MATERIALS SCREENING METHODOLOGY FOR ADDITIVE MANUFACTURING IN BIOREACTOR TECHNOLOGY

Biofabrication is used to fabricate complex tissues/organs inspired by their native structures using additive manufacturing (AM) techniques and bio-inks (biopolymers enriched with living cells). Electroactive cells such as skeletal muscle function via electrical signals and therefore, their optimum in vitro functionality requires electrical conductivity and electrical stimulations. AM can be used to precisely fabricate a bioreactor for a dynamic culture of cells and bioengineered tissues and electrical stimulation of them. In this study, we focused on a material selection methodology for AM of bioreactors with selective electrical conductivity based on Reuter [1]. The important material requirements for bioreactors are biocompatibility, chemical stability, electrical conductivity, and the capability of being sterilized. However, there is no standardized procedure for selecting materials, that are appropriate for AM of bioreactors. Our study comprises three phases which deductively narrowed down the material selection; these phases are the determination of material requirements, pre-selection, and fine selection of suitable materials. With the proposed method, a material selection for AM of functional bioreactors (consisting of bioreactor housing and integrated additively manufactured electrodes for electrical stimulation of the cells) could be efficiently made. For the bioreactor housing, two of the investigated materials, high-temperature polylactic acid (HTPLA) and polypropylene (PP) meet all requirements. The materials of the bioreactor electrodes could be narrowed down to polyethylene with copper particles (PE-Cu) and poly lactic acid with graphene nanoplates (PLA-GNP), where PE-Cu fulfilled all requirements besides the biocompatibility. PLA-GNP matches all requirements besides the high temperature resistance. For a final selection of the material for the bioreactor electrodes, further tests are required. However, this approach enabled to reduce the amount of biocompatibility testing from 16 different materials to only four (- 75%), saving material, time, capacity and costs.Mechanical Engineerin

Stromerzeugung aus Windenergie

Im Gegensatz zu der direkten Sonnenenergie ist die Windenergie eine indirekte Art der Sonnenenergie. Die Einstrahlung der Sonne erwärmt die Erdoberfläche und die darüber liegenden Luftschichten unterschiedlich – d. h., wegen ihrer niedrigen Wärmekapazität werden im Sommerhalbjahr die Kontinentalflächen bei Tag stärker erwärmt als die Ozeane. Dies bewirkt auf verschiedenen Gebieten der Erdoberfläche Dichte- und Druckunterschiede, die in fluktuierenden Luftströmungen ihren Ausgleich finden. Diese fluktuierenden Luftströmungen bzw.Winde können technisch durchWindenergieanlagen (WEA) genutzt werden, die in den strömenden Luftmassen enthaltene kinetische Energie in elektrische Energie umwandeln. Dabei wird die Energie des Windes über die Rotorblätter zunächst in mechanische Rotationsenergie und dann über einen Generator in elektrische Energie umgewandelt (Abb. 7.1)