Extrusion-based 3D Printing Research Articles

Advancements in Additive Manufacturing of Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs), also known as proton conducting solid oxide fuel cells, are a promising low-temperature (400-600oC) fuel cell technology. Compared to conventional oxygen-ion conducting ceramic materials, proton conducting ceramic electrolyte materials have lower activation energy (< 50 eV), which can enhance fuel cell efficiency and power output. Additive manufacturing has the potential to revolutionize PCFC manufacturing, as it enables fabrication of both dense and porous structures with desirable mechanical and electrochemical properties. In this study, we employed extrusion-based 3D printing to fabricate PCFCs using BaZr0.3Ce0.5Y0.15O3-δ and BaZr0.4Ce0.4Y0.1Yb0.1O3-δ as electrolytes, NiO as anode, and BaCo0.4Fe0.4Zr0.1Y0.1O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ as cathode. For comparison, we also printed oxide conducting ceramic fuel cells using gadolinium-doped-ceria (GDC ) as electrolyte. We investigated the printable pastes' rheological properties using dynamic light scattering, viscometer, tensiometry, differential scanning calorimetry, and thermal gravimetric analysis. We also characterized the cells using current-voltage measurements, electrochemical impedance spectroscopy, and various spectroscopic and microscopic techniques (HR-TEM-EELS, SEM-EDX) to understand the underlying mechanisms. Finally, we conducted a systematic study to optimize the sintering temperature for optimal fuel cell performance and investigate degradation mechanisms to improve stability.

Investigating the mechanical properties of sintered 440 C stainless steel produced by an extrusion-based 3D printer

Extrusion-based 3D printing of parts is one of the simplest, cheapest, and most widely used additive manufacturing (AM) methods. The raw materials in this process are generally filaments with a constant diameter. By equipping extrusion-based 3D printers with the barrel and screw system and removing the filament manufacturing step, a wide range of materials can be 3D printed. In this research, the parts were 3D printed using a feedstock of metal powder injection molding process and with a direct granule extruder system equipped with a barrel and screw. Then, on the printed parts, debinding, sintering, and grinding processes were performed, and finally, their tensile and impact mechanical properties were evaluated. The average tensile strength and modulus are equal to 295 MPa and 85 GPa, respectively, the average of impact resistance is equal to 12.5 J and the hardness number is equal to 118 HB. In addition, by calculating the amount of porosity in the samples, the low value of the mechanical properties of the samples was justified.

Three-Dimensional Printing of Biomass–Fungi Biocomposite Materials: The Effects of Mixing and Printing Parameters on Fungal Growth

Biomass–fungi biocomposite materials are derived from sustainable sources and can biodegrade at the end of their service. They can be used to manufacture products that are traditionally made from petroleum-based plastics. There are potential applications for these products in the packaging, furniture, and construction industries. In the biomass–fungi biocomposite materials, the biomass particles (made from agricultural waste such as hemp hurd) act as the substrate, and a network of fungal hyphae grow through and bind the biomass particles together. Typically, molding-based methods are used to manufacture products using these biocomposite materials. Recently, the authors reported a novel extrusion-based 3D printing method using these biocomposite materials. This paper reports a follow-up investigation into the effects of mixing parameters (mixing time and mixing mode) on fungal growth in biomass–fungi mixtures prepared for 3D printing and the effects of printing parameters (printing speed and extrusion pressure) on fungal growth in printed samples. The fungal growth was quantified using the number of fungal colonies that grew from samples. The results show that, when mixing time increased from 15 to 120 s, there was a 52% increase in fungal growth. Changing from continuous to intermittent mixing mode resulted in an 11% increase in fungal growth. Compared to mixtures that were not subjected to printing, samples printed with a high printing speed and high extrusion pressure had a 14.6% reduction in fungal growth, while those with a low printing speed and low extrusion pressure resulted in a 16.5% reduction in fungal growth.

