Chitons are marine mollusks found worldwide in the intertidal or subtidal zones of cold water as well as in tropical waters. These organisms have evolved an amazing feeding structure called a radula. The radula is a ribbon-like structure that consists of abrasion resistant teeth anchored to a flexible stylus that the organism uses to abrade rocky substrates to reach endolithic and epilithic algae. In this work, we investigated the radula in Cryptochiton stelleri, the largest of the chitons. Using various microscopic and spectroscopic techniques, an ultrastructural analysis and investigation of mechanical properties of fully mineralized radular teeth from C. stelleri, as well as the mineralization process of these teeth, has been performed to gain insights into structure-function relationships of the abrasion resistant, impact tolerant, and anti-fatigue composites synthesized by nature. Shape, wear patterns, and feeding positions of the teeth have been analyzed to provide teeth working conditions that can be used in finite element analysis modeling of the tooth, which helps to provide a foundation to produce abrasion-resistant, impact-tolerant and anti-fatigue materials.

An overall analysis of mature radular teeth using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy revealed a magnetite containing hard shell with an iron phosphate containing soft core. α-chitin was also identified in mature teeth with powder XRD. Energy-dispersive X-ray spectroscopy (EDS) analysis uncovered the higher carbon concentration at the core region than at the shell. Hardness and modulus gradients from the leading edge to the trailing edge of the teeth, which contributes to a self-sharpening mechanism, were revealed by nanoindentation. The mechanical measurements revealed the teeth had the highest hardness (12.5 GPa) and modulus (125 GPa) of any biomineral reported to date.

Phase transformation and structural development during the biomineralization process of the radular teeth were analyzed with EDS, synchrotron XRD, Micro- X-ray Fluorescence (µXRF), SEM and TEM. The phase transformation from ferrihydrite to magnetite, which occurred at the tip of the leading edge, along with aggregation of mineral particles and shrinkage of organic fibers were discovered.

Regional micro- and nanostructures as well as the mechanical properties of the mature teeth were characterized via SEM analysis of the fracture surfaces, TEM and nanoindentation. Nanorods structures were found at the trailing edges and the surfaces of the leading edges of teeth. The middle of the leading edge of the tooth is made of close-packed particles and exhibited the highest hardness and modulus. The rods at the trailing edge were orientated along the surface curvature of the trailing edge, while the rods at the surface of the leading edge were rotated 90°. The diameters of the rods at the trailing edge were larger than those at the leading edge. Tooth performance was simulated with FEM analysis on a radular tooth model obtained from confocal microscopy imaging. Tensile stresses were concentrated at the leading edge, while the compressive stresses were concentrated at the trailing edge. Both of the stress directions are guided along the surface curvature, following the major orientation of the rods. The combination of regional ultrastructural features of these teeth, consisting of the highest hardness and modulus mineral known in Nature, enables the radular teeth to be optimized abraders during the feeding process.

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hyper-mineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one such species, Odontodactylus Scyllarus, exhibit an impressive set of characteristics adapted for surviving high velocity impacts with the heavily mineralized prey species on which they feed. Consisting of a multi-phase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high energy loading events. The study of this organism and its relatives has lead to design cues, which were incorporated into prototype composite materials designed for applications in aviation, body armor, and entertainment.

Biological composites provide valuable design guidelines to produce the next generation of engineering materials. Incorporating readily available resources in environmentally friendly method, these biological organisms produce lightweight, strong, and tough materials with superior mechanical properties to engineering counterparts. The key to this success results from their hierarchical organization as well as structural and compositional gradients imparted by an ordered self-assembly of organic material. In this work we study the structure-mechanical property relationship and multifunctional nature of a compression resistant beetle elytra able to withstand crushing and piercing attacks from predators while thriving in an arid desert environment. We uncover the macro and microstructural architectural features responsible for transferring stress and imparting localized stiffness and compliance to toughen the bulk biological composite. These insights are then subsequently applied to the fabrication of bioinspired fiber reinforced composites using conventional engineering materials and additive manufacturing. Validating their performance, mechanical testing was used to highlight the enhanced performance of these biological materials compared to industry standard designs. This work may further provide insights into the fabrication of lightweight, strong, and tough structural materials for use in engineering applications.

Lithium ion batteries provide a high energy density, higher voltage as well as a long shelf life compared to traditionally used lead acid, NiMH and NiCd batteries. Thus, they are a very promising energy storage system for our daily life. As one of the most important components in a battery, cathode materials have been investigated intensively in recent years as they play a key role in determining the cell voltage and discharge capacity in a battery. Both layered Li(Ni1/3Co1/3Mn1/3)O2 (NCM) and olivine-structured LiFePO4 (LFP) materials are promising cathode candidates. However, these cathodes also have some disadvantages that have hindered further commercialization. The main issue with NCM is its rapid performance decay upon cycling. In addition, LFP is hindered by a low rate capacity and low lithium ion diffusivity.

