National Repository of Grey Literature 49 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Tribology of hydrogels for articular cartilage replacement
Křížová, Michaela ; Ranuša, Matúš (referee) ; Vrbka, Martin (advisor)
The bachelor's thesis deals with the description of the tribological properties of focal joint implants in the place of a cartilage defect. The application of focal implants is aimed at a group of younger patients who have to undergo surgery to repair damaged cartilage, but a total replacement is not suitable for them due to its lifetime. The contact of the focal implant and the opposite cartilage was simulated using metal samples and hydrogel, which has very similar properties to natural cartilage. For a possible comparison of values, a tribological measurement of the cartilage samples against the hydrogel was carried out. This pair serves as a model for defining friction in a healthy joint. The main task of this thesis was to determine the coefficient of friction of Ti6Al4V, Ti6Al4V+DLC, CoCrMo and cartilage against the hydrogel. The experiments were carried out using a tribometer in a pin-on-plate configuration. The Ti6Al4V alloy without coating and with DLC coating came out with the lowest coefficient of friction for both variants, almost identically 0.0526. Higher friction was measured for CoCrMo, but it differed from the titanium alloy to one-hundredth. On the contrary, the highest coefficient of friction was unexpectedly manifested in the cartilage samples, where the lowest friction was assumed. The error was due to poor selection of cartilage samples. The thesis simply describes the tribological behaviour of focal implants and the result is a material with the lowest coefficient of friction. The measurements performed could help further research into the issue of focal implants.
Design of a simulator for studying eye friction and lubrication
Snopek, Lukáš ; Horák, Zdeněk (referee) ; Vrbka, Martin (advisor)
This work deals with the design of a tribometer, which simulates the interaction between the human eye and the eyelid, and simultaneously measures the friction between them and the thickness of the tear film. The tribometer will be used for research and development of artificial tears based on hyaluronic acid. The aim of the work was to design experimental conditions, conceptual and design solutions, as well as to ensure the production, assembly, and validation of the device. The experimental conditions were determined based on critical research. Four different conceptual solutions were proposed, of which two were selected for further development in the design solution. Based on the engineering documentation, the production of non-standardized components and assembly were ensured. Validation experiments demonstrated that the simulator enables the measurement of friction and tear film thickness at the contact area under the desired conditions, with both conforming and non-conforming types of contact. The contribution of this work lies in the construction of a new device that allows for measuring the coefficient of friction and film thickness during conforming contact, offering new opportunities in the study of human eye biotribology.
Friction and lubrication of fascia
Chmelík, Jiří ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
The diploma thesis was part of the project "Regeneration and lubrication of fascia with hyaluronan" of the company Contipro a.s., whose main goal is the development of an injectable medicinal product. The number of patients suffering from so-called myofascial lower back pain is increasing. The cause of the pain is increased hyaluronic acid, which is produced between the layers of the fascia. If the viscosity is low, the fascia layers are not affected and the coefficient of friction is low. The purpose of the product is to improve the sliding movement of the fascia and relieve patients of pain. The main component of the medicine is hyaluronic acid. The project included rheological and tribological analysis of hyaluronic acid samples. A tribological model of fascia in a pin-on-plate configuration was created for the analysis of the coefficient of friction. Based on the fascia models used, the dependence between the coefficient of friction and viscosity of native hyaluronic acid solutions was found. For models and real fascias, the native solution (Bonharen) was found to have better friction properties than hyaluronic acid derivatives. These analyzes have contributed not only to the development of the drug, but also to the emergence of other studies that would like to address the biotribology of fascia.
Comparison of frictional properties of cosmetic massage products
Dohnal, Petr ; Čípek, Pavel (referee) ; Vrbka, Martin (advisor)
This bachelor’s thesis examines tribological properties of massage products (creams and oils). Its aim is to create a comparison of the selected products. Tribometer in the pin-on-plate configuration was used for the experiment because of its ability to simulate the process of rubbing the product on the skin. Cowhide was used as a model of human skin. The attributes of products were compared based on the characteristics of the coefficient of friction during the measurements. Through the experiments a suitable parameter was found for easy comparison of the product's durability. According to the results the best oil was selected in terms of durability and lubrication. The thesis could be used as a basis for creating a standardised method for evaluation and selection of products suitable for massage purposes.
