The interaction at the surfaces of load bearing implant biomaterials with tissues and physiological fluids is an area of crucial importance to all kinds of medical technologies. To achieve the best clinical outcome and restore the function of the diseased tissue, several surface engineering strategies have been discussed by scientific community throughout the world. In the current work, we are focusing on one such technique based on laser surface engineering to achieve the appropriate surface morphology and surface chemistry. Here by using a pulsed and continuous wave laser direct melting techniques we synthesize three dimensional textured surfaces of calcium phosphate (Ca-P) based surface chemistry on Ti-6Al-4V. The influence of each processing type on the micro texture and phase evolution and thereby its associated effect on wettability, in vitro bioactivity, and in vitro biocompatibility are systematically discussed. For samples processed using the pulsed laser, it was realized that with increasing laser scan speed and laser pulse frequency there was a transition from surface textures with sharp circular grooves to surface textures with radial grooves and thereby improved hydrophilicity. For CW laser processing the results demonstrated improved hydrophilicity for the samples processed at 100 μm line spacing as compared to the samples processed at 200 μm line spacing. Owing to the importance of Si for cartilage and hard tissue repair, a preliminary effort for synthesizing Ca-P-SiO2 composite coating on Ti-6Al-4V surface were also conducted. As a future potential technique we also explored the Laser Interference Patterning (LIP) technique to achieve the textured surfaces and developed understanding on their wetting behavior. In the current work, by adjusting the laser processing parameters we were able to synthesize textured coatings with biocompatible phases. The in vitro bioactivity and in vitro vi biocompatibility of the coatings were proved by the precipitation of an apatite like phase following immersion in simulated body fluid (SBF), and increased proliferation and spreading of the MC3T3-E1 like cells. The results and understanding of the current research is encouraging in terms of looking at other bio-ceramic precursor compositions and laser process parameter window for synthesizing better textured biocompatible coatings.

Nanoindentation is a method of contacting a material whose mechanical properties are unknown with another material whose properties are known. Nanoindentation has the advantage of being able to probe a material’s microstructure while being sensitive enough to detect variations in mechanical properties. However, nanoindentation has some limitations as a testing technique due to the specific formation and structure of some biomaterials. The main objective of this research is to identify any factors that influence the nanoindentation measurement of wood cell walls (a typical biomaterial). The function of the embedding media in describing the properties of wood cells is poorly understood. This research demonstrated that Spurr’s resin, when diffused into wood cell wall during the embedding process, enhanced both the Young’s modulus and hardness of the cell walls. A substitute sample preparation method was developed to avoid this resin penetration into cell wall and was determined to be both effective and easy to perform. The nanoindentation procedure involves the application of a monitor and an analysis of the load-displacement behavior and the response in the material. It can be anticipated that various ways of loading, including the maximum force, the loading time, and others, will cause a variety of mechanical properties. Thus, our second aim was to study the effect of load function on nanoindentation measurement in wood. It was discovered that a fast loading rate contributed to greater contact depth and lower hardness. Increasing the holding time decreased measured values for both Young’s modulus and hardness. However, no significant difference of Young’s modulus and hardness among three loading functions with different unloading rates. The final part of the research was to study the effect of moisture content on the micromechanical properties of wood material. Several nanoindentations were performed on the wood cell wall while varying the moisture content of wood. Results indicated that both the Young’s modulus and hardness decreased significantly with an increase of moisture content. A rheology model was developed to describe the nanoindentation behaviors of wood cell walls at different moisture contents. Five parameters were extracted from Burger’s model, and the relationships among those five parameters were quantified.