Poly(L-co-D,L-lactic acid-co-trimethylene carbonate) for extrusion-based 3D printing: Comprehensive characterization and cytocompatibility assessment

Extrusion-based 3D printing is a well-established material processing technique that has shown promise in employing a variety of polymers. Poly(lactic acid) is the most studied and widely used raw material in 3D printing, which can be modified by copolymerization with trimethylene carbonate (TMC), for tissue engineering applications. In this study, the aim was to explore the characterization of Poly(L-co-D,L-lactic acid-co-trimethylene carbonate) (PLDLA-TMC) at different ratios (60/40, 70/30, 80/20, and 90/10), focusing on their physicochemical, thermal, and rheological characterization, as well as their cytocompatibility. The results demonstrated shear-thinning behavior and highlighted the influence of TMC content on viscoelastic properties. The printing speed of 4 mm s−1 allowed the obtaining of scaffolds with rectangular pores and controlling of extrusion temperature promoted the formation of uniform filaments with high print quality. Additionally, the cytocompatibility assessment of the scaffolds revealed the terpolymer's potential for tissue engineering across a wide range of applications.

Fused Deposition Modelling (FDM) of Thermoplastic-Based Filaments: Process and Rheological Properties-An Overview.

The fused deposition modeling (FDM) process, an extrusion-based 3D printing technology, enables the manufacture of complex geometrical elements. This technology employs diverse materials, including thermoplastic polymers and composites as well as recycled resins to encourage sustainable growth. FDM is used in a variety of industrial fields, including automotive, biomedical, and textiles, as a rapid prototyping method to reduce costs and shorten production time, or to develop items with detailed designs and high precision. The main phases of this technology include the feeding of solid filament into a molten chamber, capillary flow of a non-Newtonian fluid through a nozzle, layer deposition on the support base, and layer-to-layer adhesion. The viscoelastic properties of processed materials are essential in each of the FDM steps: (i) predicting the printability of the melted material during FDM extrusion and ensuring a continuous flow across the nozzle; (ii) controlling the deposition process of the molten filament on the print bed and avoiding fast material leakage and loss of precision in the molded part; and (iii) ensuring layer adhesion in the subsequent consolidation phase. Regarding this framework, this work aimed to collect knowledge on FDM extrusion and on different types of rheological properties in order to forecast the performance of thermoplastics.

Geopolymer Materials for Extrusion-Based 3D-Printing: A Review.

This paper examines how extrusion-based 3D-printing technology is evolving, utilising geopolymers (GPs) as sustainable inorganic aluminosilicate materials. Particularly, the current state of 3D-printing geopolymers is critically examined in this study from the perspectives of the production process, printability need, mix design, early-age material features, and sustainability, with an emphasis on the effects of various elements including the examination of the fresh and hardened properties of 3D-printed geopolymers, depending on the matrix composition, reinforcement type, curing process, and printing configuration. The differences and potential of two-part and one-part geopolymers are also analysed. The applications of advanced printable geopolymer materials and products are highlighted, along with some specific examples. The primary issues, outlooks, and paths for future efforts necessary to advance this technology are identified.

Development of CNT-Based Nanocomposites with Ohmic Heating Capability towards Self-Healing Applications in Extrusion-Based 3D Printing Technologies

In the present study, a series of carbon-based nanocomposites based on recycled thermoplastic polyurethane (TPU) matrix and MWCNT fillers synthesized in a laboratory environment were prepared at various loadings and assessed in terms of their functional thermal, dielectric, and rheological properties, as well as their ohmic heating capability, for self-healing applications in extrusion-based 3D printing technologies. The synthesis of nanomaterials focused on the production of two different types of carbon nanotubes (CNTs) via the chemical vapor deposition (CVD) method. A comparative assessment and benchmarking were conducted with nanocomposite filaments obtained from commercial nanomaterials and masterbatches with MWCNTs. For all the polymer nanocomposites, samples were prepared at additive contents up to 15 wt.% and filament feedstock was produced via the melt-extrusion process for 3D printing; these were previously characterized by rheological tests. The measurements of thermal and electrical conductivity resulted in a selected composition with promising ohmic heating capability. As a preliminary assessment of the self-healing ability of the above samples, artificial cracks were introduced on the surface of the samples and SEM analysis took place at the crack location before and after applying voltage as a measure of the effectiveness of the material remelting due to the Joule effect. Results indicate a promising material response with a partial restoration of artificial cracks.

