This report summarizes a method for constructing a Seebeck coefficient tester, the basics behind its operation as well as analyzation of SrxBa1-xNb2O6. Thermoelectric oxides have a very promising and bright future for waste heat recovery, and it is the aim of this project to learn more about them and develop some new materials. The goal of this project is to be able to analyze the Seebeck coefficient of materials at very high temperatures. Current technology is only around 1000 K, and the goal of this project is to be able to measure the Seebeck coefficient of materials to be around 1300 C. The tester is being constructed using our own designs, and a LabView program was created to enable the measurement and operation of the instrument. The setup is fairly straightforward using a 4 point probe test to measure the voltage and temperature difference. For these tests we are using R-type thermocouples instead of the usual K-type thermocouples, as it can handle the very high temperature that is desired. Through developement of a high temperature Seebeck tester there will be greater possibilities in the future for use of various thermoelectric materials.  This report summarizes mainly on constructing the tester to make it fully operational then beginning to obtain measurements, and finally the process of gathering necessary data for accurate measurements.

In the past few years there have been large amounts of research done on the benefits of adding metallic nanoparticles into carbon fiber reinforced epoxy composites. The goal of this study is to estimate the effect of nanoparticle additives on the residual stress development in a Double Box Beam carbon fiber reinforced composite structure. Carbon fiber composites are being used in many aerospace applications as a means of weight savings due to their high strength to weight ratio. If residual stress can be reduced, the carbon fiber composite will have increased strength, fatigue resistance, and allow for more precise manufacturing tolerances. The through-hole drilling method is used to test for residual stresses induced by the thermal curing process. Using ASTM Standard Test Method E 837, the test shows the strains before and after the hole was drilled which is associated with the relaxation strain. Working backwards from this relationship and using the equations associated with this method, a value for residual stress was found. Looking at the effect nanoparticles have had on previous research, we can estimate the amount of residual stress present in the Double Box Beam structure with nanoparticles. If time permits values will be validated experimentally by a Double Box Beam with nanoparticles incorporated. Compiling this data gives a clear understanding of how nanoparticles will affect the curing cycle and the residual stress.

Recent experimental observations of draining colloid-laden liquid films show stepwise film thinning, as opposed to continuous thinning that occurs in films without colloid particles. The steps are also shown to propagate at a rate that depends on the diameter of the film. In this project, a mathematical model of a thin liquid film containing colloidal particles is derived from the laws of fluid dynamics in a cylindrical coordinate system. The particles in the film give rise to an oscillatory component of the disjoining pressure that is absent in particle free films. Solutions of the model show that a uniform film is unstable to layering. The overall goal of the work is to predict the stepwise thinning behavior seen in experiments, and to understand the physical reasons behind this and other observed film behaviors.

The thermoacoustic effect provides many benefits compared to current cooling methods. The process can achieve stable and reliable cooling without the use of refrigerants or environmentally hazardous chemicals. Strontium Barium Niobate (SBN) is a relaxer ferroelectric ceramic material that exhibits piezoelectric properties due to its tetragonal tungsten-bronze crystal structure.  A piezoelectric is a material that when subjected to mechanical deformation, undergoes polarization which creates electricity and vice verse.  The purpose of this project was to identify piezoelectric properties of SBN, and utilize an SBN piezo crystal for fine-tuned sound generation in a thermoacoustic cooler. In order to achieve this, understanding the physical phenomena behind thermoacoustic cooling and building a prototype thermoacoustic cooler were first accomplished. From there, identifying the piezoelectric characteristics of SBN and construction of a miniaturized model was initiated. Comparisons were made between the macroscopic and miniature models to determine device properties and characteristics. Device miniaturization reveals a variety of challenges that were previously unobserved in the macroscopic device. A cooling effect was observed and a temperature gradient was achieved in both the macroscopic and miniaturized prototypes. However, the efficiency factor of the micro device was highly correlated to the device geometry and construction. Ultimately, the goal of this project was to achieve thermoacoustic cooling on the micro scale which can only be achieved by understanding the nanostructure and the relationship between grain size and domain polarization mechanisms. Piezoelectrics provide an excellent avenue to achieve this goal due to their high overall efficiency of converting lattice distortions into electrical energy, high curie temperature, their idealized frequency response time and their relative environmental stability.

