Transactions on Additive Manufacturing Meets Medicine
Additive manufacturing (AM) is increasingly recognized as a transformative technology in medicine, offering unprecedented opportunities for patient-specific solutions, complex geometries, and rapid prototyping of medical devices. Despite its growing clinical relevance, the integration of AM into biomedical applications presents significant scientific and technical challenges. The fabrication of implants, prosthetics, scaffolds for tissue engineering, and other medical devices via layer-wise deposition processes involves complex thermophysical and physicochemical phenomena—such as melting, solidification, polymer cross-linking, and material consolidation. These processes are not yet fully understood, particularly in the context of biological compatibility, sterilizability, and long-term performance in vivo. Critical knowledge gaps remain in modeling and controlling the process–structure–property relationships that determine the dimensional accuracy, mechanical integrity, porosity, and surface characteristics of AM-produced biomedical components. Moreover, regulatory compliance, reproducibility, and integration with clinical workflows continue to be active areas of research. To advance scientific understanding and interdisciplinary collaboration in this domain, the Transactions on Additive Manufacturing Meets Medicine (Trans. AMMM) serves as a peer-reviewed platform focused on the convergence of additive manufacturing technologies and medical innovation. Trans. AMMM is a peer-reviewed, open-access scientific journal. Contributions to the affiliated AMMM conference may be submitted as either a one-page abstract or a full-length original research article. Accepted abstracts are published in the Supplement of Transactions on Additive Manufacturing Meets Medicine (ISSN: 2699-1977), while accepted full papers appear in the regular issue of the journal. Both formats are eligible for presentation at the annual AMMM scientific conference.
Transparent and flexible patient-specific aneurysm models for device testing
Patient-specific intracranial aneurysm models play a pivotal role in the in vitro evaluation of endovascular devices. To enable robust testing and reflect physiological conditions, these models must be optically transparent, anatomically accurate, mechanically stable, and elastic. This study explores a multi-material, variable-thickness fabrication strategy using stereolithography 3D-printing (SLA) to optimize medical IA. IA models were constructed by [1]: a) segmenting vessels from medical radiological images (region growing, marching cube’s algorithms, MevisLab, MeVis Medical solution); b) manual correction of segmentation errors; c) addition of vessel wall and flow connectors; d) 3D printing (Form 3, Formlabs). A Clear V4 Resin (Material-1, Formlabs) was used to produce transparent models. The initial vessel wall was uniform with a thickness of 3 mm and offered sufficient structural durability. However, the optical visibility through the model was suboptimal. A modified design strategy was introduced, implementing a localized wall thickness reduction (?1 mm) at the aneurysmal sac while retaining thicker walls (3 mm) otherwise. This approach preserved model integrity during mechanical handling and connection to experimental circuits while enhancing visibility in regions critical for evaluating the efficiency of the endovascular devices. In addition, two elastomeric SLA materials (Formlabs), Elastic 50A (Material-2) and Flexible 80A (Material-3), at various wall thicknesses (1.0 mm, 0.8 mm, and 0.4 mm) were evaluated to mimic the biomechanical properties of human vasculature. Models produced with Material-2 were more transparent than Material-1 and -3 but failed to maintain form stability, especially at 0.4 mm. Material-3 improved tear resistance compared to Material-2 at 0.8 mm, albeit with reduced optical clarity. The investigation of Material-3 with 0.4 mm vessel wall thickness is ongoing. Wall thickness and material modifications can be used to balance transparency and mechanical performance. The proposed fabrication strategy supports the development of anatomically accurate, optically clear, and mechanically robust models for use in in vitro testing of endovascular devices.
Copyright (c) 2025 Harsha Prakasam Prabhakaran; Mariya Pravdivtseva, Jan - Bernd Hovernor, Olav Jansen, Raman Bedi, Naomi Larsen, Faizan Ghauri https://creativecommons.org/licenses/by/4.0
Regulatory considerations on physical anatomical models
This presentation serves as an introduction to regulatory issues regarding physical anatomical models in the medical field. Application areas such as product development, operation planning and diagnostic purposes will be reviewed. Currently, there is no clear guidance regarding the regulatory qualification and risk classification of such physical anatomical models in the EU. According to the Regulation (EU) 2017/745 (“MDR”), such anatomical models might be classified as class I devices. In the USA, they are classified as class II devices according to a software related rule which has been adapted in 2021. The FDA pursue the approach that a physical anatomical model that was produced by using a picture and communication system according to this rule will be classified correspondingly as class II device. In Australia, an individual rule was introduced in 2021 classifying anatomical models as class IIa devices. According to this rule, a physical anatomical model itself is classified similar to the classification of radiology related products that are considered as class IIa device. Another interesting aspect is how to handle in-house manufacturing of the anatomical models by a health facility for such purposes. From a logistic and medical point of view, manufacturing anatomical models at the point-of-care has several advantages. However, regulatory challenges with regard to the responsibilities and accountabilities of the different parties for the various steps from the design and development to the production and use of medical device production systems (“MDPS”) have to be resolved. Potential regulatory concepts will be discussed from an international and EU perspective. The presentation will focus on the current regulatory discussion regarding personalized and simulated patient diagnostics and treatment.
