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Johannes Nowak, Caroline Barhold, Christian Kessler, Stefan Odenbach
Gelation of a Nanocomposite-Hydrogel system and its dependency on mechanical loads

Appl. Rheol. 27:5 (2017) 52850 (6 pages)

Hydrogels are cross-linked polymer networks which are water-insoluble. They are suitable for several technical and biomedical applications due to the ability of some gels to swell and deswell as reaction to external stimuli. Such gels are synthesized and shift from a fluid-like liquid with solved components towards the final polymeric network with gel-like properties. Monitoring and characterizing this process is fundamental on the one hand to understand the chemical and physical behavior and on the other hand to adopt the application and production of such gels. Therefore, this investigation focuses on the characterization of the gelation of a nanocomposite hydrogel system based on PNIPAm with and without mechanical loads applied, using rheology. Measurements are conducted featuring rotational and oscillating rheometry and the results found are compared and evaluated. Furthermore the impact of a strong pre-shear, preventing the gelation, prior to the actual gelation, is investigated. The results found show a strong influence of the applied load as well as of an applied pre-shear on the gelation and furthermore on the mechanical properties of the final hydrogels. Therefore those parameters be taken into account for future investigations as well as for the large scale productions of hydrogels.

Cite this publication as follows:
Nowak J, Barhold C, Kessler C, Odenbach S: Gelation of a Nanocomposite-Hydrogel system and its dependency on mechanical loads, Appl. Rheol. 27 (2017) 52850.

Johannes Nowak, Christoph Nowak, Stefan Odenbach
Consequences of sheep blood used as diluting agent for the magnetoviscous effect in biocompatible ferrofluids

Appl. Rheol. 25:5 (2015) 53250 (8 pages)

Magnetic nanoparticles suspended in suitable carrier liquids can be adopted for use in biomedicine. For this to be achieved, the biocompatibility of these ferrofluids needs to be ascertained. In cancer treatment, potential applications currently under investigation include, e.g. drug targeting by using magnetic fields and the destruction of diseased cells by applying alternating magnetic fields, which cause heating of magnetic nanoparticles. To enable the use of ferrofluids in the actual biomedical context, detailed knowledge of the flow characteristics is essential to ensure safe treatment. From ferrofluids used in the engineering context, a rise of viscosity when a magnetic field is applied - the magnetoviscous effect - is well known. This effect, which leads to an increased viscosity and profound alteration of a fluid's rheological behaviour, has also been demonstrated for biocompatible ferrofluids used in the aforementioned applications. In biomedical applications, ferrofluids will be diluted in the blood stream. Therefore, the interaction between whole blood and the ferrofluid has to be investigated. This is the focus of the current experimental study, which makes use of two different ferrofluids diluted in sheep blood to gain a deeper understanding of the fluid mixtures primarily regarding the relative change in viscosity if an external magnetic field is applied. The results demonstrate a strong interaction between blood cells and structures formed by the magnetic nanoparticles and show a high deviation of results compared to ferrofluids diluted in water. These findings have to be taken into account for future research and applications of similar biocompatible fluids to guarantee safe and effective use in living organisms.

Cite this publication as follows:
Nowak J, Nowak C, Odenbach S: Consequences of sheep blood used as diluting agent for the magnetoviscous effect in biocompatible ferrofluids, Appl. Rheol. 25 (2015) 53250.

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