Exploring the Biomedical Potential of PLA/Dysprosium Phosphate Composites via Extrusion-Based 3D Printing: Design, Morphological, Mechanical, and Multimodal Imaging and Finite Element Modeling.

The present investigation demonstrates the feasibility of dysprosium phosphate (DyPO4) as an efficient additive in polylactide (PLA) to develop 3D printed scaffolds through the material extrusion (MEX) principle for application in bone tissue engineering. Initially, uniform sized particles of DyPO4 with tetragonal crystal setting are obtained and subsequently blended with different concentrations of PLA to extrude in the form of filaments. A maximum of 20 wt % DyPO4 in PLA matrix has been successfully drawn to yield a defect free filament. The resultant filaments were 3D printed through material extrusion methodology. The structural and morphological analysis confirmed the successful reinforcement of DyPO4 throughout the PLA matrix in all of the 3D printed components. All of the PLA/DyPO4 composites exhibited magnetic resonance imaging and computed tomography contrasting properties, which were dependent on the dysprosium content in the PLA matrix. The detailed mechanical evaluation of the 3D printed PLA/DyPO4 composites ensured good strength accomplished by the reinforcement of 5 wt % DyPO4 in PLA matrix, beyond which a gradual decline in the strength is noticed. Representative volume elements models were developed to realize the intrinsic property of the PLA/DyPO4 composite, and finite element analysis under both static and dynamic loading conditions has been performed to account for the reliability of experimental results.

Poly-Lactic Acid-Bagasse Based Bio-Composite for Additive Manufacturing.

Beer bagasse is a residue waste produced in great amounts; nevertheless, it is still underestimated in the industry. The aim of this paper is to develop an innovative and efficient methodology to recycle the beer bagasse by producing Poly-lactic acid(PLA)-based bio-composites, in the forms of pellets and filaments, to be used in additive manufacturing processes. To assess the suitability of beer bagasse for extrusion-based 3D printing techniques, it was, firstly, physically and chemically characterized. Then, it was added in combination with different kinds of plasticizers to PLA to make bio-composites, analyzing their thermal and physical properties. The results prove the great potential of bagasse, evidencing its printability. Both composites' pellets and filaments were used in two different 3D printing machines and the mechanical properties of the 3D-printed models were evaluated as a function of the composition and the kind of technology used. All the used plasticizers improved processability and the polymer-bagasse interface. Compared to neat PLA, no changes in thermal properties were detected, but a lowering of the mechanical properties of the 3D-printed composites compared to the neat polymers was observed. Finally, a comparison between the efficiency of the two 3D printing techniques to be used with the bio-based composites was performed.

Development of new formulation for soft material in paste extrusion-based 3D Printer

