Implantoitavat paineanturit

Tämä kandidaatintutkielma on kirjallisuustutkimus implantoitavista paineantureista. Tutkielmassa keskitytään implantoitavien paineantureiden perusrakenteeseen ja kahteen yleiseen sovellukseen: kallonsisäisen paineen ja kardiovaskulaarisen paineen mittaamiseen. Implantoitava paineanturi asetetaan osittain tai kokonaan kehon sisälle. Paineanturi rakentuu painetta mittaavasta elementistä, sekä joko johdoista tai langattomasta toteutuksesta, jolla mitatut painearvot saadaan kuljetettua monitorille, lääkäreille analysoitaviksi. Langattomassa toteutuksessa painearvot yleensä lähetetään monitorille joko radioaalloilla tai induktiivisen linkin avulla. Kallonsisäisen paineen mittaaminen on erityisen tärkeää vakavan päähän kohdistuneen vamman jälkeen. Implantoitavilla paineantureilla saadaan tarkempia ja jatkuvia mittaustuloksia, mitkä ovat tärkeitä ominaisuuksia, sillä lääkäreiden on pystyttävä reagoimaan nopeasti mikäli painearvot alkavat kohota. Kardiovaskulaarista painetta mittaavilla implantoivilla paineantureilla tarkastellaan esimerkiksi sydämen toimintaa sydänkammion tukilaitteen asennuksen jälkeen. Lopuksi tutkielma käsittelee biohajoavia implantoitavia paineantureita, jotka tulevat käyttöön tulevaisuudessa. Tällä hetkellä biohajoavat paineanturit ovat testattavana laboratorioissa ja eläinkokeissa. Monet testien tuloksista ovat lupaavia. Biohajoavat implantoitavat paineanturit tiputtavat tulehdusriskiä, sillä ne eivät tarvitse toista leikkausta kuten ei-hajoavat paineanturit, jotka tarvitsevat poistoleikkauksen

Design, development and validation of iron-based composites for biodegradable implant applications

