Organic solar cells (OSCs) have gained increasing attention as a promising alternative to conventional silicon photovoltaics due to their lightweight, flexible, and cost-effective nature. By integrating novel high-efficiency polymers with small acceptor molecules, power conversion efficiencies exceeding 20% have been achieved. [1] However, for practical applications, achieving both scalable fabrication and long-term stability remains a major challenge.

This study investigates advanced deposition techniques, such as spray-coating and slot-die coating, for large-scale OSC fabrication. These methods offer high-throughput processing, roll-to-roll compatibility, and reduced material waste, making them promising for industrial applications. Despite these advantages, OSCs are highly susceptible to environmental degradation, including moisture and oxygen exposure, interfacial instability, and morphological changes, which significantly impact their operational stability. [2,3]

Here, we present experimental insights into scalable processing techniques and key degradation mechanisms affecting OSC performance. This work provides a bridge between laboratory-scale development and commercial implementation, such as functional sun blinds, contributing to the advancement of OSC technology.

Surface crystalline defects on polymer films affect their performance, highlighting the importance of detailed structural investigation. This study employes two-dimensional chord distribution functions (CDF) derived from small-angle X-ray scattering (SAXS) to investigate the lamellar structural differences between surface crystalline and non-crystalline defect locations in uniaxially stretched polymeric films. The CDF, representing the interface distribution function[1-3], was calculated using the second derivative of the electron density autocorrelation function, obtained via fast two-dimensional Fourier transformation of the scattering intensity I(s12, s3) weighted by 4π²s². Background signal was minimized using low-pass filter, and image refinement was achieved with MATLAB, involving gap correction, noise suppression, and enhancement of two-dimensional CDF images. (figure 1)
The results reveal that crystalline defects exhibit significantly higher scattering intensity and lamellar density compared to non-crystalline defect regions. CDF analysis indicates more orderly stacked lamellae at crystalline defects, with a lamellar thickness (Lc) of 3.9 nm and a long period (L) of 11.0 nm, compared to 3.5 nm and 11.9 nm, respectively, at non-crystalline regions. (figure 2) Wide-angle X-ray scattering (WAXS) corroborates these findings by identifying distinct crystalline diffraction peaks at crystalline defects and amorphous peaks at non-crystalline regions. (figure 3) These observations suggest that faster crystallization kinetics at crystalline defects during casting result in larger, tightly packed lamellae, while slower crystallization at non-crystalline regions leads to smaller, loosely packed lamellae.
This study highlights the utility of two-dimensional CDF in characterizing microstructural differences in anisotropic polymeric materials and provides theoretical guidance for addressing surface crystalline defects in polymer films.

Controlling the residual amount of water in the reaction system for polyurethane (PU) synthesis is as crucial as ensuring the proper formulation of polyol and isocyanate components. Excessive water content leads to side reactions and disruption of the stoichiometry, affecting the mechanical properties and performance of the final products. Conventionally, Karl-Fischer (KF) titration is the industry standard for water quantification in polyols. However, this method is not suited for real-time feedback, needed in continuous manufacturing, such as reactive extrusion. Although Near-Infrared (NIR) spectroscopy is a robust process analytical technique, its capability for effective monitoring of water content and simultaneous tracking of reactive aspects of PUs have not been determined. In this study, we present a concept for rapid quantification of water in poly(ethylene glycol) (PEG) polyol with NIR spectroscopy. We have targeted two use-cases: (1) on-line characterisation using an optical probe integrated into an extrusion process, enabling continuous monitoring, and (2) at-line determination with diffuse reflection spectroscopy, allowing for periodic quality checks. By using KF as a reference method and advanced chemometric analysis of the NIR spectra, partial least squares regression models to predict the water content of PEG were generated. Furthermore, we explored the options for parallel determination of water and isocyanate in the system of PU reagents, addressing the challenges posed by their overlapping characteristic peaks in the NIR range. This approach shows the potential of a single measuring technique adaptable to various processing lines, providing comprehensive insight into PU systems for enhanced production control in large-scale applications.

Efficiently measuring and differentiating wear in polymer-polymer tribological systems presents a significant challenge due to the simultaneous material loss of both counterparts. Historically, research in this area has focused on metal-polymer contacts, as distinguishing individual wear contributions in fully polymeric systems has remained difficult.

Our research group has developed a method for in-situ wear differentiation in polymer-polymer systems using a line laser scanner to record the shape of the wearing components in a ball-prism tribometer. This data is used to calculate the wear volume of the ball during measurement, enabling differentiation between ball and prism wear. Initially, high noise levels made it unfeasible to apply this approach in real-world applications. However, further modifications to the technique reduced measurement noise by over 90%, allowing precise differentiation of wear on both the ball and prism. To enhance measurement speed, the method was expanded to assess five material combinations simultaneously. This advancement provides a way to track and differentiate the wear of polymer-polymer counterparts over time, even when both materials exhibit significant wear.

