Rheology as an analysis method has only little awareness in fields of medical science. Commonly polymers are investigated considering flow dynamic properties, mechanical strength or viscoelastic behavior. With a closer look to biological fluids, such as the cerebrospinal fluid (CSF), some similarities to polymeric solutions can be found. CSF is an aqueous solution which contains a certain amount of macromolecules, such as different proteins. These macromolecular components are only present in low concentrations, but they are responsible for the specific flow behavior. This study focused on investigating the flow behavior of CSF. In order to compare laboratory parameters to viscoelastic behavior a cumulative methodology for the evaluations was consulted. The so-called cumulative storage factor was already established in fields of polymeric materials. [1] The viscoelastic properties are important especially for samples that do not confirm the ideal viscous or ideal elastic behavior. The cumulative storage factor is calculated from the frequency sweep and describes the rigidity behavior. In this study CSF samples were rheologically characterized and thereof the cumulative storage factor was used to correlate laboratory parameters as erythrocyte and leucocyte count, glucose, lactate and the total protein concentration with viscoelastic behavior. The overall goal is to evaluate whether rheological parameters may help for prediction of shunt dependance for hydrocephalus patients in the clinical routine.

To increase micromechanical adhesion between polymer and metal for direct joining realised by overmolding, metal surface structuring is often most expected [1-3]. The purpose of this study was to evaluate the infiltration efficiency of the microstructure of laser-engraved steel by molten polymer material as a function of melt flow length on structured metallic surface. Polymer-metal joints were prepared from austenitic steel (316) and polyamide 6. The surfaces of the metal inserts were microstructured by the engraving with using a low power (60 W) pulsed laser fiber. Four different microstructures were produced on steel plates. The process of injection molding (overmolding) of 316 steel inserts was carried out with the use of preheating their surface with an external infrared radiator, which was moved in the gripper by the additional manipulator (Fig. 1a). A series of bi-material joints were made without heating and with preheating of the inserts surface before the overmolding. Evaluation of the degree of infiltration of grooves on metal inserts as a function of the polymer melt flow distance (150 mm) was carried out on the basis of selected roughness parameters and related to microstructural variants and as in the case of cold and hot inserts. A gradually decrease in the value of Ra and Rz [μm ] parameters from the gate to the edge was observed in case of cold insert, while in case of preheated inserts no signifficant changes of Ra parameter was seen (Fig. 1b,c). This research was financially supported by the PUT, internal subsidy 0613/SIGR/2403.

The functionalization of polymer coatings dedicated to textiles, including those intended for personal protective equipment, can be obtained by physical or chemical modifications as well as by the application of mineral nanofillers such as basalt or silica[1]. Nanoparticles of basalt are used to reinforce hybrid epoxy composites and application of silica as a filler in the polymeric coatings for textiles increases their mechanical resistance[2]. Moreover, higher viscosity of the polymer coating layer covering the textile, obtained by increase in mineral filler content, may increase the anti-cut properties of coated material[3-4].
The main aim of the study was application of inorganic mineral fillers to composite coating layer to improve cut resistance. Experimental samples were made of an aramid knitted fabric coated with a three-dimensional latex layer containing mineral fillers. The polymer coating was made of thermoplastic material molds using 3D printing. Coatings with various three-dimensional geometries were obtained. The cut resistance was tested using a termodynamometer (P.I.Kontech.Ltd, Poland) with a blade load from 1.0N to 40.0N and the cutting speed 2.5 cm/s. Samples were also evaluated using optical microscopy (OPTA-TECH, Poland) and electron microscopy (HITACHI SU-8010, Japan) to assess their geometry and porous structure. The cut resistance increased from 10.9N to 24.0N compared to the reference sample. Furthermore it was assessed that mineral fillers in the polymer coating penetrate between the fibers, thus preventing the formation of porous structures, ensuring the formation of layers with higher cut resistance.