Regulatory Challenges in Additive Manufacturing of Medical Devices
Copyright (c) 2025 Stefan Marschall; Alberto Di Benedetto, Folker Spitzenberger https://creativecommons.org/licenses/by/4.0
Porous zinc structures using molten metal jetting additive manufacturing
The demand for bioresorbable, patient-specific implants has increased interest in additive manufacturing techniques capable of processing biodegradable metals. This work explores the use of Molten Metal Jetting (MMJ) for fabricating porous zinc scaffolds, aiming to develop customized degradable structures for biomedical applications. Zinc is a promising candidate due to its moderate degradation rate and essential biological function in human metabolism. However, its implementation through MMJ remains unexplored [1], [2]. This study uses magnetohydrodynamic (MHD) actuation forces to eject molten zinc droplets towards a moving substrate to form the desired 3D shape. This approach allows precise control over droplet formation and ejection. The influence of jetting parameters is currently being investigated. This early study examines how MMJ jetting parameters, such as firing frequency and drop spacing, affect the printed structures. The effect of these variables on the percentage of porosity, the pore size, and degradation behavior are analyzed [3]. Printed structures were characterized using micro-computed tomography (?CT), revealing average porosity values ranging from 3.5% to 12%, with pore diameters between 95 and 650 µm. In vitro degradation testing was conducted in cell culture media over 72 hours in a dissolution machine. During this period, the pH of the media decreased from 7.4 to 6.2 ± 0.3, and cumulative zinc ion release reached 5.6 ± 0.4 mg/L. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses confirmed localized corrosion and the formation of ZnO-rich surface layers. Three-dimensional reconstruction of the specimens confirmed this result by comparing the initial and final scaffold geometries. These initial findings demonstrate that MMJ additive manufacturing can potentially enable the fabrication of zinc scaffolds with tunable porosity and predictable degradation behavior. References [1] H. Kabir, K. Munir, C. Wen, and Y. Li, “Recent research and progress of biodegradable zinc alloys and composites for biomedical applications: Biomechanical and biocorrosion perspectives,” Bioact Mater, vol. 6, no. 3, pp. 836–879, 2021, doi: 10.1016/j.bioactmat.2020.09.013. [2] Y. Li et al., “Additively manufactured biodegradable porous zinc,” Acta Biomater, vol. 101, pp. 609–623, 2020, doi: 10.1016/j.actbio.2019.10.034. [3] M. Meda, P. Mehta, C. Mahajan, B. Kahn, and D. Cormier, “Magnetohydrodynamic liquid metal droplet jetting of highly conductive electronic traces,” Flexible and Printed Electronics, vol. 6, no. 3, 2021, doi: 10.1088/2058-8585/ac0fee.
Material Properties, Structural Designs, and Printing Technologies
Copyright (c) 2025 Valeria Marin-Montealegre, Paarth Mehta, Ankit Rochani, Denis Cormier https://creativecommons.org/licenses/by/4.0
Mechanical properties and biocompatibility of bioresorbable ceramic bone implants printed by lithography-based manufacturing
Critical-sized bone defects often require surgical intervention due to their limited healing capacity. The use of autologous bone grafts for the treatment of these defects is still considered as gold standard in surgery. However, these grafts reveal different limitations underscoring the need for synthetic alternatives. Lithography-based ceramic manufacturing (LCM) offers the potential to fabricate patient-specific scaffolds with an optimized architecture that facilitates mechanical strength as well as an effective integration in terms of vascularization and the ingrowth of new bone from peri-implant tissue. Bioresorbable ceramics, such as hydroxyapatite (HA) and tricalcium phosphate (TCP) are considered to promote bone regeneration by mimicking native bone minerals, while degrading during new tissue formation. The aim of this study is to compare LCM printed bone constructs based on different materials (HA 480, TCP 300, Lithabone, Lithoz) and internal scaffold architectures, evaluating their mechanical properties and the cellular response of human mesenchymal stem cells (hMSCs). Scaffolds with three distinct lattice structures (NaCl, Gyroid, and Voronoi) and two pore sizes (1.6 mm and 1.16 mm) were printed via LCM (CeraFab, Lithoz; Vienna, Austria). The scaffolds were designed as cylinders (9 mm diameter, 3 mm height) with a uniform porosity of 50%. Mechanical compression testing (Zwick/Roell, Ulm, Germany) was conducted at a compression speed of 2 mm/min with a preload of 5 N. For biocompatibility testing of the scaffolds, hMSCs were seeded at a density of 2 × 10? cells/scaffold and cultured for 14 days followed by analyzing the cell response using different methods. Scaffolds with a NaCl structure and a pore size of 1.6 mm exhibited the highest compressive strength independent from the material and in agreement with the increased wall thickness of this scaffold design. Scanning electron microscopy (SEM) revealed material-dependent differences in surface microstructure of the scaffolds. HA480 exhibited a slightly smoother surface structure compared to TCP300, which may influence cellular adhesion along with other material related factors, such as the calcium phosphate crystalline structure. After 14 days, viability staining confirmed a high cellular viability and confluent colonization of all scaffold types by hMSCs. First results from DNA quantification to quantify the cell numbers on the different scaffold types indicated comparable cell numbers after 14 days. Osteogenic differentiation was assessed via staining for calcium deposition (OsteoImageTM) and PCR analysis of osteogenic markers (collagen type 1, alkaline phosphatase and osteocalcin). Initial results for calcium deposition indicated early signs of cell-mediated mineralization in TCP scaffolds seeded with hMSCs compared to cell-free controls. First PCR results indicate elevated osteocalcin expression in hMSCs cultured on HA scaffolds, suggesting a material-dependent enhancement of osteogenic differentiation. However, further experiments are necessary and might provide a more comprehensive understanding of material or design-related cellular responses.