Fused Deposition Modelling is a form of additive manufacturing where solid filament is heated into molten state and deposited onto a heating platform to create three-dimensional objects layer-by-layer. Since heating and cooling processes are involved in Fused Deposition Modelling (FDM), this restricts the use of thermoplastic polymers such Room Temperature Vulcanizing (RTV) silicones and gels. Others concern are with the right rheological properties for extrusion and the ability to provide desired mechanical qualities upon quick solidification. To develop a suitable silicone printing technology, it is crucial to understand the silicone polymerization mechanism in terms of its rheological and mechanical characteristics. Due to the numerous factors that can influence silicone paste mixtures, this study utilized the Taguchi method to design experiments, optimize factors, and predict properties, thereby avoiding extensive and resource-intensive experimental work. The study specifically considered the factors of curing method, mass ratio of silicone thinner, and fumed-silica in the silicone paste formulation. Among the 9 samples generated through the Taguchi method, only one sample demonstrated favourable results in terms of mechanical properties and the curing process, with a mixture ratio of base silicone, silicone thinner, and fumed-silica at 15g, <1g, 0.1g; respectively. However, further investigation into the fixed amount of silicone and fumed silica in the selected mixture ratio indicate that the amount of silicone thinner must be less than 1g or can be omitted as the silicone paste can be used as printing ink for the extruder. The shore hardness testing for the silicone samples revealed with zero percent silicone thinner exhibited a hardness value of 21.5 HA (Shore A) while the sample obtained less than 1g displayed a significantly lower hardness value of 10.5 HA. These findings indicate that the addition of silicone thinner in the silicone paste formulation, as optimized through the Taguchi method, contributed to a reduction in the hardness of the material for shore A scale. This suggests that the presence of silicone thinner affects the elasticity and flexibility of the silicone paste, resulting in a lower Shore hardness value. The discrepancy in hardness values between the samples further highlights the significance of formulation optimization to achieve desired material properties for silicone paste-based applications in 3D printing.

3-D printed meat alternatives based on pea and single cell proteins and hydrocolloids: Effect of paste formulation on process-induced fibre alignment and structural and textural properties

Extrusion-based 3D food printing can be used as an alternative structuring technique to traditional extrusion processing for creating meat-like structures. This study focused on 3-D food printing to generate structures analogous to meat by using various combinations of texturized pea protein fibrils, microbial Single Cell Protein (SCP) and hydrocolloids locust bean gum and/or sodium alginate. Simple moulding was utilized as benchmarking to better understand the 3D printing-induced structural effects. To gain understanding of the interactions between proteins of different origin (plant and SCP) and with hydrocolloids, structural, textural and rheological properties were analysed. Oscillatory stress sweeps of all printing pastes revealed elastic-dominant rheological behaviour (G′ 4000–6000 Pa) with a defined yield stress (25–60 Pa) explaining their printability and shape stability. X-ray microtomography of ion-crosslinked analogues showed a printing-induced preferential alignment of fibrils in the direction of nozzle movement, while moulding led to a random orientation. Textural characterization via bi-directional cutting tests demonstrated higher cutting force in transversal (FT) over longitudinal (FL) direction in 3D-printed samples and equal forces in moulded samples. The anisotropy index (AI = FT/FL) of printed samples ranged between 1.4 and 2.5, indicating anisotropic texture, and 0.8–1 for moulded samples indicating isotropic texture. This study demonstrated the applicability of paste-extrusion in generating anisotropic structures analogous to meat by process-induced fibril alignment. The results support further development of 3D food printing technology in design of sustainable meat alternatives resembling whole-muscle meat.

Enhancing the Piezoelectric Properties of 3D Printed PVDF Using Concurrent Torsional Shear Strain.

Extrusion-based polymer 3D printing induces shear strains within the material, influencing its rheological and mechanical properties. In materials like polyvinylidene difluoride (PVDF), these strains stretch polymer chains, leading to increased crystallinity and improved piezoelectric properties. This study demonstrates a 400% enhancement in the piezoelectric property of extrusion-printed PVDF by introducing additional shear strains during the printing process. The continuous torsional shear strains, imposed via a rotating extrusion nozzle, results in additional crystalline β-phases, directly impacting the piezoelectric behavior of the printed parts. The effect of the nozzle's rotational speed on the amount of β-phase formation is characterized using FTIR. This research introduces a new direction in the development of polymer and composite 3D printing, where in-process shear strains are used to control the alignment of polymer chains and/or in-fill phases and the overall properties of printed parts.