Our results demonstrate that the modified method delivers accurate, reproducible data, making it a valuable tool for future tribological research in fields such as 3D-printed non-assembly mechanisms, seals, biomedical devices, and polymer-based bearing technology.

The presentation will summarize the original method, the introduced modifications, and the resulting improvements in measurement accuracy, offering new insights into polymer-polymer tribological systems where both counterparts undergo simultaneous wear.

The limitations of photopolymerization techniques for epoxy-based composites, such as the low penetration of light rays or the inefficiency of the process in the presence of opaque additives, have led to the need to develop new polymerization techniques. Radical induced cationic frontal polymerization (RICFP)1 combines photopolymerization with thermal radical polymerization, achieving to overcome the aforementioned limitations. Frontal polymerization is a unique type of polymerization where the polymerization process moves from a localized initiation point and propagates in a front, typically in the form of a moving reaction zone. This can be contrasted with typical bulk polymerizations, where the process occurs throughout the material uniformly. In this work, different formulations have been developed to evaluate the viability of performing RICFP at room temperature of an epoxy resin and its composites. The formulations studied are based on a bisphenol A diglycidyl ether diglycidyl ether (BADGE) epoxy resin, in which the concentration of a diluent based on a cycloaliphatic epoxy resin, named CE, has been varied. The rheological properties of the formulations studied were determined to establish the relationship between the viscosity of the system and the viability of carrying out RICFP. Subsequently, the gel content, the glass transition temperature, the crosslinking density and the mechanical properties of the most promising formulations have been determined. Finally, composite formulations with different fibres have been evaluated.

In the past decades, considerable efforts have been made to develop bio-based and biodegradable solutions to replace fossil-based materials. Sophisticated architectures, such as multilayer structures, composites or fibers, have been designed to obtain the properties usually achieved with petroleum-derived materials. Among these, fibers offer several advantages: they can contain fillers or can be incorporated into composites. With their high surface area, fibers present interesting release properties and barrier properties for biomedical applications, packaging or membranes1,2. However, petroleum-based fibers are usually produced by melt-processing, under conditions that are not compatible with the characteristics of natural materials. Therefore, alternative processing methods must be considered. In this work, we investigated cellulose derivatives as greener materials for fibers produced by solution spinning. Cellulose is one of the most abundant polymers on earth, and cellulose derivatives have already been used to produce environmentally friendly materials with suitable optical, mechanical and barrier properties3. Among them, hydroxypropyl cellulose (HPC) is a low-cost alternative material that is transparent and rigid, with high strength and good barrier properties. Despite these numerous properties, HPC cannot be prepared by melt-processing techniques, which limit the production of HPC fibers. However, this work presents, for the first time, a rapid and reliable method to produce transparent HPC fibers by wet spinning. HPC fibers have a higher Young’s modulus, tensile strength and degree of crystallinity than solvent-casted HPC films4, which makes them a good alternative to replace petroleum-based fibers, such as polyvinyl alcohol fibers, used in fiber-reinforced composites, packaging materials, sanitary products or cosmetics.

With the rising demand for electric and hybrid vehicles, the development of advanced battery technologies has become a significant growing area of research amongst polymer and rheology communities. Battery designs have primarily emphasized thermal and energy density, often overlooking the importance of mechanical performance, especially the pressure applied to cells, which directly affects the cell life1. Traditional foam-based solutions fail to adequately address the dimensional challenges within battery systems, highlighting the need for innovative approaches. This work explores the potential use of thermoplastic elastomers (TPEs) as a viable alternative to aluminum compression plates in battery modules. TPEs, which combine the characteristics of both thermoplastics and elastomers, offer key advantages such as recyclability, low density, and flexibility for multi-material designs and ease of processing by injection molding technology. This study investigates the influence of processing conditions—particularly high pressure, high shear, and elongational flows—on the final phase morphology of injection-molded TPEs. The findings of this study aim to provide insights into the optimization of processing conditions, thereby contributing to the advancement of more sustainable and durable battery designs.

