Current significance and future perspective of 3D-printed bio-based polymers for applications in energy conversion and storage system

The increasing global population has led to a surge in energy demand and the production of environmentally harmful products, highlighting the urgent need for renewable and clean energy sources. In this context, sustainable and eco-friendly energy production strategies have been explored to mitigate the adverse effects of fossil fuel consumption to the environment. Additionally, efficient energy storage devices with a long lifespan are also crucial. Tailoring the components of energy conversion and storage devices can improve overall performance. Three-dimensional (3D) printing provides the flexibility to create and optimize geometrical structure in order to obtain preferable features to elevate energy conversion yield and storage capacitance. It also serves the potential for rapid and cost-efficient manufacturing. Besides that, bio-based polymers with potential mechanical and rheological properties have been exploited as material feedstocks for 3D printing. The use of these polymers promoted carbon neutrality and environmentally benign processes. In this perspective, this review provides an overview of various 3D printing techniques and processing parameters for bio-based polymers applicable for energy-relevant applications. It also explores the advances and current significance on the integration of 3D-printed bio-based polymers in several energy conversion and storage components from the recently published studies. Finally, the future perspective is elaborated for the development of bio-based polymers via 3D printing techniques as powerful tools for clean energy supplies towards the sustainable development goals (SDGs) with respect to environmental protection and green energy conversion.

Supported TiO2-ZnWO4 Photocatalytic Nanofibrous Membranes for Flow-Through and Fixed-Bed Reactors

We developed utilization models of supported electrospun TiO2-ZnWO4 photocatalytic nanofibrous membranes for air and water purifications using a noncomplex system with facile adaptation for large-scale processes. For this uniquely designed and multimode catalyst, ZnWO4 is selected for a visible light activity, while TiO2 is incorporated to enhance physical stability. Morphological structures of the TiO2-ZnWO4 membrane are characterized by scanning electron microscopy and scanning electron microscopy-energy-dispersive X-ray spectroscopy. The distinguished growth of ZnWO4 nanorods at the surface of the TiO2-ZnWO4 membrane is revealed by transmission electron microscopy (TEM). The relaxation process and charge transfer mechanism are proposed following the examination of interface and band gap (2.76 eV) between TiO2 and ZnWO4 particles via HR-TEM and UV-vis spectrophotometry. For the gas-phase reaction, a transparent photocatalytic converter is designed to support the pleated TiO2-ZnWO4 membrane for toluene decomposition under visible light. To obtain a crack-free and homogeneous fiber structure of the pleated TiO2-ZnWO4 membrane, 1 h of nanofibrous membrane fabrication via a Nanospider machine is required. On the other hand, a fiberglass-supported TiO2-ZnWO4 membrane is fabricated as a fixed-bed photocatalyst membrane for methylene blue decomposition under natural sunlight. It is observed that using the calcination temperature at 800 °C results in the formation of metal complexes between fiber glass and the TiO2-ZnWO4 membrane. The TiO2-ZnWO4 membrane successfully decomposes toluene vapor up to 40% under a continuous-flow circumstance in a borosilicate photocatalytic converter and 70% for methylene blue in solution within 3 h. Finally, the mechanically robust and supported TiO2-ZnWO4 nanofibrous membranes are proven for an alternate potential in environmental remediation.

Wet Spinning of Graphene Oxide Fibers with Different MnO2 Additives

We present the fabrication of graphene oxide (GO) and manganese dioxide (MnO₂) composite fibers via wet spinning processes, which entails the effects of MnO₂ micromorphology and mass loading on the extrudability of GO/MnO₂ spinning dope and on the properties of resulted composite fibers. Various sizes of rod and sea-urchin shaped MnO₂ microparticles have been synthesized via hydrothermal reactions with different oxidants and hydrothermal conditions. Both the microparticle morphology and mass loading significantly affect the extrudability of the GO/MnO₂ mixture. In addition, the orientation of MnO₂ microparticles within the fibers is largely affected by their microscopic surface areas. The composite fibers have been made electrically conductive via chemical or thermal treatments and then applied as fiber cathodes in Zn-ion battery prototypes. Thermal annealing under an argon atmosphere turns out to be an appropriate method to avoid MnO₂ dissolution and leaching, which have been observed in the chemical treatments. These rGO/MnO₂ fiber cathodes have been assembled into prototype Zn-ion batteries with Zn wire as the anode and xanthan-gum gel containing ZnSO₄ and MnSO₄ salts as the electrolyte. The resulted electrochemical output depends on the annealing temperature and MnO₂ distribution within the fiber cathodes, while the best performer shows stable cycling stability at a maximum capacity of ca. 80 mA h/g.