Sintering energy conservation in extrusion-based 3D printing of porcelain ceramics blended with copper and allied alloys: A sustainable approach

This study investigates the use of copper particles in porcelain ceramics for reduced sintering temperature effort as a part of a sustainable environment. Porcelain powder is mixed with 10 wt% copper powder, 25.3 wt% water, and 12.6 wt% ethanol, and the rheological characterization is made. The rheological characterization of the initial slurry and the phases that evolved during sintering at various temperatures were studied. With suitable rheology of slurry, prototype parts are manufactured by 3D printing. The length-to-diameter ratio of the nozzle, stand-off distance, and type of underlying substrates are also observed to influence the printability. The sintering is performed in the temperature range of 500 °C–1200 °C. The sintered parts were characterized for various phases in the selected temperature range. In addition, a study was conducted to find sintering temperature variation with the percentage of copper addition made by mixing brass and bronze with multiple compositions of zinc and tin, respectively. Once the standards are established with copper in a research-based printer, porcelain with other elements is printed on a bulk printer, ensuring repeatability. The retention of natural binder kaolinite at various temperatures is also verified. This study also opens a new dimension for sustainable multi-material ceramic 3D printing with increased solid loading at ease with required customization. The results showed that adding copper particles to the porcelain powder reduced the sintering temperature by up to 200 °C. The study concluded that adding copper particles to porcelain is a promising method for sustainable 3D printing of ceramics.

Advancing bovine in vitro fertilization through 3D printing: the effect of the 3D printed materials.

Nowadays there is an increasing demand for assisted reproductive technologies due to the growth of infertility problems. Naturally, fertilization occurs in the oviduct, where the oviductal epithelial cells (OECs) secrete many molecules that affect the embryo's metabolism and protect it from oxidative stress. When the OECs are grown in 3D culture systems, they maintain a great part of their functional characteristics, making them an excellent model for in vitro fertilization (IVF) studies. In this work, we aimed to evaluate the suitability of different 3D-printing processes in conjunction with the corresponding set of commercially available biomaterials: extrusion-based processing using polylactic acid (PLA) and polycaprolactone (PCL) and stereolithography or digital-light processing using polyethylene-glycol-diacrylate (PEGDA) with different stiffness (PEGDA500, PEGDA200, PEGDA PhotoInk). All the 3D-printed scaffolds were used to support IVF process in a bovine embryo assay. Following fertilization, embryo development and quality were assessed in terms of cleavage, blastocyst rate at days 7 and 8, total cell number (TCN), inner cell mass/trophectoderm ratio (ICN/TE), and apoptotic cell ratio (ACR). We found a detrimental effect on cleavage and blastocyst rates when the IVF was performed on any medium conditioned by most of the materials available for digital-light processing (PEGDA200, PEGDA500). The observed negative effect could be possibly due to some leaked compound used to print and stabilize the scaffolds, which was not so evident however with PEGDA PhotoInk. On the other hand, all the extrusion-based processable materials did not cause any detrimental effect on cleavage or blastocyst rates. The principal component analysis reveals that embryos produced in presence of 3D-printed scaffolds produced via extrusion exhibit the highest similarity with the control embryos considering cleavage, blastocyst rates, TCN, ICN/TE and ACR per embryo. Conversely, all the photo-cross linkable materials or medium conditioned by PLA, lead to the highest dissimilarities. Since the use of PCL scaffolds, as well as its conditioned medium, bring to embryos that are more similar to the control group. Our results suggest that extrusion-based 3D printing of PCL could be the best option to be used for new IVF devices, possibly including the support of OECs, to enhance bovine embryo development.

Influence of surface engineering on 3D printed Ti lattice structure towards enhanced tissue integration: An in vitro and in vivo study