Effect of toothpaste abrasiveness on friction and wear of dental fillings
Formánková, Pavla ; Čípek, Pavel (referee) ; Vrbka, Martin (advisor)
This bachelor thesis dealt with research, that links dental hygiene issues with tribology. The aim of the thesis was to analyze the effect of abrasive particles of toothpastes on friction and wear of dental fillings. The friction coefficient was evaluated in a tooth brushing simulation on an UMT TriboLab tribometer that lasted 260 minutes. The tribological system consisted of a toothbrush, a sample of composite material and a solution of artificial saliva with a selected toothpaste. Each paste was defined by an RDA value from 0 to 250, expressing the degree of abrasiveness therefore the ability of the toothpastes to wear the material. Wear was analysed on a Bruker Contour GT-X optical profilometer. From the measured values it was found that the influence of abrasive particles is significant in terms of wear of dental fillings. For both the friction coefficient and the material loss when measured only in the presence of artificial saliva, the resulting values were generally lower. However, the material loss in the toothpastes measurments did not increase linearly with the RDA value as expected. Literature studies and measurements have shown that this may be due to other factors affecting wear. Future research on these factors could lead to the selection of more gentle toothpastes in dentistry and thus prevent the increase in wear of dental fillings
The Effect of Synovial Fluid Constituents on Friction and Lubrication of Articular Cartilage
Čípek, Pavel ; Dr. Prashant K. Sharma (referee) ; Muňoz, Anna Neus Igual (referee) ; Vrbka, Martin (advisor)
Práce se zabývá problematikou biotribologie modelu synoviálního kloubu. Cílem práce je popsat vliv složek synoviální kapaliny na formování mazacího filmu v modelu synoviálního kloubu. Práce je zaměřena na experimentální analýzu součinitele smykového tření a jeho propojení s pozorováním adsorbovaného mazacího filmu v kontaktu pomocí fluorescenční mikroskopie. Součástí práce je návrh tribometru, který umožňuje vizualizaci v průběhu experimentů. Tribometr je vyroben, kalibrován a verifikován pomocí komerčního tribometru. Dále je součástí práce návrh metodiky experimentů včetně návrhu postupu pro zpracování a hodnocení výsledků. Pro zpracování záznamu z vizualizace kontaktu byl navržen speciální software, který pracuje na principu segmentace obrazu. Poslední část práce je zaměřena na aplikaci vyvinuté metodologie spolu s nově navrženým tribometrem, což umožňuje posoudit roli složek modelové kapaliny u formování mazacího filmu v modelu synoviálního kloubu. Experimentální část je založena na měření tření za současné vizualizace kontaktu. Tato práce prezentuje originální výsledky rozšiřující oblast biotribologie synoviálního kloubu, které mohou pomoci dalšímu rozvoji účinné léčby pacientů s nemocnými klouby.
Effect of Viscosupplementation on Friction of Articular Cartilage
Rebenda, David ; Sawae, Yoshinori (referee) ; PhD, Axel C Moore, (referee) ; Vrbka, Martin (advisor)
Disertační práce se zabývá experimentálním studiem viskosuplementů na bázi kyseliny hyaluronové, které se aplikují do synoviálních kloubů postižených osteoartrózou. Hlavní pozornost byla věnována objasnění vlivu koncentrace a molekulové hmotnosti kyseliny hyaluronové na tření v kontaktu kloubí chrupavky resp. změnám tření v kontaktu po smíchání osteoartritické synoviální kapaliny s exogenní kyselinou hyaluronovou. Důležitou součástí experimentů bylo rovněž studium reologických vlastností synoviální kapaliny a kyseliny hyaluronové. Výsledky ukázaly, že molekulová hmotnost kyseliny hyaluronové významně ovlivňuje viskozitu a viskoelastické vlastnosti roztoku. Výrazná závislost mezi reologickými vlastnostmi kyseliny hyaluronové a třením v kontaktu však nebyla pozorována. Přimíchání kyseliny hyaluronové do synoviální kapaliny způsobí výrazný pokles součinitele tření v kontaktu. Rozdíly mezi viskosuplementy obsahující kyselinu hyaluronovou s různou molekulovou hmotností ale nijak výrazné nejsou. Nicméně, výsledky poukazují na možné ovlivnění režimu mazání v důsledku vysoké molekulové hmotnosti kyseliny hyaluronové. Tyto původní výsledky rozšiřují pochopení mechanizmů, ke kterým dochází v kloubu bezprostředně do vstříknutí kyseliny hyaluronové a mohou být použity při dalším vývoji viskosuplementů či v klinické praxi.