We studied the crystal growth behavior and performance of both Li(Ni1/3Co1/3Mn1/3)O2 and LiFePO4 cathodes in order to develop synthesis-structure-function relationships. Three different crystal growth behaviors were observed for the NCM annealing process: surface, volume and grain boundary diffusion. Further exploration of the mechanism of NCM performance decay revealed that microstructural changes were related to the strain accommodation ability in this system and that nanostructured materials were more stable during cycling. In the LFP synthesis, we observed both oriented attachment (OA) and Ostwald ripening (OR) during growth in a triethylene-glycol system. Both polycrystalline and single crystalline particles evolved as a function of a time-dependent pH change. Thus, the lithium ion diffusion rate of LiFePO4 was improved by tailoring the morphology and size though our modification of the precursor environment, revealing that polycrystalline LFP displayed better performance than single crystalline particles. Finally, the electronic conductivity of LiFePO4 was successfully increased via a polymer solution coating method. By producing more uniform, thin and coherent coatings on LiFePO4 particles, we were able to produce batteries with significantly less carbon (i.e., 0.41 wt.%) while has comparable performance (discharge capacity of 80mAh/g at 2C) compared to traditionally synthesized carbon-coated LiFePO4 with higher carbon loadings (ca. 2.64 wt.%). This will enable us to produce batteries with higher active material loading and therefore, significantly larger energy densities.

There is an alarming increase of energy issues due to significant fossil fuel consumption. Some progress has been made to replace fossil fuels with renewable sources, among which, solar energy has always been considered as the ultimate solution to solve these problems. As a relatively new evolved type of solar cell, Dye-sensitized solar cells (DSSC), have been investigated intensively in recent years and they are very promising for their cost-effectiveness properties. Zinc oxide (ZnO) is one of best candidates for DSSC due to its low cost and high electron mobility, amongst others. In this thesis, highly branched ZnO nanostructures are synthesized with biologically inspired methods to control the crystal growth and the mechanism by which these grow are investigated. Further explorations of the structure-function relationships reveal potential pathways towards the improvement of DSSC performance.

Besides DSSC, it is necessary to transform the solar energy to storable energy so it can be utilized during the night. Titanium dioxide (TiO2) for hydrogen generation through photoelectrolysis is one of the most promising candidates. We synthesize TiO2 nanowire arrays by homoepitaxial growth on templates, and precisely control the nanostructured properties such as nanowire diameter, length, density, etc.. In addition, photoelectrochemical performance has been conducted on TiO2 thin films with different nanostructures to investigate structure-function relationships.

Another significant concern involves environmental pollution due to the discharge or emission of a variety of new chemicals, which are threatening environmental and public health. ZnO, as a photocatalytic material, can effectively degrade organic pollutants without byproducts. In this work, we utilized biologically inspired methods to template the synthesis of Zn-organic compound materials using organic scaffolds. The complex material was heat-treated to produce a ZnO-carbon composite material. The processing conditions have been extensively studied and it has been demonstrated that the composite material can effectively improve the photocatalytic performance versus carbon-free ZnO nanostructured materials.

There is an alarming increase of a variety of new chemicals that are now being discharged into the wastewater system causing increased concern for public health and safety because many are not removed by typical wastewater treatment practices. Titanium Dioxide (TiO₂) is a heterogeneous photocatalytic material that rapidly and completely mineralizing organics without harmful byproducts. TiO₂ is synthesized by various methods, which lack the necessary control of crystal size, phase, and morphological features that yield optimized semiconductor materials. Mineralizing organisms demonstrate how nature can produce elegant structures at room temperature through controlled organic-mineral interactions.

Here, we utilize biologically-inspired scaffolds to template the nucleation and growth of inorganic materials such as TiO₂, which aid in controlling the size and phase of these particles and ultimately, their properties. Nanosized rutile and anatase particles were synthesized under solution conditions at relatively low temperatures and mild pH conditions. The effects of reaction conditions on phase and grain size were investigated and discussed from coordination chemistry and coarsening mechanisms. Photocatalytic characterization of TiO₂ phase mixtures was performed to investigate their synergistic effect. The suspension conditions of these catalytic nanomaterials were modulated to optimize the degradation rate of organic analytes.

