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Compatibility of piezoelectric semicrystalline polymerand osteoblastic cells
Havlíková, Tereza
For the improvement of tissue regeneration,functional polymer scaffolds that can mimic the extracellularmatrix of human tissue are extremely desirable. Depending on thetissue that the scaffolds are intended to resemble, these scaffoldsmust satisfy highly precise requirements such as non-toxicity orfibrous structure. High piezoelectricity and hydrophilicity alsoproved to have convenient effects. Due to their innate capability tocreate surface charges under mechanical stress, piezoelectricmaterials such as polyvinylidene fluoride (PVDF) become excellentcandidates for creating functional scaffolds. It is desired for PVDFto also have hydrophilic properties. Otherwise, it could preventadequate cell adhesion and growth necessary for the constructionof biomimetic scaffolds. For this study, electrospinned PVDFnanofibers covered by human or mouse osteoblasts were subjectedto Raman spectroscopy, measurement of the contact angle of theliquid wettability on the sample surface to observe hydrophobicityand hydrophilicity, and scanning electron microscopy (SEM) toassess properties of the material in relation to oxygen plasmatreatment.
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Measuring the Parameters of Piezo Energy Harvesters
Kunz, Jan ; Novák,, Martin (referee) ; Hadaš, Zdeněk (referee) ; Beneš, Petr (advisor)
This dissertation deals with the measurement of piezoenergy harvester parameters, in particular the measurement of their efficiency. The first part of the thesis summarizes important metrics for their comparison and reviews existing measurement systems for measuring harvester performance parameters. The measurement of harvester efficiency is simplified due to the complexity of power measurement and harvester efficiency is calculated from its parameters. However, this method is not accurate because it neglects mechanical losses and has a large measurement uncertainty. For this reason, the main objective of this work is to find a way to directly measure the harvester power input and thus measure its efficiency by definition, i.e. including mechanical losses. By analyzing the power flow in the harvester power chain, a way to achieve this goal has been found. Then, I have created an automated measurement system that allows to measure the harvester power parameters and also its efficiency including the determination of measurement uncertainties. In the last section, the performance, parameters and especially the two types of efficiency for commercially available harvesters are compared. As expected, the efficiency evaluated according to the definition come out smaller than in the case of its simplified version. However, this ratio varies widely for different harvester types, with the new efficiency being approximately one-third for PZT harvesters but only one-hundredth for PVDF harvesters. This significant difference shows that the different types of harvesters have large differences in mechanical losses, this difference could not be measured until now and thus remained neglected.
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Electrospinning and characterization of fibrous structure for piezoapplications
Svobodová, Anežka ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
The master’s thesis deals with the preparation and characterization of PVDF-based composite fibrous layers prepared by electrospinning. Ceramic particles TiO2, BaTiO3 and BCZT were used as fillers. The fibers were prepared containing 10, 20, 30, 40 and 50% of these particles and then their morphology, piezoactive phase representation and dielectric characterization were characterized. The effect of the presence of particles on the fiber diameter and on the crystallinity fraction of the polymer was shown. Particle size significantly influenced their distribution in the fibers. Piezoelectric particles further influenced the content of electroactive phases beta and gamma. The highest proportion of electroactive phases was determined in BaTiO3 filled fibers, which reached up to 98%. For the BaTiO3 filled fibers, the dielectric constant values were also measured, which reached lower values than expected due to the high porosity of the prepared fibers The as-prepared fibers can be considered promising not only for piezoapplications, therefore, optimization of their preparation and measurement of electrical characteristics will be further studied.
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Characterization and preparation of PVDF nanofiber matrices for wearable electronics
Zajacová, Lucia ; Papež, Nikola (referee) ; Macků, Robert (advisor)
The presented bachelor thesis deals with the process of production PVDF nanofiber matrices uising electrospinning and subsequent electrical characterization of the produced material. At the beginning, it introduces nanotechnologies and their undeniable importance in medical applications. It focuses on the influence of process parameters, production enviroment and the very properties of the spinning solution itself, leading to final character of the spun fiber. Various morphological differences obtained by individual process settings then continue to influence their piezoelectric properties, which are the subject of the reaserch in the experimental part of this thesis. The obtained results are applied to devices uising the piezoelectric effect with the potential for application in the biotechnological fields.
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Triboelectric Sensing Systems
Riha, David
Triboelectric phenomenon, historically, is one of many problems which engineers wantedto be avoid. However nowadays this phenomenon seems to be useful source of electrical signalfor displacement measurement. In this work all sensing elements are made from pure PVDF byelectrospinning manufacturing method. Nano fibres, which are result of the process are placed toaluminium foil naturally without mechanical rectifying. Used material was tested only for triboelectriccharge generation, although piezoelectric phenomenon was expected. We were not able toquantify it by standard methods, probably due to chaotic structure and fabric behaviour of the finalproduct. Triboelectric phenomenon is possible to measure directly, and systems are more predictable.Finally, two modes were tested, and potential advantages and disadvantages were qualified.
