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1 The Microsystem Fabrication Laboratory at the Naval Post Graduate School (NPS) focuses on the fabrication of microelectromechanical systems (MEMS). We report on the development of a microfabrication process of a terahertz metamaterial developed to absorb high levels of THz radiation. The metamaterial was designed to 1) be simple and low-cost to implement, 2) match the resonant frequency of the illumination source while providing structural support, 3) maintain thermomechanical properties, and 4) provide optical read-out access. The design consists of a periodic array of aluminum squares separated from a homogenous aluminum (Al) ground plane by a thin film of SU-8 photoresist (dielectric layer). This metamaterial acts as an absorbing portion of a THz detector. Absorbed incident THz radiation by a detector in the absorbing structure of the metamaterial transforms it into heat that transfers to detector’s bimaterial legs. Consequently, the detector’s structure deforms proportionally to the absorbed power. Deformation occurs due to the difference in thermal coefficients of Al and SU-8. A quantum cascade laser (QLC) emitting THz radiation is to be used as the illuminating source in the imaging system.
INTEGRATION OF NATURAL DYE, ANTHOCYANIN, INTO SOLID-STATE SOLAR CELLSEduardo Valle, Aliaksandr Zaretski, Darren Lipomi.
University of California, San Diego, La Jolla, CA.
Anthocyanins are small molecules that are responsible for the dark purple to bright red colors of many fruits and vegetables. The major role of anthocyanins in plants is to absorb specific wavelengths of sunlight, from 520 nm to the ultraviolet. In doing so, they protect the plant from solar damage. This photosynthesizing property of anthocyanins has caught the attention of the solar cell community and has led to the development of dye-sensitized solar cells (DSSC) that use anthocyanins as the electron donor, hole producer in the cell’s active layer. Current DSSCs have been able to achieve high efficiencies (~12%). The problem with DSSCs is that the electrolytic fluid cannot be preserved for long periods of time. Our goal is to create a solid organic solar cell (OSC) using anthocyanins paired with an electronaccepting compound to overcome the obstacle presented by the electrolyte. We start by extracting and purifying anthocyanins from purple corn, a crop that can be grown over large areas in many climates, via vacuum filtration and column chromatography. The purified anthocyanin (a p-type semiconductor) is then spin-coated onto glass bearing a layer of a transparent conductive polymer. An n-type small molecule is spin-coated on top of the anthocyanin layer, and a drop of eutectic gallium-indium as the top electrode completes the device. The cell will then be placed in a solar simulator to test its performance. Preliminary results suggest that anthocyanin and a derivative of C60 form working solar cells, and we seek to improve them.
HIGH SENSITIVITY METAL-ORGANIC HYBRID TERAHERTZ METAMATERIALAzucena Yzquierdo1, Erik Bautista1, Dragoslav Grbovic2.
Hartnell College, Salinas, CA, 2Naval Post Graduate School, Monterey, CA.
1 The Microsystem Fabrication laboratory, at the Naval Post Graduate School (NPS), focuses on the fabrication of microelectromechanical systems (MEMS). We report on the development of a microfabrication process of a terahertz metamaterial developed to absorb high levels of THz radiation. The metamaterial was designed to 1) be simple and low-cost to implement, 2) match the resonant frequency of the illumination source while providing structural
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support, 3) maintain thermomechanical properties, and 4) provide optical read-out access. The design consists of a periodic array of aluminum squares separated from a homogenous aluminum (Al) ground plane by a thin film of SU-8 photoresist (dielectric layer). This metamaterial acts as an absorbing portion of a THz detector. Absorbed incident THz radiation by a detector in the absorbing structure of the metamaterial transforms it into heat that transfers to detector’s bimaterial legs. Consequently, the detector’s structure deforms proportionally to the absorbed power. Deformation occurs due to the difference in thermal coefficients of Al and SU-8. A quantum cascade laser (QLC) emitting THz radiation is to be used as the illuminating source in the imaging system. Indicative of its flexible design and high sensitivity, further tuning can be achieved by modifying the dimensions of the patterned squares to match the absorption frequency to the illumination source for real-time THz imaging applications for military and medical purposes. We compare the outcome of etching versus the lift-off process for patterning the upper layer of metamaterial, which was implemented previously in search of metamaterial microfabrication optimization.
