A large and increasing number of cancer interventions, including both diagnosis and therapy, involve precise placement of needles, which is extremely difficult. This challenge is due to lack of proper actuation of the needle (i.e., actuated from the proximal end, which is far away from the needle tip). To overcome this challenge, we propose to bend the needle using a smart actuator that applies bending forces on the needle body; thereby, improving the navigation of the needle. The smart actuator is designed with shape memory alloy (SMA) wires, namely Nitinol, due to their unique properties such as super-elasticity, shape memory effect, and biocompatibility. For accurate steering of the smart needle, there is a need to understand Nitinol thermo-mechanical behaviors. Various existing SMA constitutive models were investigated and compared. Since SMA is used as an actuator in this project, only one dimensional constitutive models are considered. Two distinct models with different phase transformation kinetic approaches were chosen. The first model was proposed by Terriault and Brailovski (J. Intell. Mat. Systems Structures, 2011) using a modified one dimensional Likhachev formulation. The second model was developed by Brinson (J. Intell. Mat. Systems Structures , 1993). Since all SMA constitutive models are empirically based, several important materials' constants such as Phase Transformation Temperatures are needed. The four Transformation Temperatures are: Martensite start (Ms), Martensite finish (Mf), Austenite start (As), Austenite finish (Af). Differential Scanning Calorimetry (DSC) was used to obtain these constants. These temperatures are also influenced by stress, defined by the Clausius-Clayperon coefficients. The coefficients were obtained by measuring Nitinol temperature and displacement response under various constant stress conditions. In order to study its actuation behavior, Nitinol wires under constant strain configuration and resistance heating were tested for their force response. The thermo-mechanical responses were then compared with numerical simulations. While Terriault and Brailovski resistance heating formulation agrees strongly with temperature responses, the model cannot be used to simulate the actuator mechanical responses. Brinson model simulations of the force responses were found to agree well with experimental results. In conclusion, Terriault and Brailovski resistance heating formulation should be coupled with Brinson model to accurately simulate Nitinol actuation behavior for the smart needle. / Mechanical Engineering

Needle-based intervention insertion is one of the common surgical techniques used in many diagnostic and therapeutic percutaneous procedures. The success of such procedures highly depends on the accuracy of needle placement at target locations. An active needle has the potential to enhance the accuracy of needle placement as well as to improve clinical outcome. Bending forces provided by the attached actuators can assist the maneuverability in order to reach the targets following a desired trajectory. There are three major research parts in the development of active needle project in the Composites Laboratory of Temple University. They are thermomechanical characterization of shape memory alloy (SMA) or Nitinol as an actuator for smart needle, mechanical modeling and design of smart needles, and study of tissue needle interaction. The characterization of SMA is the focus of this dissertation. Unique thermomechanical properties of Nitinol known as shape memory effect and superelasticity make it applicable for different fields such as biomedical, structural and aerospace engineering. These unique behaviors are due to the comparatively large amount of recoverable strain which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain (also known as residual strain); which limits their applicability. Therefore, for applications that rely on the strain response in repetitive loading and unloading cycles, it is important to understand the generation of the unrecovered strain in the Nitinol wires. In this study, the unrecovered strain of Nitinol wires with various diameters was investigated, using two experimental approaches: constant stress and uniaxial tensile tests. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible at temperatures of 70 to 80C depending on the wire diameter. Wire diameters varied from 0.10 to 0.29 mm were tested and different ranges of critical stress were found for different wire diameters. The transformation temperatures of different wire diameters at zero stress have been achieved by performing the Differential Scanning Calorimetry (DSC) test. The actuation force created by Nitinol wire is measured through constant strain experiment. X-Ray Diffraction (XRD) study was also performed to investigate the phase of Nitinol wires under various thermomechanical loading conditions. In summary, the effect of wire diameter on the required critical stresses to avoid the unrecovered strain between first and second cycle of heating and cooling are presented and the results of both mechanical tests are justified by the results obtained from the XRD study. / Mechanical Engineering