THE BIOCHEMICAL PROCESS OF LUBRICANT FILM FORMATION INSIDE HIP JOINT REPLACEMENT
Rufaqua, Risha ; Ruggiero,, Alessandro (referee) ; Muoz, Anna Neus Igual (referee) ; Vrbka, Martin (advisor)
The dissertation thesis deals with the lubricant film formation chemistry on hip implant material surfaces with synovial fluid components. Biochemical and tribological properties of synovial fluid after joint replacement are focused, precisely on the chemical composition of the formed lubricating film and chemical structural changes of the associated constituents under mechanical loading. Nevertheless, the synovial fluid components‘ chemical structural changes after the joint replacement are rarely addressed and require further attention. Including metal and ceramics, various combination implant materials were applied within the lubricants of synovial fluid constituents separately and different model synovial fluids to reveal the biochemical reactions and frictional coefficients for understanding the possible lubrication mechanism. Raman Spectroscopic technique is manifested as the most appropriate method to explain the biochemical behaviour of synovial fluid and chemisorption on the surface of the implant material. The method is depicted presenting two different studies focusing on the chemical structure of the synovial fluid film on the implant surface and frictional coefficient measurement of the contact pair within the artificial hip joint. This latest methodological precedent also facilitates to evaluate the chemical structural change of the synovial fluid due to the tribological activity in the hip prosthesis. The thesis expounds original results concerning biotribology to increase the depth of knowledge on joint replacement procedure and to enhance the longevity of the orthopaedic implantations.
Design of a simulator module for analysis of friction and wear of teeth during cleaning
Snopek, Lukáš ; Streďanská, Alexandra (referee) ; Vrbka, Martin (advisor)
This thesis focuses on the design of a module for the tribological simulator Bruker UMT TriboLab, which will be used in research in the field of analysis of wear of hard dental tissues and filling materials due to tooth cleaning. The aim of this work was the design of experimental conditions, module construction, creation of drawing documentation, production and subsequent implementation of a validation experiment. The conditions of the experiment were determined on the basis of research and to create an optimal design solution, prototypes were continuously produced using the 3D printing method. Finally, two toothbrush fixtures and two dental filling sample fixtures were made based on the drawing documentation. Subsequent assembly of the fixtures and the implementation of the experiment on the tribometer verified their functionality, which makes it possible to declare all the goals successfully met. Now these fixtures will be part of several research tasks in the field of oral biotribology.
Biotribology of artificial tears for the treatment of dry eye syndrome
Černohlávek, Mikuláš ; Daniel, Matej (referee) ; Vrbka, Martin (advisor)
This master thesis is a part of the project TAČR TREND, which aim is the development of new ingredient for treatment of dry eye syndrome. Developed ingredient is derivative of hyaluronic acid, which is in this thesis compared with native hyaluronic acids and commercial eye drops. Aim of this thesis is to describe rheological and tribological properties of measured samples in terms of viscosity, mucoadhesivity and coefficient of friction. Coefficient of friction was measured on created tribological model of the eye in pin-on-plate configuration which represents physiologically relevant sliding speeds of blinking. Comparison with native hyaluronic acids and commercial products of eye drops showed, that derivative reaches higher values of viscosity, has mucoahesive properties and has low values of coefficient of friction. Those key parameters show that modification of hyaluronic acid is promising way for drug development for dry eye disease.

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