The conversion of natural biopolymers, such as starch, cellulose, and chitosan, into viable alternatives to synthetic polymers has garnered significant attention in the field of sustainable materials science. The plasticization process of these natural polymers presents unique challenges due to the extensive hydrogen bonding networks inherent in their molecular structure. This investigation demonstrates that the utilization of efficacious plasticizers can yield flexible bioplastics with mechanical properties comparable to certain polyolefin-based materials, which can be fabricated using conventional polymer processing techniques. [1, 2] It is observed that processing parameters significantly influence the polymer's structural configuration, which in turn has a direct impact on the mechanical and physical properties of the resultant plastic. The application of appropriate modifiers facilitates the production of versatile material amenable to various forming processes, including extrusion, compression molding, thermoforming, and injection moulding (Figure1). Furthermore, the research investigates the effects of five distinct filler systems on the properties of starch-based plastics, with a particular focus on viscoelasticity and rheological characteristics. The fillers examined include eggshell, wood flour, silk, zein, and lignin. Additionally, the study explores the chemical modifications induced by the incorporation of these fillers into the biopolymer matrix. This comprehensive analysis contributes to the growing body of knowledge on biopolymer-based plastics, offering insights into their processing-structure-property relationships and the potential for property enhancement through strategic filler incorporation [3]

Volumetric 3D printing has emerged as an innovative approach that allows for the creation of complex structures within minutes, with resolutions up to 20 m. This approach builds the entire object in one step, unlike traditional layer-by-layer techniques, offering greater freedom in design while drastically reducing production time. Recent advances, as demonstrated in our research group, underscore its potential[1] [2] [3].

Multi-material objects allow overprinting during a second printing operation. A significant challenge for multi-material volumetric 3D printing is the light transparency of the initial structure. Light scattering caused by crystalline microstructures in the first material results in resolution loss during the second printing. The first material must exhibit high transparency (greater than 99%) at 405 nm for successful second printing.

Amorphic polymers show high transparency due to no crystalline microstructures. To leverage this, we created an amorphous 3-armed star (bio)polyester derived from trimethylolpropane, ε-caprolactone, and δ-valerolactone in a 1:1 molar ratio. The star-polyester was end-capped using allyl isocyanate to give -ene endcaps used in thiol-ene photo crosslinking volumetric printing. Through H-NMR, UV-vis, and photorheological measurements, compositions, -ene content (mmol/g), transparency, and crosslinking conditions were determined. High CAD/CAM mimicry was confirmed via CT imaging, optical and scanning electron microscopy.

Developing transparent, mechanically stable, and biodegradable 3D structures tackles a critical hurdle for multi-material volumetric 3D printing.

This work draws inspiration from nature, specifically the remarkable ability of spiders to manipulate their local environment within the silk gland, enabling the transformation of a proteinaceous solution into a tough silk. This environmental control involves changes in pH, ion type, and ion concentration. Despite being a water-based processing approach, spider silk remains a highly tough and water-insoluble material, offering an environmentally friendly alternative to the more toxic methods currently employed in fiber production.[1][2]
In this work, we take inspiration from this mechanism by gradually changing the ionic strength of a complex coacervate in a microfluidic chip. Complex coacervation is a form of associative liquid-liquid phase separation driven by electrostatic interactions between oppositely charged (bio-)macromolecules and the release of bound counter-ions, typically resulting in the formation of a polymer dense phase (the coacervate) and a dilute supernatant.[3] Through the modification of the local ionic strength, the physical properties of this coacervate phase can be tuned from a free-flowing viscoelastic fluid to a stiff polyelectrolyte complex.[4] Recent work in our group has provided insights into the effect of the desaltation rate on the porosity of formed complex coacervates, facilitating the creation of highly porous polymeric materials. The goal of this work is to gradually desalt a complex coacervate using microfluidics, allowing for the creation of novel fibrous materials through a green processing approach.

A source for post-consumer recycled (PCR) polypropylene (PP) is household waste, which mainly consists of packaging waste made from injection moulding [1]. Its melt viscosity is low, with melt-flow rates (MFR, @ 230°C, 2.16 kg) above 10 g/10min. This makes these PCR-PPs perfect to again use them for injection moulding, but not for methods that require high melt viscosities such as extrusion (0-3 g/10min). Thus, the market for extrusion grade PCR-PP is scarce and recycling facilities need strategies to lower the MFR value of PCR-PP, to offer it in extrusion grade to their customers.
One strategy to reduce the MFR of PCR-PP is to irradiate it via e-beam radiation in presence of a cross-linking molecule [2]. Melt-rheology and gel content measurements show that this effect results from a change from a linear PP chain to a microgel structure, where cross-linked microparticles disperse in a PP matrix.
Contrary to their virgin counterparts, PCR-PPs often contain polyethylene (PE), which readily cross-links under irradiation. Due to fluctuations in consumer behavior, the amount of PE in pre-sorted waste bales of PCR-PP varies by up to 10 wt.% [1]. Thus, the amount of insoluble fraction in PCR-PP after irradiation varies too, which affects the change in MFR value significantly. This talk highlights three aspects: 1) accurate analytics for PE in PCR-PPs is necessary as well as 2) viable sorting machines to minimize fluctuations in pre-sorted waste bales and 3) e-beam irradiation of PCR-PP is a strategy to adapt its MFR to a different processing technique.

