New Approaches to Multi-functional Soft Materials

Soft robotics is a relatively new, but fast-developing field of science and technology that utilizes soft materials such as polymers in their body structure. Despite significant progress in soft robotic devices, robots that can sense their environments are still very rare. Although some soft robots have exhibited sensing capabilities, they still have not demonstrated synergistic coupling of sensing and actuation. From our perspective, this type of coupling may take us one step closer to fabricate soft robots with autonomous feedback dynamics. In this work, we present new approaches to soft robotic devices, which are fabricated from responsive soft materials and are able to exhibit synergistic coupling of structural color-based sensing and actuation in response to environmental stimuli. Cephalopods, such as cuttlefish, are excellent models of coupled sensing and actuation. They demonstrate remarkable adaptability to the coloration and texture of their surroundings by modulating their skin color and surface morphology simultaneously and reversibly, for adaptive camouflage and signal communication. Inspired by this unique feature of cuttlefish skins, we present a general approach to remote-controlled, smart films that undergo simultaneous changes of surface color and morphology upon infrared (IR) actuation. The smart film has a reconfigurable laminated structure that comprises an IR-responsive nanocomposite actuator layer and a mechanochromic elastomeric photonic crystal layer. Upon global or localized IR irradiation, the actuator layer exhibits fast, large, and reversible strain in the irradiated region, which causes a synergistically coupled change in the shape of the laminated film and color of the mechanochromic elastomeric photonic crystal layer in the same region. Complex 3D shapes, such as bending and twisting deformations, can be created under IR irradiation, by modulating the strain direction in the actuator layer of the laminated film. Finally, the laminated film has been used in a remote-controlled inchworm walker that can directly couple a color-changing skin with the robotic movements. Such IR-actuated, reconfigurable films could enable new functions in soft robots and wearable devices. A crucial aspect of soft robotics is the sensing capabilities of the robot. Colorimetric sensing based on structural colors, mostly photonic crystals, has been explored. A major challenge is overcoming the problems of limited scalability and time-consuming fabrication process, which affect the real-world applications of photonic crystals. Herein, we have developed a new scalable and affordable platform technology for fabrication of stimuli-responsive, interference colored films. Our system is composed of a thin film of a transparent polymer deposited on a metal-coated substrate. The facile fabrication process allows us to create full spectrum of interference colors on both rigid and soft substrates by simply adjusting the thickness of the polymer layer. Furthermore, our films have been used as colorimetric sensors which undergo fast and reversible change of surface color upon changes in environmental humidity. Such polymer-based, responsive interference coloration could empower colorimetric sensing of various environmental stimuli (e.g. humidity, chemicals, heat, and mechanical forces), which could enable a wide range of applications

Graphene Based Metamaterials For Terahertz Cloaking And Subwavelength Imaging

Graphene is a two-dimensional carbon crystal that became one of the most controversial topics of research in the last few years. The intense interest in graphene stems from recent demonstrations of their potentially revolutionary electromagnetic applications – including negative refraction, subdiffraction imaging, and even invisibility – which have suggested a wide range of new devices for communications, sensing, and biomedicine. In addition, it has been shown that graphene is amenable to unique patterning schemes such as cutting, bending, folding, and fusion that are predicted to lead to interesting properties. A recent proposed application of graphene is in engineering the scattering properties of objects, which may be leveraged in applications such as radar-cross-section management and stealth, where it may be required to make one object look like another object or render an object completely invisible. We present the analytical formulation for the analysis of electromagnetic interaction with a finite conducting wedge covered with a cylindrically shaped nanostructured graphene metasurface, resulting in the scattering cancellation of the dominant scattering mode for all the incident and all the observation angles. Following this idea, the cylindrical graphene metasurface is utilized for cloaking of several concentric finite conducting wedges. In addition, a wedge shaped metasurface is proposed as an alternative approach for cloaking of finite wedges. The resolution of the conventional imaging lenses is restricted by the natural diffraction limit. Artificially engineered metamaterials now offer the possibility of creating a superlens that overcomes this restriction. We demonstrate that a wire medium (WM) slab loaded with graphene sheets enables the enhancement of the near field for subwavelength imaging at terahertz (THz) frequencies. The analysis is based on the nonlocal homogenization model for WM with the additional boundary condition in the connection of wires to graphene. The principle of the operation of the proposed lens depends on the enhancement of evanescent waves, wherein the excited surface plasmons at the lower and upper graphene interfaces are coupled by an array of metallic wires. The resolution and the operating frequency of the subwavelength imaging device are mainly determined by the tunability of graphene and the structural parameters of the WM slab. The proposed structure has a resolution better than λ/10 with the advantages of broad bandwidth, low sensitivity to losses, and tunability with respect to the chemical potential even if the distance between two graphene sheets is a significant fraction of wavelength. As a supplementary study, the performance of WM slab loaded with nanostructured graphene metasurfaces as a novel sub-diffraction imaging lens is studied. It is observed that the dual nature (capacitive/inductive) of the nanostructured graphene metasurface can be utilized to design a dual-band lens in which the subwavelength imaging simultaneously at two tunable distinct frequencies is possible. The analytical results which are presented throughout this thesis, are validated with the full-wave electromagnetic simulator, CST Microwave Studio