An efficient and environmentally benign means of creating semiconducting polymers is necessary for the commercialization of organic electronics. Furthermore, it is crucial that as much control as possible be exerted over the polymerization process. To these ends, two polymerization methods are useful – C-H activation and living polymerization. First, C-H activation is a collection of synthetic techniques where C-H bonds undergo direct catalytic alteration to yield new homo- or heteroatom linkages. Whereas organometallic reagents were traditionally used to achieve these results, C-H activation allows for shorter syntheses utilizing less-hazardous reagents and broader functional group compatibility. Living polymerization is a form of addition polymerization and in our case, the number of chains is constant during the reaction and dependent on the catalyst-to-monomer ratio. This allows for much narrower mass distributions of the desired polymer and more consistent growth. To achieve this, benzoxazole-based monomers containing a C-O electrophile are to be reacted in the presence of a zero-valent nickel species with electron-rich phosphine ligands. By increasing the electron density on the metal center, we aim to facilitate a “ring-walking” mechanism at higher temperatures than previously thought possible. Monomer synthesis and polymerization results are detailed.

Solar energy is arguably the most promising source of renewable energy because it is thought to be both the cleanest and most abundant source. Several types of photovoltaics are now available, including inorganic, organic, and hybrid organic-inorganic. While inorganic photovoltaics have high efficiencies, good charge carrier mobilities, and relatively long charge carrier times, their widespread implementation has suffered from expensive production and materials competition with the microelectronics industry. Organic photovoltaics are solution processable and applicable to flexible substrates; however, their output has been hindered by their low charge carrier mobilities and short exciton diffusion lengths. Hybrid organic-inorganic photovoltaics have been introduced in an attempt to overcome the shortcomings of both organic and inorganic photovoltaics. Inorganic semiconductors are used in hybrid photovoltaics as the electron acceptor due to the ease of changing their size and shape, and therefore the bandgap, of these materials, which allows them to contribute to the photocurrent of the cell while being solution processable and potentially enhancing the conductivity. Conjugated polymers are used as electron donors due to their large absorption cross-section and solution processability. This project addresses the synthesis of hybrid cadmium selenide (CdSe) nanotetrapods, which we believe will facilitate control of the direction of electron motion in the active layer of the cell. Amines are needed for CdSe tetrapod functionalization with semiconducting polymers according to our reaction scheme. Tetrapods tend to convert into quantum dots because dots are thermodynamically favorable; our approach to have kinetic control, and thus have the tetrapods retain their shape, has involved synthesizing the tetrapods with amines as ligands. The reaction time, growth temperature, ligand type, and monomer concentration are used to control the synthesis, and the effects of each variable on the size and shape of the tetrapods will be studied via transmission electron microscopy (TEM).

For centuries, mankind has used adhesives as a means of joining materials together. A simple technology, adhesives bond materials, distribute stress, and improve flexibility. In nature, the organic-inorganice composite material nacre features very thin organic interlayers that serve as an ahdesive to hold together single platelets in a "brick and mortar" composite microstructure. This project addresses whether varying the thickness of nacre-like adhesive layers influences the mechanical properties of the composite. Typical standardized tensile tests listed in the American Society for Testing and  Materials (ASTM) will be modified to simulate nacre's structure. Our approach is to linearize the loading path, by performing the double lap shear configuration suggested in ASTM D3528 on a Shimadzu tensile tester. A digital microscope is used to focus on the interactions at the interfaces, while the Scanning Electron Microscope (SEM) focuses on the fibril formation in the adhesive. The adherends we will use are glass, bonded together with varying adhesive thicknesses and placed in the Shimadzu's metal grips for testing. The results display lap shear strengths as a function of lap length with constant lap width. By plotting lap shear versus lap length over adherend thickness (L/t),  we can compare the lap shear performances for the varying thicknesses. If the bond width is held constant it is expectd the bond area decrease with decreasing L/t so shear strength increases as a function of decreasing lap area. The use of transparent glass slides determines if the fracture patterns in bending would spread energy over a larger volume depending on the thickness of the adhesive. The effect of varying the adhesive thickness within the material is discussed as a function of the material's ability to transfer the load over a larger volume more readily during bending, and thereby control the energy dissipation. 