Material Extrusion Additive Manufacturing (MEAM) is gaining importance due to its ability to produce complex, customized parts while reducing costs, waste and production time. However, this technique faces technical limitations, notably warpage, caused by uneven layer shrinkage due to temperature variations during the deposition [1]. Infrared cameras has enabled a better understanding of thermal fluctuations like temperature peaks caused by neighboring layer deposition and crystallisation, showing how the printing condition affects temperature distribution and layer solidification [2]. This study investigates the effect of crystallisation rate on the warpage of polypropylene homo- and copolymers. In situ infra-red camera temperature measurement is used to gain insight into the actual temperature profile of the printed parts. The crystallization kinetics of the different polymers are taken into account by considering a parameter, defined as the distance between crystallization temperature and bed temperature, which shows a good correlation to the measured warpage.

Biobased polymers have been extensively studied over the last decade due as the need to reduce the carbon footprint becomes ever greater [1-2]. While biopolymers are often more expensive than conventional polymers, their properties can be significantly improved by the addition of biobased fillers—particularly agricultural waste—which helps to maintain biodegradability and reduce overall material costs [3].
Waste for the corn industry -such as corncobs, husks, and stalks—can be used to enhance the mechanical and functional properties of biodegradable polymers, improving strength, thermal stability, and flexibility [4]. These key properties are essential for a range of 3D printing applications, from prototyping to functional end-use components.
In this work the properties of biocomposites, their processing methods, and the challenges and opportunities associated with their application in 3D printing technologies are investigated. The study was conducted using corn cobs, a residue from the corn starch industry which is mainly composed of cellulose and hemicellulose. Grinding of the corn cob and introducing it into in formulations with biopolymers such as PLA (polylactic acid) and PBAT (polybutylene terephthalate) in a 3D printing technology improves the physicochemical and mechanical properties of the polymers. Various filaments were produced and then 3D printed. The biocomposites were then analyzed for their thermal, mechanical, and morphological properties.

Incorporating lignin from wood industry wastes into 3D printed photocurable resins offers a simple, low-cost pathway for designing high-value, bio-based products1. This communication summarizes our group's efforts to develop novel acrylic formulations for digital light processing (DLP), with higher bio-based content using lignin, aiming for applications in electronics and biomedicine.
Designing suitable DLP formulations involves adjusting the content of fillers, photoinitiators, and monomers to ensure appropriate viscosity and polymerization speed. The structural heterogeneity and UV absorbance of lignin and conducting fillers increase challenges, limiting their incorporation into the acrylic matrix. These aspects were addressed with the aid of rheology, real-time infrared spectroscopy and Jacob’s working curves2,3.
Two studies explored the use of lignin in synthetic acrylic resins. Unmodified organosolv lignin (1 wt.%) was added to a flexible resin containing p-toluene sulfonic acid doped polyaniline as conductive filler, to improve its dispersion, resulting in more homogeneous samples with enhanced electrical conductivity3. In another approach, polyaniline modified with lignin was employed as filler to develop a flexible, portable pressure sensor. Lignin improved filler integration within the matrix, enhancing printability. A piezocapacitive prototype transducer, built from the printed composites, showed a response to a human footfall4.
To reduce environmental impact we are currently exploring the use of acrylic monomers derived from renewable sources. The compatibility of bio-resins with various types of lignin, both modified and unmodified, is studied, along with their effect on printability and final properties5. The potential application of high bio-content resins in wastewater treatment is also being explored

The demand for sustainable and biocompatible materials in additive manufacturing has increased interest in renewable raw materials for 3D (bio)printing.[1] Cellulose stands out due to its abundance, biodegradability, and excellent thermal and mechanical properties. Moreover, cellulose can also be chemically modified, which increases its suitability for various applications.[2]
Allyl cellulose (AC), a cellulose derivative with allyl groups, is a promising candidate for renewable feedstocks due to its chemical tunability and mechanical properties.[3]
Two cellulose sources were used in this work: Avicel® and industrial cellulose pulp. The physicochemical properties of the photopolymerizable AC derivatives, such as rheological behaviour, thermal stability and printability, were investigated, demonstrating compatibility with different 3D printing techniques, especially extrusion-based and vat photopolymerization processes.
The results showed that AC precursors can be used alone or in combination with other natural polymers to produce dimensionally stable, free-standing 3D objects with good resolution and shape fidelity. Despite the low polymer concentration in the formulation (up to 5 wt.%), the AC inks showed fast curing kinetics and produced hydrogels with good mechanical properties that could withstand compressive loads up to 135 kPa. In addition, the printed hydrogels absorbed significant amounts of water (up to 427%) while maintaining their shape and integrity in acidic and alkaline media. Furthermore, the printed materials were found to be cytocompatible towards a fibroblast cell line.
These promising results point to new applications of cellulose hydrogels in additive manufacturing, impacting areas such as bioinks, drug delivery systems, tissue engineering and soft robotics.