<p> New electrophoretic deposition methods for the fabrication of advanced organic-inorganic composite coatings on metallic substrates for biomedical applications have been developed. In the proposed methods, chitosan was used as a matrix for the fabrication of multilayer and functional graded chitosan- hydroxyapatite (HA) coatings. The HA particles showed preferred orientation of c-axis parallel to the layer surface, which is similar to the bone structure. Electrochemical studies showed that the obtained coatings provided corrosion protection of the metallic substrates, such as stainless steel and Nitinol.</p> <p> The feasibility of co-deposition of chitosan and heparin has been demonstrated. Composite chitosan-heparin layers were used for the surface modification of chitosan-HA coatings. Obtained results paved the way for the electrophoretic fabrication of novel coatings for biomedical implants with improved blood compatibility.</p> <p> The feasibility of co-deposition of hyaluronic acid and HA has also been demonstrated. The co-deposition of hyaluronic acid and HA resulted in the fabrication of novel nanocomposite films by electrodeposition. The chemical composition, microstructure, corrosion protection, and other functional properties of the nanocomposites have been investigated. Co-deposition of hyaluronic acid and multiwalled carbon nanotubes has been studied by TGA/DT A and SEM studies.</p> <p> The feasibility of deposition of novel composites based on alginic acid has been demonstrated. New electrochemical strategies were used for the fabrication of alginic acid-HA, alginic acid-heparin and alginic acid -hyaluronic acid nanocomposites. The composition of these nanocomposite coatings can be varied by variation in bath composition for EPD.</p> <p> The electrochemical mechanisms for the fabrication of all these advanced organic-inorganic composite coatings have been developed.</p> / Thesis / Master of Applied Science (MASc)

Une hernie abdominale survient lorsqu’un organe émerge de la cavité abdominale à travers une faiblesse musculaire. La cure de hernie est une des procédures chirurgicales les plus fréquemment réalisée. Une prothèse synthétique est souvent utilisée lors des procédures pour diminuer le taux de récidives. L’implantation de prothèse peut entraîner certaines complications, dont les infections chroniques. Certains facteurs dans la conception de la prothèse peuvent diminuer les taux d’infections. Plusieurs études ont montré que le Nitinol et certaines nanoparticules possèdent des propriétés antimicrobiennes. Les objectifs de cette étude sont d’examiner les surfaces d’échantillons de prothèses en Nitinol revêtis de nanoparticules d’argent et cuivre, ainsi que d’évaluer préliminairement leurs propriétés antimicrobiennes. Trois échantillons de prothèses ont été examinés : une en Nitinol seul et deux autres avec un revêtement de nanoparticules d’argent et cuivre, KJ103 et KJ501. L’étude de surface fut réalisée à l’École Polytechnique de Montréal. L’étude des propriétés antimicrobiennes fut réalisée dans les laboratoires de l’Institut de Cardiologie de Montréal. Les échantillons en Nitinol et une prothèse commerciale en polypropylène ont été exposés à trois micro-organismes habituellement retrouvés dans les infections chroniques : Staphylococcus aureus, Staphylococcus epidermidis et Candida albicans. Après une période d’incubation, des biofilms étaient visibles sur toutes les prothèses. Qualitativement, les prothèses en Nitinol semblaient moins susceptibles aux micro-organismes, en particulier l’échantillon KJ501. Les hernies abdominales sont fréquemment diagnostiquées en médecine. Les prothèses utilisées lors des chirurgies servent à prévenir les récidives. Par contre, les prothèses sont à risque de causer des infections chroniques. Cette expérience préliminaire suggère que les prothèses expérimentales en Nitinol ayant des nanoparticules d’argent et cuivres semblent moins susceptibles aux micro-organismes comparativement à une prothèse en polypropylène. / An abdominal hernia occurs when an organ protrudes through a weakness in the abdominal wall. Hernia repair is one of the most frequently performed surgeries. During the repair, a synthetic mesh is often used to decrease recurrence rates. Meshes can be associated with complications, such as chronic infections. Certain properties of the mesh itself can decrease infection rates. Several studies have shown that Nitinol, as well as silver and copper nanoparticles, have anti-microbial properties. The objectives of this study were to examine some surface properties of samples of Nitinol mesh with silver and copper nanoparticles and to preliminarily evaluate their antimicrobial properties. Three mesh samples were examined; one made uniquely with Nitinol and two others with silver and copper nanoparticle coatings, KJ103 and KJ501. The surface study was done at the École Polytechnique of Montréal. The study of the antimicrobial properties was performed at the laboratories of the Institut de Cardiologie de Montréal. The Nitinol samples and a commercially sold polypropylene mesh were exposed to three micro-organisms commonly found in mesh infection: Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans. After the incubation period, biofilms were visible on all the meshes. Qualitatively, the Nitinol mesh showed less biofilm growth, in particular the KJ501 sample. Hernias are frequently diagnosed in medicine. Meshes are used during surgery to prevent recurrences. However, meshes are at risk of chronic infections. This preliminary experiment suggests that the Nitinol mesh with silver and copper nanoparticles are less prone to develop microbial biofilms when compared with a polypropylene mesh.