Low noise, directional microphones are critical for hearing aid applications. This thesis is focused on further development of a biomimetic micromachined directional microphone based on the ear structure of the Ormia Ochracea, a parasitic fly able to locate sound sources in the audio frequency range with high accuracy. The development efforts have been on implementing a version of the microphone for a behind the ear (BTE) package while improving the overall optical efficiency and noise level, demonstrating pulsed laser operation for reduced power consumption, and electrostatic control of the microphone diaphragm position for stable operation over a long time. The new packaging method for the microphone addressed the need for tighter placement tolerances along with a redesigned diaphragm and integration of a microscale optical lens array to improve the optical efficiency of the device. The completed packages were characterized for sensitivity improvement and optical efficiency. The overall optical efficiency was significantly increased from less than 1% to the photo diode array collecting 50% of the emitted optical power from the Vertical Cavity Surface Emitting Laser (VCSEL). This, coupled with the new diaphragm design, improved the acoustic performance of the microphones. Consequently, the noise levels recorded on the devices were about 31 dBA SPL, more than 15dB better than conventional directional microphones with nearly 10 times larger port spacing. Since the application for this technology is hearing aids, the power consumed by the working device needs to be at an acceptable level. The majority of the power used by the microphone is from continuously operating the VCSEL with 2mW optical output power. To reduce this power requirement, it was suggested to pulse the VCSEL at high enough frequency with low duty cycle so that the acoustic signals can be recovered from its samples. In this study, it was found that the VCSEL can be pulsed with little to no degradation in signal to noise ratio as long as the thermal mechanical noise dominated the noise spectrum. The results also indicated that a pulse train with a duty cycle of around 20% can be used without a major loss of performance in the device, meaning the device can effectively run at 1/5 of its original power under pulsed operation mode. Finally, a control technique to overcome some inherent problems of the microphone was demonstrated. Since the optical sensitivity of the microphone depends on the gap between the diaphragm grating and the integrated mirror, it is important to keep that bias gap constant during long term operation against environmental variations and charging effects. Using a simple electrostatic bias controller scheme, the sensitivity variation of the microphone was improved by a factor of 7.68 with bias control. Overall, this thesis has addressed several important aspects of a micromachined biomimetic microphone and further demonstrated its feasibility for hearing aid applications.

Nanoindentation is a method of contacting a material whose mechanical properties are unknown with another material whose properties are known. Nanoindentation has the advantage of being able to probe a material’s microstructure while being sensitive enough to detect variations in mechanical properties. However, nanoindentation has some limitations as a testing technique due to the specific formation and structure of some biomaterials. The main objective of this research is to identify any factors that influence the nanoindentation measurement of wood cell walls (a typical biomaterial).The function of the embedding media in describing the properties of wood cells is poorly understood. This research demonstrated that Spurr’s resin, when diffused into wood cell wall during the embedding process, enhanced both the Young’s modulus and hardness of the cell walls. A substitute sample preparation method was developed to avoid this resin penetration into cell wall and was determined to be both effective and easy to perform.The nanoindentation procedure involves the application of a monitor and an analysis of the load-displacement behavior and the response in the material. It can be anticipated that various ways of loading, including the maximum force, the loading time, and others, will cause a variety of mechanical properties. Thus, our second aim was to study the effect of load function on nanoindentation measurement in wood. It was discovered that a fast loading rate contributed to greater contact depth and lower hardness. Increasing the holding time decreased measured values for both Young’s modulus and hardness. However, no significant difference of Young’s modulus and hardness among three loading functions with different unloading rates.The final part of the research was to study the effect of moisture content on the micromechanical properties of wood material. Several nanoindentations were performed on the wood cell wall while varying the moisture content of wood. Results indicated that both the Young’s modulus and hardness decreased significantly with an increase of moisture content. A rheology model was developed to describe the nanoindentation behaviors of wood cell walls at different moisture contents. Five parameters were extracted from Burger’s model, and the relationships among those five parameters were quantified.

CNT membrane platforms are biomimetic polymeric membranes imbedded with carbon nanotubes which show fast fluid flow, electric conductivity, and the ability to be grafted with chemistry. A novel micro-dialysis probe nicotine concentration sampling technique was proposed and proved in vitro, which could greatly improve the efficiency and accuracy of future animal transdermal studies. To enhance the scope of transdermal drug delivery which was limited to passive diffusion of small, potent lipophilic drugs, a wire mesh lateral electroporation design was also proposed which could periodically disrupt the skin barrier and enhance drug flux. It was shown that AMP binding aptamer at the tip of carbon nanotubes may act as gatekeepers and regulate ionic transport through CNT membrane. Multiple cycle gating of ionic transport upon AMP binding/unbinding which changes the aptamer conformation was displayed. This CNT membrane-aptamer system closely mimics how protein ion channels modulate ion flow by responding to stimuli, which may have significant impact on active membrane transport. Finally an enhanced electroosmosis concept by “ratchet” functionalization at both ends of carbon nanotubes in was discussed. Direct observation of water transport by electroosmosis was made possible through enhanced flow in vertically aligned high flux CNT membranes.

