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MECHANICS, VIBRATIONS, AND TENSION MEASUREMENT OF THIN WEBS IN ROLL-TO-ROLL MANUFACTURING FOR FLEXIBLE AND PRINTED ELECTRONICSDan Feng (10723848) 29 April 2021 (has links)
<div>Roll-to-roll processes provide a low-cost and high-throughput scheme for scalable flexible devices manufacturing. Multiple processes are used in roll-to-roll manufacturing, such as functional printing, evaporation/drying, UV curing, hot embossing, laser/heat annealing, laser ablation, plasma/ chemical growth, and sputtering. These processes change the web temperature field and/ or local properties. In addition, residual stresses by the process and web tension can destabilize the process and lead to wrinkling or undesirable performance of the products.</div><div>This dissertation investigates three different multi-physics problems relevant to the roll-to-roll processes, which are web thermomechanics, air-coupled web vibrations, and the measuring of nonuniform web tension. First, a mathematical model for predicting the in-plane temperature and heat induced stress distributions in a flexible, axially moving web under arbitrary shape of heat flux is presented. The computational approach is validated on experiments performed on moving paper and PET webs with infrared laser heating source. Second, a closed-form, semi-analytical, universal hydrodynamic functions is developed to accurately predict the lowest symmetric and anti-symmetric transverse frequency responses for any uniaxially tensioned web of arbitrary material and aspect ratio used in roll-to-roll processes with the surrounding air acting as distributed added mass. Experimental validation is carried out by using pointwise laser measurements of acoustically excited webs with different pre-tensions, web materials, and aspect ratios. Finally, we develop and test a non-contact resonance method and a gentle contact stiffness mapping method based on the first principles mechanical models of a tensioned plate to accurately measure the average web tension and its linear variation for a wide range of web properties, web path, web tension, measurement configurations, and environmental conditions. The two methods are cross-validated on a stationary test stand and the non-contact resonance method is used to study the web tension distribution within a commercial roll-to-roll system.</div><div><br></div>
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DEVELOPMENT OF ELECTROCHEMICAL AND COLORIMETRIC SENSING PLATFORMS FOR AGRICULTURE AND HEALTHCARE APPLICATIONSAna Maria NA Ulloa Gomez (14209715) 04 December 2022 (has links)
<p>Fully portable, rapid, and user-friendly sensors can successfully lead to the continuous monitoring of toxins present in the ecosystem as well as the detection of biomarkers to prevent diseases. Towards this goal, we explore electrochemical and colorimetric methods to develop platforms for the on-site detection of pesticides, heavy metals, and inflammation biomarkers. </p>
<p>This thesis presents work with the primary aim of developing non-biological and biological-based platforms. Chapter 2 describes a fully roll-to-roll electrochemical sensor with high sensing and manufacturing reproducibility for detecting nitroaromatic organophosphorus pesticides (NOPPs). This sensor is based on a flexible, screen-printed silver electrode modified with a graphene nanoplatelets coating and a zirconia coating. This chapter outlines the evaluation of the electrocatalytic activity of zirconia towards the reduction of NOPPs, using methyl parathion as a pesticide sample. Furthermore, it describes the fundamentals of electrochemistry focused on voltammetry techniques used for surface characterization and quantification. The topics reviewed serve as the first step to further manufacturing sensors through large-scale methods (e.g., roll-to-roll). Chapter 3 describes the development of a dual-modality sensing system for the detection of mercury in river waters with high accuracy and precision. The objective of this project was to incorporate colorimetric platforms into the electrochemical methods to create a dual detection design and avert false positives and negatives. Here, novel bio-functional aptamers were incorporated in a sensor containing a paper test that detects mercury by a color change and an electrochemical test that measures charge transfer resistance changes upon aptamer-target interaction. For this platform, the colorimetric test demonstrates the utilization of two systems that consist of silver and gold citrate-capped nanoparticles bio-functionalized with highly specific aptamers. The mechanism of detection of these two systems is through Ps-AgNPs and Ps-AuNPs aggregation as a result of ssDNA-Hg2+ interaction. Using Ps-AuNPs microparticles, Chapter 4 describes a fully colorimetric and smartphone-based biosensor for detecting cardiac troponin T, a biomarker for diagnosing acute myocardial infarction. Here, a comparison in detection performance between Whatman grade 1 and high-flow filter paper is reviewed. Finally, Chapter 5 evaluates the colorimetric detection performance of Ps-AuNPs microparticles towards imidacloprid and carbendazim, two of the pesticides most found in imported produce in the United States. The chapter compares gold-based microparticles in which different aptamers were immobilized, and image acquisition approaches.</p>
<p>All sensors reported in this thesis are especially suitable for environmental contaminants monitoring or point-of-care diagnosis applications. The materials selection, use or synthesis, and platforms’ performance optimization, development, and feasibility for scale-up manufacturing are expected to advance on-site biosensing technologies and their commercialization.</p>
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Field Assisted Roll-to-Roll Manufacturing of Novel Multifunctional Piezoelectric CompositesArmen Yildirim (9148748) 10 September 2022 (has links)
