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Plasma‐enhanced chemical vapor deposition is a highly promising tool for coating deposition due to its versatility, tunability, low chemical consumption, and cost‐effectiveness, with an increasing scope of deposition methods at both low and atmospheric pressure. Adhering to green chemistry principles, biobased precursors have recently shifted into the focus of research interests. This review gives an overview of the main biogenic substance classes that have been used for the deposition of plasma polymer coatings, including natural oils, terpenes, enzymes, and lactic acid‐based precursors. The common feature of these precursors is not only their biogenic origin, but additionally the manifold properties of the resulting plasma‐deposited thin films, ranging from antimicrobial properties to tunable surface‐wetting characteristics, electrical conductivity, or biodegradability. This combination of unique features makes plasma‐derived polymers based on natural precursors immensely attractive for manifold applications.

Due to its unique material properties, paper offers many practical advantages as a viable platform for sensing devices. In view of paper-based microfluidic biosensing applications, the covalent immobilization of enzymes with preserved functional activity is highly desirable and ultimately challenging. In the present manuscript, we report an efficient approach to achieving the covalent attachment of certain enzymes on paper fibers via a surface-bound network of hydrophilic polymers bearing protein-modifiable sites. This tailor-made macromolecular system consisting of polar, highly swellable copolymers is anchored to the paper exterior upon light-induced crosslinking of engineered benzophenone motifs. On the other hand, this framework contains active esters that can be efficiently modified by the nucleophiles of biomolecules. This strategy allowed the covalent immobilization of glucose oxidase and horseradish peroxidase onto cotton linters without sacrificing their bioactivities and performance upon surface binding. As a proof-of-concept application, a microfluidic chromatic paper-based glucose sensor was developed and achieved successful glucose detection in a simple yet efficient cascade reaction.

This study identifies important factors for designing an effective biomimetic paper‐based fog harvesting substrate by examining the harvesting properties of different surfaces, including glass, polyethylene, and superhydrophobic paper. In laboratory‐scale fogging tests, the wetting behavior of the substrates is characterized, and the importance of the tilt angle of the respective surface relative to the fog flow is elaborated. Because successful fog harvesting requires both efficient accumulation of water droplets on the surface (by condensation and collision) and sufficient but not excessive roll‐off of the liquid, the amount of water finally collected is clearly related to the pinning effect, which should prevent the smallest droplets from being carried away by the wind but must not lead to full and permanent wetting of the surface. Coalescence is identified as a major phenomenon to improve droplet roll‐off. In this context, superhydrophobic paper indicates to be a more effective water collector than glass or polyethylene, especially when oriented vertically, since it allows the droplets to roll off very efficiently. Finally, the addition of glass particles to the superhydrophobic coating is proposed as a means of enhancing pinning and improving the fog harvesting efficiency.

Enhancing paper hydrophobicity is of key importance for many paper-based applications. Fatty acids or vegetable oils and their derivatives replace environmentally harmful conventional coating materials but still require challenging chemical reactions for covalent attachment onto paper. Here, we show that simple storage of olive oil-coated cotton linter paper at 70 °C and subsequent Soxhlet extraction is able to endow paper with hydrophobic properties, reaching water contact angles above 130°. In-depth chemical and morphological analytics show the relevance of temperature and air accessibility during the aging process compared with aging at ambient temperature and under the exclusion of oxygen, underlining the importance of assessing a coating’s long-term performance and stability under diverse storage conditions. Simple storage of vegetable oil-coated paper at elevated temperatures followed by extraction proves to be an easy way to produce stable covalently attached hydrophobic paper coatings with exceptionally low coating amounts.