O presente trabalho apresenta um estudo do tratamento duplex para o biomaterial Nitinol (NiTi). Este tratamento consiste em nitretação a plasma para a formação do nitreto de titânio (TiN), seguido de deposição de um filme fino de nitreto de zircônio (ZrN) sobre a superfície nitretada. O estudo das fases cristalinas presentes no sistema foi realizado pela técnica de difração de raios X (DRX). A morfologia e espessura da camada nitretada e do filme fino depositado foram avaliadas por microscopia eletrônica de varredura (MEV). As propriedades mecânicas foram estudadas mediante ensaios de nanoindentação. Para avaliar a resistência à corrosão foram realizados testes de polarização potenciodinâmica em solução de saliva artificial. Os resultados mostram que a temperatura de nitretação tem forte influência na formação do TiN na superfície do substrato. O filme de ZrN depositado sobre as amostras nitretadas apresenta propriedades de dureza e resistência à corrosão que dependem da temperatura de nitretação, mesmo tendo sido depositados sem variação de temperatura. Esse comportamento sugere que os filmes são influenciados pela condição inicial da superfície antes da deposição. Os melhores resultados em termos de dureza e resistência à corrosão foram obtidos nas amostras tratadas em temperaturas mais elevadas. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-05T18:07:33Z No. of bitstreams: 1 Dissertacao Juliane Carla Bernardi.pdf: 2940702 bytes, checksum: 376b73745f740260fc19e7a6e8b5d900 (MD5) / Made available in DSpace on 2014-06-05T18:07:33Z (GMT). No. of bitstreams: 1 Dissertacao Juliane Carla Bernardi.pdf: 2940702 bytes, checksum: 376b73745f740260fc19e7a6e8b5d900 (MD5) / The present work aims to study about duplex treatment on the biomaterial Nitinol (NiTi). This treatment consists in titanium nitride (TiN) formed by plasma nitration, followed by zirconium nitride (ZrN) thin film deposition upon the nitrated surface. The study of crystalline phases present in the system was performed by X-ray diffraction technique (XRD). The morphology and thickness of the nitrated layer and thin film were evaluated by scanning electron microscopy (SEM). The mechanical properties were studied by nanoindentation analysis. In order to evaluate corrosive resistance tests of potenciodynamic polarization were performed in solution of saliva artificial. Results demonstrate that nitration temperature has a strong influence in the formation TiN on the substrate surface. The ZrN film depositated upon nitrated samples present hardness and corrosive resistance properties that depend on nitration temperature, even though ZrN films were depositated without temperature variation. This behaviour suggests that films are influenced by the initial surface condition before depositon. The best results in terms of hardness and corrosive resistance were obtained in samples treated at higher temperatures.

O presente trabalho apresenta um estudo do tratamento duplex para o biomaterial Nitinol (NiTi). Este tratamento consiste em nitretação a plasma para a formação do nitreto de titânio (TiN), seguido de deposição de um filme fino de nitreto de zircônio (ZrN) sobre a superfície nitretada. O estudo das fases cristalinas presentes no sistema foi realizado pela técnica de difração de raios X (DRX). A morfologia e espessura da camada nitretada e do filme fino depositado foram avaliadas por microscopia eletrônica de varredura (MEV). As propriedades mecânicas foram estudadas mediante ensaios de nanoindentação. Para avaliar a resistência à corrosão foram realizados testes de polarização potenciodinâmica em solução de saliva artificial. Os resultados mostram que a temperatura de nitretação tem forte influência na formação do TiN na superfície do substrato. O filme de ZrN depositado sobre as amostras nitretadas apresenta propriedades de dureza e resistência à corrosão que dependem da temperatura de nitretação, mesmo tendo sido depositados sem variação de temperatura. Esse comportamento sugere que os filmes são influenciados pela condição inicial da superfície antes da deposição. Os melhores resultados em termos de dureza e resistência à corrosão foram obtidos nas amostras tratadas em temperaturas mais elevadas. / The present work aims to study about duplex treatment on the biomaterial Nitinol (NiTi). This treatment consists in titanium nitride (TiN) formed by plasma nitration, followed by zirconium nitride (ZrN) thin film deposition upon the nitrated surface. The study of crystalline phases present in the system was performed by X-ray diffraction technique (XRD). The morphology and thickness of the nitrated layer and thin film were evaluated by scanning electron microscopy (SEM). The mechanical properties were studied by nanoindentation analysis. In order to evaluate corrosive resistance tests of potenciodynamic polarization were performed in solution of saliva artificial. Results demonstrate that nitration temperature has a strong influence in the formation TiN on the substrate surface. The ZrN film depositated upon nitrated samples present hardness and corrosive resistance properties that depend on nitration temperature, even though ZrN films were depositated without temperature variation. This behaviour suggests that films are influenced by the initial surface condition before depositon. The best results in terms of hardness and corrosive resistance were obtained in samples treated at higher temperatures.

