|
|
3d shaping of UV curable ceramic feedstock
Mišák, Jiří ; Salamon, David (oponent) ; Graule, Thomas (vedoucí práce)
The aim of this study was the development of printable, UV curable colloidal pastes for 3D robotic deposition of complex ceramic fibre networks. Additionally, shaping techniques of printed structures have been demonstrated. Printable and functional ceramic pastes based on hydroxyapatite have been successfully developed from UV curable compositions. Complex printed ceramic fibre networks and multilayers as well as enhancement of the fibre surface quality have been realised. It has been found that the control of particle-monomer/oligomer-surfactant interactions is essential to achieve printable pastes with adequate rheological properties. Using linear and cross-linking UV curable oligomers as dispersion media, very flexible structures result after UV curing. All printed, cured and additionally shaped structures have been transformed to macroscopic ceramics via thermal debinding and sintering without cracks or delamination between the layers. This has been achieved by using argon atmosphere during curing to prevent oxygen inhibition. The 3D robotic deposition in combination with UV curing is a novel and promising technique to produce complex functional ceramic structures. In this work, the benefits from the combination of 3D robotic deposition and UV solidification have been demonstrated in a new way by using cured and flexible 2 layer structures for folding processes, which lead to 3D structures that are very difficult or impossible to achieve with the employment of just direct 3D robotic deposition. On the basis of this research, versatile theory about preparing ceramic pastes for 3D robotic deposition of complex structures for various applications can be deduced.
|
|
|
Synthesis of foamed bioceramics for potential medical applications
Doboš, Petr ; Šoukal, František (oponent) ; Palou, Martin (vedoucí práce)
The main aims of the diploma work were focused on the preparation of porous hydroxyapatite ceramics for potential biomedical applications. Hydroxyapatite slurries were synthesized by sol-gel and precipitation method. Then, the slurries were dried and calcinated at 1000 °C for phase control. These samples of HAP were analyzed by SEM, FTIR, and XRD. To prepare apatite porous ceramics, the slurries were foamed by polymeric sponge method and direct foaming method including (polymeric expancel and glass bubbles). The sintering temperature was established after 1000 °C by sponge method and 1200 °C by direct foaming. The microstructure measurement by SEM and structure analysis by MIP of both porous hydroxyaptite indicates the regular porosity including macro, meso and micropores with different pore size distribution. The average size of pores prepared by sponge method is found between 1-5 µm with mono-dispersed porosity. The total porosity is 63.5 % with the total surface area 3.048 1 m/g. Porous hydroxyapatite prepared from expancel showed a poly-dispersed porosity with three main areas: 50–100 µm, 5–10 µm and the third one in range 0.5–1 µm, respectively. The total porosity is 67.6 % with total surface area 19.090 3 m/g. The bioactivity of both was tested in SBF for 7 days. It was found that in precipitation method was observed non-compact bioactive layer. The results were measered by SEM analysis.
|
|
|
Rheological properties of biodegradable thermosensitive copolymers
Chamradová, Ivana ; Poláček, Petr (oponent) ; Vojtová, Lucy (vedoucí práce)
The general goal of the proposed diploma work was preparation, characterization and rheological study of well-defined “smart” injectable hydrogels from biodegradable, biocompatible, controlled life-time copolymers based on hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(lactic acid)—co—poly(glycolic acid) (PLA/PGA) copolymer. Resulted thermosensitive PLGA—PEG—PLGA copolymer, which gels at body temperature, was additionally functionalized by itaconic anhydride (ITA) from renewable resources, bringing both reactive carbon double bonds and functional —COOH groups to polymer ends. Additionally, the PLGA—PEG—PLGA copolymer was modified by inorganic bioactive hydroxyapatite (HAp) for usage as injectable bone bioadhesive. Both functionalized ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp polymer composite affected rheological properties of original PLGA—PEG—PLGA copolymer deciding whether or not would be the new polymeric material suitable as injectable drug carrier or bone adhesive in medical applications. Experimental part of this thesis describes mainly characterization of viscoelastic properties of both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymer by test tube inverting method (TTIM) and dynamic rheological analysis. Advantage of TTIM is sol-gel visualization with determination of the critical gelation temperature and the critical gelation concentration. The rheological measurements provide information about viscosity and elasticity of the gel by the changes storage (G´) and loss (G´´) modulus. The prepared copolymers were additionally characterized by 1H NMR and GPC. Surface and HAp particles size was determined by both SEM and Laser Particles Size Analyzer. Both unmodified and ITA or HAp modified PLGA—PEG—PLGA copolymers exhibited sol-gel transitions induced by increasing temperature. Rheological properties of copolymers’ 6 to 24 wt% water solutions investigated either by TTIM or by rheometer were in good agreement. Evaluating by rheometer, the copolymers showed two cross-points, where G´= G´´. The first one very well corresponded with the first sol-gel transition found via TTIM. The maximum values of G´ representing the highest gel stiffness lie in the white gel observed by TTIM. The second cross-point constituted to the gel-suspension transition where white polymer is precipitated from the water. The gel stiffness grows with increasing polymer concentration in water. In comparison, ITA modification or addition of HAp (0, 10, 20, 30, 40, 50 wt%) caused increasing the gel stiffness of unmodified PLGA—PEG—PLGA copolymer and approximating the temperature of G´max closer to body temperature (37 °C). Investigated both ITA/PLGA—PEG—PLGA/ITA copolymer and PLGA—PEG—PLGA/HAp composite were proved to be suitable candidates as injectable systems for drug delivery or regenerative medicine in orthopedics or dental applications, respectively.
