Compound Semiconductor-Based Thin-Film and Flexible Optoelectronics.

Compound semiconductors are the basis of modern optoelectronics due to their intrinsically superior optical and electronic properties compared with elemental semiconductors. However, their applications remain limited due to a prohibitive substrate cost. This limitation has driven the development of epitaxial lift-off (ELO) technology that separates the thin-film epitaxial layer from the substrate by selectively removing a sacrificial layer between them. However, ELO has its own limitations including a long process time, complicated transfer to a secondary, low cost host substrate, and wafer surface degradation which prevents wafer recycling. In this thesis, we address all of these limitations by developing a new, non-destructive ELO (ND-ELO) process. When combined with adhesive-free cold-weld bonding of the wafer directly to a plastic substrate, ND-ELO provides an approximately 100 times reduction in process time, and a considerably simplified transfer process compared with conventional ELO. Furthermore, it allows indefinite wafer reuse by employing the epitaxial protection layers, eliminating surface degradation of the parent wafer encountered in conventional ELO. We demonstrate the feasibility and generality of this process by applying it to optoelectronic devices including photovoltaic cells, LEDs, MESFETs and photodetectors on two compound semiconductor systems, InP and GaAs. Furthermore, we present an approach that can achieve an estimated cost of only 3% that of conventional GaAs solar cells using an accelerated ND-ELO wafer recycling process, and integrated with lightweight, thermoformed plastic, truncated mini-compound parabolic concentrators (CPC) that avoid the need for active solar tracking. Using solar cell/CPC assemblies, without daily solar tracking, the annual energy harvesting is increased by 2.8 times compared with planar solar cells. This represents a drastic cost reduction in both the module and balance of systems costs compared with heavy, rigid conventional modules and trackers that are subject to wind loading damage and high installation costs. The demonstration of cost-efficient and high performance compound semiconductor-based flexible thin-film optoelectronics is a critical step toward allowing their widespread deployment in mainstream state-of-the-art applications including wearable, flexible and conformal devices.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111479/1/kyusang_1.pd

3D Printed Masks and Transfer Stamping Process to Enable the Fabrication of the Hemispherical Organic Photodiodes

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138391/1/admt201700090_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138391/2/admt201700090.pd

A lab-on-a-disc platform enables serial monitoring of individual CTCs associated with tumor progression during EGFR-targeted therapy for patients with NSCLC

Rationale: Unlike traditional biopsy, liquid biopsy, which is a largely non-invasive diagnostic and monitoring tool, can be performed more frequently to better track tumors and mutations over time and to validate the efficiency of a cancer treatment. Circulating tumor cells (CTCs) are considered promising liquid biopsy biomarkers; however, their use in clinical settings is limited by high costs and a low throughput of standard platforms for CTC enumeration and analysis. In this study, we used a label-free, high-throughput method for CTC isolation directly from whole blood of patients using a standalone, clinical setting-friendly platform. Methods: A CTC-based liquid biopsy approach was used to examine the efficacy of therapy and emergent drug resistance via longitudinal monitoring of CTC counts, DNA mutations, and single-cell-level gene expression in a prospective cohort of 40 patients with epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer. Results: The change ratio of the CTC counts was associated with tumor response, detected by CT scan, while the baseline CTC counts did not show association with progression-free survival or overall survival. We achieved a 100% concordance rate for the detection of EGFR mutation, including emergence of T790M, between tumor tissue and CTCs. More importantly, our data revealed the importance of the analysis of the epithelial/mesenchymal signature of individual pretreatment CTCs to predict drug responsiveness in patients. Conclusion: The fluid-assisted separation technology disc platform enables serial monitoring of CTC counts, DNA mutations, as well as unbiased molecular characterization of individual CTCs associated with tumor progression during targeted therapy

Improved power conversion efficiency of InP solar cells using organic window layers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98676/1/ApplPhysLett_98_053504.pd

Low-Thermal-Budget Ferroelectric Field-Effect Transistors Based on CuInP2S6 and InZnO

In this paper, we demonstrate low-thermal-budget ferroelectric field-effect transistors (FeFETs) based on two-dimensional ferroelectric CuInP2S6 (CIPS) and oxide semiconductor InZnO (IZO). The CIPS/IZO FeFETs exhibit non-volatile memory windows of ~1 V, low off-state drain currents, and high carrier mobilities. The ferroelectric CIPS layer serves a dual purpose by providing electrostatic doping in IZO and acting as a passivation layer for the IZO channel. We also investigate the CIPS/IZO FeFETs as artificial synaptic devices for neural networks. The CIPS/IZO synapse demonstrates a sizeable dynamic ratio (125) and maintains stable multi-level states. Neural networks based on CIPS/IZO FeFETs achieve an accuracy rate of over 80% in recognizing MNIST handwritten digits. These ferroelectric transistors can be vertically stacked on silicon CMOS with a low thermal budget, offering broad applications in CMOS+X technologies and energy-efficient 3D neural networks

Grading system for periodontitis by analyzing levels of periodontal pathogens in saliva