Copyright (c) 2025 Julie Kühl, Christian Polley, Birk Urmersbach, Stanislav Nicolai Gorb, Andreas Seekamp, Hermann Seitz, Sabine Fuchs https://creativecommons.org/licenses/by/4.0
Printed highly bio-tolerant Ti/Nb/Ta alloys
Titanium alloys are state-of-the art implant materials featuring good biocompatibility and osseointegration. Unfortunately, they have a high Young’s modulus of 108 – 115 GPa, which contrasts with the better elasticity of the human bones, having a Young’s modulus of 12 – 25 GPa. This mismatch increases the risk of stress-shielding and can lead to of implant rejection. In addition, the use of only biocompatible and non-allergenic elements is beneficial for an increased biocompatibility. Suitable alternatives are Ti/Nb/Ta (TNT) alloys, consisting exclusively of biocompatible elements, providing the favorable combination of high elasticity, strength, reliable fatigue properties and good biocompatibility
Copyright (c) 2025 Melanie Stenzel; Markus Weinmann, Nicole Kuek, Oliver Morgan https://creativecommons.org/licenses/by/4.0
Dexamethasone and ciprofloxacin release and bio-efficacy after autoclavation of 3D printed external ear canal implants
Introduction: Patients with chronic stenosis of their ear canal may benefit from additively manufactured individualized drug containing external ear canal implants (EECI) [1] that keep the ear canal open and support the healing of the affected tissue. To guarantee the safety of the patients, the sterilization of implants is important. Autoclaving is a fast and well-established sterilization method, but the heat of the process may damage any drug contained within the implants. To evaluate the suitability of autoclaving EECIs, we tested samples for bio-efficacy and the released drug amount within 3 days. Methods: Three EECIs were 3D printed with an EnvisionTEC Bioplotter (Manufacturer Series, Desktop Metal, Burlington, USA) using UV-Silicone 60A MG (Momentive, Niskayuna, USA) [1] loaded with 1 (w/w) % dexamethasone (DEX, caelo, Hilden, Germany) and 0.3 (w/w) % Ciprofloxacin (Cipro, Sigma Aldrich, Hamburg, Germany). Samples were autoclaved with a Lisa Remote Plus Sterilizer (W&H, Bad Reichenhall, Germany) at a maximum temperature of 134°C for the duration of 350s. Next, the samples were incubated at 37°C for 72 h in isotonic sodium chloride solution (0.9 (w/v) % NaCl, 1 ml NaCl per 0.2 g sample). For the analysis of released drug content within the incubated NaCl, an Ultra High Precision Chromatograph (Xevo Qtof MS, Waters, Germany) coupled with a time-of-flight micro-mass spectrometer (Q-TOF, Waters) was used [2]. The bio-efficacy was assessed using a TNF? (tumor necrose factor-?) reduction assay [1], pure DEX (35,33 µg/ml) served as positive control. Results: 12.94 ± 0.29 µg/ml of DEX and 1.67 ± 0.06 µg/ml Cipro were released from the samples within 72h. The TNF? production was reduced by 80.66 ± 0,02 % (pure DEX) and 58.45 ± 0,10 % (sterilized samples). Conclusion: Since the supernatant of the sterilized samples induce TNF? reduction it can be concluded that an effective amount of DEX survives the autoclaving. The bio-efficacy of the released ciprofloxacin will be evaluated via a zone of inhibition test. Overall, autoclaving may be used to sterilize DEX- containing 3D printed silicone implants. Whether the samples will have a therapeutic effect in the patient will have to be shown by future studies. Author’s statement Conflict of interest: Authors state no conflict of interest. Animal models: Not applicable. Informed consent: Not applicable. Ethical approval: Not applicable. Acknowledgments: We thank M. Kreienmeyer for her help. Research funding: This work was funded by the Graduate School RNApp and the Institute for Biomedical Translation (IBT) Lower Saxony. References [1] Matin-Mann, F.; Gao, Z.; Schwieger, J.; Ulbricht, M.; Domsta, V.; Senekowitsch, S.; Weitschies, W.; Seidlitz, A.; Doll, K.; Stiesch, M.; et al. Individualized, Additively Manufactured Drug-Releasing External Ear Canal Implant for Prevention of Postoperative Restenosis: Development, In Vitro Testing, and Proof of Concept in an Individual Curative Trial. Pharmaceutics 2022, 14, 1242. doi: 10.3390/pharmaceutics14061242 [2] Guo, MF; Zhou, J; Zhang, HH; Zhong, P; Xu, JD; Zhou, SS; Long, F; Zhu, H; Mao, Q; Li, SL. UPLC-QTOF-MS/MS assisted UPLC-TQ-MS/MS strategy to comparatively investigate the rat pharmacokinetics of N-acetyldopamine oligomers derived from Cicadae Periostracum, Journal of Chromatography B 2023, Volume 1226, doi: 10.1016/j.jchromb.2023.123806.
Scaffolds, Implants and Drug Delivery Systems
Copyright (c) 2025 Martina Knabel, Gerald Dräger, Thomas Lenarz, Verena Scheper https://creativecommons.org/licenses/by/4.0
Case study: Including 3D printing in prosthetic fabrication for young children
3D printing enhances pediatric prosthetics by improving customization, comfort, and adaptability. This study examines multi-year cases, highlighting the balance between additive and traditional craftsmanship. A hybrid approach ensures flexibility, optimizing fabrication for individual needs while maintaining clinical reliability.
Copyright (c) 2025 Johannes Karl-Christian Lippert, Gunar Liebau, Andreas Kohn; Christian Eschenburg https://creativecommons.org/licenses/by/4.0
Electropolishing of porous beta-Ti21S implant: balancing mechanics and biocompatibility
A porous beta-Ti21S scaffold with a triply periodic minimal surface (TPMS) Gyroid and bowtie auxetic structure was designed and fabricated using via powder bed fusion (L-PBF) technology for potential application in total hip replacement prostheses. In a previous study [1], the material and geometry were studied from mechanical and biological perspectives to enhance biocompatibility. However, a major challenge in additively-manufactured (AM) metal implants is the presence of adhered, partially melted powder particles. These surface-adhered particles pose two critical issues: (1) they can detach post-implantation, triggering inflammatory reactions and bone resorption, potentially leading to implant loosening; and (2) they induce localized stress concentrations, which may initiate cracks under cyclic loading, thereby compromising the scaffold’s fatigue performance [2]. To improve surface quality and eliminate residual powders, electropolishing was applied to both bulk and porous samples. Electropolishing removes material via an electrochemical reaction between an anodic workpiece and a cathodic electrode, with process parameters varying by material. Achieving uniform roughness in lattice structure L-PBF components is particularly challenging due to the intricate geometry and internal porosity of the implant. Furthermore, balancing mechanical and biological responses to surface roughness remains a key concern. Surface roughness has been associated with cell adhesion [3], proliferation [4], and differentiation [5], whereas smoother surfaces reduce notch effects and improve fatigue performance [6]. This issue is even more critical for porous additively-manufactured structures, where cracks may originate from internal regions that are inaccessible to traditional polishing methods. This study aims to optimize electropolishing parameters to achieve an optimal surface roughness that balances mechanical durability and biological performance, thereby enhancing the applicability of porous titanium alloy scaffolds in bone tissue repair.
