Nanowire Alignment: Techniques, Quantification, and Applications in Large-Area Devices

Nanowire alignment is essential for their integration into large-area devices, as well as to obtain certain functionality such as the ability to polarize light and increase surface-enhanced Raman scattering. Various nanowire alignment methods have been developed, however, major drawbacks have limited their application such as complex processing, high cost, limited compatible nanowire materials, and limited scalability. In addition, the methods used to quantify the quality of nanowire alignment are lacking in accuracy, speed, and applicability to all kinds of nanowires. In this thesis, two simple and large-area alignment methods are studied that are applicable for nanowires synthesized by any method and compatible with large-area electronic device fabrication processes. The first method is accomplished by depositing nanowires on polyvinyl alcohol films followed by film stretching, which achieves high-quality alignment (with an order parameter S=0.93). Nanowire breakage, which is commonly encountered in similar techniques, is minimized and the average length of nanowires after alignment is nearly the same (~99.3%) as before alignment. The second alignment method is accomplished directly during rod-coating deposition of the nanowires, without the need of any additional step. Two image processing methods based on edge-detection and skeletonication are presented to recognize nanowires from microscopy images. Then an order parameter and an orientational distribution function are used for alignment quantification. Compared with previously reported studies, these methods are fast and automated, reliable without bias, generally applicable, easy to implement, and computationally efficient. The alignment methods described above are applied in two applications. Firstly, the electrical and optical anisotropy of slightly aligned silver nanowire films, which can be used as transparent electrodes, are investigated. Their transparency to polarized light is increased by 7.3 percentage points compared to typical randomly oriented silver nanowire films, which may benefit end uses such as liquid crystal displays and the touch sensors on top of them. Secondly, a crossed film structure consisting of semiconductor nanowires aligned in one direction and metal nanowires orthogonally aligned is designed. The metal nanowires are intended to act as interconnects to substantially reduce semiconductor nanowire-nanowire junction resistances while avoiding lithographically-defined metal pads, the latter which can have poor mechanically flexibility and involve fabrication processes not desired for large-area electronics. Such a device structure can be developed further for use in large-area flexible devices such as light, strain and chemical sensors and energy generators

Nanopore-Based DNA Analysis via Graphene Electrodes

We propose an improvement for nanopore-based DNA analysis via transverse transport using graphene as transverse electrodes. Our simulation results show conspicuous distinction of tunneling current during translocation of different nucleotides through nanopore. Applying the single-atom thickness property of graphene, our findings demonstrate the feasibility of using graphene as transverse electrodes in future rapid and low-cost genome sequencing

A Comprehensive Technological Survey on the Dependable Self-Management CPS: From Self-Adaptive Architecture to Self-Management Strategies

Cyber Physical Systems (CPS) has been a popular research area in the last decade. The dependability of CPS is still a critical issue, and few surveys have been published in this domain. CPS is a dynamic complex system, which involves various multidisciplinary technologies. To avoid human errors and to simplify management, self-management CPS (SCPS) is a wise choice. To achieve dependable self-management, systematic solutions are necessary to verify the design and to guarantee the safety of self-adaptation decisions, as well as to maintain the health of SCPS. This survey first recalls the concepts of dependability, and proposes a generic environment-in-loop processing flow of self-management CPS, and then analyzes the error sources and challenges of self-management through the formal feedback flow. Focusing on reducing the complexity, we first survey the self-adaptive architecture approaches and applied dependability means, then we introduce a hybrid multi-role self-adaptive architecture, and discuss the supporting technologies for dependable self-management at the architecture level. Focus on dependable environment-centered adaptation, we investigate the verification and validation (V&V) methods for making safe self-adaptation decision and the solutions for processing decision dependably. For system-centered adaptation, the comprehensive self-healing methods are summarized. Finally, we analyze the missing pieces of the technology puzzle and the future directions. In this survey, the technical trends for dependable CPS design and maintenance are discussed, an all-in-one solution is proposed to integrate these technologies and build a dependable organic SCPS. To the best of our knowledge, this is the first comprehensive survey on dependable SCPS building and evaluation

Landscape of enhancer disruption and functional screen in melanoma cells

Abstract Background The high mutation rate throughout the entire melanoma genome presents a major challenge in stratifying true driver events from the background mutations. Numerous recurrent non-coding alterations, such as those in enhancers, can shape tumor evolution, thereby emphasizing the importance in systematically deciphering enhancer disruptions in melanoma. Results Here, we leveraged 297 melanoma whole-genome sequencing samples to prioritize highly recurrent regions. By performing a genome-scale CRISPR interference (CRISPRi) screen on highly recurrent region-associated enhancers in melanoma cells, we identified 66 significant hits which could have tumor-suppressive roles. These functional enhancers show unique mutational patterns independent of classical significantly mutated genes in melanoma. Target gene analysis for the essential enhancers reveal many known and hidden mechanisms underlying melanoma growth. Utilizing extensive functional validation experiments, we demonstrate that a super enhancer element could modulate melanoma cell proliferation by targeting MEF2A, and another distal enhancer is able to sustain PTEN tumor-suppressive potential via long-range interactions. Conclusions Our study establishes a catalogue of crucial enhancers and their target genes in melanoma growth and progression, and illuminates the identification of novel mechanisms of dysregulation for melanoma driver genes and new therapeutic targeting strategies

Structural Biology of NOD-Like Receptors

The nucleotide-binding domain (NBD) and leucine-rich repeat (LRR) containing (NLR) proteins are a large family of intracellular immune receptors conserved in both animals and plants. Mammalian NLRs function as pattern recognition receptors (PRRs) to sense pathogen-associated molecular patterns (PAMPs) or host-derived danger associated molecular patterns (DAMPs). PAMP or DAMP perception activates NLRs which consequently recruit pro-caspase-1 directly or indirectly. These sequential events result in formation of large multimeric protein complexes termed inflammasomes that mediate caspase-1 activation for pyroptosis and cytokine secretion. Recent structural and biochemical studies provide significant insights into the acting mechanisms of NLR proteins. In this chapter, we review and discuss these studies concerning autoinhibition, ligand recognition, activation of NLRs, and assembly of NLR inflammasomes