Periodontitis is an infectious disease that is associated with microorganisms that colonize the tooth surface. Clinically, periodontal condition stability reflects dynamic equilibrium between bacterial challenge and host response. Therefore, periodontal pathogen assessment can assist in the early detection of periodontitis. Here we developed a grading system called the periodontal pathogen index (PPI) by analyzing the copy numbers of multiple pathogens both in healthy and chronic periodontitis patients. We collected 170 mouthwash samples (64 periodontally healthy controls and 106 chronic periodontitis patients) and analyzed the salivary 16S rRNA levels of nine pathogens using multiplex, quantitative real-time polymerase chain reaction. Except for Aggregatibacter actinomycetemcomitans, copy numbers of all pathogens were significantly higher in chronic periodontitis patients. We classified the samples based on optimal cut-off values with maximum sensitivity and specificity from receiver operating characteristic curve analyses (AUC = 0.91, 95% CI: 0.87-0.96) into four categories of PPI: Healthy (1-40), Moderate (41-60), At Risk (61-80), and Severe (81-100). PPI scores were significantly higher in all chronic periodontitis patients than in the controls (odds ratio: 31.7, 95% CI: 13.41-61.61) and were associated with age, scaling as well as clinical characteristics including clinical attachment level and plaque index. Our PPI grading system can be clinically useful for the early assessment of pathogenic bacterial burden and follow-up monitoring after periodontitis treatment

Genome-wide data from two early Neolithic East Asian individuals dating to 7700 years ago.

Ancient genomes have revolutionized our understanding of Holocene prehistory and, particularly, the Neolithic transition in western Eurasia. In contrast, East Asia has so far received little attention, despite representing a core region at which the Neolithic transition took place independently ~3 millennia after its onset in the Near East. We report genome-wide data from two hunter-gatherers from Devil's Gate, an early Neolithic cave site (dated to ~7.7 thousand years ago) located in East Asia, on the border between Russia and Korea. Both of these individuals are genetically most similar to geographically close modern populations from the Amur Basin, all speaking Tungusic languages, and, in particular, to the Ulchi. The similarity to nearby modern populations and the low levels of additional genetic material in the Ulchi imply a high level of genetic continuity in this region during the Holocene, a pattern that markedly contrasts with that reported for Europe.V.S. was supported by the Gates Cambridge Trust. R.P. was funded by the European Research Council (ERC) starting grant ADNABIOARC (263441) and the Irish Research Council Advanced Research Project Grant from January 2014 to December 2016. M.H. was supported by ERC Consolidator Grant 310763 “GeneFlow.” This work was supported by the Research Fund (1.140113.01) of Ulsan National Institute of Science and Technology to J.B. This work was also supported by the Research Fund (14-BR-SS-03) of Civil-Military Technology Cooperation Program to J.B. and Y.S.C. M.G.-L. was supported by a Biotechnology and Biological Sciences Research Council Doctoral Training Partnerships studentship. A.M. and A.E. were supported by the ERC Consolidator Grant 647787 “LocalAdaptation.” D.G.B. was funded by ERC Investigator grant 295729-CodeX

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Biomechanical response of the human body inside a military vehicle exposed to AP mine explosion was studied using the finite element method. The main focus was placed on evaluation of the injury potential of the human body, particularly the brain, neck (cervical spine), and legs. Injury criteria used to evaluate the injury potential were HIC, IARV's, and some others. The military vehicle used in this research was M 1097A2, the basic model of HUMVEE. In addition to the evaluation of the injury potential, some design modifications to the present vehicle were consideredin order to reduce the injury potential to the crew of the vehicle.http://archive.org/details/biomechanicalres1094532659NAKorean Army author.Approved for public release; distribution is unlimited

The Studies of Polymer Adhesion Using Segmental Dynamics Model

157 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.Polymer adhesives play a very important role in many applications. However, because it is very hard to observe an amorphous polymer at the molecular level, there are many questions about adhesion and failure mechanisms. Several computer simulation techniques have been of great success in describing the dynamics of generic polymers, but are unable to reliably simulate the mechanical deformation of polymer adhesives. Therefore, it was necessary to develop improved coarse-grained potentials for a method we call Segmental Dynamics. Segmental Dynamics employs extensive atomistic Monte Carlo simulations to develop the interaction potentials custom-made for a specific polymer. This makes it possible to study the dynamics of larger scale polymer systems, which is not possible with conventional molecular dynamics techniques. The method was first applied to bulk polybutadiene, and the model was found to describe the density, bulk modulus, and cohesive energy fairly well. The model was further verified by investigating the structure and dynamics of bulk polybutadiene. Also, the effects of high density and high pressure on the dynamic properties of bulk polymers were investigated. Both of these effects significantly increase internal friction coefficients and thus slow down the diffusion of the polymer. Then, the model was applied to dynamic mechanical simulations of an adhesive film between two surfaces at a constant temperature. The equilibrated structure of the polymer revealed that the loop and tail structures are randomly distributed, but are very sensitive to the anchor group density. A series of simulated tensile tests were carried out with varying anchor group densities, and the effects of the bond strength of anchor groups, strain rate, chain length, plasticizers, and surface roughness were identified.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD