Search Results
4D Biofabrication of fibrous artificial nerve graft for neuron regeneration
2020, Apsite, Indra, Constante, Gissela, Dulle, Martin, Vogt, Lena, Caspari, Anja, Boccaccini, Aldo R., Synytska, Alla, Salehi, Sahar, Ionov, Leonid
In this paper, we describe the application of the 4D biofabrication approach for the fabrication of artificial nerve graft. Bilayer scaffolds consisting of uniaxially aligned polycaprolactone-poly(glycerol sebacate) (PCL-PGS) and randomly aligned methacrylated hyaluronic acid (HA-MA) fibers were fabricated using electrospinning and further used for the culture of PC-12 neuron cells. Tubular structures form instantly after immersion of fibrous bilayer in an aqueous buffer and the diameter of obtained tubes can be controlled by changing bilayer parameters such as the thickness of each layer, overall bilayer thickness, and medium counterion concentration. Designed scaffolds showed a self-folded scroll-like structure with high stability after four weeks of real-time degradation. The significance of this research is in the fabrication of tuneable tubular nerve guide conduits that can simplify the current existing clinical treatment of neural injuries. © 2020 The Author(s). Published by IOP Publishing Ltd.
Beamline-implemented stretching devices for in situ X-ray scattering experiments
2022, Euchler, E., Sambale, A.K., Schneider, K., Uhlig, K., Boldt, R., Stommel, M., Stribeck, A., Schwartzkopf, M., Rothkirch, A., Roth, S.V.
Two recently developed experimental devices for investigating soft matter deformation are presented. Both devices exploit the capabilities of a modern synchrotron beamline to enable advanced and highly precise materials-science experiments in which X-ray scattering is registered. The devices can be operated both in monotonic as well as cyclic mode and are implemented into a beamline at DESY, Hamburg (Germany). Hence, relevant experimental parameters, such as displacement, force and temperature, are recorded synchronously with the individual X-ray scattering patterns. In addition, spatial variation of materials deformation can be monitored and recorded with optical microscopy. This unique sample environment enables in situ X-ray experiments in transmission, i.e. small- or wide-angle X-ray scattering (SAXS or WAXS), and in grazing-incidence geometry, i.e. grazing-incidence (GI-) SAXS or WAXS. One device with stepper motors is designed for studies of slow, (quasi-) static deformation and the other one with pneumatic actuators can be used for fast, impact deformation. Both devices are available to external beamline users, too.
MWCNT induced negative real permittivity in a copolyester of Bisphenol-A with terephthalic and isophthalic acids
2020, Özdemir, Zeynep Güven, Daşdan, Dolunay Şakar, Kavak, Pelin, Pionteck, Jürgen, Pötschke, Petra, Voit, Brigitte, SüngüMısırlıoğlu, Banu
In the present study, the negative real permittivity behavior of a copolyester of bisphenol-A with terephthalic acid and isophthalic acid (PAr) containing 1.5 to 7.5 wt% multi-walled carbon nanotubes (MWCNTs) have been investigated in detail. The structural and morphological analysis of the melt-mixed composites was performed by Fourier transform infrared spectroscopy using attenuated total reflection (FTIR-ATR), atomic force microscopy (AFM), X-ray diffraction (XRD), and light microscopy. The influences of the MWCNT filler on the AC impedance, complex permittivity, and AC conductivity of the PAr polymer matrix were investigated at different operating temperatures varied between 296 K and 373 K. The transition from a negative to positive real permittivity was observed at different crossover frequencies depending on the MWCNT content of the composites whereas pure PAr showed positive values at all frequencies. The negative real permittivity characteristic of the composites was discussed in the context of Drude model. © 2020 The Author(s). Published by IOP Publishing Ltd.
Field-induced interactions in magneto-active elastomers - a comparison of experiments and simulations
2020, Metsch, P., Schmidt, H., Sindersberger, D., Kalina, K.A., Brummund, J., Auernhammer, G.K., Monkman, G.J., Kästner, M.
In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations—the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems' response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers.
Multifunctional-high resolution imaging plate based on hydrophilic graphene for digital pathology
2022, Lee, Geonhee, Oh, Yuna, Nam, Jung Tae, Ji, Seulgi, Jang, A.-Rang, Jeong, Du Won, Kang, MinSoung, Lee, Sun Sook, Chae, Soosang, Cho, Donghwi, Hwang, Jun Yeon, Lee, Kyungeun, Lee, Jeong-O.
In the present study, we showed that hydrophilic graphene can serve as an ideal imaging plate for biological specimens. Graphene being a single-atom-thick semi-metal with low secondary electron emission, array tomography analysis of serial sections of biological specimens on a graphene substrate showed excellent image quality with improved z-axis resolution, without including any conductive surface coatings. However, the hydrophobic nature of graphene makes the placement of biological specimens difficult; graphene functionalized with polydimethylsiloxane oligomer was fabricated using a simple soft lithography technique and then processed with oxygen plasma to provide hydrophilic graphene with minimal damage to graphene. High-quality scanning electron microscopy images of biological specimens free from charging effects or distortion were obtained, and the optical transparency of graphene enabled fluorescence imaging of the specimen; high-resolution correlated electron and light microscopy analysis of the specimen became possible with the hydrophilic graphene plate.