Photothermal heating of nanoparticles by electromagnetic radiation, which has potential applications including cancer treatment, requires consideration of the the electric field produced inside the nanoparticles. For most particle geometries, the electric field cannot be solved for exactly, so numerical methods are required. One such method is the Discrete Dipole Approximation (DDA), which models a target as an array of interacting point dipoles whose polarizations can be solved for. In this research, the DDA is used to simulate the electric field inside silicon and gold nanoparticles with spherical morphology. Particle sizes simulated range from 100 nm to 1000 nm, with a wavelength of 1000 nm. It is found that the particles exhibit morphology dependent resonance (MDR) at certain sizes. This is indicated by an increased electric field strength relative to the incoming wave, as well as an electric field  pattern corresponding to constructive reflection in the spheres. These resonances would lead to increased heating if the particles were used for photothermal applications.

Interest in renewable energy resources has increased in recent years due to the rising demand and dwindling supply of fossil fuels. While inorganic materials, such as silicon, have traditionally dominated the solar energy market, the use of organic photovoltaics (OPVs) has grown more popular due to their potential to be low cost, light weight, and their ability to comply with flexible substrates. Poly(3-hexylthiophene) (P3HT) is a polymer that readily self-assembles into nanowires under proper conditions, resulting in nanowire domain sizes that are on the order of the exciton diffusion length. Directing polymer self-assembly provides an opportunity to control the structure property relationships of OPVs and can greatly improve charge transport within the active layer. The regioregularity of a polymer is a measure of the uniformity of its geometric isomers. Because individual P3HT chains begin to kink into S-like shapes during self-assembly, a correlation between the P3HT regioregularity and the frequency of resulting nanowire defects is expected. In an attempt to understand the process of self-assembly, we would like to determine if these defects are incorporated into the nanowires during self-assembly, or if they are excluded from their crystalline domains. To investigate this, P3HT nanowires were made from solutions of anisole and chloroform in varying ratios, heated at 70 °C and thoroughly mixed for 24 hours, then removed from heat and allowed to self-assemble for at least three days. These solutions were then filtered to separate the nanowires from the decanted solution, and analyzed separately. A variety of characterization methods were used to study the presence of nanowire defects as well as their effects, including nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, atomic force microscopy, and matrix-assisted laser desorption/ionization spectroscopy.

Biological systems coordinate themselves through cues such as ion currents and membrane electric potentials. This communication utilizing membrane proteins such as membrane receptors, channels, and pumps allows biological systems to form hierarchies of control over their systems that have yet to be achieved in conventional electronic systems. Integrating such biological components with nanoelectronics could allow exciting new developments in the field of biomimetic energy conversion. However, this approach requires the seamless incorporation of biological structures into electronics. In order to use membrane proteins, they must be integrated with a lipid bilayer which is essential to create a cell membrane mimicking environment. Lipid bilayers have previously been integrated on solid substrates for electrophysiological measurements and the construction of organic-inorganic hybrid devices, but have yet to be formed on PdH_x. In this work, we build the foundation towards harnessing this biology-based method of control by forming a lipid bilayer composed of DPhPC/DPhPE/PI/Cholesterol on PdH_x contacts. The formation and deposition of electrochemically robust liposomes on a PdH_x surface was confirmed using dynamic light scattering (DLS) measurements, atomic force microscopy (AFM), and resistance measurements with a PdH_x proton field effect transistor (H⁺-FET). Vesicle formation was proven through DLS by determining size of the lipid structures in aqueous solutions. These vesicles were then deposited onto a PdH_x contact and formed solid-supported bilayers on PdH_x surfaces by the process of spontaneous vesicle adsorption and rupture as confirmed by AFM. Finally, the electrical stability of the bi-lipid membrane was characterized through electrical measurements with an H⁺-FET, confirming minimal H⁺ leakage across the bilayer. Future work includes embedding an ion pumping membrane protein, bacteriorhodopsin, into the bi-lipid membrane to enable electrochemical gating of the PdH_x H⁺-FET through optical or other environmental cues for biomimetic energy conversion.