Developing better models for laminar and turbulent burning velocities for H2, H2-CH4 and H2-NH3 mixed with air at different Equivalence Ratios.

The study of laminar and turbulent burning velocities is critical for understanding combustion behavior and developing efficient and safe combustion systems. This thesis provides an in-depth investigation of the factors that influence burning velocities, particularly for hydrogen mixtures, and the mathematical models used to predict them. We reviewed the historical development of measurement techniques for burning velocities and highlighted the challenges associated with their measurement. Our research revealed that laminar burning velocity is significantly affected by factors such as initial temperature and pressure, equivalence ratio, fuel concentration, and the Lewis number. We explored the impact of these factors on burning velocities and provided mathematical formulations that link burning velocity with the chemical time scale, Lewis number, fuel concentration, and Product temperature. Furthermore, we critically examined various models for predicting burning velocities, including the FLACS mixing rule. Our research underscores the importance of incorporating parameters such as the Lewis number and chemical time scales in predictive models for accurate results. This study contributes to the field of combustion studies by offering an understanding of laminar and turbulent burning velocities, as well as the factors and models that influence them. The insights gained from this research are mainly usable for CFD modelling of explosion hazards. The improved accuracy of the burning velocity models will allow for more accurate predictions of the flame propagation speed and flame stability. This information can be used to optimize the design of combustion systems to improve efficiency and reduce emissions.Master's Thesis in Process TechnologyPRO399MAMN-PR

Identification of Genomic Regions Associated With Color-Related Traits in Durum Wheat

Durum wheat (Triticum turgidum L. ssp. durum Desf.) is one of the main crops for human consumption, and it is an essential ingredient for pasta production. The color of pasta can range from bright yellow to dim brown. Pasta brightness and yellowness are important quality indicators for producers and customers. Releasing durum wheat cultivars capable of producing pasta products with high yellow color can be an important goal for breeders. Yellow pigment content (YPC) is one of the important components that affect pasta color. The yellow color of pasta is not necessarily dictated by the presence of YPC; soluble brown pigment (SBP) and enzymes such as polyphenol oxidase (PPO) and peroxide (POD) are other factors that contribute to pasta color. Marker-assisted selection (MAS) can accelerate the selection process for breeding programs that develop new durum wheat cultivars with high yellow color. This dissertation used quantitative trait loci (QTL) mapping to identify QTL for these color-related traits. Two populations, each with 192 recombinant inbred lines (RILs), were developed from crosses between Joppa and D12118 (Population one [POP1]) and Mountrail and Carpio (Population two [POP2]). The phenotyping of these traits was carried out in two locations in North Dakota, USA. Genotyping of the RIL populations was conducted using the wheat Illumina iSelect 90K SNP assay. There were significant phenotypic differences among the genotypes for all traits. In POP1, entry lines 32 and 78 with both high YPC and low SBP, and in POP 2 entry lines 1, 82, and 101 with high YPC could be excellent sources for improving the yellow color in durum wheat. In this study, 31 Additive QTL (A-QTL) and 370 minor digenic epistatic QTL (DE-QTL) associated with all four traits were identified. In Pop1, the most significant A-QTL were detected on Chromosomes 5A (D1.SBP5A.ndsu) for SBP and 5B (D1.YPC5B.ndsu) and 6B (D1.YPC6B.ndsu) for YPC. In POP2, major A-QTL were found on chromosomes 7A (D2.YPC7A.ndsu), 2A (D2.PPO2A.ndsu), and 3A (D2.POD3A.ndsu) for YPC, PPO, and POD, respectively. The information provided in the current study could be employed with MAS to increase selection efficiency and improve the color of durum wheat

Synthesis of peptide-based porous material

Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 201

Compressed Sensing Based Reconstruction Algorithm for X-ray Dose Reduction in Synchrotron Source Micro Computed Tomography

