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Atomic force microscopy of soft materials
Šudáková, Anna ; Havlíková, Martina (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on atomic force microscopy (AFM), mainly on studying the measurement procedure and optimalization of measurement conditions with future perspective on imaging hydrogels and measuring mechanical properties (such as adhesion or stiffness) of hydrogels and semi-rigid materials at the microlevel. Atomic force microscopy is gaining significant importance in research due to its versatility, when it can provide topographical image of conductive and non-conductive samples while measuring mechanical properties of the samples, such as adhesion, elasticity or stiffness. Advantage of AFM method is that it can provide mechanical properties of the samples not only on macro levels as we are used to, for example, from rheology, but also on local level. Optimalization was performed on standard sample, one micrometre polystyrene nanoparticles , when the individual modes were measured, such as non-contact (AC Mode Imaging) mode and quantitative mode (QITM Advanced Imaging). This was followed by the measurement of a PVA foils, the measurement was performed because they are xerogels and will be studied more in the future. They were made with polyvinyl alcohol and chitosan. The internal environment of the hydrogels has been modified by adjusting the pH (NaOH) or by changing the ionic strength (NaCl). Furthermore, the effect of freezing on the PVA foils was observed, it is one of the possible ways of preparation of physically linked hydrogels. This work also examines the effect of porosity on concentration of physically linked thermoreversible agarose gels.
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The utilization of atomic force microscopy for study on hydrogels
Lišková, Kateřina ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
The presented bachelor thesis deals with the study of atomic force microscopy (AFM), especially the optimization of the measuring procedure for imaging the surface of variously crosslinked hydrogels in the hydrated state. The most attention was given to the physically crosslinked polysaccharide hydrogel (termoreversible agarose) in hydrated state, where the surface of the samples with mass concentration of 4, 2, 1, 0,75 and 0,5 % was measured. Subsequently, the surface of the ionically crosslinked 2 % alginate gel with calcium ions was measured. Based on a literature research, measurements were performed in water using the method of quantitative imaging (QITM Advanced Imaging), which is especially suitable for soft samples with uneven surfaces. Multiple cantilever were tested for measurement, finally the SNL-10 cantilever was selected, which showed versatility for imaging samples in any measuring environment, especially aqueous. The pore sizes of the agarose hydrogels were monitored by image analysis ImageJ. For the measurement of hydrogels in the swollen state, the procedure of measuring their surface using atomic force microscopy has been optimized, but for different types of hydrogels, individual optimization of both preparation and instrument setup will be required.
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Cross-correlation of mechanical properties of hydrogels on micro/macro-scale studied by atomic force microscopy and oscillation rheometry
Kuzník, Pavel ; Szabová, Jana (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on measurement of mechanical properties of hydrogels on local and macroscopic level by atomic force microscopy (AFM) and oscillation rheometry. Both techniques allows measurement of hydrogel in hydrated state which provides native state of measured samples and prevents them from inserting artefacts into measurements made by AFM, which could negatively change measured values. AFM has more measuring modes, but for measurement in this bachelor thesis was used tapping mode called Contact mode force mapping. The largest part of this work is concentrated on measurement of agarose hydrogel, which pertains to category of physical hydrogels, concretely concentration line and time dependency (syneresis of hydrogel) were measured by both techniques. Suitability of AFM for measuring of mechanical properties of hydrogels was tested on other hydrogel samples with different type of crosslinking. Hydrogel based on sodium alginate crosslinked by calcium ionts (Ca2+) was tested. Furthermore were measured two chemical gels including polyethylenglycol (PEG) hydrogel and organogel of ethylene propylene-diene monomer (EPDM). Measurement of PEG hydrogel included time dependency due to its swelling and absorption behaviour, which led into dissolving of PEG hydrogel. EPDM organogel is not dissolving in water, so it was measured as a standard for AFM measurements. In addition to Young’s modulus as a base parameter for measurement of hydrogels in swollen state, was adhesion and work of adhesion tested in case of EPDM gels.
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The utilization of atomic force microscopy for study on hydrogels
Lišková, Kateřina ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
The presented bachelor thesis deals with the study of atomic force microscopy (AFM), especially the optimization of the measuring procedure for imaging the surface of variously crosslinked hydrogels in the hydrated state. The most attention was given to the physically crosslinked polysaccharide hydrogel (termoreversible agarose) in hydrated state, where the surface of the samples with mass concentration of 4, 2, 1, 0,75 and 0,5 % was measured. Subsequently, the surface of the ionically crosslinked 2 % alginate gel with calcium ions was measured. Based on a literature research, measurements were performed in water using the method of quantitative imaging (QITM Advanced Imaging), which is especially suitable for soft samples with uneven surfaces. Multiple cantilever were tested for measurement, finally the SNL-10 cantilever was selected, which showed versatility for imaging samples in any measuring environment, especially aqueous. The pore sizes of the agarose hydrogels were monitored by image analysis ImageJ. For the measurement of hydrogels in the swollen state, the procedure of measuring their surface using atomic force microscopy has been optimized, but for different types of hydrogels, individual optimization of both preparation and instrument setup will be required.
|
|
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Atomic force microscopy of soft materials
Šudáková, Anna ; Havlíková, Martina (referee) ; Smilek, Jiří (advisor)
This bachelor thesis focuses on atomic force microscopy (AFM), mainly on studying the measurement procedure and optimalization of measurement conditions with future perspective on imaging hydrogels and measuring mechanical properties (such as adhesion or stiffness) of hydrogels and semi-rigid materials at the microlevel. Atomic force microscopy is gaining significant importance in research due to its versatility, when it can provide topographical image of conductive and non-conductive samples while measuring mechanical properties of the samples, such as adhesion, elasticity or stiffness. Advantage of AFM method is that it can provide mechanical properties of the samples not only on macro levels as we are used to, for example, from rheology, but also on local level. Optimalization was performed on standard sample, one micrometre polystyrene nanoparticles , when the individual modes were measured, such as non-contact (AC Mode Imaging) mode and quantitative mode (QITM Advanced Imaging). This was followed by the measurement of a PVA foils, the measurement was performed because they are xerogels and will be studied more in the future. They were made with polyvinyl alcohol and chitosan. The internal environment of the hydrogels has been modified by adjusting the pH (NaOH) or by changing the ionic strength (NaCl). Furthermore, the effect of freezing on the PVA foils was observed, it is one of the possible ways of preparation of physically linked hydrogels. This work also examines the effect of porosity on concentration of physically linked thermoreversible agarose gels.
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