"Thèse en cotutelle : Doctorat en génie des matériaux et de la métallurgie, Université Laval, Québec, Canada, Philosophiæ doctor (Ph. D.) et Politecnico di Milano, Milano, Italie."Récemment, le Fe et ses alliages ont montré leur potentiel en tant que matériaux dégradables pour des applications biomédicales. Néanmoins, la vitesse de corrosion lente limite leurs performances dans certaines situations. Les matériaux composites à matrice de fer représentent une approche possible, non seulement pour améliorer leurs propriétés mécaniques, mais aussi pour accélérer et ajuster la vitesse de corrosion dans un environnement physiologique. Dans ce travail, des composites à base de Fe renforcés par des particules Mg2Si ont été proposés. Les poudres initiales ont été préparées par différentes combinaisons de procédés de mélange et de broyage, et finalement consolidées par laminage à chaud. L'influence de la microstructure sur les propriétés mécaniques et le comportement à la corrosion de Fe/Mg2Si a été étudiée. Les échantillons contenant des particules Mg2Si plus petites présentaient une distribution plus homogène du renforcement. Le rendement et l’état limite ultime à la traction ont augmenté par rapport à ceux du Fe pur. La présence des particules de renforcement a joué un rôle crucial dans la susceptibilité à l'attaque de corrosion localisée dans les composites à base de Fe. L'initiation de la corrosion et son développement ont été systématiquement suivis pour étudier le mécanisme de corrosion. L'importance des particules de Mg2Si dans le déclenchement des processus de corrosion a été expliquée. Des mesures électrochimiques et des tests d'immersion statique ont indiqué que l'ajout de Mg2Si pourrait augmenter le taux de corrosion du Fe. Il a été constaté que la taille et la distribution des particules de renfort jouaient un rôle crucial à l'uniformité de l'attaque de corrosion. Après, une série de tests d'immersion à différents intervalles d'exposition (20, 50 et 100 jours) à la solution modifiée de Hanks a été réalisée à fin d’évaluer le comportement de dégradation des composites Fe/Mg2Si et Fe pur préparés par différentes techniques de métallurgie des poudres. Les résultats ont révélé l’importance du Mg2Si dans la composition et la stabilité des films protecteurs formés lors des expériences de corrosion statique. Les composites Fe/Mg2Si présentaient des taux de dégradation plus élevés que le Fe pur à toutes les étapes du test d'immersion. Les taux de dégradation à des intervalles d'exposition distincts dépendaient fortement de la composition et de la stabilité des films protecteurs d'oxyde, d'hydroxyde, de carbonate et de phosphate formés sur les surfaces dégradées. La libération d'ions Fe dans la solution aux stades ultérieurs de l'expérience était limitée en raison de l'effet de barrière dû au dépôt insoluble. Cette étude fondamentale a servi de base aux processus de formation de film protecteur dans la solution de Hanks modifiée, permettant une identification détaillée de leurs caractéristiques.Fe-based alloys have shown a potential as a degradable material for biomedical applications. Nevertheless, the slow corrosion rate limits their performance as a biodegradable implant. One approach to control and modify their corrosion properties is the reinforcement addition, to create metal matrix composites in which the second phase is aimed at tuning not only the mechanical properties but also the corrosion mode and rate in a physiological environment. This thesis presents an original and thorough contribution on a very pertinent topic, the design, development, and validation of a new Fe/Mg2Si composites prepared powder metallurgy. The initial powders were prepared by different combinations of mixing and high energy ball milling processes and finally consolidated by hot rolling. Mechanical properties, microstructural features, as well as the corrosion performance, were extensively investigated in relation to the reinforcement size and distribution. The composites made of small size reinforcement particles showed a general increase in tensile strength. For instance, high energy ball milled samples exhibited better tensile performances (YS = 523 MPa, UTS = 630 MPa) while having the lower ductility (around 4%). A fundamental understanding of corrosion initiation, protective film formation, and growth on Fe-based materials and leads to a design of smarter and surface responsive biomaterials with modulable degradation rates, at distinct stages of the corrosion process. Here, the corrosion performance of Fe/Mg2Si composites varied with the reinforcement size and distribution. The predominant localized pitting corrosion in Fe/Mg2Si prepared by mixing was replaced by a more uniform pattern found in samples produced by mechanical milling. Further, it was found that Mg2Si plays a significant role in the composition and stability of the protective films formed during the static corrosion experiments. Fe/Mg2Si showed a higher corrosion rate compared to that of pure Fe at all stages of the corrosion experiment (1, 10, 20, 50 and 100 days). Moreover, the final degradation products varied with the substrate chemical composition and microstructure. In case of pure Fe, low solubility (Fe3(PO4)2) covered the entire surface, while Fe/Mg2Si exhibited the presence of carbonates at the latest stages of the test. The details about the degradation behaviour during long-term exposure times to the physiological environment highlighted in this work add a new knowledge on corrosion mechanism of degradable implant materials. In particular, the ability to tune mechanical and corrosion behavior of the composites as a function of reinforcement properties and manufacturing method was experimentally verified, highlighting the microstructure-corrosion property relationship.I biomateriali in ferro puro e in leghe a base di ferro presentano una combinazione interessante di proprietà meccaniche, elettrochimiche e biologiche; per questo motivo, questa classe di materiali metallici possono trovare utilizzo in applicazioni di tipo impiantistico biomedicale. Malgrado ciò, nonostante le sue soddisfacenti proprietà meccaniche, questo elemento impiegato allo stato puro mostra un inconveniente rilevante - un basso tasso di degradazione. L’oggetto di questa tesi è lo studio di un nuovo gruppo di materiali biodegradabili compositi a matrice ferrosa (Fe/Mg2Si), in cui il Fe costituisce la matrice e il Mg2Si è impiegato come rinforzo; questi materiali sono stati sviluppati con tecniche di metallurgia delle polveri, e presentano un, alta resistenza meccanica come caratteristica principale. Le polveri che costituiscono i materiali di partenza sono stati preparati con diverse combinazioni di procedure oltre al semplice mescolamento e/o high energy ball milling (macinatura in mulino a sfere a alta energia). Tutte le formulazioni preparate sono state compattate attraverso laminazione a caldo. Le proprietà meccaniche, le caratteristiche microstrutturali, la composizione delle fasi e le prestazioni in termini di corrosione sono state studiate dettagliatamente, in relazione alla dimensione delle particelle di rinforzo e della loro distribuzione. Lavori precedenti hanno confermato l’efficacia dell’aggiunta di una seconda fase, soprattutto se finemente dispersa, per aumentare il tasso di degradazione di materiali metallici per applicazioni biomedicali a base Fe: gli esperimenti condotti in questo lavoro hanno confermato che i compositi Fe/Mg2Si hanno mostrato, rispetto al Fe puro che compone la matrice, non solo una resistenza meccanica più elevata, ma anche un tasso di degradazione più alto negli esperimenti di laboratorio in vitro. Infine, i materiali ottenuti tramite high energy ball milling, presentano una resistenza alla trazione migliore (carico di snervamento= 523 MPa, resistenza alla trazione = 630 MPa), ma contemporaneamente una ridotta duttilità (circa 4%). Una attenzione particolare è stata posta nello studio degli effetti della presenza di Mg2Si sui meccanismi di corrosione.Tutti i compositi studiati hanno mostrato un tasso di degradazione più elevato rispetto alla matrice fabbricata con la stessa procedura; inoltre, la formazione del film di prodotti di degradazione sulla superficie del materiale cambiava in maniera rilevante in funzione della composizione chimica del substrato e della sua microstruttura. Nel caso del Fe puro, cristalli isolati di vivianite (Fe3(PO4)2) erano presenti su tutta la superficie, mentre carbonati di Fe si formavano principalmente sulla superficie dei compositi, specialmente negli ultimi stadi del processo di degradazione