Chitosan and alginate are widely used natural polymeric biomaterials that are biocompatible, biodegradable, and non-toxic. Chitosan is cationic as well as hydrophobic in nature whereas alginate is anionic and hydrophilic in nature. Ionic interaction between the amine and carboxyl group causes the formation of polyelectrolyte complex in the scaffold and thus enhancing the mechanical properties of the scaffold. Mechanical properties of the scaffolds are dependent on the fabrication process, cross-linking process, and sterilization process. Similarly, porosity plays a crucial role in determining the mechanical strength of the scaffold which relates to the lyophilization process and molecular weight of the polymer used. Chitosan-Alginate (CA) scaffolds are prepared by mixing equal wt% amounts of each polymer and due to chitosan's hydrophobic nature, acetic acid was added. The solution was mixed using a Thinky mixer at 2000 rpm for five minutes. After obtaining a homogeneous mixture, pH was tested and solution  casted into desired well plates. The solution was then refrigerated at 4 degree Celsius for 12 h at 20 degree Celsius overnight, and lyophilized for 24 hours. Scaffolds were then cross-linked with 70% CaCl2, and sterilized with Phosphate-buffered saline (PBS). Scanning electron microscope (SEM) is used in to image pore morphology of the scaffold. High mechanical strength and porous structure is presented in pore size ranges of 100-500 micrometers which is required for bone tissue engineering. Mechanical strength of the scaffold is obtained by performing compressive test. Samples are compressed at 4.00 mm/min using micro-tensile tester with 1N load cell. Dry samples were found to have a young's modulus (YM) of 1-2 MPa, whereas wet samples were found to have a YM of 1-2 KPa.  CA scaffolds were found to be mechanically strong with good porosity which was directly impacted by fabrication process. Mechanically strong CA scaffolds with proper porosity were achieved with the fabrication process used. Further work will allow an optimization of CA scaffolds for specific applications and cell lines.  

The study of naturally occurring materials for use in every-day applications can result in innovative advancements in current technologies. Nacreous shell structure (nacre) is one such material. This nacre is a composite of ceramic in a tiny, organic, viscoelastic matrix meaning it exhibits time-dependent viscous and elastic behavior. This allows the normally brittle ceramic to be crack tolerant rather than to show high fracture toughness. Other complex composites have been shown to retain much of their strength after cracking, and this means high levels of energy dissipation. Because other structures with many thin organic layers have large damping abilities, it was suspected that nacre would also show such damping, but these damping abilities have not been tested. We hope to gain a better understanding of the damping effects of nacre by looking at tan (δ) through Dynamic Mechanical Analysis (DMA). Tan (δ) is a measure of energy dissipation by damping. A high amount of energy dissipation would have practical applications in creating safer buildings in the case of an earthquake. The viscoelastic matrix that allows for a crack tolerant material could allow for buildings to retain some of their structural integrity while people safely evacuate the building. As viscoelastic components are not typically used in structural ceramic composites, this could provide the basis for a new class of industrial composite materials.