Copyright (c) 2025 Melika Babaei; Lorena Emanuelli, Raffaele De Biasi, Eleonora Fadelli, Francesca Agostinacchio, Anton du Plessis, Antonella Motta, Michele Fedel, Matteo Benedetti, Massimo Pellizzari https://creativecommons.org/licenses/by/4.0
Sterilization Effects on Dimensional Accuracy of 3D-Printed Carbon Fiber-Reinforced Nylon
Ensuring dimensional stability of additively manufactured (AM) medical components during sterilization is a critical yet understudied challenge. This study investigates the influence of geometry, continuous carbon fiber (CCF) reinforcement, and sterilization methods on the dimensional accuracy of fused filament fabricated (FFF) CCF reinforced nylon composites. 40 specimens of standard (ASTM D3039) and non-standard geometries were produced using Onyx®, both with and without CCF reinforcement. Printed samples were subjected to ethanol disinfection or steam autoclaving under ISO guidelines. MicroCT imaging was conducted before and after sterilization, and 3D geometric analysis was performed. Sterilization type did not affect surface deviation post treatment (p=0.1643), but deviations were primarily influenced by part geometry (p<0.001) and CCF reinforcement (p=0.0031). Non-standard geometries with concentric fiber paths demonstrated significantly greater resistance to warping compared to standard rectilinear patterns (p<0.001). Standard geometry without CCF reinforcement showed the highest deviations of all tested groups with a max deviation of 0.5 mm on average. Void fraction analysis further indicated that both, geometry and CCF reinforcement, contribute to porosity variations (p= 0.0038; p= 0.0044), with reinforced components displaying marginally higher (>1%) void fractions. These findings emphasize that optimizing print resolution, reinforcement strategies, and geometric design can help define production guidelines for 3D-printed composite implants compatible with sterilization protocols in healthcare. Future research should explore alternative sterilization techniques and advanced composite materials to further refine the applicability of AM in medical device manufacturing.
Copyright (c) 2025 Giles Michael Cheers, Abbey Goodwin, Andreas Heede, Jana Milite, Melissa Johnston, Anthony Morris, Marie-Luise Wille, Paige Little, Sinduja Suresh https://creativecommons.org/licenses/by/4.0
3D Printed Embolization Module for Treatment Training of Chronic Subdural Hematomas in Interventional Neuroradiology
Minimally invasive techniques have revolutionized the treatment of cerebrovascular disease, including middle meningeal artery embolization (MMAE) as a promising alternative to open surgical treatment of chronic subdural hematoma (cSDH). However, training in MMAE still requires the use of animal models, which have ethical concerns and are not anatomically realistic. This study presents the development of a 3D printed, interchangeable MMA embolization module for integration into the HANNES neurointerventional simulator with the previously developed MMA model to enable realistic simulation of cSDH treatment with the liquid embolic agent Onyx. The module was designed in a patient-like geometry and manufactured using stereolithography (SLA) printing with two different materials. A detailed evaluation of the manufacturing parameters showed that the choice of material and print orientation had a significant impact on post-processing efficiency. The final module was tested in a realistic angiography suite with original treatment instruments and its performance was evaluated by experienced neuroradiologists. The module received high marks for anatomical realism, flow characteristics and embolic agent distribution. The results highlight the potential of the module as an effective tool for neurointerventional training, reducing the need for animal models while providing a standardized, reproducible training platform. Future work could focus on integrating the module into structured training courses, exploring its application for radiation-free learning due to its transparency, and incorporating objective evaluation metrics to assess procedural performance and skill acquisition.
Copyright (c) 2025 Eve Sobirey; Jonte Schmiech, Fabian Flottmann, Matthias Bechstein, Maximilian Jungnitz, Martin Oertel, Jens Fiehler, Dieter Krause https://creativecommons.org/licenses/by/4.0
X-ray inspection and pore-classification in additive manufacturing: A systematic study on Al-alloys
In recent years, additive manufacturing (AM) of metals gains more and more interest in the automotive and aerospace industries as well as medicine. Thus, the associated component analysis - especially with focus on safety aspects - has become increasingly important. In this context, the non-destructive evaluation of the porosity within the material and its minimization by optimization of AM-printing parameters are of great interest. In addition to overall porosity and density reduction, this study emphasizes the classification of pore types. This allows to categorize the material and accordingly improve the printing processes, where the combined usage of artificial intelligence (AI) opens the door for an efficient way of material development optimization.
Copyright (c) 2025 Kevin Eickhoff, Rafael Meinhardt, Stefan Grottker, Frank Herold https://creativecommons.org/licenses/by/4.0
Guided Bone Regeneration: A novel approach to 3D-printed biodegradable meshes
Guided Bone Regeneration (GBR) is a standard surgical procedure to augment jawbone volume, conventionally using titanium meshes or collagen membranes - each with inherent limitations such as stress shielding, imaging artifacts, or insufficient mechanical stability. Here, we introduce a novel 3D-printed, patient-specific biodegradable mesh fabricated via Arburg plastic freeforming (APF) using PLDLLA/?-TCP composite. Three design variants were fabricated: A solid configuration for maximal strength, a porous structure (50% infill) to minimize fibrous tissue ingrowth, and a gyroid design to promote angiogenesis. Our results demonstrate high dimensional accuracy (<1% deviation) and pore sizes of 243±17 µm (porous) and 620±64 µm (gyroid). Mechanical testing revealed that the solid design achieved a biaxial flexural strength of 129±13 MPa, significantly outperforming the porous (26±5 MPa) and gyroid designs (23±2 MPa). These results lay the foundation for further optimization, including hybrid designs that integrate robust mechanical support with favorable biological properties, ultimately eliminating the need for secondary surgery.