Acknowledgments:This research was funded in whole by National Science Centre, Poland; Grant number:2021/41/N/ST8/04281.

Organic phase change materials (PCMs) have been widely exploited in passive cooling applications due to their ability to store latent heat in melting. Several studies were conducted on shape stabilization of PCMs, however, very little research was conducted in fused deposition of thermoplastic polymers loaded with PCMs. 3D printing offers advantages in the realization of complex geometries, making easier the realization of thermal management systems with high exchanging surface area with both the device to be cooled and environment for heat dissipation. In this work, high density polyethylene is selected as printable supporting matrix, because of its relatively low melting point which permits to process the blend without PCM degradation. A fatty acid mixture was chosen as PCM for thermal management of electronic devices like batteries or photovoltaic cells. Expanded graphite (EG) was preliminary vacuum impregnated with the PCM to realize a first stabilization and enhance thermal conductivity, necessary for high charging/discharging rates. Subsequently, HDPE was melt compounded with the impregnated graphite and the obtained blend was extruded to realize a filament which was finally printed. Thermal and mechanical properties were analysed in a temperature range covering the entire PCM phase transition. The result is a high PCM content composite with enhanced thermal conductivity, which does not present leakage issues upon PCM melting. HDPE plays a fundamental role for the shape stabilization, giving good mechanical properties to the final products, demonstrating their suitability for thermal management of electronic devices.

This work investigates the ppossibility of repurpose waste glass materials in the field of 3D printing of slurries via vat polymerization technologies, using biobased photocurable formulations. The formulations are prepared with acrylated epoxidized soybean oil (AESO) developed in our previous work [1]. Waste materials like mineral wool and glass from the vitrification of ash from municipal waste incinerators were ball milled and sieved under 25 µm. The as-obtained powders were morphologically characterized using field emission scanning electron microscopy (FESEM) and thermally using dynamic scanning calorimetry (DSC), hot stage microscopy (HSM) and dilatometry. These powders were mixed with AESO formulations to prepare photocurable slurries with loadings of 40 to 60 wt%. Rheological and photo-rheological analyses determined printing parameters including exposure time and layer thickness. Then, porous like structure were 3D printed using Vat photopolymerization techniques. Post printing thermal treatments were carried out to consolidate the printed objects, removing the resin component and yielding glass-ceramic structures. The results indicate significant potential for manufacturing of porous-like glass-ceramic materials through this method, with promising results for sustainable material reuse and advanced manufacturing processes.

4D printing, an evolution of traditional additive manufacturing, incorporates stimuli-responsive smart materials that change shape or function over time when exposed to specific environmental conditions [1-3]. In order to have a successful functionality of a 4D printed structure, high-performance smart materials must be developed and implemented. Adding smart materials complements the ability of additive manufacturing's (AM) capacity to produce complex and dynamic personalized structures. Shape Memory Polymers (SMPs) are one of the main categories of the smart materials for programmable and responsive structures due to their special ability to "remember" and return to their original shape in response to external stimuli like heat or magnetic fields. Their lightweight nature, flexibility, and tunable mechanical properties enable complex, dynamic movements while maintaining structural integrity [4, 5].
In this study, soft magnetic particles (Fe3O4) are dispersed into a dissolved SMP matrix , ensuring uniform distribution and magnetic responsiveness. Developed dried material is then pelletized and directly 3D-printed using a direct pellet printing technique. These 3D printed structures exhibit remote actuation functionality, allowing shape transformations under magnetic fields without direct contact or heating. The combination of shape memory behavior with magnetic responsiveness, using an affordable and widely accessible extrusion-based 3D printing technique, making it ideal for cutting-edge applications in soft robotics and biomedical devices. The use of SMPs as the smart material in this work shows the promise of responsive and programmable polymer systems in next-generation additive manufacturing.

The development of low cost printable materials with functional properties is necessary to meet the demands of the electronics manufacturing industry1. The vat photopolymerization-based digital light processing (DLP) allows for high-speed and high-resolution printing with complex geometries, but its expansion is limited by the scarcity of photocurable conductive resins, particularly those derived from renewable resources2. Following the research line of our group3, this communication describes the printability challenges in obtaining new electrically conductive flexible composites by DLP, using bio-based acrylic monomers and a polyaniline/multiwalled carbon nanotube filler (PANI-MWCNT)
Firstly, several PANI/CNT fillers with increasing CNT content were synthesized and characterized. The most suitable one, a PANI/MWCNT composite with 70 wt% CNT, was selected based on the particle size, compatibility with acrylic monomers, and electrical conductivity,
Subsequently, acrylic composites filled with 0–3 wt.%. of the selected PANI/MWCNT were prepared by DLP. A comprehensive printability study was conducted to optimize the curing rate and the resolution of printed specimens4. For each formulation, the photoinitiator content and the printing conditions—such as bottom exposure, exposure time per layer, and layer thickness—were adjusted based on UV absorption, filler’s size and morphology, and parameters obtained from Jacob's curves.
Finally, the physicochemical and electrical properties of the printed samples were studied, with particular attention given to the accuracy of the printed parts and the percolation threshold, as these aspects are essential for the design of future sensors.

As 3D printing continues to evolve, the development of new printable materials is crucial for advancing a wide range of applications in this field. Zein, a by-product of corn processing, is a biodegradable biopolymer and sustainable alternative to synthetic polymers. It has gained attention for its biocompatibility and versatility in various applications, including 3D printing.
This research study explores the development of a zein-based ink for pneumatically driven extrusion 3D printing. It investigates two approaches to modifying zein through methacrylation to achieve a UV-crosslinkable ink formulation. The first route involves a two-step process: initially, hydroxyl groups are introduced onto the zein backbone through esterification, followed by methacrylation of these hydroxyl groups using methacrylic acid. This approach is designed to enhance the reactivity of zein and improve the efficiency of the methacrylation process. The second route streamlines the process by using a single-step methacrylation with the monomer 2-hydroxypropyl methacrylate. Furthermore, the ink formulation optimization process involves iterative adjustments, exploring the blending of methacrylated zein with other biopolymers to enhance the ink's properties.
This study includes the validation of zein methacrylation using Fourier Transform Infrared (FTIR) and Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy, analysis of the ink's shear-thinning behavior via rheology, evaluation of its 3D printability, photo-crosslinking of printed constructs, and assessment of biocompatibility.
These findings contribute to the limited research on zein-based 3D printing, highlighting its potential for sustainable manufacturing and soft tissue engineering while addressing the need for environmentally friendly ink formulations.

As a modern processing technique, 3D printing has revolutionized catalyst fabrication by enabling complex geometries like triply periodic minimal surface structures, which enhance surface area, mass transfer, and mechanical stability, improving overall catalysts efficiency. Metal-based catalysts, such as zinc, manganese, and titanium, have proven effective in the chemical recycling of polyethylene terephthalate (PET). However, concerns regarding toxicity and environmental impact highlight the need for less toxic alternatives. Sustainable catalysts such as sodium carbonate have been investigated for PET glycolysis, providing an environmentally friendly approach.
Building on prior research that successfully integrated metals like titanium oxide into resins for SLA 3D printing, respectively nickel nitrate into polylactic acid for FDM 3D printing, this study explores sodium carbonate as a sustainable 3D-printed catalyst for polymer degradation. It focuses on optimizing dispersion for integration into a printable matrix, followed by 3D printing and evaluating structural stability and catalytic performance in PET degradation. Catalyst characterization involves micro-computed tomography, thermogravimetric analysis, and solvent resistance, while the final degradation product will be analyzed using nuclear magnetic resonance and Fourier transform infrared spectroscopy.
This study integrates additive manufacturing with eco-friendly catalysts, offering significant potential to advance polymer recycling methods and reduce environmental impact. Furthermore, the ability to easily remove and reuse 3D-printed catalysts enhances the sustainability of plastic waste management efforts, supporting global sustainability goals. This approach is particularly relevant to the growing field of catalytic degradation of synthetic polymers like PET, offering promising solutions for more effective plastic waste management.