 Beryllium Oxide is a ceramic material most notably used in the electronics industry due to its outstanding thermal conductivity. Because of this property it is also of interest for use as an insulator under high density plasma exposure. Post exposure the beryllium samples undergo a very specific series of characterization steps. Samples are subject to optical microscopy, in an attempt to identify noticeable surface changes when compared to a control sample. Specific spots show maximum exposure, and are further investigated via XPS. X-ray Photoelectron Spectroscopy shows chemical changes in regions of maximum exposure. Specific depth profiling is utilized to identify possible Deuterium migration, lanthanide exposure, and oxidation effects. XPS is critical for providing detail of the depth of deuterium exposure throughout the material, along with possible deuterium implantation within the crystal lattice of the existing beryllium oxide. X-ray Diffraction comparison between irradiated and control samples shows lattice expansion and residual strain throughout the material. This is a crucial discovery when comparing the impact of the residual strain to the maximum tensile stress. Peak broadening shown on the 2ϴ XRD plot identifies the extent of intergranular strain left by possible deuterium implantation into the beryllium oxide crystal lattice identified through XPS. Thermal conductivity of irradiated samples is tested to ensure that the most redeeming quality of the material is consistent post exposure.

Plasmonic nanoparticles (NPs) have been reported to improve the performance of organic solar energy harvesting devices. Gold (Au) and silver (Ag) are two of the more commonly researched plasmonic nanoparticles. The plasmonic effect occurs when incident light induces a fluctuation of electron clouds within a metal. This phenomenon resonates at a specific wavelength depending on NP size, geometry and the dielectric constants of the metal and medium. Previous publications have shown that inclusion of combined Ag and Au NPs increases light absorption and can enhance the power conversion efficiency by 20 percent. This study evaluates the effect of varying concentration of Ag and Au NPs on power conversion efficiencies within a bulk heterojunction (BHJ) organic solar cell, and examines the mechanisms behind the enhancement. Lumerical FDTD Solutions was used to model scattering and plasmonic resonance in OPV devices with different combinations of 40 nm Ag and Au NPs within the PEDOT:PSS charge transport layer. Light enhancement and absorption was modeled as a function of wavelength and spatial arrangement. The results indicated that the absorption profile for the mixed NP device was dominated by the contribution of the Ag NPs, which prompted the investigation into the ideal NP concentrations/ratios. OPV devices were constructed on an ITO substrate with a PTB7:PC70BM active layer. Power conversion efficiencies were determined experimentally as a function of open-circuit voltage, short-circuit current density, and fill factor. Device morphologies were evaluated using atomic force microscopy (AFM). The absorption profiles of the devices were measured using UV-Vis spectroscopy. The optimal concentrations of Ag and Au NPs were determined. Future research on this topic should focus on optimizing particle geometry, ligands, and dielectric NP coatings.

The brain is the most powerful computer in existence, possessing roughly 100 billion neurons with one-quadrillion synapse connections between them. Mimicking the synapse of a neuron could lead to increasing processing power, a better understanding of brain functions, or enhanced biomedical device integration. We have previously demonstrated proton-conducting devices with synaptic behaviors utilizing protons as charge carriers in a palladium source-drain system. Altering the design of these devices to become more useful to the biomedical field would be highly advantageous. Due to nature’s naturally curved geometry, we aim to develop flexible devices capable of matching these parameters for biomedical integrations. Flexible devices allow a much broader scope of applications, including health sensors on the human body that might require soft or curved morphologies. The mechanical engineering and processing conditions to create flexible devices is currently being investigated. I propose starting device fabrication with a pre-strained substrate. When palladium is deposited on this substrate, it will compress and exhibit wave-like patterning upon the release of the substrate’s strain. This is critical to the device flexibility, as previous palladium tension tests showed a high fracture rate. With a pre-induced compression in the palladium, tension would result in a more relaxed state and limit fracture in the devices to allow flexibility. Future works involve determining buckling strains for various palladium thicknesses to obtain wave-like patterns of compression, determining a suitable substrate material, and comparison of electrical properties to our current palladium devices.

Tissue engineering is a field of study where porous scaffolds made of materials such as polymers and/or ceramics are used to promote tissue regeneration. This is important for treatment of tissue defects resulting from trauma or disease where repair does not occur via normal, physiological processes. In this work we fabricated 3D, porous scaffolds made of naturally-derived polymers, chitosan and alginate, using a phase separation and lyophilization technique. This chitosan-alginate (CA) scaffold is promising for tissue engineering because it is made of sustainable materials and is biocompatible, biodegradable, and cost-effective. We characterized the porosity of the scaffolds using scanning electron microscopy and observed interconnected pores on the order of 100 microns in diameter. As a first step in determining the potential of this CA scaffold for muscle tissue engineering, we cultured C2C12 mouse myoblasts and evaluated cell viability and proliferation using the Alamar Blue assay. The scaffolds support cell attachment and viability and we expect to observe cell proliferation.

