Three-dimensional printing technologies exhibit tremendous potential in the advancing fields of tissue engineering and regenerative medicine due to the precise spatial control over depositing the biomaterial. Despite their widespread utilization and numerous advantages, the development of suitable novel biomaterials for extrusion-based 3D printing of scaffolds that support cell attachment, proliferation, and vascularization remains a challenge. Multi-material composite hydrogels present incredible potential in this field. Thus, in this work, a multi-material composite hydrogel with a promising formulation of chitosan/gelatin functionalized with egg white was developed, which provides good printability and shape fidelity. In addition, a series of comparative analyses of different crosslinking agents and processes based on tripolyphosphate (TPP), genipin (GP), and glutaraldehyde (GTA) were investigated and compared to select the ideal crosslinking strategy to enhance the physicochemical and biological properties of the fabricated scaffolds. All of the results indicate that the composite hydrogel and the resulting scaffolds utilizing TPP crosslinking have great potential in tissue engineering, especially for supporting neo-vessel growth into the scaffold and promoting angiogenesis within engineered tissues.

Additive manufacturing of Nitinol is a promising field, as it can circumvent the challenges associated with its conventional production processes and unlock unique advantages. However, the accompanying surface features such as powder adhesions, spatters, ballings, or oxide discolorations are undesirable in engineering applications and therefore must be removed. Plasma electrolytic polishing (PeP) might prove to be a suitable finishing process for this purpose, but the effects of post-processing on the mechanical and functional material properties of additively manufactured Nitinol are still largely unresearched. This study seeks to address this issue. The changes on and in the part caused by PeP with processing times between 2 and 20 min are investigated using Nitinol compression springs manufactured by Laser Beam Melting. As a benchmark for the scanning electron microscope images, the differential scanning calorimetry (DSC) measurements, and the mechanical load test cycles, conventionally fabricated Nitinol springs of identical geometry with a medical grade polished surface are used. After 5 min of PeP, a glossy surface free of powder adhesion is achieved, which is increasingly levelled by further polishing. The shape memory properties of the material are retained without a shift in the transformation temperatures being detectable. The decreasing spring rate is primarily attributable to a reduction in the effective wire diameter. Consequently, PeP has proven to be an applicable and effective post-processing method for additively manufactured Nitinol.

In many cases, the functional performance of additively manufactured components can only be ensured by finishing the functional surfaces. Various methods are available for this purpose. This paper presents a procedure for selecting suitable processes for finishing laser beam melting additive–manufactured parts which is ultimately based on technological knowledge. It was experimentally proven that the use of several consecutive finishing processes is beneficial to achieve better surface quality. One finishing process chain was particularly effective (namely particle blasting/vibratory grinding/plasma electrolytic polishing) and the technological limits of this method were investigated in this study. The optimal parameters for this process combination ensured a surface roughness Sa < 1 µm.

Background: Bioprinting is one of the most rapidly developing fields in medicine. Plastic and reconstructive surgery will be affected enormously by bioprinting, due to its original purpose of restoring injured or lost tissue. This article in particular has the purpose to analyze the current state of bioprinted tissues as well as research engagement for its application in plastic and reconstructive surgery. Material and methods: A systematic search for the time span between 2000 and 2022 was performed on EMBASE, Pub-Med, Scopus, and Web of Science databases according to the PRISMA Guidelines. Criteria for the selection of publications were in vitro, animal in vivo, and human in vivo studies where three-dimensional bioprinting of tissue was performed. We extracted data such as (a) author’s country of origin, (b) in vitro study, (c) animal in vivo study, and (d) human in vivo study and categorized the publications by topics such as (1) neural tissue, (2) vascularization, (3) skin, (4) cartilage, (5) bone, and (6) muscle. Additionally, recent discoveries of in vivo animal trials were summarized. - Results: Out of a pool of 1.629 articles, only 29 publications met our criteria. Of these publications, 97% were published by university institutions. Publications from China (28%, n=8), the USA (28%, n=8), and Germany (10%, n=3) led the publication list on 3D bioprinting. Concerning the publications, 45% (n=13) were in vitro studies, 52% (n=15) in vivo studies on animal models, and 3% (n=1) pilot clinical studies on humans as reported by Zhou et al. (EBioMedicine 28: 287–302, 2018). Regarding the classification of topics, our study revealed that publications were mainly in the field of 3D printing of cartilage (n=13, 39%), skin (n=7, 21%), bone (n=6, 18%), and vascularization (n=5, 15%). - Conclusions: To this date, it has not been yet possible to bioprint whole tissue systems. However, the progress in threedimensional bioprinting is rapid. There are still some challenges, which need to be overcome regarding cell survival before and during the printing process, continuation of architecture of bioprinted multilinear cells, and long-term stabilization and survival of complex tissues. Level of evidence: Not ratable.