Copyright (c) 2025 Till Strunk, Florian Markus Thieringer, Nadja Rohr, Neha Sharma https://creativecommons.org/licenses/by/4.0
A clinician-friendly patient-specific scaffold design suite for treating bone defects
Scaffold-guided bone regeneration (SGBR) is a newly emerging bone defect treatment facilitated by the in-situ guidance of new bone tissue regeneration using a 3D-printed biodegradable structural support called a ‘scaffold’ that is customized to the patient's bone defect. SGBR has demonstrated efficacy in both pre-clinical and clinical studies in large bone defects. However, widespread clinical adoption remains limited due to the lack of a streamlined, cost-effective, and user-friendly design and manufacturing system. Preliminary work by the team [1], [2] resulted in a digital design workflow that can semi-automatically generate a scaffold design. It has been validated via two complex clinical cases, in the latter of which the scaffolds were successfully implanted. However, the current digital workflow, built within Rhinoceros 3D and Grasshopper, presents usability challenges for clinicians unfamiliar with computer aided design (CAD) platforms. For clinical uptake not only is a user-friendly software solution with an intuitive and simple interface required, but also a scaffold manufacturing system that can be implemented in clinical settings. In close collaboration with surgeons and a 3D printing company, we are developing a standalone application for designing patient-specific scaffolds that can be readily 3D-printed using a compact cleanroom 3D printer. It features a modular interface which surgeons can intuitively combine to generate a scaffold design, without requiring extensive CAD expertise. Here, we present the first prototype of this software solution, which will be tested on 15 retrospective clinical cases.
Copyright (c) 2025 Buddhi Herath, Kim MinJoo, Giles Cheers, Markus Laubach, Yooseok Chae, Sinduja Suresh, Christoph Thorwächter, Paul Reidler, Stefan Leonhardt, Arnaud Bruyas, Susanne Mayer-Wagner, Boris Holzapfel, Dietmar Hutmacher, Marie-Luise Wille https://creativecommons.org/licenses/by/4.0
3D printing functionally graded structures with different cellular architecture
Functionally graded structures are widely observed in nature, including in bone, plants, bamboo and seashells. Drawing inspiration from these biological systems, this study integrates thermoplastic polyurethane (TPU) with 3d printing techniques and varied cellular architectures (scaffolds) to examine their deformation behaviour under compressive loading, which will inform the design of soft tissue implants. To evaluate the mechanical properties of 3d-printed TPU scaffolds, this study investigates varying cellular architecture based on rectilinear and gyroid patterns. Building upon previous research, TPU-based scaffolds manufactured using the Flashforge Creator 3 Pro printer and TPU filament from Bilby 3D Pty Ltd, featuring a highly porous gyroid lattice were identified as a model for scaffolds that have a high flexibility requirement (e.g. breast implants). In this study, functionally gradient structures of gyroid and rectilinear patterns with porosities of 90%, 94%, and 96% were explored and compared to their constant porosity counterparts. These porosities were incorporated into 18 groups (each group containing five specimens) formed by 2-graded and sandwich structures with different stacking sequences. 2-graded structures consist of two stacked porosity layers, whereas sandwich structures incorporate a high-porosity outer layer and a denser core. All samples underwent static compression (ASTM D1621) and fatigue testing (ASTM E606). Results indicate that rectilinear 2-graded structures exhibit approximately a 38% increase in stiffness in their initial deformation region, while maintaining comparable stiffness in the later deformation, compared to their constant porosity counterpart. Also, rectilinear-gradient samples exhibited a decline during dynamic loads after 1000 cycles, while gyroid-gradient groups showed relatively stable performance in the fatigue test. This research underscores the potential of integrating cellular architectures with functionally graded structures to optimize mechanical performance, paving the way for future advancements in medical applications.
Copyright (c) 2025 Shuya Tian, Sinduja Suresh, Marie-Luise Wille, Dietmar W Hutmacher https://creativecommons.org/licenses/by/4.0
Medical Device Research & Innovation - Status Quo, Challenges & Opportunities to Drive Global Healthcare Innovation
Stryker is a global MedTech company that is driven to make healthcare better together with their customers. In this presentation, I will share insights on the novel strategic approach on innovation road mapping at Stryker to align technological advancements with business goals, enabling research to anticipate and navigate future challenges. This three-dimensional innovation process plays a crucial role in identifying emerging trends, regulatory changes, and market demands. By incorporating forefront research, this disruptive methodology ensures to remain at the cutting edge of innovation, from device design to regulatory approval and commercialization. The three-dimensional innovation process fosters collaboration across multidisciplinary teams, driving R&D investments, and ensuring that products meet both patient needs and business needs. Through collaborations with academic institutions, patient advocacy groups, industry forums, and cross-sector partnerships, I will share insights on challenges, risks, and successes from an industry perspective on the potential and future of 3D printed biodegradable patient-specific implants.