Polymerized Luteolin Nanoparticles: Synthesis, Structure Elucidation, and Anti-Inflammatory Activity

Luteolin is an anti-inflammatory flavonoid commonly found in many edible plants. The compound is popularly consumed as a supplement regardless of its poor water solubility (27.8 μg/mL at 25 °C) and low bioavailability. Here, mild one-pot polymerization of luteolin into water-dispersible nanospheres, with an average dry size of 234.8 ± 101.6 nm, an aqueous size distribution of 379.1 ± 220.5 nm (PDI = 0.338), an average ζ-potential of -36.2 ± 0.2 mV, and an 89.3 ± 4.8% yield, is described. The nanospheres consist of polymerized luteolin (polyluteolin) with a weight-average molecular mass of around 410000 Da. The chemical structure of polyluteolin is identified through ¹H-¹H correlated spectroscopy (COSY), ¹H-¹³C heteronuclear single-quantum coherence (HSQC), and ¹H-¹³C heteronuclear multiple-bond correlation (HMBC) NMR spectroscopic analyses of the oligomers, and a polymerization mechanism is proposed. Unlike luteolin that showed both dose-dependent anti-inflammatory activity and cytotoxicity when tested in lipopolysaccharide-stimulated macrophages, the polyluteolin nanoparticles possess dose-dependent anti-inflammatory activity without causing cell death even at high concentrations.

Water-dispersible unadulterated α-mangostin particles for biomedical applications

α-Mangostin, the extract from pericarp of Garcinia mangostana L . or mangosteen fruit, has been applied in various biomedical products because of its minimal skin irritation, and prominent anti-inflammatory, antimicrobial and immune-modulating activities. Owing to its low water solubility, the particle formulations are necessary for the applications of α-mangostin in aqueous media. The particle formulations are usually prepared using surfactants and/or polymers, usually at a larger amount of these auxiliaries than the amount of α-mangostin itself. Here, we show the self-assembly of α-mangostin molecules into water-dispersible particles without a need of any polymers/surfactants. Investigations on chemical structure, crystallinity and thermal properties of the obtained α-mangostin particles, in comparison to the conventional α-mangostin crystalline solid, confirm no formation of the new compound during the particle formation and suggest changes in intermolecular interactions among α-mangostin molecules and significantly more hydroxyl functionality positioned at the particles' surface. The ability of the water suspension of the α-mangostin to inhibit the growth of Propionibacterium acnes, the acne-causing bacteria, is similar to that of the solution of the conventional α-mangostin in 5% dimethyl sulfoxide. Moreover, at 12.7 ppm in an aqueous environment of RAW 264.7 cell culture, α-mangostin suspension exhibits five times higher anti-inflammatory activity than the conventional α-mangostin solution, with the same acceptable cytotoxicity of less than 20% cell death.

Color and shape reversible, recoverable and repeatable mechanochromic shape memory polycaprolactone: a single material with dual functions

A polycaprolactone-based mechanochromic shape memory material exhibits reversible and repeatable shape and color as a result of its crystallinity.

Rice flour-based nanostructures via a water-based system: transformation from powder to electrospun nanofibers under hydrogen-bonding induced viscosity, crystallinity and improved mechanical property

Rice flour is a naturally abundant and renewable biodegradable and biocompatible material.

Starch-based and multi-purpose nanofibrous membrane for high efficiency nanofiltration

The objective of the present work is to develop nanofibrous membranes from rice-flour based nanofibers containing PVA for high efficiency filtration.

Mechanically robust, multifunctional and nanofibrous membranes for tuberculosis elimination

Mechanically robust and potent antibacterial membranes are fabricated for total elimination of water- and airborne tuberculosis (TB) bacteria.

Hydroxyapatite-hybridized chitosan/chitin whisker bionanocomposite fibers for bone tissue engineering applications

Biomimetic nanofibrous scaffolds derived from natural biopolymers for bone tissue engineering applications require good mechanical and biological performances including biomineralization. The present work proposes the utility of chitin whisker (CTWK) to enhance mechanical properties of chitosan/poly(vinyl alcohol) (CS/PVA) nanofibers and to offer osteoblast cell growth with hydroxyapatite (HA) mineralization. By using diacid as a solvent, electrospun CS/PVA nanofibrous membranes containing CTWK can be easily obtained. The dimension stability of nanofibrous CS/PVA/CTWK bionanocomposite is further controlled by exposing to glutaraldehyde vapor. The nanofibrous membranes obtained allow mineralization of HA in concentrated simulated body fluid resulting in an improvement of Young's modulus and tensile strength. The CTWK combined with HA in bionanocomposite is a key to promote osteoblast cell adhesion and proliferation. The present work, for the first time, demonstrates the use of CTWKs for bionanocomposite fibers of chitosan and its hydroxyapatite biomineralization with the function in osteoblast cell culture. These hydroxyapatite-hybridized CS/PVA/CTWK bionanocomposite fibers (CS/PVA/CTWK-HA) offer a great potential for bone tissue engineering applications.

Thermal relaxation in combination with fiberglass confined interpenetrating networks: a key calcination process for as-desired free standing metal oxide nanofibrous membranes

Using Pd/Pt-decorated solar light active ZnWO₄/mixed-phased TiO₂ nanofibers as a model subject, we investigate the prerequisites for the construction of mechanically stable metal oxide nanofibrous membranes.