homopolymer (6FDA-TrMPD) with CO2 permeability of 144 barrer and CO2/CH4 selectivity of 45. The new W-shaped CANAL diamines, prepared by one-step synthesis, were used as microporosity generators in polyimides and revealed promising gas transport performance with the same selectivity relative to cellulose acetate by 23-fold higher permeability (CANAL-PI-3-MeNH2). Therefore, developing advanced polymers for membrane-based gas separation can be obtained by an ideal combination between kinked monomers, side chains, and stable materials.

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• CONTACTLinda J. Sapolu
• EMAILLinda.Sapolu@kaust.edu.sa

Abstract:

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• CONTACTEmmanuelle Sougrat

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• CONTACTKarema S. Alaseef

Abstract:  This research was undertaken to develop state-of-the-art interfacially polymerized (IP) defect-free thin-film composite (TFC) membranes and understand their structure-function-performance relationships. Recent research showed the presence of defects in interfacially polymerized commercial membranes which potentially deter performance in liquid separations and render the membranes inadequate for gas separations.

Firstly, a modified method (named KRO1) was developed to fabricate interfacially polymerized defect-free TFCs using m-phenylene diamine (MPD) and trimesoyl chloride (TMC). The systematic study revealed the ability to heal defects in-situ by tweaking the reaction time along with considerably improving the membrane crosslinking by controlling the organic solution temperature. The two discoveries were combined to produce highly crosslinked, defect-free MPD-TMC polyamide membranes which showed exceptional performance for separating H2 from CO2. Permeance and pure-gas selectivity of the membrane increased with temperature. H2 permeance of 350 GPU and H2/CO2 selectivity of ~100 at 140 °C were obtained, the highest reported performance for this application using polymeric materials to date.

Second, the membranes produced using KRO1 were tested for reverse-osmosis (RO) performance which revealed significantly improved boron rejection compared to commercial membranes reaching a maximum of 99% at 15.5 bar feed pressure at pH 10. The study also unveiled direct correlations between membrane crosslinking and salt separation performance in addition to the membrane surface roughness.
This was followed by replacing the conventional IP TMC monomer with a large, rigid and contorted tetra-acyl chloride (TripTaC) monomer to enhance the performance of IP TFCs. The fabricated TFCs showed considerable performance boosts especially for separating of small solutes from organic solvents such as methanol. A rise in H2 permeance was also observed compared to the conventional MPD-TMC TFCs while reaching a maximum H2/CO2 selectivity of 9 at 22 °C.

Finally, the research was completed by showing the potential of KRO1 for fabrication of defect-free TFCs using a range of aqueous diamine monomers. KRO1 enabled defect-free gas properties for all monomers used showing exceptional performance for separating H2-CO2 and O2-N2 mixtures. It was further shown that the formulation could also improve the RO separation of interfacially polymerized polyamide TFCs beyond those shown by commercially available TFCs.   

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• CONTACTLinda J. Sapolu
• EMAILLinda.Sapolu@kaust.edu.sa

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• CONTACTKarema S. Alaseef