Copyright (c) 2025 Nils Reimers https://creativecommons.org/licenses/by/4.0
Marine biopolymers for DLP-bioprinting of vital bone constructs
Osteoarthritis is a degenerative cartilage disease, induced by multiple factors, including aging and mechanical or inflammatory stress. During disease progression, bone tissue is affected, leading to osteochondral defects. Traditional and systemically applied treatments, often reveal limited success creating the need for more targeted approaches. In this context hydrogels can be used to manufacture vital implants e.g. by digital light (DLP) bioprinting. This technology allows to print precise implants loaded with cells, bioactive factors or photoactive delivery systems by UV mediated gelation of hydrogels. The biophysical properties of marine biopolymers may offer advantages for this technology not yet explored. In this study, we printed marine polymer-based 3D constructs including vital osteogenic cells. Bioprinting was performed using methacrylated alginate combined with jellyfish collagen in different concentrations for the hydrogels. Bioinks included a photoabsorber and photoinitiators as reported elsewhere1. 3*106 osteogenic cells/ml were mixed with the bioinks. The printing process was performed using a Lumen X at 37 °C. The STL file for the construct (h: 3.64 mm, d: 7 mm) was designed with 500 and 2000 µm pores. After printing, the constructs were additionally crosslinked with 50 mM CaCl2. Cellular viability and morphology was investigated using calcein-AM/Hoechst, staining for focal adhesion kinase/actin and confocal microscopy, DNA quantification, and scanning electron microscopy at different time points. Methacrylated alginate showed excellent properties for DLP printing; however it lacks binding sites for cell adhesion and thus profits from combination with other extracellular matrix components such as collagen. The use of rat collagen for bioprinting at 37 °C is difficult due to gelation above 20°C. However, experiments indicated that the use of marine collagen (lower melting point) is beneficial and supports the viability of cells in the investigated time frame. Calcein-AM, DNA quantification and SEM indicated cellular viability and a bone cell like morphology over 14 days. CaCl2 for additional crosslinking was essential to ensure stability of the constructs.
Copyright (c) 2025 Sabine Fuchs; Julie Kühl, Andreas Seekamp, Birk Urmersbach, Stanislav Gorb https://creativecommons.org/licenses/by/4.0
Advanced Hip Implants: Combining a novel metastable beta-Ti alloy and lattice structures to reduce stress shielding
Total Hip Replacement is a widely performed and highly effective procedure for restoring hip function in patients with degenerative joint conditions [1]. However, stress shielding remains a major challenge, as the stiffness mismatch between the bone and the implant may cause bone resorption and implant instability, potentially leading to the need for revision surgeries. This study explores a combined strategy to address this issue by integrating Ti21S, a promising novel beta-metastable titanium alloy for biomedical applications with a lower elastic modulus than conventional Ti6Al4V, and lattice structures, to enhance stiffness compatibility and osteointegration [2]. Two prosthetic designs were investigated: the first incorporates TPMS (Triply Periodic Minimal Surface) and auxetic lattice structures, while the second relies solely on TPMS, both with varying relative densities to optimize load distribution. TPMS structures are particularly advantageous for orthopedic devices due to their high surface area, interconnected porosity, zero-mean curvature and mechanical properties that closely mimic trabecular bone, promoting osteointegration and reducing stiffness mismatch [3]. Furthermore, the integration of auxetic structures in a specific implant region subjected to compressive-loading is designed to leverage the negative Poisson’s ratio, ensuring continuous bone adhesion and stimulation [4]. Mechanical performance was assessed through fatigue and quasi-static compression tests, while Digital Image Correlation (DIC) was used to analyze surface deformation. Microstructural analysis identified potential manufacturing defects, and Finite Element Method (FEM) simulations, simplified via homogenization, were conducted to validate experimental findings. Results showed that the proposed designs achieved promising stiffness values comparable to bone, but fatigue resistance remained suboptimal due to printing defects, the absence of heat treatments, and the application of testing standards designed for bulk implants rather than lattice-based structures. This study highlights the potential of combining low-modulus metastable beta-titanium alloys with mechanical metamaterials to develop next-generation orthopedic implants that reduce stress shielding, minimize bone resorption, and improve long-term stability, ultimately decreasing the need for revision surgeries. [1] S.A. Naghavi, M. Tamaddon, P. Garcia-Souto, M. Moazen, S. Taylor, J. Hua, C. Liu, A novel hybrid design and modelling of a customised graded Ti-6Al-4V porous hip implant to reduce stress-shielding: An experimental and numerical analysis, Front. Bioeng. Biotechnol. 11 (2023) 1–20. https://doi.org/10.3389/fbioe.2023.1092361. [2] L. Emanuelli, M. Babaei, R. De Biasi, A. Plessis, A. Trivisonno, F. Agostinacchio, A. Motta, M. Benedetti, M. Pellizzari, Optimising ? -Ti21S Alloy Lattice Structures for Enhanced Femoral Implants?: A Study on Mechanical and Biological Performance, Materials (Basel). 18 (2025) 170. https://doi.org/10.3390/ma18010170. [3] F.S.L. Bobbert, K. Lietaert, A.A. Eftekhari, B. Pouran, S.M. Ahmadi, H. Weinans, A.A. Zadpoor, Additively manufactured metallic porous biomaterials based on minimal surfaces: A unique combination of topological, mechanical, and mass transport properties, Acta Biomater. 53 (2017) 572–584. https://doi.org/10.1016/j.actbio.2017.02.024. [4] H.M.A. Kolken, A.F. Garcia, A. Du Plessis, C. Rans, M.J. Mirzaali, A.A. Zadpoor, Fatigue performance of auxetic meta-biomaterials, Acta Biomater. 126 (2021) 511–523. https://doi.org/10.1016/j.actbio.2021.03.015.
Copyright (c) 2025 Sofia Vignali, Raffaele De Biasi; Lorena Emanuelli; Melika Babaei, Anton du Plessis, Massimo Pellizzari, Matteo Benedetti https://creativecommons.org/licenses/by/4.0
Development of an Oxygen-Sensitive Hydrogel for Monitoring Oxygen Diffusion in Tissue Engineering
Additive manufacturing has revolutionized the development of biomaterials by enabling precise control over structural properties at the microscale. In tissue engineering, oxygen transport remains a major challenge, particularly in the development of vascularized artificial tissues. To address this, we present an oxygen-sensitive hydrogel fabricated using one-photon polymerization and two-photon polymerization (2PP), designed for real-time observation of oxygen diffusion characteristics. The hydrogel, based on polyethylene glycol diacrylate (PEGDA), incorporates oxygen-sensitive dyes to enable a colorimetric response to varying oxygen concentrations. The hydrogel formulation and fabrication were optimized for biocompatibility, tunable permeability, and stable optical readout. Diffusion experiments were conducted to analyze the oxygen transport behavior under different conditions, including variations in hydrogel thickness and environmental oxygen levels. The results demonstrate that the hydrogel allows for controlled oxygen diffusion, provides a measurable response to oxygen gradients and that the hydrogel’s permeability can be tailored via additive manufacturing. This approach offers a valuable tool for studying oxygen supply in engineered tissues and could enhance the design of microfluidic organ-on-a-chip systems. Our findings indicate that oxygen-sensitive hydrogels hold great potential for improving in vitro tissue models by enabling precise monitoring of oxygen distribution, which is essential for cell viability and function. Future research will focus on integrating these hydrogels into microfluidic systems to simulate vascularized environments more accurately.