Development of a hierarchical electrospun scaffold for ligament replacement

2018 Spring.Includes bibliographical references.The anterior cruciate ligament (ACL) is a dense collagenous structure that connects the femur to the tibia and is vital for joint stability. The ACL possesses complex time-dependent viscoelastic properties and functions primarily to prevent excessive translations and rotations of the tibia relative to the femur. It is estimated that 400,000 ACL tears occur in the United States annually and the monetary burden of these injuries and their subsequent treatment is approximately $1 billion annually. After injury allografts and autografts are commonly implanted to reconstruct the torn ACL in an attempt to restore joint stability, prevent pain, and limit damage to surrounding tissues. However surgical reconstructions fail to completely restore knee functionality or prevent additional injury and regardless of intervention technique radiographic osteoarthritis is present in 13% of patients 10 years after ACL rupture. Drawbacks to traditional treatments for ACL ruptures motivate the development of a synthetic ACL replacement. Tissue engineering is the use of a scaffold, cells, and signaling molecules to create a replacement for damaged tissue. The goal of this work is to develop a polymer scaffold that can be utilized as a replacement for the ACL. A tissue engineered ACL replacement should replicate the hierarchical structure of the native ACL, possess reasonable time zero mechanical properties, and promote the deposition of de novo collagenous tissue in vitro. Additionally, the scaffold should be implantable using standard surgical techniques and should maintain in situ tibiofemoral contact mechanics. Thus, four specific aims are proposed: 1) Fabricated and characterize an aligned 3-dimensional electrospun scaffold for ACL replacement. 2) Assess the in vitro behavior of ovine bone marrow-derived stems cells seeded on the scaffold in the presence of conjugated growth factor. 3) Evaluate the performance of the electrospun scaffold using uniaxial mechanical testing. 4) Assess the effect of the electrospun scaffold on ovine stifle joint contact mechanics. Development of a tissue engineered ACL replacement that mimics the structure and function of the native ACL would provide a novel treatment to improve outcomes of ACL injuries