<p>The recent advances in flexible piezoelectric technologies have sparked a great interest in developing multifunctional next-generation transducers and actuators that are increasingly becoming high demand for a range of challenging applications, including self-powered structural and personal health monitoring systems to flexible loudspeaker devices. </p><p>In this research, novel <i>quasi </i>1–3 piezoelectric nanocomposites are introduced with record-high piezoelectric voltage coefficients (g<sub>33</sub>), reaching up to 0.709 Vm N<sup>−1</sup> (approximately 20 percent greater than the recently reported highest g<sub>33</sub> value in the literature). These materials are produced via dielectrophoretic process where both piezoelectric lead zirconate titanate (PZT) nanoparticles and graphene nanoplatelets (GNPs) are simultaneously aligned in a silicone-based polymer matrix (polydimethylsiloxane—PDMS) at a range of concentrations up to 13 vol%, leading to densely structured cone-shaped "nanocolumn forests" in the thickness direction. It is shown that the electric field induced alignment of particles not only improves the overall piezoelectric properties of the composite at relatively low filler concentrations, but also increases the transparency of the system by enabling the light to travel with little scattering or absorption in the “Z” direction through the particle depleted zones created between micro- and nano-sized columns. The details of these unique column morphologies are investigated by various off-line and on-line characterization techniques such as microcomputed tomography—microCT and real-time light transmission measurements to better understand the effect of both material (i.e., concentration) and process-based parameters (e.g., electric field, frequency) on pearl-chain formation. </p><p>To show its versatility and high-performance, the applications comprising both direct (e.g., force sensing, energy harvesting, structural and personal health monitoring) and inverse (e.g., loudspeaker) piezoelectric effect are also demonstrated and extensively characterized. </p><p>Additionally, to demonstrate the scalability of the process, large-area samples are also produced via the continuous dielectrophoretic process (utilizing a novel 44 ft long custom designed multifunctional roll-to-roll (R2R) manufacturing line), resulting in the largest single piece piezoelectric films ever reported in the literature. </p>
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Design and Manufacturing of Flexible Optical and Mechanical MetamaterialsDebkalpa Goswami (9006635) 23 June 2020 (has links)
<p>Metamaterials
are artificially structured materials which attain their unconventional macroscopic
properties from their cellular configuration rather than their constituent
chemical composition. The judicious design of this cellular structure opens the
possibility to program and control the optical, mechanical, acoustic,
or thermal responses of metamaterials. This Ph.D. dissertation focuses on
scalable design and manufacturing strategies for optical and
mechanical metamaterials.<br>
<br>
</p>
<p>The
fabrication of optical metamaterials still relies heavily on low-throughput
process such as electron beam lithography,
which is a serial technique. Thus, there is a growing need for
the development of high-throughput, parallel processes to make the fabrication
of optical
metamaterials more accessible and cost-effective. The first part of this
dissertation presents a scalable manufacturing method, termed “roll-to-roll
laser induced superplasticity” (R2RLIS), for the production of
flexible optical metamaterials, specifically metallic near-perfect absorbers. R2RLIS
enables the rapid and inexpensive fabrication of ultra-smooth metallic
nanostructures over large areas using conventional CO<sub>2</sub> engravers
or inexpensive diode lasers. Using low-cost metal/epoxy nanomolds,
the minimum feature size obtained by R2RLIS was <40 nm,
facilitating the rapid fabrication of flexible near-perfect absorbers at
visible
frequencies with the capability to wrap around non-planar surfaces.</p>
<p> </p>
<p>The
existing approaches for designing mechanical metamaterials are mostly <i>ad hoc</i>,
and rely heavily on intuition and
trial-and-error. A rational and systematic approach to create functional and
programmable mechanical metamaterials is therefore desirable to unlock
the
vast design space of mechanical properties. The second part of this
dissertation introduces a systematic, algorithmic design strategy based on Voronoi
tessellation to create architected soft machines (ASMs)
and twisting mechanical metamaterials (TMMs) with programmable motion and properties.
ASMs are a new class of soft machines that benefit from their
3D-architected structure to expand the range of mechanical properties and
behaviors achievable
by 3D printed soft robots. On tendon-based actuation, ASMs deform according
to
the topologically encoded buckling of their structure to produce a wide range
of motions such
as contraction, twisting, bending, and cyclic motion. TMMs are a new class of
chiral mechanical metamaterials which exhibit compression-twist coupling, a
property absent in isotropic materials. This property manifests
macroscopically and is independent of the flexible
material chosen to fabricate the TMM. The nature of this compression-twist
coupling can be programmed by simply tuning two design parameters, giving
access to distinct twisting regimes and tunable onset
of auxetic (negative Poisson’s ratio) behavior. Taking a
metamaterial approach toward the design of soft machines substantially
increases their number of degrees of freedom in deformation, thus blurring
the boundary between materials and machines.</p>
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