Im Fokus der Dissertation steht die Erforschung nachhaltiger Effekte durch Informationssysteme, insbesondere Ansatzpunkte zur Nachhaltigkeitstransformation der Gesellschaft durch Methoden und Artefakte der Green Information Systems (Green IS). Als Green IS werden sozio-technische Informationssysteme bezeichnet, die neben wirtschaftlichen Kriterien der ressourceneffizienten Bereitstellung von Informationen, der Koordination und Kommunikation auch die ökologische und soziale Dimension gemäß der „Triple Bottom Line“ (Drei-Säulen-Modell der nachhaltigen Entwicklung) adressieren. Der Anwendungsbereich von Green IS liegt auf der Reduktion von Umweltbelastungen und der Bewältigung komplexer Umweltherausforderungen durch sozio-technische Informationssysteme. Neben Forschungsthemen der (Wirtschafts-)Informatik und der Wirtschaftswissenschaften werden Bereiche der Psychologie und Sozialwissenschaften zu Fragen der digitalen Nachhaltigkeitstransformation, der Nachhaltigkeitsbewertung sowie Akzeptanzforschung behandelt. Aufgrund der Komplexität und Vielschichtigkeit des Themas wird ein multimethodischer Forschungsansatz verfolgt, indem sowohl qualitative als auch quantitative Methoden zum Einsatz kommen. Die zentralen Forschungsfragen lauten dabei wie folgt: FF1. Welchen Beitrag können Green IS auf Makro- und Meso-Ebene zur Nachhaltigkeitsbewertung leisten und welchen Reifegrad weisen sie auf? FF2. Inwiefern können digitale Geschäftsmodelle zur unternehmerischen und gesellschaftlichen Nachhaltigkeitstransformation beitragen? FF3. Kann durch gezieltes Nachhaltigkeitsmarketing die Akzeptanz von Green IS in der Gesellschaft gefördert werden? Gemäß der Design Science Research werden Verfahren zur Nachhaltigkeitsbewertung für Smart City Mobilitätsstrategien und betriebliche Umweltinformationssysteme (BUIS) des produzierenden Gewerbes konstruiert. Es wird ein Prototyp zum webbasierten Benchmark solcher Smart City Initiativen realisiert. Das entwickelte Geschäftsprozessmodell zeigt auf, inwiefern eine Transformation zur Plattformorganisation im Rahmen von Open Innovation für Industriebetriebe erfolgreich gelingen kann. Die quantitativen Erhebungen zeigen auf, das vor allem hochpreisige Informations- und Kommunikationstechnologie (IKT) für Geschäftsmodelle der Sharing Economy geeignet ist sowie, dass die Akzeptanz nachhaltiger IKT in der Gesellschaft bereits insbesondere bei Zugehörigen des "Lifestyle of Health and Sustainability" (LOHAS) vorhanden ist und der weiteren Förderung durch geeignete Verbraucher-Symbole bedarf.

