Rapid prototyping for biomedical engineering: current capabilities and Challenges

A new set of manufacturing technologies has emerged in the past decades to address market requirements in a customized way and to provide support for research tasks that require prototypes. These new techniques and technologies are usually referred to as rapid prototyping and manufacturing technologies, and they allow prototypes to be produced in a wide range of materials with remarkable precision in a couple of hours. Although they have been rapidly incorporated into product development methodologies, they are still under development, and their applications in bioengineering are continuously evolving. Rapid prototyping and manufacturing technologies can be of assistance in every stage of the development process of novel biodevices, to address various problems that can arise in the devices' interactions with biological systems and the fact that the design decisions must be tested carefully. This review focuses on the main fields of application for rapid prototyping in biomedical engineering and health sciences, as well as on the most remarkable challenges and research trends

Three-Dimensional Cell and Tissue Patterning in a Strained Fibrin Gel System

Techniques developed for the in vitro reproduction of three-dimensional (3D) biomimetic tissue will be valuable for investigating changes in cell function in tissues and for fabricating cell/matrix composites for applications in tissue engineering techniques. In this study, we show that the simple application of a continuous strain to a fibrin gel facilitates the development of fibril alignment and bundle-like structures in the fibrin gel in the direction of the applied strain. Myoblasts cultured in this gel also exhibited well-aligned cell patterning in a direction parallel to the direction of the strain. Interestingly, the direction of cell proliferation was identical to that of cell alignment. Finally, the oriented cells formed linear groups that were aligned parallel to the direction of the strain and replicated the native skeletal muscle cell patterning. In addition, vein endothelial cells formed a linear, aligned vessel-like structure in this system. Thus, the system enables the in vitro reproduction of 3D aligned cell sets replicating biological tissue patterns

HYDROGEN IN STAINLESS STEEL AND Fe-Ni ALLOYS

La répartition de l'hydrogène et les interactions avec les atomes de fer dans l'acier inoxydable et les alliages Fe-Ni, ont été étudiées par spectrométrie Mössbauer du 57Fe. Le spectre paramagnétique de l'acier inoxydable hydrogéné et analysé en deux composantes. L'une provient des atomes de fer qui ne sont pas affectés par l'hydrogène, l'autre de ceux qui sont profondément affectés par l'hydrogène. Le grand déplacement isomérique de cette dernière composante ne peut être expliqué par la dilatation du réseau mais plutôt par l'accroissement du nombre des électrons 3d du fer du fait des interactions avec l'hydrogène. Le sextuplet ferromagnétique des Fe-Ni hydrogénés comporte aussi deux contributions, l'une venant de la phase γ' dans laquelle les atomes ont peu d'interaction avec l'hydrogène du fait de la distribution homogène, et l'autre provenant d'une phase hybride de type β, dans laquelle les atomes de fer interagissent obligatoirement avec les atomes voisins d'hydrogène ; leur moment magnétique est réduit de 15 %. Il apparaît que la distribution de l'hydrogène dans les alliages de fer n'est pas uniforme et qu'il existe des interactions importantes entre fer et hydrogène.By means of 57Fe Mössbauer effect, distribution of hydrogen and its interaction with iron in stainless steel and Fe-Ni alloys are studied. Paramagnetic single line spectrum of hydrogenated stainless steel is analyzed into two components. One arises from the iron atoms totally unaffected by hydrogen and the other from those largely affected by hydrogen. A large positive isomer shift of the latter can not be explained by the lattice expansion but by the increase in the number of 3d electrons of iron due to the interaction with hydrogen. Ferromagnetic six line spectra of hydrogenated Fe-Ni alloys also consist of two parts, one being from the γ' phase, in which iron atoms have little interaction with hydrogen because of its inhomogeneous distribution, and the other from the hydride like β phase, in which the iron atoms inevitably interact with nearby hydrogen atoms and their magnetic moment is reduced by 15%. This experiment shows non-uniform distribution of infused hydrogen in iron alloys and, at the same time, remarkable effects of the electronic interaction between hydrogen and iron. Disagreements in the past experiments are well interpreted from the above results and point of view