Journal articles and book contributions

Biobased poly(butylene succinate) (PBS) represents one promising sustainable alternative to petroleum-based polymers. Its sensitivity to thermo-oxidative degradation is one reason for its limited application. In this research, two different varieties of wine grape pomaces (WPs) were investigated as fully biobased stabilizers. WPs were prepared via simultaneous drying and grinding to be used as bio-additives or functional fillers at higher filling rates. The by-products were characterized in terms of composition and relative moisture, in addition to particle size distribution analysis, TGA, and assays to determine the total phenolic content and the antioxidant activity. Biobased PBS was processed with a twin-screw compounder with WP contents up to 20 wt.-%. The thermal and mechanical properties of the compounds were investigated with DSC, TGA, and tensile tests using injection-molded specimens. The thermo-oxidative stability was determined using dynamic OIT and oxidative TGA measurements. While the characteristic thermal properties of the materials remained almost unchanged, the mechanical properties were altered within expected ranges. The analysis of the thermo-oxidative stability revealed WP as an efficient stabilizer for biobased PBS. This research shows that WP, as a low-cost and biobased stabilizer, improves the thermo-oxidative stability of biobased PBS while maintaining its key properties for processing and technical applications.

Nanoporous gold is a three-dimensional bulk material that is percolated with a random network of nanometer-sized ligaments and made by selective corrosion of bimetallic alloys. It has intriguing geometric, catalytic, and optical properties that have fascinated scientists for many decades. When such a material is made into the form of small, 100-nm-sized particles, so-called nanosponges emerge that offer much flexibility in controlling their geometric, electronic, and optical properties. Importantly, these particles act as an antenna for light that can efficiently localize optical fields on a deep subwavelength scale in certain hotspots at the particle surface. This makes such nanosponges an interesting platform for plasmonic sensing, photocatalysis, and surface-enhanced Raman spectroscopy. Since the optical properties of these nanosponges can be controlled to a large degree by tuning their geometry and/or composition, they have attracted increasing attention in recent years. Here, we provide a concise overview of the current state of the art in this field, covering their fabrication, computational modeling, and specifically the linear and nonlinear optical properties of individual and hybrid nanosponges, for example, plasmon localization in randomly disordered hotspots with a size <10 nm and a long lifetime with an exceptionally high Purcell factor. The resulting nonlinear optical and photoemission properties are discussed for individual and hybrid nanosponges. The results presented have strong implications for further applications of such nanosponges in photonics and photocatalysis.

Conductive and stretchable filaments are crucial for advancing additive manufacturing, particularly in flexible electronics. However, existing conductive filaments suffer from limitations in conductivity and stretchability. To overcome these challenges, this study presents a highly conductive and stretchable filament for material extrusion type 3D printing. The developed filament achieves an initial electrical conductivity of 558 S/cm and maintains low resistance up to 60 % strain with 10 vol% silver loading. This significantly surpasses the performance of commercial filaments and previous literature reports. The addition of polyethylene glycol (PEG) as a plasticizer for the silver filled thermoplastic polyurethane (Ag-TPU) composite enhances extrusion and improves filament surface quality. The printability of the filament in material extrusion 3D printing was evaluated, and the electrical conductivity of the printed objects was assessed. Two demonstrator structures, an electrical interconnection and a capacitive strain sensor, were successfully prototyped, showcasing the potential applications of this filament in stretchable electronics. The developed filament paves the way for creating intricate and stretchable electronic devices using material extrusion printing techniques. These advancements contribute to the field of additive manufacturing and enable the fabrication of flexible electronic components with enhanced conductivity and stretchability.

Aiming at circular economy we must provide strategies for reuse of EoL (end of life) glass products, for maintenance and increase high material recycling quotas and be open for new technologies. The well-established returnable bottle system in Germany is an almost perfect example for product recycling, albeit in a confined market segment for certain beverages. On the other hand, recycling nonpackaging glass is tremendously far from closed cycles. The glass packaging market has grown slowly but successfully in spite of the competition from PET and other plastics. Glass producers struggle with even higher energy prices and will focus more and more on renewable energies. Consumers are aware that glass offers an alternative to increasing packaging waste. Which future tasks result from this situation? Three main topics arise for container glass: less one-way packaging, more returnable packaging, and innovative strategies for collection and sort- ing. Knowledge on the best practice examples is expected to be transferred to non-container glasses. An overview on the current status of demands is being documented with the goal of more ideas being generated to assist in glass recycling.