Copyright (c) 2025 Lisa Marie Ehlers; Lukas Rennpferdt, Hoc Khiem Trieu https://creativecommons.org/licenses/by/4.0
The validation and performance comparison of imaging modalities, particularly magnetic particle imaging (MPI), requires standardized procedures and phantoms. A challenge for MPI phantoms is the incorporation of structures smaller than 1 mm to demonstrate the high-resolution capabilities, while excluding magnetic or electrically conductive materials. A hydrogel-based phantom is presented, specifically designed for evaluating an in-house developed MPI scanner. Conventional phantom production methods typically involve hollow bodies filled with a magnetic nanoparticle (MNP) solution. As an extension, additive manufacturing enables precise geometric realization by printing phantoms as hollow bodies, allowing for flexibility in intricate structures. An alternative option is the direct 3D printing of phantoms by integrating the MNPs into the print material. Here, a resolution phantom is presented that has been directly manufactured via semi-solid extrusion, utilizing a suspension of MNPs in a hydrogel. In this initial experiment, a self-sealing phantom holder incorporating a circular print bed with a diameter of 29 mm was developed for integration with a bioprinter and hydrogel used. The imageable ink suspension was synthesized by combining the hydrogel, with ~110 mg of MNPs. The phantom was designed with four lines converging from the center at uniform 24° angular spacing, originating at a radius of 4.1 mm, extending 7.3 mm in length, and maintaining a thickness of 0.4 mm. The print was completed using a 3 ml pneumatic printhead with a 0.2 mm (27G) nozzle. The printed phantom was imaged using the MPI scanner, with slice images obtained by a custom hybrid reconstruction method closely resembling the phantom and demonstrating high imaging quality. The presented work provides a robust foundation for future studies and considerations aimed at advancing the production of MPI phantoms by leveraging the unique capabilities of additive manufacturing. High-resolution phantoms created with tuneable materials can efficiently address the rigorous requirements of various imaging.
Copyright (c) 2025 Eric Aderhold, Annika Dell, Pascal Stagge, André Behrends, Mandy Ahlborg, Thomas Friedrich, Dennis Kundrat, Thorsten Buzug https://creativecommons.org/licenses/by/4.0
Engineering of a Polycaprolactone-Stabilized Alginate Hydrogel for 3D Bioprinting of Patient-Specific Implants enabling Sustained Local Dexamethasone Delivery in Inner Ear Therapy
There is an unfulfilled need for local inner ear therapy to treat hearing disorders. We developed a silicone implant enabling drug diffusion from the middle ear into the inner ear. This implant is precisely tailored to conform to the unique anatomical contours of each patient's round window niche, thereby facilitating controlled diffusion of therapeutic agents into the inner ear. To improve the approach biodegradation of the implant would be beneficial to avoid the potential need of explanting the drug delivery device. Alginate hydrogels, while well-established for their cytocompatibility and biodegradability, are inherently limited by insufficient viscosity and suboptimal mechanical integrity, restricting their applicability in 3D bioprinting. To overcome these deficiencies, we engineered a composite hydrogel system through the incorporation of polycaprolactone particles (PCL) to modifying the printability. The composite material was 3D printable and compression tests and rheological tests determined the elastic properties of the hydrogel and the structural stability under a certain load. Investigations into swelling kinetics and morphological stability under simulated physiological conditions substantiated the material's durability and functional integrity within 7 days and subsequent degradation over time. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed a homogeneous microarchitecture conducive to controlled drug diffusion, as corroborated by in vitro release kinetics of dexamethasone quantified through high-performance liquid chromatography (HPLC). Cytotoxicity tests demonstrated biocompatibility, and the dexamethasone-loaded hydrogel elicited anti-inflammatory responses in vitro. The PCL-reinforced alginate hydrogel is a promising platform for the fabrication of personalized, biodegradable, and pharmacologically active implants.
Copyright (c) 2025 Verena Scheper, Yanjing Luo, Thomas Lenarz, Gerrit Paasche, Jan Drexler, Gerald Dräger, Hongzheng Zhang, Jie Tang https://creativecommons.org/licenses/by/4.0
Design and analysis of mechanical and permeability properties of stochastic scaffolds for biomedical applications
Bioengineered scaffolds with optimized osteoconductive and osteoinductive properties are highly desirable in bone tissue regeneration. Stochastic porous structures, resembling human trabecular bones, have gained increasing attention due to their suitability and superior performance in bone healing compared to regular porous architectures. In this study, we designed six trabecular-like porous scaffolds with varying porosity and surface area-to-volume (S/V) ratios. The scaffolds were fabricated using pure Titanium via selective laser melting (SLM), and their morphological characteristics were analyzed via micro computed tomography (µCT). Quasi-static compression testing was conducted to assess mechanical properties. The results showed that the as-built scaffolds exhibited a porosity range 67–71%, an average pore diameter ranging 440–565 µm, a quasi-elastic gradient between 2.6–3.5 GPa, and a yield strength of 44–58 MPa. These values closely match those of the cortical bone, indicating potential for orthopedic applications by mitigating stress shielding and enhancing implant longevity. Additionally, the permeability and wall shear stress (WSS) were measured to predict cell growth performance in the scaffolds. The as-built models have a satisfactory permeability range of 6x10-9 to 15x10-9 m2, which is higher than that of cancellous bone, benefitting prospects for nutrient flow and by-product removal that encourage osteoblastic mineralization.