Three-dimensional (3D) printing has become broadly available and can be utilized to customize clamping mechanisms in biomechanical experiments. This report will describe our experience using 3D printed clamps to mount soft tissues from different anatomical regions. The feasibility and potential limitations of the technology will be discussed. Tissues were sourced in a fresh condition, including human skin, ligaments and tendons. Standardized clamps and fixtures were 3D printed and used to mount specimens. In quasi-static tensile tests combined with digital image correlation and fatigue trials we characterized the applicability of the clamping technique. Scanning electron microscopy was utilized to evaluate the specimens to assess the integrity of the extracellular matrix following the mechanical tests. 3D printed clamps showed no signs of clamping-related failure during the quasi-static tests, and intact extracellular matrix was found in the clamping area, at the transition clamping area and the central area from where the strain data was obtained. In the fatigue tests, material slippage was low, allowing for cyclic tests beyond 105 cycles. Comparison to other clamping techniques yields that 3D printed clamps ease and expedite specimen handling, are highly adaptable to specimen geometries and ideal for high-standardization and high-throughput experiments in soft tissue biomechanics.

Innerhalb dieser Arbeit wird ein Fertigungsverfahren entwickelt und erprobt, das den additiven Aufbau von großvolumigen faserverstärkten Kunststoffbauteilen in Skelettbauweise erlaubt. Dafür wird ein modifizierter Extruder zusammen mit einer speziellen Kinematik genutzt. Der Fokus liegt auf der Analyse des Einflusses der Steuergrößen auf geometrische und mechanische Eigenschaften, sowie Haftung im Bauteil. Hinsichtlich der geometrischen Eigenschaften wird ein Prozessmodell entwickelt, das die Abhängigkeit der Strangbreite und -höhe von den Steuergrößen darstellt. Durch experimentelle Untersuchungen werden die Prozessgrenzen und an diesen auftretende Effekte ermittelt. Das Verfahren weist hier große Freiräume auf. So können z.B. mit einer 1 mm Düse Strangbreiten von 1,2 bis 3,2mm erzielt werden. Die mechanischen Eigenschaften in Strangrichtung erreichen im 3D-Druck annähernd die Steifigkeit und Festigkeit der Spritzgießreferenz. Prozessbedingt ist eine Porosität im Material nicht ganz vermeidbar, allerdings sind die Fasern stark ausgerichtet und die Faserlänge im Granulat bleibt im Prozess weitestgehend erhalten. Mittels direktem 3D-Drucken auf endlosfaserverstärktes Tape kann mit Vorheizen des Tapes ein guter Haftverbund generiert werden. Ergänzend wurden zwei Komponenten entwickelt, die für eine Industrialisierung des Prozesses entscheidend sind: Zum einen wurde ein neues Düsenkonzept vorgestellt, das eine schnelle Anpassung des Massestroms während des 3D-Druckens ermöglicht. Zum anderen wurde eine Temperierdüse vorgestellt, mit der mittels Konvektion der abgelegte Strang gekühlt bzw. erhitzt werden kann.:1 Einleitung 2 Zielstellung 3 Literaturübersicht 4 Konzeption eines neuartigen 3D-Druck-Verfahrens 5 Analyse der kinematischen Eigenschaften 6 Betrachtung der Haftungsmechanismen 7 Untersuchung der mechanischen Eigenschaften 8 Weiterentwicklung von Anlagenkomponenten 9 Zusammenfassung und Ausblick / In this thesis, a manufacturing process is presented which enables the additive manufacturing of largevolume fibre-reinforced plastic components in skeleton construction by using an extruder together with special kinematics. The focus is on the analysis of the influence of the control variables on geometric and mechanical properties, as well as adhesion in the component. With regard to the geometric properties, a process model is being developed that shows the dependence of the strand width and height on the control variables. Experimental investigations are used to determine the process limits and the effects occurring at these limits. The procedure knows here large free spaces, so e.g. with a 1 mm nozzle strand widths of 1,2 bis 3,2mm can be obtained. The mechanical properties in the strand direction in 3D printing approximate the stiffness and strength of the injection molding reference. Due to the process, porosity in the material cannot be completely avoided, however, the fibers are strongly oriented and the fiber length in the granulate is largely retained in the process. Direct 3D printing on continuous fiber-reinforced tape can be used to generate a good adhesive bond by preheating the tape. In addition, two components were developed that are decisive for industrializing the process: On the one hand, a new nozzle concept was introduced that enables rapid adjustment of the mass flow during 3D printing. On the other hand, a nozzle was presented with which the deposited strand can be cooled or heated by convection.:1 Einleitung 2 Zielstellung 3 Literaturübersicht 4 Konzeption eines neuartigen 3D-Druck-Verfahrens 5 Analyse der kinematischen Eigenschaften 6 Betrachtung der Haftungsmechanismen 7 Untersuchung der mechanischen Eigenschaften 8 Weiterentwicklung von Anlagenkomponenten 9 Zusammenfassung und Ausblick