Hold down release mechanisms (HDRMs) are used for tightly attaching segments of bodies together when it is desired to release them rapidly at some point. When transporting sensitive payloads on launch vehicles, the challenge arises of releasing the fastened segments of the spacecraft without risking damage to the costly equipment. Non-explosive HDRMs are favourable from a safety perspective as there is a lower risk of producing potentially destructive shock-waves throughout the structure.  One variant of a non-explosive HDRM uses a so called 'split spool initiator'. This initiator can only be used once in the actuator mechanism and to reuse the HDRM the initiator must be replaced. The purpose of this thesis is to design an improved split spool initiator which can be reusable while conserving the functionality aspects of the existing design. To achieve this, different ideas were considered and ultimately a solution using shape memory alloys (SMAs) was explored. A prototype was constructed to demonstrate the functionality of the design and simulations are done to determine the forces acting on different parts of the mechanism. / Hold down release-mekanismer (HDRM) används för att säkert kunna fästa samman delar av strukturer för att sedan kunna lossa dessa vid rätt tillfälle. När det transporteras känslig last på exempelvis rymdfarkoster uppkommer utmaningen att göra så på ett sätt som inte riskerar att skada den ofta dyra utrustningen. Det finns en mängd olika HDRM, dessa kan delas upp i två typer som är icke explosiva release-mekanismer och pyrotekniska release-mekanismer. Icke explosiva release-mekanismer har en fördel över pyrotekniska som är att de inte producerar potentiellt destruktiva chock-vågor som sprids genom strukturen. En typ av icke-explosiva release-mekanismer är den så kallade split spool-initieraren. Denna kan endast användas en gång när fästelementet är aktiverat och för att kunna använda fästelementet igen måste hela initieraren bytas ut. Syftet med denna studie har varit att att designa en förbättrad split spool-initierare som är återanvändbar, medan funktionaliteten hos den ursprungliga designen är bevarad. För att åstadkomma detta övervägdes olika idéer och slutligen valdes en lösning som använder minnesmetaller eller Shape memory alloys på engelska (SMA). En prototyp konstruerades för att demonstrera funktionaliteten hos designen. Simuleringar gjordes även för att bestämma krafter som agerade på split spool-strukturen och för att få en överblick över spänningsfördelningen genom initieraren.

Additive manufacturing of Nitinol is a promising field, as it can circumvent the challenges associated with its conventional production processes and unlock unique advantages. However, the accompanying surface features such as powder adhesions, spatters, ballings, or oxide discolorations are undesirable in engineering applications and therefore must be removed. Plasma electrolytic polishing (PeP) might prove to be a suitable finishing process for this purpose, but the effects of post-processing on the mechanical and functional material properties of additively manufactured Nitinol are still largely unresearched. This study seeks to address this issue. The changes on and in the part caused by PeP with processing times between 2 and 20 min are investigated using Nitinol compression springs manufactured by Laser Beam Melting. As a benchmark for the scanning electron microscope images, the differential scanning calorimetry (DSC) measurements, and the mechanical load test cycles, conventionally fabricated Nitinol springs of identical geometry with a medical grade polished surface are used. After 5 min of PeP, a glossy surface free of powder adhesion is achieved, which is increasingly levelled by further polishing. The shape memory properties of the material are retained without a shift in the transformation temperatures being detectable. The decreasing spring rate is primarily attributable to a reduction in the effective wire diameter. Consequently, PeP has proven to be an applicable and effective post-processing method for additively manufactured Nitinol.

