@article{2278, abstract = { Three-dimensional printing enables building objects shaped with a large degree of freedom. Additional functionalities can be included by modifying the printing material, e.g., by embedding nanoparticles in the molten polymer feedstock, the resin, or the solution used for printing, respectively. Such composite materials may be stronger or more flexible, conductive, magnetic, etc. Here, we give an overview of magnetic composites, 3D-printed by different techniques, and their potential applications. The production of the feedstock is described as well as the influence of printing parameters on the magnetic and mechanical properties of such polymer/magnetic composites. }, author = {Ehrmann, Guido and Blachowicz, Tomasz and Ehrmann, Andrea}, issn = {2073-4360}, journal = {Polymers}, keywords = {fused deposition modeling (FDM), magnetic hydrogel, photopolymerization, stereolithography (SLA), hydrogel, shape memory polymer (SMP), magneto-rheological behavior, electromagnetic shielding}, number = {18}, publisher = {MDPI AG}, title = {{Magnetic 3D-Printed Composites—Production and Applications}}, doi = {10.3390/polym14183895}, volume = {14}, year = {2022}, } @article{1589, abstract = { Poly(lactic acid) (PLA) is one of the most often used polymers in 3D printing based on the fused deposition modeling (FDM) method. On the other hand, PLA is also a shape memory polymer (SMP) with a relatively low glass transition temperature of ~60 °C, depending on the exact material composition. This enables, on the one hand, so-called 4D printing, i.e., printing flat objects which are deformed afterwards by heating them above the glass transition temperature, shaping them and cooling them down in the desired shape. On the other hand, objects from PLA which have been erroneously deformed, e.g., bumpers during an accident, can recover their original shape to a certain amount, depending on the applied temperature, the number of deformation cycles, and especially on the number of broken connections inside the object. Here, we report on an extension of a previous study, investigating optimized infill designs which avoid breaking in 3-point bending tests and thus allow for multiple repeated destruction and recovery cycles with only a small loss in maximum force at a certain deflection. }, author = {Koske, Daniel and Ehrmann, Andrea}, issn = {2072-666X}, journal = {Micromachines}, keywords = {3D printing, poly(lactic acid) (PLA), fused deposition modeling (FDM), shape-memory polymer (SMP), 4D printing, infill patterns}, number = {10}, publisher = {MDPI AG}, title = {{Advanced Infill Designs for 3D Printed Shape-Memory Components}}, doi = {10.3390/mi12101225}, volume = {12}, year = {2021}, } @article{1609, abstract = { Shape-memory polymers (SMPs) can be deformed, cooled down, keeping their new shape for a long time, and recovered into their original shape after being heated above the glass or melting temperature again. Some SMPs, such as poly(lactic acid) (PLA), can be 3D printed, enabling a combination of 3D-printed shapes and 2D-printed, 3D-deformed ones. While deformation at high temperatures can be used, e.g., to fit orthoses to patients, SMPs used in protective equipment, bumpers, etc., are deformed at low temperatures, possibly causing irreversible breaks. Here, we compare different typical infill patterns, offered by common slicing software, with self-designed infill structures. Three-point bending tests were performed until maximum deflection as well as until the maximum force was reached, and then the samples were recovered in a warm water bath and tested again. The results show a severe influence of the infill pattern as well as the printing orientation on the amount of broken bonds and thus the mechanical properties after up to ten test/recovery cycles. }, author = {Koske, Daniel and Ehrmann, Andrea}, issn = {2227-7080}, journal = {Technologies}, keywords = {poly(lactic acid) (PLA), shape-memory polymer (SMP), fused deposition modeling (FDM), 3D printing, infill pattern}, number = {2}, publisher = {MDPI AG}, title = {{Infill Designs for 3D-Printed Shape-Memory Objects}}, doi = {10.3390/technologies9020029}, volume = {9}, year = {2021}, }