|
|
|
Reologie hydrogelů kolagenu a jeho nanokompozitů
Voldánová, Michaela ; Vojtová, Lucy (oponent) ; Jančář, Josef (vedoucí práce)
Tato bakalářská práce směřuje k fenomenologickému popisu reologického chování čistého kolagenu I i jeho nanokompozitů s příměsí hydroxyapatitu ve čtyřech koncentracích. Měření bylo prováděno na reometru v konfiguraci kužel – deska pro rozsah smykových rychlostí od 0 s-1 do 100 s-1 za definovaných podmínek. Při teplotě 4 °C je kolagen ve vzorcích o daném složení rozpuštěn, zachovává si zde svůj nativní charakter a prekurzory hydrogelů setrvávají v kapalném stavu. Zahříváním vodného roztoku kolagenu o neutrálním pH dochází k spontánnímu procesu zesítění do fibrilárních struktur. Při 37 °C fibrily dorůstají do struktury gelu, ovšem rychlost jeho vzniku je závislá na obsahu kolagenových vláken. Naměřená data jsou zpracována ve formě tokových a viskozitních křivek, z nichž je vyhodnoceno a porovnáno reologické chování vzorků či strukturální a transformační změny jako odezva na mechanické zatížení a změnu teploty. Tyto poznatky mohou být využity při manipulaci s hydrogely. Obecně mohou posloužit jako základ pro další výzkum kolagenu, jeho interakcí s HAP a faktorů ovlivňujících jejich stabilitu či účinnost.
|
|
|
Stress-strain analysis of skull implant
Hřičiště, Michal ; Borák, Libor (oponent) ; Marcián, Petr (vedoucí práce)
Cranial implants are used as a substitute for parts of cranial bones that lost its function due to trauma or disease. An important factor, that influences function of the cranial implant structure, is its mechanical behavior. This thesis briefly summarizes current knowledge in the field of cranial defect reconstruction and provides comparison of different types of materials and implant wall shapes, based on stress-strain analysis of Computer Tomography based neurocranial model with placed implant and loaded by intracranial pressure and external load.
|
|
|
Studium biokeramických materiálů na bázi fosforečnanů vápenatých
Kolář, Martin ; Maca, Karel (oponent) ; Cihlář, Jaroslav (vedoucí práce)
Byla připravena rešerše na téma „Biokeramické materiály“ se zaměřením na vrstevnaté biomateriály na bázi fosforečnanů vápenatých. Na základě získaných informací byly navrženy a provedeny experimenty přípravy vrstevnatých materiálů na bázi fosforečnanů vápenatých metodou spin-coating se zaměřením na optimalizaci podmínek nanášení vrstev. Dále byly provedeny experimenty přípravy objemové hydroxyapatitové keramiky uniaxiálním lisováním s následným tepelným zpracovaním. Připravená vrstevnatá a objemová keramika byla hodnocena z hlediska bioaktivních vlastností testováním interakcí se simulovanou tělní tekutinou.
|
|
|
Příprava biokeramických materiálů pro medicínské aplikace
Doboš, Petr ; Šoukal, František (oponent) ; Palou, Martin (vedoucí práce)
Cílem práce bylo připravit vzorky práškového hydroxyapatitu pomocí sol-gel a precipitační metody. Po syntéze byly prášky vylisovány a vypáleny při teplotách 500 °C, 800 °C a 1100 °C. Vzorky HAP byly podrobeny analýze FTIR, XRD, SEM. Výsledné měření poukazuje na velikost HAP částic v rozmezí mikro až nano rozměrů. Průměrná velikost dominantních zrn je v oblasti kolem 5 – 8 µm pokryté menšími částicemi o rozměru 1 µm. Byla sledována mikrostruktura materiálu a bioaktivita in vitro v simulovaném krevním roztoku po 4 týdnech. Bioaktivita byla ovlivněna teplotou výpalu, od které závisí mikrostruktura. Je zřejmé, že tloušťka vrstvy hydroxyapatitu na povrchu roste s teplotou výpalu.
|
|
|
Particulate composites based on nano HA/TCP particles for bone graft replacements
Suchý, Tomáš ; Rýglová, Šárka ; Balík, Karel ; Sucharda, Zbyněk ; Denk, F.
Particulate composite materials have been developed for applications in the form of an intervertebral cage (for use in spine treatment). The intervertebral cage is composed of a bearing cage made of PEEK and a composite core with the surface contacting the bone surface and ensuring elastic linkage of two vertebral bodies, resulting in good adhesion to the bone. Mechanical analysis of different kinds of particulate composites was performed. The effect of hydroxyapatite and tri-calcium phosphate nanofiller volume fractions on the mechanical properties of particulate composites was investigated.
|
|
|
Biocompatibility optimization of fabric composites by calcium phosphates
Sochor, M. ; Balík, Karel ; Suchý, Tomáš ; Sucharda, Zbyněk
Composite materials based on a polyamide fabric and a polydimethylsiloxane matrix were designed for application in bone surgery. In order to increase the bioactivity, 2, 5, 10, 15, 20 and 25 vol. % of nano/micro hydroxyapatite and tricalcium phosphate were added. The effect of the additives on the mechanical properties was studied. Simultaneously, changes in the inner structure of the composites were investigated by means of image analysis.
|
|
| |
host ::
RSS.