Microfluidic paper combines pump-free water transport at low cost with a high degree of sustainability, as well as good availability of the paper-forming cellulosic material, thus making it an attractive candidate for point-of-care (POC) analytics and diagnostics. Although a number of interesting demonstrators for such paper devices have been reported to date, a number of challenges still exist, which limit a successful transfer into marketable applications. A strong limitation in this respect is the (unspecific) adsorption of protein analytes to the paper fibers during the lateral flow assay. This interaction may significantly reduce the amount of analyte that reaches the detection zone of the microfluidic paper-based analytical device (µPAD), thereby reducing its overall sensitivity. Here, we introduce a novel approach on reducing the nonspecific adsorption of proteins to lab-made paper sheets for the use in µPADs. To this, cotton linter fibers in lab-formed additive-free paper sheets are modified with a surrounding thin hydrogel layer generated from photo-crosslinked, benzophenone functionalized copolymers based on poly-(oligo-ethylene glycol methacrylate) (POEGMA) and poly-dimethyl acrylamide (PDMAA). This, as we show in tests similar to lateral flow assays, significantly reduces unspecific binding of model proteins. Furthermore, by evaporating the transport fluid during the microfluidic run at the end of the paper strip through local heating, model proteins can almost quantitatively be accumulated in that zone. The possibility of complete, almost quantitative protein transport in a µPAD opens up new opportunities to significantly improve the signal-to-noise (S/N) ratio of paper-based lateral flow assays.

Lignin als nachwachsendes, erneuerbares Biopolymer, welches als Nebenprodukt in der Zellstoffindustrie anfällt, besitzt das Potenzial Materialien auf der Basis von endlichen, fossilen Rohstoffen ganz oder teilweise zu ersetzen. Ziel der Arbeit war es Adsorptionsmaterialien auf der Basis von Lignin in Form von Hydrogelen herzustellen und ihre Adsorptionseigenschaften zu untersuchen. Hierfür wurden zunächst verschiedene technische Lignine (Kraftlignine, Ligninsulfonate und Sodalignine) eingehend charakterisiert, zu Hydrogelen vernetzt und die Adsorptionseigenschaften an den Metallionen Cu(II), Ni(II) und Zn(II) untersucht. Weiterhin wurde der Einfluss der Fraktionierung des Lignins auf die Adsorptionseigenschaften der resultierenden Ligninhydrogele untersucht. Hierfür wurde das Kraftlignin mittels Aceton : Wassermischungen über die unterschiedliche Löslichkeit der Fraktionen aufgetrennt. Die Fraktionierung des Ligninsulfonates erfolge über die Membranfiltration, bei der ein Reinigungsschritt mit kleinem Porendurchmesser vorausgesetzt wurde. Durch chemische Modifizierung des Ausgangslignins konnten die Adsorptionseigenschaften des Ligninhydrogels verändert werden. Hierfür wurden drei verschiedene Synthesewege durchgeführt: Die Einbringung von Dihydroxybenzol über eine sauerkatalysierte Substitutionsreaktion, das Anbinden von Iminodiessigsäure über die Mannich-Reaktion und mittels Epichlorhydrin, sowie die Einbringung von stickstofffunktionellen Gruppen mittels oxidativer Ammonolyse. Ferner wurden weitere Eigenschaften wie die Zyklenstabilität und Selektivität der Ligninhydrogele untersucht. Die während der Adsorption ablaufenden die Schrumpf- und Quelleigenschaften des Hydrogels konnten ausgenutzt werden, um ein Konzept für ein Sensorsystem zu entwickeln. Dazu wurde das Ligninhydrogel an kovalent an einen ITO-Träger angebunden und die Schrumpf- und Quellprozesse mittels QCM am Beispiel von verschieden konzentrieren Magnesium- und Natriumionenlösungen untersucht. An Aer