La conception de biomatériaux actifs est actuellement encouragée par le manque de thérapies régénératives efficaces pour des tissus endommagés présentant une faible capacité d’autoréparation. Les progrès récents concernant les techniques de préparation de matériaux structurés (électrospinning, microfluidique) ainsi que la découverte du fort potentiel régénératif des cellules souches ont suscité un regain d’intérêt pour des projets collaboratifs à l’interface entre biologie et sciences des matériaux. Une approche prometteuse de régénération tissulaire repose donc sur la combinaison de cellules souches et de biomatériaux implantables. Des biomatériaux innovants, injectables et servants à la fois de support aux cellules et de réservoir de molécules actives telles que des protéines ou des agents de thérapie génique (Matrice Génétiquement Activée) ont été développés. Se plaçant plus particulièrement dans le contexte de l’ingénierie du cartilage, ce travail a pour objectif de développer une stratégie complémentaire concernant l’orientation de la différenciation de cellules souches mésenchymateuses (CSM) grâce au mécanisme d’interférence ARN.La principale difficulté rencontrée lors de l’utilisation d’acides nucléiques pour induire la différenciation des CSM reste leur faible capacité à traverser les membranes cellulaires, due à leur nature hydrophile et leur charge négative. De plus, les acides nucléiques sont dégradés très facilement par les nucléases extracellulaires, ce qui rend nécessaire l’utilisation d’un vecteur. Les vecteurs non-viraux sont d’excellents candidats pour des applications in vivo en raison de leur faible coût de production et leur faible immunogénicité. Toutefois, la plupart des systèmes de vectorisation trouvés dans la littérature présentent un manque de reproductibilité associé à une cytotoxicité vis-à-vis des cellules primaires. Nous souhaitions donc développer un système de transfection synthétique à la fois efficace et biocompatible. Pour cela, nous nous sommes basés sur les résultats encourageants concernant l’utilisation des micelles de complexes polyioniques (PIC) pour la transfection des cellules dendritiques. Ces micelles sont formées par complexation de deux polyélectrolytes : un copolymère à blocs double-hydrophiles (CBDH) avec un bloc anionique et un homopolymère cationique. Dans ce travail, nous avons évalué le polyoxyde d’éthylène – b – polyacide méthacrylique en tant que CBDH et la poly-L-lysine ou le polyéthylènimine en tant que polycation. L’influence des caractéristiques des composantes (asymétrie du CBDH, nature du polycation, taille des blocs, ratio de charges…) sur les propriétés physico-chimiques des micelles formées (taille, charge de surface) a d’abord été étudiée. Puis, la possibilité de complexation d’un siRNA au sein des micelles ainsi que leur stabilité en conditions physiologiques ont été évaluées. La formulation des micelles a été conçue pour permettre une dissociation des objets à un pH comparable à celui des endosomes ; ceci a été vérifié par diffusion dynamique de la lumière. Une analyse par cytométrie en flux avec un siRNA marqué TAMRA ont démontré l’internalisation effective des micelles dans les CSM. Plus important encore, l’inhibition spécifique d’un gène cible, Runx2, a été démontrée à un niveau comparable à celui d’un vecteur commercial standard, la Lipofectamine2000®. La seconde partie de la thèse a consisté en l’élaboration de microparticules. A cet effet, nous avons préparé des microsphères de collagène par un dispositif de microfluidique, et ce à partir de diverses sources de collagène (murin, porcin, bovin). Des expériences préliminaires démontrent qu’il est possible d’imprégner les micelles dans les microsphères. De même, de premiers résultats encourageants ont été obtenus quant à la capacité du système globale à assurer l’adhésion cellulaire et permettre une transfection efficace des CSM dans un environnement 3D par les micelles PIC vectorisant un siRNA anti-Runx2. / The relative lack of efficient regenerative therapies for damaged tissues with low capacity for self-repair is one major motivation for the design of new active biomaterials. Recent progress in hierarchical materials processing techniques (electrospinning, microfluidics…) and the demonstration of the strong regenerative potential of stem cells have prompted renewed interest for collaborative projects at the biology / materials science interface. The combination of stem cells and active implantable materials has emerged as a high potential approach for the regeneration of damaged tissues. In particular, injectable cell carriers also acting as a reservoir for active molecules like proteins or gene therapy agents (Gene Activated Matrices) bring about innovative solutions to current issues in the field of tissue engineering. In the context of cartilage regeneration, the main objective of this work was to investigate a complementary strategy to orient mesenchymal stem cell (MSC) fate by the use of RNA interference. One major difficulty to reach high transfection levels and efficiently direct MSC differentiation comes from the low ability of nucleic acids (NA) to cross cellular membranes, largely due to their hydrophilicity and negative charge. This, along with a strong susceptibility to extracellular nucleases, calls for efficient gene delivery vectors. Their low production cost and low immunogenic potential make non viral vectors good candidates for in vivo applications. Besides, most systems reported in the literature show reproducibility and cytotoxicity issues with primary cells that we intended to address to achieve a safe and efficient synthetic vector for MSC. Based on previous encouraging results on the transfection of dendritic cells, we chose to investigate tripartite polyionic complex (PIC) micelles. Their formation is based on the polyelectrolyte complexation of a polyanionic double-hydrophilic block copolymer (DHBC) with a cationic homopolymer. In this work, we investigated polyethylene oxide – b – polymethacrylic acid as the DHBC and Poly-L-Lysine or Polyethyleneimine as the polycation. One major part of the work was to study the influence of micelles components characteristics (block size, DHBC asymmetry, polycation nature and molecular weight, polyelectrolyte charge ratios, etc.) on the physical characteristics (dimensions, surface charge) of the obtained nanoparticles. We then studied the ability of micelles to stably complex siRNA at high loading levels, and their stability in physiological conditions. Importantly, the PIC micelles’ formulation was designed to allow for pH-triggered disassembly in acidic conditions similar to those found in endosomes, as assessed by light scattering measurements. These nanoparticles were shown to be efficiently internalized inside MSC by flow cytometry using a fluorescently labeled SiRNA-TAMRA. Most importantly, they were shown to efficiently down-regulate Runx2 mRNA in MSC, at levels similar to those reached with the gold standard Lipofectamine2000®. The second major step for the development of a GAM suited for cartilage regeneration was to elaborate injectable microparticles. To this purpose, we prepared collagen microspheres through a microfluidic-based process and with different collagen sources (murine, bovine, and porcine). Preliminary experiments show that micelles can be efficiently loaded into the microspheres. First encouraging results were also obtained regarding the ability of the created GAM to support cell adhesion, and to allow for the efficient transfection of MSC in this 3D environment, thanks to an anti-runX2 siRNA vectorized with PIC micelles. This proof-of-concept study has demonstrated that the main elements of the nano-in-micro system are ready and mostly meet the assigned requirements. This opens the way for further work to assess the ability of this GAM to effectively improve MSC chondrogenesis and ultimately cartilage repair.

