Polymeric Janus Fibers.

Janus fibers are a class of composite materials comprising mechanical and chemical to biological functionality. Combining different materials and functionalities in one micro- or even nanoscale fiber enables otherwise unreachable synergistic physicochemical effects with unprecedented opportunities for technical or biomedical applications. Here, recent developments of processing technologies and applications of polymeric Janus fibers will be reviewed. Various examples in the fields of textiles, catalysis, sensors as well as medical applications, like drug delivery systems, tissue engineering and antimicrobial materials, are presented to illuminate the outstanding potential of such high-end functional materials for novel applications in the upcoming future.

Shape, size, and polymer dependent effects of microplastics on Daphnia magna.

The effects of microplastic (MP) pollution on organisms are gaining increasing attention. To date, a variety of polymers of different shapes and sizes are used in ecotoxicology. Although polystyrene (PS) is the predominant polymer type used in effect studies, it is still unclear whether the observed effects derive from the polymer itself or from a certain particle shape and size. To elucidate whether the effects are polymer specific, we conducted a systematic study on Daphnia magna by comparing various PS-MPs to nonplastic control particles with similar properties. In chronic exposure experiments, we used PS beads (6 µm; 20 µm), fibers (Ø 3 µm, length: 75.5 µm), and fragments (5.7 µm; 17.7 µm) in two different size classes and two different concentrations (500 and 5000 particles ml-1) and in-house-produced control particles of comparable size, shape, concentration and, if possible, density. Although most PS properties did not elicit effects on the tested endpoints, we observed sublethal effects on D. magna life history and morphology for small PS beads and fragments. Interestingly, no adverse effects were detected for any of the control particles. Hence, the observed effects are polymer-specific, related to the size and shape of the polymer, and do not result from particle exposure per se.

Roll-to-Roll Production of Spider Silk Nanofiber Nonwoven Meshes Using Centrifugal Electrospinning for Filtration Applications.

Filtration systems used in technical and medical applications require components for fine particle deep filtration to be highly efficient and at the same time air permeable. In high efficiency filters, nonwoven meshes, which show increased performance based on small fiber diameters (e.g., using nanofibers), can be used as fine particle filter layers. Nanofiber nonwoven meshes made by electrospinning of spider silk proteins have been recently shown to exhibit required filter properties. Needle-based electrospinning, however, is limited regarding its productivity and scalability. Centrifugal electrospinning, in contrast, has been shown to allow manufacturing of ultrathin polymer nonwoven meshes in an efficient and scalable manner. Here, continuous roll-to-roll production of nonwoven meshes made of recombinant spider silk proteins is established using centrifugal electrospinning. The produced spider silk nanofiber meshes show high filter efficiency in the case of fine particulate matter below 2.5 µm (PM2.5) and a low pressure drop, resulting in excellent filter quality.