Reconstruction of segmental defects are popularly approached with surface engineered additively manufactured scaffolds owing to its enhanced post-surgery tissue integration properties. The present work is aimed at fabrication of Ti lattice structures using 3D printing, with a novel approach of silane chemistry-based surface modification of those Ti-surfaces with osteogenic peptides (OGP). The lattice structures with 0.6 mm strut-diameter having 0.5 mm inter-strut distance were chosen for fabrication using an extrusion-based 3D printing. Based on the evidence, it could be concluded that extrusion-based 3D printing is an optimal alternative as compared to those high cost incurring additive manufacturing processes. Therefore, OGP were grafted on the pristine Ti-surfaces using a silane chemistry based novel vapour deposition process. In vitro assessments of the surface modified scaffolds using human amniotic derived mesenchymal stem cells showed evidence of enhanced cell adhesion and viability. In vivo subcutaneous study in rat models of the surface modified Ti-scaffolds also showed enhanced tissue integration in terms of Collagen I deposition around the boundary of the tissue-integrated struts as compared to those of pristine scaffolds. The study has established that the novel surface modification technique is capable to engineer the Ti-surfaces towards enhanced tissue integration in vivo.

On the reproducibility of extrusion-based bioprinting: round robin study on standardization in the field

The outcome of three-dimensional (3D) bioprinting heavily depends, amongst others, on the interaction between the developed bioink, the printing process, and the printing equipment. However, if this interplay is ensured, bioprinting promises unmatched possibilities in the health care area. To pave the way for comparing newly developed biomaterials, clinical studies, and medical applications (i.e. printed organs, patient-specific tissues), there is a great need for standardization of manufacturing methods in order to enable technology transfers. Despite the importance of such standardization, there is currently a tremendous lack of empirical data that examines the reproducibility and robustness of production in more than one location at a time. In this work, we present data derived from a round robin test for extrusion-based 3D printing performance comprising 12 different academic laboratories throughout Germany and analyze the respective prints using automated image analysis (IA) in three independent academic groups. The fabrication of objects from polymer solutions was standardized as much as currently possible to allow studying the comparability of results from different laboratories. This study has led to the conclusion that current standardization conditions still leave room for the intervention of operators due to missing automation of the equipment. This affects significantly the reproducibility and comparability of bioprinting experiments in multiple laboratories. Nevertheless, automated IA proved to be a suitable methodology for quality assurance as three independently developed workflows achieved similar results. Moreover, the extracted data describing geometric features showed how the function of printers affects the quality of the printed object. A significant step toward standardization of the process was made as an infrastructure for distribution of material and methods, as well as for data transfer and storage was successfully established.

Extending applicability of 3D-printable geopolymer to large-scale printing scenario via combination of sodium carbonate and nano-silica

Adequate printable time is crucial for the application of extrusion-based concrete 3D printing. 3D-printing geopolymer concrete (3DPGC) possesses a rapid hardening feature intrinsically, limiting its applicability in large-scale printing scenarios. Herein, we jointly use Na2CO3 (Nc) and nano-silica (Ns) to improve the printability (particularly extending printable time) and mechanical properties of 3DPGC. We first evaluated the effects of Nc replacement to a traditional activator (waterglass) on the 3D-printing-related rheology and mechanical properties to obtain an optimum Nc dosage. Subsequently, the influences of Ns incorporation on rheology, extrudability, buildability, bulk mechanical strengths, and interlayer properties were investigated based on the optimum Nc dosage. The combination of Nc and Ns (Nc-Ns) manifested a much better extrudability with a sixfold longer printable time (>120 min) due to the decreased hardening rate. Better buildability, higher compressive strengths and a stronger interlayer strength retention capacity were further achieved simultaneously. Nc adoption enables a slower hardening process owing to the lower solution alkalinity and the existence of carbonate, while the overall hardening profile can be adjusted with Ns addition. We successfully printed a special-shaped structure for validation, which requires a long printable time (>40 min). It demonstrates the exceptional printability of the proposed mixture formulation. This work contributes a feasible solution for 3DPGC in large-scale printing scenarios from the material perspective.

3D-Printed Capsaicin-Loaded Injectable Implants for Targeted Delivery in Obese Patients.