Synchrotron computed tomography requires a large number of angular projections to reconstruct tomographic images with high resolution for detailed and accurate diagnosis. However, this exposes the specimen to a large amount of x-ray radiation. Furthermore, this increases scan time and, consequently, the likelihood of involuntary specimen movements. One approach for decreasing the total scan time and radiation dose is to reduce the number of projection views needed to reconstruct the images. However, the aliasing artifacts appearing in the image due to the reduced number of projection data, visibly degrade the image quality. According to the compressed sensing theory, a signal can be accurately reconstructed from highly undersampled data by solving an optimization problem, provided that the signal can be sparsely represented in a predefined transform domain. Therefore, this thesis is mainly concerned with designing compressed sensing-based reconstruction algorithms to suppress aliasing artifacts while preserving spatial resolution in the resulting reconstructed image. First, the reduced-view synchrotron computed tomography reconstruction is formulated as a total variation regularized compressed sensing problem. The Douglas-Rachford Splitting and the randomized Kaczmarz methods are utilized to solve the optimization problem of the compressed sensing formulation. In contrast with the first part, where consistent simulated projection data are generated for image reconstruction, the reduced-view inconsistent real ex-vivo synchrotron absorption contrast micro computed tomography bone data are used in the second part. A gradient regularized compressed sensing problem is formulated, and the Douglas-Rachford Splitting and the preconditioned conjugate gradient methods are utilized to solve the optimization problem of the compressed sensing formulation. The wavelet image denoising algorithm is used as the post-processing algorithm to attenuate the unwanted staircase artifact generated by the reconstruction algorithm. Finally, a noisy and highly reduced-view inconsistent real in-vivo synchrotron phase-contrast computed tomography bone data are used for image reconstruction. A combination of prior image constrained compressed sensing framework, and the wavelet regularization is formulated, and the Douglas-Rachford Splitting and the preconditioned conjugate gradient methods are utilized to solve the optimization problem of the compressed sensing formulation. The prior image constrained compressed sensing framework takes advantage of the prior image to promote the sparsity of the target image. It may lead to an unwanted staircase artifact when applied to noisy and texture images, so the wavelet regularization is used to attenuate the unwanted staircase artifact generated by the prior image constrained compressed sensing reconstruction algorithm. The visual and quantitative performance assessments with the reduced-view simulated and real computed tomography data from canine prostate tissue, rat forelimb, and femoral cortical bone samples, show that the proposed algorithms have fewer artifacts and reconstruction errors than other conventional reconstruction algorithms at the same x-ray dose

Analytical and Numerical Investigation of Soliton Solutions of Coupled Equations in Quadratic Media: A Novel Approach

Solitons have been hitherto studied in Kerr media. However, we show that the optical solitons are not only limited to non-linear Kerr media. In this paper, a new method is devised to achieve the analytical approximate solutions to the soliton packages in one and two dimensions. Inputting (1) and (2) to Maxwell equations and using second-harmonic generation of type I, the coupled motion equations are obtained. Some states of spatial bright solitons are studied for large values of . The variational method is briefly reviewed and analytical approximate solution to quadratic-soliton coupled motion equations is investigated in one and two dimensions and also numerically solved. The comparison of analytical and numerical results indicates that our method is more accurate than the variational method.Key words Bright and dark solitons; Spatial optical soliton; Quadratic Kerr media; Variational method; Secondharmonic generatio

Infrared actuation-induced simultaneous reconfiguration of surface color and morphology for soft robotics

Cephalopods, such as cuttlefish, demonstrate remarkable adaptability to the coloration and texture of their surroundings by modulating their skin color and surface morphology simultaneously, for the purpose of adaptive camouflage and signal communication. Inspired by this unique feature of cuttlefish skins, we present a general approach to remote-controlled, smart films that undergo simultaneous changes of surface color and morphology upon infrared (IR) actuation. The smart film has a reconfigurable laminated structure that comprises an IR-responsive nanocomposite actuator layer and a mechanochromic elastomeric photonic crystal layer. Upon global or localized IR irradiation, the actuator layer exhibits fast, large, and reversible strain in the irradiated region, which causes a synergistically coupled change in the shape of the laminated film and color of the mechanochromic elastomeric photonic crystal layer in the same region. Bending and twisting deformations can be created under IR irradiation, through modulating the strain direction in the actuator layer of the laminated film. Furthermore, the laminated film has been used in a remote-controlled inchworm walker that can directly couple a color-changing skin with the robotic movements. Such remote-controlled, smart films may open up new application possibilities in soft robotics and wearable devices