Hydroxyapatite (HAP) coatings are used in orthopaedic surgery for bone regeneration. Current methods of phase quantification of HAP coatings suffer from drawbacks. A novel methodology of quantitative phase analysis of HAP coatings has been devised and validated. This method, based on whole pattern fitting with a fundamental parameters approach, incorporates amorphous calcium phosphate (ACP) and apatite phases into structural refinements. A comparison of the structural and chemical properties of plasma sprayed (PS) and novel electrodeposited (ED) HAP coatings has been conducted. ED coatings contained less ACP and more preferred orientation than the PS coatings, although the stoichiometry was similar. In vitro investigations of PS and ED coatings in simulated body fluid and foetal calf serum revealed that both are bioactive. A carbonated apatite layer produced on the ED coatings was -0.7μm thick with a stoichiometry and chemical constituents similar to that of natural bone apatite. PS coatings produced a nanocrystalline carbonated apatite layer (-4μm). For the first time it has been possible to model crystalline HAP and nanocrystalline apatite as independent phases and obtain accurate lattice parameters for each. A positive linear correlation has been made between microstrain and the solubility of HAP and carbonated apatites. Dissolution studies have shown that the behaviour of HAP and carbonated apatite is dominated by crystallite size at low undersaturation and by crystallite size and microstrain at high undersaturation for crystallites between -30OA- 1000A. Metastable equilibrium occurred for crystallites <_400A at low undersaturation. Carbonate content did not affect the solubility or dissolution behaviour. A novel technology for coating polymeric tape with HAP for potential use in anterior cruciate ligament reconstruction has been devised. Mechanical tests have demonstrated that no adverse properties are induced by the coating technology. Cell culture studies have shown that the HAP layer is capable of enhanced attachment, proliferation and differentiation of osteoblast cells compared to uncoated tape.