Lignin-reinforced polymer composites show promise for additive manufacturing, particularly vat photopolymerization (VPP), which uses UV light to cure liquid photopolymers layer by layer.
This study developed composites by incorporating different amounts of lignin into renewable acrylate epoxidized soybean oil (AESO) resin and fabricating 3D-printed complex parts using LCD VPP printer.
Materials included AESO as the photocurable resin, tetrahydrofurfuryl acrylate (THFA) as a reactive diluent, and phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) as a photoinitiator. UPM BioPiva™ 395 lignin served as the bio-filler. AESO and THFA were mixed in a weight ratio of 60:40 with 2 wt.% BAPO and bio-composites were prepared with 5 and 7.5 phr lignin.
Unfilled and lignin-filled composites were processed using a Phrozen Sonic Mini 8K LCD VPP 3D printer with a Linear Projection LED Module.
Viscosity measurements confirmed resin processability for VPP. Morphological analysis using Scanning electron microscopy showed that lignin particles were uniformly distributed in the polymer matrix. Fourier transform infrared spectroscopy was performed to monitor the conversion over time of the photopolymerization process. Thermal and viscoelastic properties were evaluated by thermogravimetric analysis and thermal dynamic mechanical analysis, the characterizations showed that lignin influenced the thermal and mechanical properties. Tensile properties were also tested to determine the impact of lignin on mechanical properties. Printing tests optimized the resin parameters for LCD 3D printing, producing complex and high-precision structures.
In summary, lignin-based composites were successfully fabricated with enhanced properties due to uniform lignin dispersion in AESO-based resin.

Hyaluronic acid (HA) is a biomaterial widely used in tissue engineering, regenerative medicine, and drug delivery. While HA-based bioinks support cell viability and tissue-specific functions, their low viscosity often limits printability, necessitating modifications [1]. We address this challenge by preparing microgel suspensions from HA to tailor ink viscosity by microgel size and concentration. For added functionality, microgels made from poly(N-isopropylacrylamide) (PNIPAAm), a thermo-responsive polymer chosen for its ease of functionalization, and ability to maintain cell viability, are mixed in [2]. These particle-based PNIPAAm and HA inks are combined at varying volumetric ratios, extruded via 3D printing, and exposed to UV light for inter-particle crosslinking via [2+2] cycloaddition of DMMIAAm groups on the microgel’s surface with a PEG-based crosslinker incorporating dynamic thiol-ester bonds into the microgel assembly [3, 4]. Our dual-microgel ink system provides high biocompatibility, tunable rheological properties, improved 3D printing fidelity, making it ideal for advanced bioprinting. Integration of thiol-ester bonds in the scaffolds promotes stimuli-responsive behavior, controlled degradation, and stress-relaxing properties, fostering an environment conducive to tissue regeneration, remodeling, and enhanced cell-material interactions. As a 3D printing platform, we use a modular, customizable 3D printer built from LEGO Technic bricks advancing a protocol by A. Moukachar et al [5]. platforming detail, we develop micrometer-precise extrusion nozzles, fabricated via projection-microstereolithography (PμSL), designed to fit LEGO pieces with pin-like lock geometry. Four nozzle geometries are introduced, optimizing the printing process by varying internal channel design. These nozzles improve control over material flow and prevent clogging due to microgel agglomeration.