A primeira etapa deste trabalho consiste de uma descrição geral das propriedades mecânicas, temperaturas de transformação e características microestruturais de uma liga Ni-50,2Ti(%at.) com Efeito de Memória de Forma (EMF) previamente produzida via fusão por feixe de elétrons (EBM). O comportamento mecânico foi estudado por ensaios de tração em condições controladas de temperatura e deformação. As curvas de tensão-deformação à temperatura ambiente (amostra no estado martensítico) apresentaram um platô de tensão compreendido entre 150 a 190MPa após a deformação elástica da martensita. Uma recuperação média total (RE + REMF) de 80% foi observada experimentalmente para uma amplitude de deformação variando de 2 a 8%. A influência da temperatura na resistência mecânica também foi verificada com a amostra no estado austenítico ensaiada a 100C e a 120C. Por microscopia óptica (MO) foi verificado que o material apresenta bandas de martensita deformada antes da solubilização, e uma estrutura bastante homogênea com contornos de grão após a solubilização. Além disso, foram verificados o desaparecimento e o reaparecimento do relevo de superfície devido à transformação martensítica reversa e direta, respectivamente, durante o aquecimento e resfriamento da amostra polida eletroliticamente. Por microscopia eletrônica de varredura (MEV) verificou-se que, mesmo no estado não solubilizado, a amostra apresenta fratura dúctil com presença de "dimples". Após solubilização e/ou envelhecimento, a amostra apresenta uma deformação plástica razoável com alongamento total acima de 20%. A segunda etapa deste trabalho mostra a importância de alguns parâmetros do processo na produção da liga Ni-Ti com EMF via EBM, tais como: intensidade de corrente e tempo de exposição do feixe de elétrons, velocidade longitudinal, rotação e configuração da barra de alimentação. Os lingotes foram produzidos a partir de um forno de 30kW, e posteriormente, caracterizados nos estados: bruto de fusão, solubilizado e envelhecido. Os dados de dureza revelam a influência destes tratamentos na formação de precipitados dentro da matriz Ni-Ti. Todos os lingotes apresentaram uma superfície lisa e brilhante e quase sem oxidação. As macro e microestruturas das amostras foram analisadas por MO e MEV. Dependendo da intensidade da corrente, os lingotes apresentaram uma estrutura grosseira formada principalmente por grãos colunares, ou uma estrutura refinada formada por grãos colunares e equiaxiais. Conseqüentemente, foi verificada uma dureza maior, sem vazios internos e uma maior fração volumétrica de precipitados no segundo lingote. As análises por espectroscopia por dispersão de energia (EDS) e por calorimetria exploratória diferencial (DSC) sugerem uma perda maior de níquel que titânio. No processo de Alimentação Contínua e Lingotamento Estático, a perda de peso variou de 0,5 a 1,2%, dependendo da corrente do feixe de elétrons. No processo de Fusão Estática, as temperaturas de pico da transformação martensítica (Mp) foram comparadas com a curva de referência, e indica que a composição química varia de 50,3 a 50,8%at. de níquel ao longo do comprimento da amostra. Isto também mostra que a produção da liga Ni-Ti com EMF é perfeitamente possível desde que tomados alguns cuidados.

As ligas Ti-Ni com efeito de memória de forma possuem aplicações em diversas áreas por apresentarem alta ductilidade e boa resistência à fadiga e a corrosão. É um material promissor na área biomédica devido às propriedades de efeito de memória de forma e superelasticidade. Uma possibilidade para melhorar as propriedades tribológicas e a biocompatibilidade desse material é modificação superficial através do processo de implantação iônica por imersão em plasma de nitrogênio (IIIP-N). Os materiais utilizados neste trabalho são as ligas Ti-49,93 at.% Ni, denominado VIM 47, e Ti-49,42 at.% Ni, denominado VIM 40. O processo IIIP-N foi realizado em baixa e alta temperatura. Para o material VIM 47, foram realizadas implantação em duas condições: no material fundido e em amostras solubilizadas a 900C durante 30 minutos. A implantação foi realizada em temperaturas menores que 250C e 320C. Para o material VIM 40, trabalhou-se apenas com amostras forjadas, sendo realizada IIIP-N em temperaturas menor que 250C, 290C e 560C. A técnica de espectroscopia Auger confirma a presença de nitreto de titânio nas superfícies das amostras, apresentando como melhor resultado na liga VIM 47 a amostra implantada a 320C com espessura próxima a 400 nm, duas vezes superior à camada da amostra fundida implantada na mesma condição experimental. A liga VIM 40, apresenta como melhor resultado a camada com espessura de 150 nm medida por GDOS ("Glow Discharge Optical Spectroscopy") na amostra implantada a 560C, três vezes superior à amostra implantada na temperatura menor que 250C. Nas análises de desgaste pino-sobre-disco, o coeficiente de atrito diminui significativamente através do processo IIIP-N. O melhor resultado obtido foi para amostra do material VIM 40, implantada a 560C, com coeficiente de atrito em torno de 0,1, resultado oito vezes menor comparado com a amostra de referência.