With recent advancements in biomaterial science, designing and optimizing naturally derived delivery vehicles for therapeutic agents hold great potential in treatment of a wide range of diseases. A major stepping stone to the success of this research is finding a way to mitigate the foreign body response to the material used. It has been shown that biomaterials like poly-L-lysine have the potential to induce a foreign body response, resulting in fibrotic capsules that eventually lead to necrosis of the encapsulated therapeutic agent. One application of particular interest is the artificial pancreas for type I diabetes treatment in which insulin-producing cells are encapsulated in a polymer. Fibrotic tissue formation is thought to be one of the factors in the failure of this device. It is hypothesized that functionalized polymers will have an inhibiting effect on cell migration and contractile scarring, potentially limiting fibrosis. For this work, 5 ml Petri dishes were coated with either alginate or poly-L-arginine which had been functionalized with one of an array of monomers. These Petri dishes were then seeded with 15,000 NIH 3T3 cells.
Cell migration was investigated using time-lapse video microscopy to track cell motion. Experimental results will be reported at the end of the project. Vascular endothelial growth factor will also be measured as it holds the potential to create new blood vessels, supplying the encapsulated cells with nutrients.
RESPONSIVE ENERGETIC SOL-GEL-POLYMER NANOCOMPOSITES FOR ARTIFICIAL PHOTOSYNTHESISAnthony Magdalena1, Gabriel Montano2.
University of New Mexico-Los Alamos, Los Alamos, NM, 2Center for Integrated Nanotechnologies, Los Alamos 1 National Laboratory, Los Alamos, NM.
A variety of photosynthetic organizations can be found in nature. In a majority of such complexes, membraneembedded proteins serve as scaffolds for pigments generating energetically, spatially ordered assemblies resulting in efficient light-harvesting, energy transfer, and charge separation. The ability to mimic the efficiency of natural photosynthetic systems has been a goal in biomaterials design for decades. Mesostructured and mesoporous silica made using sol-gel processing are promising host templates for encapsulation of biomolecules and creating bioinspired assemblies. The sol-gel process involves the transition of a solution system from a liquid “sol” (colloidal) into a solid “gel.” Surfactants are commonly used as templates in creating mesostructured or mesoporous silica during the sol-gel process resulting in ordered arrays. In this study, amphiphilic diblock copolymers that form micelles are being investigated as templates for forming mesostructured silica and as composite materials for creating bioinspired artificial photosynthetic assemblies. We have designed nanocomposites that incorporate porphyrin-based chromophores and carbon-based nanomaterials in varying compositions into responsive block-copolymer micelle assemblies encapsulated in sol-gel in order to generate photo-responsive bio-inspired materials. The designed nanocomposites investigated are an initial attempt to generate responsive, ordered arrays capable of performing artificial photosynthetic processes such as light-harvesting, energy transfer, and charge-separation.
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EXPERIMENTAL AND FINITE ELEMENT METHOD ANALYSIS OF THE MECHANICAL BEHAVIOR OF
SANDWICH STRUCTURESSandra Diaz, Lilian Davila.
University of California, Merced, Merced, CA.