Additive manufacturing (AM) of polymeric materials enables the manufacturing of complex structures for a wide range of applications. Among AM methods vat photopolymerization (VP) is desired owing to improved efficiency, excellent surface finish, and printing resolution at the micron-scale. Nevertheless, the major portion of resins available for VP are based on systems with limited or negligible recyclability. Here, we describe an approach that enables the printing of a resin that is amenable to re-printing with retained properties and appearance. To that end, we take advantage of the potential of polythiourethane chemistry, which not only permits the click reaction between polythiols and polyisocyanates in the presence of organic bases, allowing a fast-printing process but also chemical recycling, reshaping, and reparation of the printed structures, paving the way toward the development of truly sustainable recyclable photoprintable resins.

The ongoing growth of AM (additive manufacturing) technologies demands new smart materials with certain physical properties (such as electronic properties) for specific applications. In addition, bio-based polymers and composites are needed for the green transition of oil-based traditional polymers.
In the current work, polymer composites printable by FDM (fusion deposition modelling) were obtained with a bio-based matrix (polylactic acid or PLA) and electrically conductive nano-filler (multi-walled carbon nanotubes or MWCNT). The composites were obtained by a combination of solvent-casting and melt-mixing, getting the electrical threshold at 5 wt.% MWCNT1. Moreover, lignin, SCG (spent coffee grounds) and Ox-SCG (oil derived from SCG) were incorporated in 3 wt.% to the PLA/MWCNT composite, and the physical properties of the resulted composites were analyzed (nano-particles distribution, thermal resistance, viscoelastic, mechanical and electrical properties, 3D printability). After the characterizations, we demonstrated that SCG enhanced PLA/MWCNT electrical conductivity (getting up to 1.4±0.1 S cm-1) and mechanical resistance.
Afterwards, some flexible sensors were 3D-printed (Figure 1 A) and summited to an electromechanical test to see their performance. Next, an accelerometer was assembled (Figure 1 B, C) with the printed sensor and an Arduino for proof of concept, demonstrating the potential of fully 3D-printed sensors for low-cost applications with a high degree of customization.

Additive manufacturing, namely 3D printing, is attracting increasing interest in the industrial field since it allows obtaining parts with complex shape that are challenging to obtain with conventional processes. In particular, 3D printing of polymers is able to construct the object through the deposition of extruded bead on a deposition plate [1]. Although interesting, 3D printing of polymers is challenging due to several phenomena that are not completely understood. For instance, the presence of crystallization seeds, cause to an incomplete melting, induces a faster crystallization with consequent effects on the adhesion between adjacent beads [2]. If the crystallization is faster than the reorganization of molecules at the interface between adjacent beads, the molecules will not interact, and the adhesion will be poor. Otherwise, if crystallization occurs later in the process, it will increase the interaction at the interface, and the adhesion will be strong [3]. This work aims at assessing the effect of previous crystallization on the mechanical performances of 3D printed parts. A polylactic acid (PLA) filament has been obtained by extrusion and annealed at different temperatures to achieve desired crystallization degree. The filament has been used during the process conducted with different extrusion ratios to obtain the parts. The higher the extrusion ratio, which means flow rate, the higher the crystallinity and the orientation of the part are. The crystallinity degree and the orientation achieved during the process are correlated with the residence time of polymer inside the extruder.

The study analyzes the geometric influence of 3D-printed multilayer structures using polylactic acid (PLA), conductive PLA, and thermoplastic polyurethane (TPU) for radar stealth applications. The multilayer structures consist of triangular and honeycomb geometric layers designed to optimize radar wave absorption, as schematically illustrated in Figure 1.
Experimental tests evaluated reflection loss (RL) performance by comparing different material configurations in the geometric multilayer structure in two orientations: horizontal and vertical. The best result was obtained when conductive PLA was placed in the middle layer in vertical Direction with RL of -16 dB. This configuration improved electromagnetic wave attenuation, demonstrating strong potential for stealth applications.
The geometric layering played a crucial role in wave absorption. The honeycomb structure exhibited superior dispersion and impedance matching, enhancing absorption efficiency. Meanwhile, the triangular layer provided structural stability and further contributed to electromagnetic wave attenuation by improving wave dispersion.
The results also emphasize the importance of material distribution within the multilayer structure. Positioning conductive PLA in the middle layer optimizes wave interference and energy dissipation due to multiple reflections and wave dispersion, thereby reducing reflected signals. This approach holds promise for the development of lightweight, customizable, and cost-effective radar-absorbing materials.
In conclusion, the study demonstrates that 3D-printed geometric multilayer structures combining PLA or TPU with conductive PLA can achieve significant radar wave attenuation, with the best performance of -16 dB when conductive PLA is used as the middle layer. The geometric influence is key to optimizing stealth capabilities in advanced applications.