Design, fabrication and control of soft robots

Conventionally, engineers have employed rigid materials to fabricate precise, predictable robotic systems, which are easily modelled as rigid members connected at discrete joints. Natural systems, however, often match or exceed the performance of robotic systems with deformable bodies. Cephalopods, for example, achieve amazing feats of manipulation and locomotion without a skeleton; even vertebrates such as humans achieve dynamic gaits by storing elastic energy in their compliant bones and soft tissues. Inspired by nature, engineers have begun to explore the design and control of soft-bodied robots composed of compliant materials. This Review discusses recent developments in the emerging field of soft robotics.National Science Foundation (U.S.) (Grant IIS-1226883

Triboelectric Effect Enabled Self-Powered, Point-of-Care Diagnostics: Opportunities for developing ASSURED and REASSURED devices

The use of rapid point-of-care (PoC) diagnostics in conjunction with physiological signal monitoring has seen tremendous progress in their availability and uptake, particularly in low- and middle-income countries (LMICs). However, to truly overcome infrastructural and resource constraints, there is an urgent need for self-powered devices which can enable on-demand and/or continuous monitoring of patients. The past decade has seen the rapid rise of triboelectric nanogenerators (TENGs) as the choice for high-efficiency energy harvesting for developing self-powered systems as well as for use as sensors. This review provides an overview of the current state of the art of such wearable sensors and end-to-end solutions for physiological and biomarker monitoring. We further discuss the current constraints and bottlenecks of these devices and systems and provide an outlook on the development of TENG-enabled PoC/monitoring devices that could eventually meet criteria formulated specifically for use in LMICs.Ulster Universityhttp://www.mdpi.com/journal/micromachineshj2021Electrical, Electronic and Computer Engineerin

The mechanical testing of single nanofiber

Polymer nanofibers exhibit properties that make them a favorable material for the development of tissue engineering scaffolds, filtration devices, sensors, and high strength lightweight materials. Perfectly aligned PLLA Nanofibers were fabricated by an electrospinning technique under optimum conditions and the diameter of the electrospun fibers can easily be tailored by adjusting the concentration of the polymer solution. To align the nanofibers, special arrangement was made in terms of two aluminum plates. Good alignment of polymer nanofibers on specimen was confirmed by SEM observation. The effect of different electro-spinning parameters on maximum fiber length, average fiber diameter, diameter uniformity, and fiber quality was explored in this study. The force applied on the nanofiber was measured with the help of AFM by satisfying Hooke\u27s Law. The elastic properties of PLLA nanofiber were investigated with the atomic force microscope (AFM). The elasticity was calculated by analyzing the recorded force curves with the help of the Hertz model. Mechanical testing confirmed that the single aligned nanofiber can be an advancement in the commercial applications of nanofibers

Biodegradable electronics; materials and current approaches

This master’s thesis is a part of ‘Human Spare Parts’ research program by BioMediTech. The aim of the research program is to integrate different branches of biomedical engineering and stem cell research to discover new and better therapies and treatments. However, this thesis concentrates on biomaterials and sensor technology. The first part of the thesis, entitled the theoretical part is dedicated to a detailed investigation of the biodegradable electronics. This part gives an introduction to materials, existing technologies and area of applications. Polymers as organic materials, biodegradable materials, their classifications, and scope for biodegradable electronics are discussed in this part. A discussion of currently developed devices for medical and other applications are also documented. New organic materials such as, conducting, semiconducting and dielectric polymers have been developed for the facilitation of biodegradable electronics. Their ease in processing and fabricating has made them a potential candidate for organic electronics. Inorganic materials are being used as well, but the dependence is reducing with the emergence of new materials. Extremely flexible, bendable, thermally well stable and fully degradable electronic components have been demonstrated successfully. The second part of the thesis involves an experimental part. The feasibility of biodegradable encapsulation of LC resonance sensor and reliability of extractable features to monitor the water absorption and degradation processes in the polymeric materials were studied. Biodegradable encapsulation of polycaprolactone (PCL) was found to be a potential candidate for such sensor configurations. PCL exhibited a low processing temperature and was found to be stabilized after taking up water into its matrix. Based on the results, further studies are needed in order to sort out prospects in biosensor technology based on the concept of biodegradable encapsulation of LC resonance circuit