Für die Herstellung von Bindemittel- und Kunststofffreien Naturfaserformteilen stehen die Prozesse Faserguss und Pressspan zu Verfügung. Beide sind durch klare Nachteile geprägt. Außerdem besteht zur Herstellung von Naturfaserformteilen eine Entwicklungslücke. Ua. diese bedingt, dass Naturfaserformteile wenig angewendet werden. Das in dieser Arbeit entwickelte Verfahren der Vakuumpresstrocknung ermöglicht es auf eine neuartige Weise Naturfaserformteile herzustellen. Neben der Entwicklung selbst, werden Vergleiche zu herkömmlichen Herstellungsmethoden gezogen, die Prozessparameter untersucht, Trocknungsspezifiken diskutiert und ein Umweltwirkungsvergleich durchgeführt. Als Demonstrationsobjekt wird ein Freischwinger Panton Chair als Faservariante hergestellt.:Abkürzungsverzeichnis vii 1 Einleitung 1 1.1 Werkstoff des 19. Jahrhunderts 1 1.2 Motivation und Zielsetzung 3 1.3 Struktur der Arbeit 4 2 Stand der Technik 7 2.1 Nachhaltiges Wirtschaften und Werkstoffe 7 2.1.1 Ziele und Strategie der Bioökonomie 7 2.1.2 Vergleich der Naturfaserstoffe zu Kunststoffen 9 2.2 Materialien und Methoden zur Herstellung von Formteilen 13 2.2.1 Rohstoffe für Faserformteile 13 2.2.2 Urformender Fasergussprozess und dessen Trocknung 15 2.2.3 Presstrocknung sogenannter Pressspanerzeugnisse 19 2.2.4 Weiterentwicklung der Faserformverfahren 21 2.3 Trocknung relevanter Naturstoffe 24 2.3.1 Begriffe Feuchte, Wassergehalt und Trockengehalt 24 2.3.2 Trocknungsarten 24 2.3.3 Trocknung hygroskopischer kapillarporöser Stoffe 26 2.4 Zusammenfassung des Standes der Technik 29 3 Entwicklung der Vakuumpresstrocknung 31 3.1 Ideenentwicklung 31 3.1.1 Verfahrensanforderungen 31 3.1.2 Technischer Widerspruch 33 3.1.3 Lösungsprinzip Vakuum 35 3.2 Umsetzung der Vakuumpresstrocknung 37 3.2.1 Technische Veränderungen 37 3.2.2 Aufbau und technische Materialien 38 3.2.3 Ablauf der Vakuumpresstrocknung 40 4 Untersuchung der Vakuumpresstrocknung 43 4.1 Test der Funktion 43 4.1.1 Referenz Rapid-Köthen-Prozess 43 4

Biomimetic actuators are typically constructed as functional bi- or multilayers, where actuating and resistance layers together dictate bending responses upon triggering by environmental stimuli. Inspired by motile plant structures, like the stems of the false rose of Jericho (Selaginella lepidophylla), we introduce polymer-modified paper sheets that can act as soft robotic single-layer actuators capable of hygro-responsive bending reactions. A tailored gradient modification of the paper sheet along its thickness entails increased dry and wet tensile strength and allows at the same time for hygro-responsiveness. For the fabrication of such single-layer paper devices, the adsorption behavior of a cross-linkable polymer to cellulose fiber networks was first evaluated. By using different concentrations and drying procedures fine-tuned polymer gradients throughout the thickness can be achieved. Due to the covalent cross-linking of polymer with fibers, these paper samples possess significantly increased dry and wet tensile strength properties. We furthermore investigated these gradient papers with respect to a mechanical deflection during humidity cycling. The highest humidity sensitivity is achieved using eucalyptus paper with a grammage of 150 g m⁻² modified with the polymer dissolved in IPA (~13 wt%) possessing a polymer gradient. Our study presents a straightforward approach for the design of novel hygroscopic, paper-based single-layer actuators, which have a high potential for diverse soft robotic and sensor applications.

Using isocyanate-functionalized Kraft lignin as a reactive macromonomer for the preparation of polyurethane foams by a prepolymer technique is a well-known strategy to incorporate the biomacromolecule into a higher value polymer material. However, as of today the mechanical properties of the resulting materials are still insufficient for a number of possible applications. One reason for this limitation is that the reaction pathway and the morphological arrangement of such foams is of uttermost complexity and depends on a large number of influencing material-intrinsic factors. One important parameter is the reactivity of the functionalized lignin, which has a great impact on the interphase reaction kinetics and thus, on the geometry and mechanical properties of the resulting polyurethane foams. The reactivity is implied, amongst others, by the electron affinity of the isocyanate moiety. Herein, we investigate the reactivity of Kraft lignin modified with different commercially used isocyanates in the reaction with conventional polyols. Therefore, differently reactive prepolymers were synthesized, characterized and polyurethane foams were prepared thereof by using these compounds and the foam formation kinetics, morphological as well as mechanical properties were investigated. Finally, the results were supported by quantum mechanical calculations of the electron affinities of representative model compounds for the lignin-based prepolymers. This work gives rise to a better understanding of the effect of the reactivity and isocyanate structure linked to Kraft lignin on the polyurethane formation and enables rational choice of the isocyanate for pre-functionalization of lignin to prepare materials with better mechanical performance.