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Energy Dispersive X-Ray Spectroscopy Of Doped PVDF Fibers
Smejkalová, Tereza
This work aims to further improve properties of Polyvinylidene fluoride (PVDF), one ofthe most promising electroactive polymers, by the inclusion of powders of piezoactive materials.PVDF was formed by electrospinning into fibres with a thickness of 0.5 – 1.5μm and then examinedin a scanning electron microscope including energy-dispersive X-ray spectroscopy. The obtainedproperties of doped PVDF could be used in the design of sensors. Before that, it is essentialto perform a series of analysis to support or deny the use of adjusted fibres for sensor design.
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Pvdf —AN Ideal Candidate For Use In Nanogenerators
Pisarenko, Tatiana
In this work, the PVDF composite, also known as polyvinylidene fluoride in the formof thin nanofibres, was created. Subsequently, a single-fibre characterization was performed, whichproves its piezoelectric properties and describes its structure. Electron microscopy, atomic forcemicroscopy and X-ray photoelectron spectroscopy were chosen as characterization methods. Thediscussion in this paper deals with the ability of these fibres to use PVDF as a nanogenerator.
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Characterization Of Pvdf Nanofibers Created By The Electrospinning Method
Pisarenko, Tatiana
The work investigates structure and properties of composite fibers created by the electrospinning method for piezoapplications. Polyvinylidene fluoride (PVDF) was used as a precursor. As an electrospining parameter, the collector speed of 300 and 2000 rpm was selected, which significantly affects the properties of nanofibers. The structure of fibers was investigated by scanning electron microscopy (SEM) using focused ion beam (FIB). Morphology and piezoelectric domains was observed using piezoresponse force microscopy (PFM). Phase composition was identified using Raman spectroscopy and by Fourier-transform infrared spectroscopy (FTIR). Found results are essential for the design and construction of piezoelectric based structures.
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Characterization of PVDF material in nanoscale resolution
Pisarenko, Tatiana ; Dallaev, Rashid (referee) ; Sobola, Dinara (advisor)
Tato práce se zabývá charakterizací nanovláken na bázi polyvinylidenfluoridu. Zaměření práce je na piezoelektrické vlastnosti vlákna, které jsou studovány metodou piezoelektrické silové mikroskopie. Takto byly měřeny dva typy odlišných vzorků, které se lišily v parametrech výroby. Odlišnosti vláken v jejich fázovém složení byly také zkoumány za využití Ramanovy spektroskopie a infračervené spektroskopie s Fourierovou transformací. Chemická analýza povrchu a jeho stavu proběhla pomocí rentgenové fotoelektronové spektroskopie. Různé uspořádání nanovláken spolu s jejich průřezem bylo pozorováno rastrovacím elektronovým mikroskopem za využití fokusovaného iontového svazku. Rovněž byla zkoumána smáčivost a kontaktní úhel povrchu vzorků s demineralizovanou vodou. Bylo zjištěno, že vyšší rychlost otáček válce během procesu elektrostatického zvlákňování má velmi významný vliv na jejich uspořádání a tím i na parametry ovlivňující tvorbu piezoelektrického jevu a dalších materiálových vlastností.
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Electrospun fibers based on PVDF and nylon
Černohorský, Petr ; Sobola, Dinara (referee) ; Papež, Nikola (advisor)
Polymer nanofibers used for the construction of triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are new and promising technologies for energy recovery. Thanks to the generation of electrical energy based on mechanical movement (deformation), these fibers can find application in the field of self-powered electronic devices. In this work, three nanofibrous structures of materials were prepared by electrostatic spinning: pure polyvinylidene fluoride (PVDF), pure polyamide-6 (PA6) and their mixed combination PVDF / PA6. Non-destructive analyzes such as Raman spectroscopy, FTIR, XPS and electron microscopy were used to study the properties of nanofibers. Analyzes confirmed the positive effect of electrostatic spinning of polymers on the support of the formation of highly polar crystalline -phase in PVDF and , -phase in PA6. The structure arrangement of the nanofibrous material and their defects were observed by scanning electron microscopy (SEM). Furthermore, the contact angle of the wettability of the liquid on the surface was measured for the materials, and the permittivity was measured to monitor the dielectric properties. The described results make the mixed material PVDF / PA6 very promising for further research in the field of nanogenerators and functional textiles.
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