Telemedical methods enable remote patient monitoring and healthcare at a distance. Besides, fitness tracker and sport watches are currently trending electronic products to generate awareness of health parameters in daily life. Especially, the long-term and continuous measurement of electrophysiological signals such as electrocardiogramm (ECG) becomes increasingly attractive for telemedical applications. Typically used disposable Ag/AgCl wet electrodes for good skin-electrode contact can potentially cause skin irritation and rashes. This paper presents a low cost, individual and flexible substrate for skin electrodes to be applied in future consumer electronic or professional applications. It enables an alternative contact method of the electrode to the skin by applying a pressure during the measurement and hence good contact. If no measurement is needed pressure can be released and the electrode loses skin contact. The 3D printed polymer module is 4 mm thick and comprises a pressure chamber, silver electrodes and insulation layer. The airtight printed membrane of flexible filament, which expands when inflating the chamber, may be printed in different thicknesses and shapes, much thinner than the present 4mm. This enables a high individuality for various applications. Pressure up to 150 kPa was applied and leads to dilatation of 1400 μm. First tests on skin when measuring electrodermal activity (EDA) show promising results for future applications.

In diesem Beitrag wird ein Vergleich zwischen indirekten Testmethoden zur Bewertung der Verbaubarkeit von 3D-gedruckten Mörteln und Betonen vorgestellt. Die Untersuchungen erfolgten an extrudierten Proben von acht zementbasierten Mischungen mit unterschiedlichem rheologischen Verhalten. Auf der Basis der erzielten Ergebnisse werden Vorhersagen zum Material- bzw. Stabilitätsversagen getroffen und mit den Ergebnissen des Direktdruckversuchs verglichen. Anschließend werden die Vor- und Nachteile unterschiedlicher Prüfmethoden diskutiert. Zu diesen zählen die Techniken der Rotationsrheometrie mit konstanter Rotationsgeschwindigkeit (engl.: constant rotational velocity, CRV), ein schneller Penetrationstest sowie einaxiale Druckversuche mit und ohne Querdehnungsbehinderung.

Stem cell bioengineering and therapy require different model systems and materials in different stages of development. If a chemically defined biomatrix system can fulfill most tasks, it can minimize the discrepancy among various setups. By screening biomaterials synthesized through a coacervation-mediated self-assembling mechanism, a biomatrix system optimal for 2D human mesenchymal stromal cell (hMSC) culture and osteogenesis is identified. Its utility for hMSC bioengineering is further demonstrated in coating porous bioactive glass scaffolds and nanoparticle synthesis for esiRNA delivery to knock down the SOX-9 gene with high delivery efficiency. The self-assembled injectable system is further utilized for 3D cell culture, segregated co-culture of hMSC with human umbilical vein endothelial cells (HUVEC) as an angiogenesis model, and 3D bioprinting. Most interestingly, the coating of bioactive glass with the self-assembled biomatrix not only supports the proliferation and osteogenesis of hMSC in the 3D scaffold but also induces the amorphous bioactive glass (BG) scaffold surface to form new apatite crystals resembling bone-shaped plate structures. Thus, the self-assembled biomatrix system can be utilized in various dimensions, scales, and geometries for many different bioengineering applications.