Advances in biomaterials have enabled medical practitioners to replace diseased body parts or to assist in the healing process. In situations where a permanent biomaterial implant is used for a temporary application, additional surgeries are required to remove these implants once the healing process is complete, which increases medical costs and patient morbidity. Bio-absorbable materials dissolve and are metabolized by the body after the healing process is complete thereby negating additional surgeries for removal of implants. Magnesium alloys as novel bio-absorbable biomaterials, have attracted great attention recently because of their good mechanical properties, biocompatibility and corrosion rate in physiological environments. However, usage of Mg as biodegradable implant has been limited by its poor corrosion resistance in the physiological solutions. An optimal biodegradable implant must initially have slow degradation to ensure total mechanical integrity then degrade over time as the tissue heals. The current research focuses on surface modification of Mg alloy (MZC) by surface treatment and polymer coating in an effort to enhance the corrosion rate and biocompatibility. It is envisaged that the results obtained from this investigation would provide the academic community with insights for the utilization of bio-absorbable implants particularly for patients suffering from atherosclerosis. The alloying elements used in this study are zinc and calcium both of which are essential minerals in the human metabolic and healing processes. A hydrophobic biodegradable co-polymer, polyglycolic-co-caprolactone (PGCL), was used to coat the surface treated MZC to retard the initial degradation rate. Two surface treatments were selected: (a) acid etching and (b) anodization to produce different surface morphologies, roughness, surface energy, chemistry and hydrophobicity that are pivotal for PGCL adhesion onto the MZC. Additionally, analyses of biodegradation, biocompatibility, and mechanical integrity were performed in order to investigate the optimum surface modification process, suitable for biomaterial implants. The study concluded that anodization created better adhesion between the MZC and PGCL coating. Furthermore, PGCL coated anodized MZC exhibited lower corrosion rate, good mechanical integrity, and better biocompatibility as compared with acid etched.

The main objective of this work is to give contribution in both additive manufacturing (AM) and tribometry derived from the application and study of materials available with the use of biomimetic designs. Additional contributions are determining what effects treatments for flooring surfaces may have on the dynamic coefficient of friction and the effects of these products on common surfaces. The validity of the proposed methodology for a proof of concept was demonstrated by comparing measured dynamic coefficient of friction for designs using standardized equipment and comparing these values to plantar skin tested using an accepted and standardized testing method that has been extensively researched and validated. Initial biomimetic designs and characteristics unique to each design were researched and compared. Eleven designs were selected to be fabricated, tested, and compared to select the most desirable applications for further investigation. Research into potential treatments commercially available for use was done to determine the efficacy of these products. Prototype sensor designs were selected and fabricated using direct light processing (DLP) technology. Examination of the measured values was done through an analysis of the variances in the response variable and comparisons using Fisher and Tukey pairwise comparison method. Future work recommendations are provided for further development and improvement of the topics presented in this thesis.

The first portion of this thesis assesses the structural application of a bracing design inspired by the deep-sea sponge, Euplectella Aspergillum. Many studies have investigated the natural strength found in the unique skeletal structure of this species. The braced design inspired by the sponge features square frames with two sets of cross-braces that are offset from the corners of each frame, creating a pattern of open and closed cells. This study reports the results of multiple Finite Element Analysis (FEA) computations that compare the described bracing pattern to a more common bracing design used in structural design. The designs are compared in two configurations; the first is a simplified tall building design, and the second is a slender plate design. Results indicate that the sponge’s natural pattern produces considerable mechanical benefit when only considering elastic behavior. However, the same was not true when considering plastic material properties. In conclusion to these observations, the sponge-inspired lattice design is determined to be an efficient alternative to slender-solid plates but not for lateral-resisting systems intended for tall building design. The second topic of discussion in this thesis concerns the stability of thin cylindrical shells with imperfections. The structural stability of these members is highly sensitive to the size and shape of an imperfection. An accurate prediction of the capacity of an imperfect cylindrical shell can be determined using non-destructive testing techniques. This method does require previous knowledge of the characteristics of the imperfection, which realistically is unknown. In the hope of creating a technique to find the location of an imperfection, this study analyzes the trends in the stability landscapes of the surrounding area of an imperfection. The imperfection of interest in this study has an amplitude equivalent to the thickness of the shell. Using FEA to simulate non-destructive probing tests, it is established that there is a distinct area surrounding the imperfection where the axial load and peak probe force curves show the influence of the imperfection. This area is referred to as the zone of influence and can be used to create an efficient process to locate an imperfection on a thin cylindrical shell.