Diet-induced obesity and hyperlipidemia are a growing public health concern leading to various metabolic disorders. Capsaicin, a major bioactive compound obtained from natural chili peppers, has demonstrated its numerous beneficial roles in treating obesity and weight loss. Current treatment involves either administration of antiobesity drugs or surgical procedures such as Roux-en-Y-gastric bypass or sleeve gastrectomy, both of which are associated with serious side effects and poor patient acceptance. Capsaicin, a pungent molecule, has low oral bioavailability. Therefore, there is a need for the development of site-specific drug delivery system for capsaicin. The present study is aimed at preparing and characterizing 3D-printed capsaicin-loaded rod-shaped implants by thermoplastic extrusion-based 3D printing technology. The implants were printed with capsaicin-loaded into a biodegradable polymer, polycaprolactone, at different drug loadings and infill densities. The surface morphology revealed a smooth and uniform external surface without any capsaicin crystals. DSC thermograms showed no significant changes/exothermic events among the blends suggesting no drug polymer interactions. The in vitro release studies showed a biphasic release profile for capsaicin, and the release was sustained for more than three months (~ 85% released) irrespective of drug loading and infill densities. The HPLC method was stability-indicating and showed good resolution for its analogs, dihydrocapsaicin and nordihydrocapsaicin. The implants were stable for three months at accelerated conditions (40°C) without any significant decrease in the assay of capsaicin. Therefore, capsaicin-loaded implants can serve as a long-acting injectable formulation for targeting the adipose tissue region in obese patients.

Photosynthetic Living Fiber Fabrication from Algal-Bacterial Consortia with Controlled Spatial Distribution.

Living materials that combine living cells and synthetic matrix materials have become promising research fields in recent years. While multicellular systems present exclusive benefits in developing living materials over single-cell systems, creating artificial multicellular systems can be challenging due to the difficulty in controlling the multicellular assemblies and the complexity of cell-to-cell interactions. Here, we propose a coculture platform capable of isolating and controlling the spatial distribution of algal-bacterial consortia, which can be utilized to construct photosynthetic living fibers. Through coaxial extrusion-based 3D printing, hydrogel fibers containing bacteria or algae can be deposited into designated structures and further processed into materials with precise geometries. In addition, the photosynthetic living fibers demonstrate a significant synergistic catalytic effect resulting from the immobilization of both bacteria and algae, which effectively optimizes sewage treatment for bioremediation purposes. The integration of microbial consortia and 3D printing yields functional living materials with promising applications in biocatalysis, biosensing, and biomedicine. Our approach provides an optimized solution for constructing efficient multicellular systems and opens a new avenue for the development of advanced materials.

Advancing dysphagia-oriented multi-ingredient meal development: Optimising hydrocolloid incorporation in 3D printed nutritious meals

Dysphagia (DP) is a growing health concern in today's ageing population, leading to high demand for DP-oriented food. 3D printing is a promising novel technology for developing new attractive and appetising products. Therefore, we aimed to develop a 3D-printed shaped meal, to serve as a nutritious DP-oriented food. The texture was modified with the addition of different thickeners: 2.0% (w/w) k-carrageenan gum (KC) and 1.0 or 1.5% (w/w) guar gum (GG), xanthan gum (XG), locust bean gum (LBG), and gum arabic (GA). Upon characterising and mapping the rheological behaviour involved in extrusion-based 3D printing, the higher concentrations of GG, XG, LBG and GA were found to significantly increase the yield stress and apparent viscosities of the ink formulations. In addition, the colour attributes were examined, while a low population of total viable bacteria (TVC) was observed. The DP-oriented formulations had high fibre content, regulating bowel function and glucose metabolism in the elderly. According to the International dysphagia diet standardisation initiative (IDDSI), KC/XG1 and KC/LBG1 were classified as level 5 indicative of minced and moist dysphagia diet, while KC/GA1, KC/GA1.5, KC/XG1.5, and KC/GG1.5 were classified as level 4, that can be bitten or chewed if the tongue control is reduced. All ink formulations demonstrated high printing precision with excellent self-supporting capability and smooth surface texture that were easy to extrude and print complex samples. This study provides valuable insights into addressing dysphagia by developing a nutritious meal using 3D printing.