The study explores the use of biobased photopolymerizable monomers, specifically acrylate polyglycerol, to fabricate 3D-printed objects through digital light processing (DLP) technology. Conductive fillers, such as silver, copper, nickel powders, and recycled carbon fibers (RCF), were incorporated into the photopolymerizable resin.
These features offer the environmental advantages of bio-derived materials with enhanced functionalities like electrical conductivity and the ability to generate heat through the Joule effect.
The results of the characterization tests, including FT-IR spectroscopy, photo-DSC, rheology, DMTA, electrical conductivity analysis, and thermal imaging demonstrate that while increasing the filler content generally results in a decrease in the polymerization rate and an increase in viscosity, it markedly enhances the electrical conductivity of the printed objects, and, in some instances, their thermal-mechanical properties. Moreover, it was demonstrated that a significant Joule effect can be achieved, particularly with the use of Ag and RCF fillers, resulting in an isotropic heating of the printed samples.
The research demonstrates the great potential for these materials in various applications, including custom-designed medical devices for thermotherapy and intricated conductive pathways in electronics.

Selective laser sintering (SLS) is a key additive manufacturing (AM) technology for fabricating complex polymer components. Polyamide 11 (PA11), a semi-crystalline biopolymer derived from castor oil, has gained attention due to its sustainability and excellent mechanical properties [1]. However, its sensitivity to thermal effects in SLS processing leads to discoloration associated with thermo-oxidative degradation [2, 3].

This study investigates the influence of laser energy density and build chamber placement on discoloration of PA11 SLS parts. Both factors affect temperature, driving degradation and discoloration, with their correlation to mechanical and dimensional properties also examined [4, 5]. Experimental work utilized a design of experiments (DoE) approach to vary energy densities and component placements. Results revealed a strong correlation between energy density and discoloration, with higher energy densities leading to increased yellowing. Build placement significantly influenced thermal profiles, with components at the chamber center showing greater discoloration due to higher and prolonged temperatures.

Two models were developed to understand these challenges. A regression-based model was created to predict discoloration based on energy density and placement, demonstrating high accuracy within the pre-defined domain. Next, a novel numerical thermal model was developed to predict discoloration for any geometry, integrating an Arrhenius-based degradation framework. Our work demonstrates that this numerical model successfully correlates the simulated thermal history with discoloration and enables predictions for new parts.

This work enhances understanding of PA11 SLS processing and provides predictive frameworks for mitigating discoloration and optimizing part quality across varying geometries.

In recent years the field of material sciences has witnessed significant advancements in the development of technologies aimed at producing polymeric 3D-printed artifacts with shape-memory properties (SMPs)1. This innovative approach has been coined 4D-printing2, as stimuli-responsive nature of these materials is considered the “fourth dimension”. Research has primarily focused on irreversible or reversible shape-memory mechanisms that require the application of external stress3,4. However, materials capable of reversible SMPs without the need for external mechanical loads offer a transformative potential since they enable cyclic shape changes triggered by specific external stimuli. The development of such reversible SMPs through 4D printing is ongoing5 and it opens exciting new directions in polymer science, particularly in the emerging field of soft robotics.
Here, we demonstrate the design of an innovative thermo-sensitive shape-memory material based on functionalized semicrystalline triblock copolymers of poly(ε-caprolactone) (PCL) and polybutylene succinate (PBS) PCL-PBS-PCL, able to exhibit reversible SMPs after printing through extrusion-based technique at 100 °C followed by photo cross-linking. Methacrylated copolymers with different molar masses have been synthesized and thermal and rheological properties have been studied to optimize printing parameters such as temperature, pression and speed. The adjustment of cross-linking treatment enabled the production of well-defined complex structures with enhanced reversible SMPs, activated by temperature cycles between 55 and 10 °C. Furthermore, the impact of printed sample design on SMPs has been analyzed, showing that different internal patterns do not affect the reversible shape-memory effect and that multi-layered 4D-printed objects can be produced without any loss in SMPs.