The goal of this study is to evaluate and predict the mechanical properties of sandwich structures consisting of two 6061 Al sheets and a polyurethane foam core as a function of three different foam densities (96.1 kg/m3, 160 kg/ m3, and 320 kg/m3). Computer simulations and experiments are being carried out in this project in order to create an efficient procedure for future design considerations. A finite element method (FEM) program, COMSOL Multiphysics 4.3, is used to predict the critical buckling load and bending modulus of the sandwich structure when it is subjected to uniaxial compression loads and a 3-point bending test. The results are compared with previous independent experimental findings. From the FEM simulations, other mechanical properties are analyzed including the maximum von Mises stress, displacement, and volumetric strain among others. An experimental 3-point bending test is also conducted using an Instron universal testing machine to measure the mechanical properties of the sandwich structure. Predicted results show that the critical buckling load (and bending modulus) increases as foam density increases, implying that the density and strength of the foam in the sandwich structure have a direct relationship and affect the overall properties of the combined foam-sheet system. In brief, simulations and experimentation combined can be a powerful tool for the study, prediction, and design of new or advanced materials. Future work will involve assessment of the feasibility of these sandwich structures as vehicle impact absorbers, allowing future automobiles to be lighter and safer, which in return would increase fuel efficiency.
INDUCED NEGATIVE VISCOSITY AS A DEGREE OF FREEDOM IN THE ELECTROSPINNING OF POLYMERICSOLUTIONS Lina Sanchez-Botero, Alejandro Garcia, Juan Hinestroza.
Cornell University, Ithaca, NY.
This paper seeks to provide evidence for the negative viscosity effect in non-Newtonian ferrofluids and provide an avenue to investigate the new parameter of non-Newtonian behavior that is affected by both the magnetic field and shear stresses. Previous models developed by Shliomis, Felderhof, Weng, and Chen have described the phenomenon of magnetoviscosity for Newtonian (ferro) fluids from irreversible thermodynamics but, until now, there has been no work done purely on non-Newtonian ferrofluids. The induced negative viscosity effect in a polymer solution with magnetic nanoparticles is presented both from an experimental and theoretical view. As part of a new design, a linear solenoid was coiled around a ferrite hollow bar to produce higher magnetic fields. Results using a capillary rheometer indicated that the magnetic nanoparticle colloidal fluid under an AC-generated magnetic field displayed an overall reduction of viscosity under certain shear rates. Additionally, measurements demonstrate a significant reduction in viscosity of the liquid with the AC-generated field versus no field. For a Hagen-Poiseuille flow, additional measurements implementing shear also demonstrate a combination of magnetic and non-Newtonian properties. A model considering both the magnetic and non-Newtonian properties is developed, taking from the earlier models. The models of Weng and Chen, and one model of Shliomis, explore non-Newtonian behavior in Newtonian ferrofluids under a combination of magnetic fields and shear stresses, but an actual non-Newtonian fluid is not employed.
LAYOUT DESIGN FOR HYBRID ELECTRIC VEHICLE TEST PLATFORMXavier Castaneda1, Changjian Hu2, Ewan Pritchard2.
College of the Sequoias, Visalia, CA, 2North Carolina State University, Raleigh, NC.
1 Electric vehicles (EVs) and hybrid electric vehicles (HEVs) have the potential to provide efficiency benefits over vehicles with combustion engines. Current vehicle test beds available are not suitable for HEV testing purposes. An HEV test platform can provide automobile manufacturers with accessible performance tests and can also be a helpful tool for researchers to develop automobile software, components, and control strategies. The HEV test platform
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consists of a chassis with hybrid drive train, a data acquisition system, a chassis dynamometer, and a MotoHawk micro controller. In this research, we mainly focus on the layout design of the hybrid drive train converted from a pure electric drive which comes from a Department of Energy project. The conversion research begins with the 3D modeling of the existing chassis components in SolidWorks. Components were first measured, sketched, and then modeled to appropriate or representative dimensions. With all parts modeled, different layouts for the chassis can be virtually assembled for further analysis. Four different designs are proposed whose benefits and difficulties are analyzed respectively. The most appropriate design was chosen after analyzing the tradeoffs of all designs. This design research provides an optimal layout of the chassis with the hybrid drive train which will benefit the future development of the HEV test platform.
MASS AND ENERGY BALANCE QUANTIFICATION OF BIOMASS IN A PLASMA GASIFICIATION SYSTEMEngineering Alexandro Perez-Tovar, Gerardo Diaz.
University of California, Merced, Merced, CA.