The goal of my research is to  find an efficient drug delivery system to kill brain cancer cells by considering that some hydrogels change their viscosity dramatically at different temperatures (called thermosensitive). The whole project is regarded as “rocket”system, with a drug-loaded device that delivers content into the right place as a rocket and the drug  inside as an astronaut. The innovative idea of the project is that the drug-loaded system has the capability to be liquid-like at low temperature while becoming gel at body temperature, making it easy to produce and inject into tumor tissue to concentrate the effect at the tumor site. To find a stable, biocompatible and biodegradable material to be drug-loaded, we tested the in vitro stability and drug-release during 1hr, 24hr and 96hr incubation of various polymer gels including PEG-chitosan, alginate, and methyl cellulose. We then studied the drug delivery system with brain cancer cells in vitro and monitored the migration of the cancer cells towards the gel.

The aesthetic benefits of tooth whitening have led to a recent increase in the popularity of whitening procedures. Current procedures effectively whiten teeth, but do so through the use of peroxides that cause negative side-effects. These side-effects include decreased hardness and strength of tooth enamel as well as an increase in tooth sensitivity. An alternative to peroxide bleaching that holds promise in whitening teeth involves the application of agents that promote the deposition of white mineral layers on the tooth surface. One such agent is a mineralization directing peptide (MDP) derived from amelogenin, a major protein responsible for enamel development. Previous studies have shown that the application of MDP to tooth root surface yields the formation of a mineral layer with strong, functional mechanical integrity. In this project, MDP is studied for its ability to whiten the tooth enamel surface by promoting the formation of a new mineral layer. Treatment of tooth enamel with MDP could serve as a healthy alternative to current whitening procedures. To verify the mineralization capabilities of MDP, kinetics of mineralization in a Ca2+/PO43- solution was measured through a light absorpotion method. Extracted human teeth were then sectioned and etched with phosphoric acid gel for 2 minutes and coated with MDP. The tooth samples were then rinsed with DI H2O and placed in a KH2PO4-CaCl2*2H2O solution for 18 hours at 37°C. Following this step, samples were rinsed with DI H2O and observed via SEM to characterize mineral formation. Future research will be carried out to formulate an MDP product in which viscosity is optimized for spread of the product and mineralization kinetics. Upon completion of this research we will be able to identify formulations of MDP products that form mineral layers on teeth and can be used for widespread dental care.

Medical implants ranging from artificial hips to pacemakers profoundly impact millions of Americans by replacing malfunctioning body parts and restoring normalcy to patients’ everyday lives. However, microbial infection is a cause of frequent implant failure, making preventative measures vitally important to patient health as well as the efficiency of the healthcare system nationwide. The Tamerler Lab research focuses on engineering the tissue-implant interface using solid binding peptides conjugated to bioactive molecules such as antimicrobial peptides (AMPs). The focus of this project has been on engineering peptides that may reduce zirconia implant failure due to bacterial infection. Our group has been generating sets of peptides that have strong self-attachment activity and high specificity for zirconia. In conjunction with our experiments, AMPs were computationally designed, synthesized, and tested against S. mutans bacteria, one of the most prevalent infectious organisms causing failure in craniofacial implants. To prevent bacterial growth, we tested various concentrations of AMPs to find their minimum inhibition concentration (MIC). Specifically, we focused on developing an engineered peptide that has both solid binding and antimicrobial activities, and testing these peptides’ effectiveness against bacterial growth. With this aim, we first test for the MIC values and then the zirconia-binding affinities of the engineered peptides. In future work, these engineered peptides will be tested on the implant surfaces as self-organized coatings to determine their effectiveness on actual craniofacial implants.