The incorporation of step-growth polymerization in additive manufacturing techniques is a viable strategy for obtaining homogeneous and consequently tough photopolymers. On this front, the thiol-ene reaction has attracted great interest in the last years owing to its high reactivity and efficiency. Thiols, however, suffer from a set of shortcomings ranging from high toxicity, strong odor and poor storage stability [1]. A possible way to mitigate these challenges is their replacement with alcohols, as they are free of these drawbacks and even offer a wider range of available monomers [2]. As is the case for most Michael addition chemistries, the oxa-ene subtype requires a base catalyst. In literature, most oxa-Michael addition reactions involve a Brønsted base catalysis, while examples utilizing Lewis bases remain relatively scarce [3].
In this work, we introduce new Lewis photobase generators (PBG) as catalysts for light triggered oxa-Michael addition reactions. Their preparation and characterization by means of UV/Vis spectroscopy is described. A mechanistic understanding is derived from a monofunctional model study followed by testing the applicability of the PBGs in polymeric formulations, which render their 3D printing by Hot Lithography possible [4].

As space exploration advances, long-duration missions will rely on closed-loop systems to support crew members, as external resupply is not feasible. In this context, materials directly produced from whole plants present the advantage to avoid complex extraction processes [1]. Spirulina (a cyanobacterium) presents a valuable resource, serving as both a food supplement and a potential source of oxygen. Additionally, its ability to grow rapidly in controlled environments and recycle human organic waste positions spirulina as a cornerstone of sustainable space habitats. Given its combined functionalities, spirulina is an ideal candidate as a material building block [2, 3, 4].

In this presentation, we introduce a novel 3D-printable material developed from spirulina. We have established an end-to-end lab-scale process to produce this material. Following its cultivation, unfractionated spirulina is melt-blended with a plasticizer via twin-screw extrusion. Plasticized spirulina forms cohesive, recyclable materials with mechanical properties that surpass those of other biobased compounds such as thermoplastic starch, and provides additional benefits in the form of fire retardance. Following optimization of its formulation, we successfully demonstrated the printability of this material via fused filament fabrication (FFF) 3D printing. The flexural strengths of the printed parts range from 1.7 to 5.5 MPa while the moduli vary between 17 to 602 MPa depending on humidity, plasticizer content, and process conditions.

These promising mechanical properties, combined with a novel and scalable production approach, processability, recyclability, and self-extinguishing characteristics, position spirulina-based biomaterials as ideal candidates for space applications.

Climate change, limited resources and environmental pollution are motivations for sustainable end-of-life management. The growth in polymer use has contributed to environmental problems, but the impact can be reduced through improved procedures, renewable materials and recycling technologies. However, some renewable resources or novel technologies may have a greater impact than the technologies they replace1. To provide a scientific measure of a product´s actual environmental impact and sustainability of new technologies, the life cycle assessment (LCA) method is commonly used. Thereby, all related material and emission streams are measured, mapped and evaluated regarding different impact categories2.

Here, we present for the first time a comprehensive cradle-to-grave LCA for room-temperature vulcanizing silicone sealants, as one of the most commonly used adhesives, identifying greenhouse gas emission drivers3. Compared to this benchmark, the potential of waste stream utilization and alternative raw materials is discussed.