Through the addition of an organic scaffold during the synthesis reaction, a mechanically robust (elastic) composite material containing TiO₂ nanoparticles was produced. This composite was subsequently heat-treated to produce a porous, high surface area TiO₂ nanoparticulate membrane. Processing conditions were investigated to characterize the growth and phase transformation of TiO₂, which ultimately impacts photocatalytic performance. These bulk porous TiO₂ structures can be fabricated and tailored to act as stand-alone photocatalytic membranes, eliminating the need for nanoparticle recovery systems, thereby reducing processing costs and increasing amount of viable applications of photocatalytic systems.

Protective coatings are commonly used to extend the service life of components or structures to provide a barrier against unexpected damage and harsh environments by improving the surface hardness, corrosion resistance, or oxidation resistance of materials. The objective of this research is to develop a biomimetic coating inspired by the impact resistant nanocomposite coating found on the dactyl club of the Odontodactylus scyllarus (i.e., the peacock mantis shrimp). These scalable sacrificial coatings would provide added impact protection to core structural components to extend their service life or to prevent catastrophic failure during impacts or collisions. This study will investigate the protective capabilities of a manmade analog comprised of inorganic (silicon carbide) nanoparticles embedded within an organic (chitosan) matrix. By varying particle loading, we can modulate the extent of energy dissipation and damping. Drop casting or spray deposition methods are used to yield thin-film coatings which localize damage and decrease penetration depth, thus protecting underlying substrates and improving overall impact resistance. The results show that up to a certain degree, additional particle loading improves impact resistance, which shows promise in potential implementations in the automotive, aerospace, and energy industries without adding significant weight.

Biological organisms naturally synthesize complex, hierarchical, multifunctional materials through mineralization processes at ambient conditions and under physiological pH. One such example is the ultrahard and wear-resistant radular teeth found in mollusks, which are used to scrape against rock to feed on algae. Here, using various microscopical and spectroscopical characterization techniques, we reveal the biomineralization-controlled structural development of the hard, outer magnetite-containing shell of the teeth. The thin magnetite nanoparticle coating as a protective layer against abrasion is also investigated. Inspired by mineralization process in natural system, we have synthesized magnetite nanoparticles using functional polymer matrices or templates. The results from these experiments will shine light on the eco-friendly manufacture of engineering materials with controlled microstructure for high performance applications. Self-assemble strategy has been used to fabricate unique hollow nanosphere structure of tantalum nitride for visible light photodegradation.

Lithium iron phosphate (LiFePO4) is an interesting candidate for Li-ion cathode applications because of its high theoretical specific capacity, good cycle stability, and environmentally friendly nature. However, its performance is limited due to its low electrical conductivity and low ionic diffusivity. Therefore, synthesis methods need to be developed to improve its electrochemical performance. One effective approach is to learn from since inorganic-organic hybrid materials are formed through the mineralization process where of inorganic materials are nucleated and grown in the presence of an organic matrix that controls the crystal morphology, size, and orientation. Here, this work focuses on the investigation of biologically-inspired synthesis of LiFePO4 using a modified solvothermal method. Specifically, we study the crystal growth kinetics of LiFePO4 in order to establish a platform for understanding crystallization behavior at higher temperatures, where these cathodes are annealed to during carbon deposition. Secondly, we examine growth of LiFePO4 under solvothermal conditions modified with a ligating polymer that controls the solution environment and subsequently nucleation of LiFePO4 crystals. Finally, we utilize a structural polymer that acts as a scaffold to regulate porosity in order to fabricate nanoporous cathodes with enhanced Li-ion intercalation kinetics and thus, an improvement on the electrochemical performance. Crystallization is interrogated using X-ray diffraction, SEM and TEM while porosimetry is used to measure surface area and FTIR and TGA are performed to confirm the presence of organic in the samples. Cyclic voltammetry is used to measure electrochemical performance

Biologically mineralized composites offer inspiration for the design of next generation structural materials due to their environmentally friendly synthesis, low density, and combination of high stiffness and toughness, currently unmatched by engineering technologies. Such properties are the result of hierarchical structuring and well-defined compositional and mechanical gradients afforded by the organism’s ability to control the self-assembly and nucleation and growth of organic and inorganic materials, respectively. Here, we investigate structure-mechanical property relationships of two incredibly damage-tolerant and impact-resistant bio-composite materials: the mantis shrimp dactyl club and telson, which resist catastrophic failure from repeated high-energy impacts and cavitation from one of the fastest striking events observed in nature. We identify numerous multi-length scale architectural designs that play key roles in imparting stiffness, compliance as well as delocalizing stress and enhancing toughness. These design cues are then translated and implemented into biomimetic composite materials that are fabricated using traditional fiber-reinforced composites processing as well as advanced direct ink write additive manufacturing. The ability for these biomimetic composites to demonstrate enhanced damage-tolerance over traditional designs is then assess through mechanical testing. Such findings may prove useful for the on-going design and fabrication of lightweight structural materials possessing improved damage-tolerance.