Copyright (c) 2025 Mudassar Khalil; Geunhyeok Choi, Paul Conway, Carmen Torres-Sanchez https://creativecommons.org/licenses/by/4.0
Insights into a student-managed surgical simulation laboratory - SimLab.
Teaching surgical skills effectively continues to be a significant hurdle in medical education. At the University Medical Center Hamburg-Eppendorf, the student-driven simulation laboratory, SimLab – Students for Surgery, enhances traditional teaching methods by offering a educational platform that not only aids students in basic surgical skills to improve transitioning to internships and medical residency but also incorporates 3D printing to simulate surgical scenarios more realistic like fractures, appendectomies and congenital anomalies. This integration aims to refine the extracurricular teaching and preoperative training through clinical collaborations. This study aims to assess the efficacy and impact of the SimLab approach, designed models and curricula on surgical education and student motivation for surgical careers, as well as its clinical utility, to provide insights for the development of additional simulation laboratories. SimLab facilitates diverse training modules ranging from basic laparoscopy to advanced surgical simulations, employing peer teaching, 3D printing, and digital reconstructions. Models are crafted from existing CT imagery or designed with open-source software, incorporating feedback from clinical partners into every prototype. Evaluations utilize student feedback through surveys and objective measures such as procedure time, execution speed, knot integrity, and eye-tracking during training sessions. Over 150 students have engaged with SimLab training, showing marked improvements in surgical competencies and reporting high satisfaction with the feasibility and educational quality of the simulations. Clinical integration of preoperative prints has notably enhanced preoperative planning and patient consultations. SimLab offers an ethically and cost-effective approach to surgical training, potentially increasing the safety and efficacy of surgical interventions and thereby hopefully benefiting patient care in the long-term.
3D Printing for Education and Instruction
Copyright (c) 2025 Hans Christian Schmidt; Jama Wahid, Abdulrahman Al-Harazi, Martin Oertel, Lucas Cröpelin, Florian Rapp, Hajera Khaleqi, Sarina Sczech, Atielsadat Nasr Esfahani, Kim Seifert, Julia Inhoff, Amani Nasser https://creativecommons.org/licenses/by/4.0
The ISO/IEC 17025 accreditation journey for additive manufacturing in medical engineering
Over the recent years, additive manufacturing has undergone rapid development towards industrial application, so that more and more products and components can be manufactured additively. However, since critical properties of printed parts are strongly influenced by complex interdependencies among process parameters, quality control is facing different challenges as with other, more traditional, means of fabrication. This opens a wide field of new needs for testing standards and procedures for the application and material specific manufacturing of parts, especially in the highly regulated domain of medical engineering. In order to address this need, we have set up a testing laboratory for additively manufactured parts (metals and polymers) according to ISO/IEC 17025, which has its accreditation certificate by the German accreditation body (DAkkS) since the end of February 2025. The particular challenge for research in the section of medical engineering is to integrate the regulatory requirements right into the development of new devices, to avoid additional development loops. Therefore, a quality management system, to be applied in the testing laboratory as defined by ISO/IEC 17025, had to be implemented. In addition, the necessary operating and work instructions were defined for the testing procedures of geometrical and defect analysis, both based on high resolution (for small parts up to 150nm) computed tomography. This includes the development of a supporting document that covers the entire testing process from the customer inquiry to the submission of the test report, ensuring that every testing laboratory employee can be sure that they have completed all steps of the testing process. Among other things, it is now possible to 3D print circuit boards, where special care must be taken, to ensure that the conductor tracks are not interrupted by printing errors. This is an example for the development of new testing methods and quality standards, that can be realized within the testing laboratory, to address the specific requirements of additively manufactured medical devices that has not yet been defined in detail. We share the experience,, which we have gained through the implementation so far, with the community.
Copyright (c) 2025 Franziska Seidensticker, Britta Pirnay-Duscher, Folker Spitzenberger, Maximilian Wattenberg, Alberto Di Benedetto, Thomas Friedrich https://creativecommons.org/licenses/by/4.0
A 3D-printed sensor adapter for liposuction cannulas for in-situ force sensing
In aesthetic surgery, shape-altering procedures are increasingly being performed on the human body at the request of patients or out of medical necessity to improve their well-being. Liposuction is the most frequently performed aesthetic procedure. Additive manufacturing, sensors and data are used to optimise the procedure and the medical devices required for it. 3D-printed adapters for liposuction cannulas enable effective sensor integration and rapid prototyping of corresponding medical components. This shortens development times and costs and enables customisation to the user's needs.
Copyright (c) 2025 Erik Westphal, Eric Schwarz, Hermann Seitz https://creativecommons.org/licenses/by/4.0
Development of an additively manufactured head and neck phantom for computed tomography studies
Additive manufacturing (AM) offers significant potential for the design of medical phantoms used in quality assurance for medical imaging and treatment planning. This study presents the design and fabrication of a head and neck phantom for computed tomography (CT) quality assurance. Appropriate infill densities of Polylactic acid (PLA) were selected to achieve tissue-equivalent CT values, enabling the integration of many anatomical structures in the head and neck region. A bone surrogate material was incorporated post-processing to achieve high density values that are unachievable with common 3D printing materials. CT validation confirmed the phantom’s ability to replicate appropriate Hounsfield unit (HU), demonstrating its suitability for imaging-based assessments. This phantom provides a reproducible and customizable solution for treatment verification in head and neck cancer therapies.
Copyright (c) 2025 Marie Wegner, Nina Hinrichsen, Maike Rosendahl, Dieter Krause, Elisabetta Gargioni https://creativecommons.org/licenses/by/4.0
3D-Printed Fixture for Biological Tissue Training on the Lübecker Toolbox
Surgical training simulators are essential in medical education, allowing trainees to develop technical skills in a controlled environment. Many simulators, including the default Lübecker Toolbox fixtures, fail to replicate the tactile and mechanical properties of the living tissue. This gap between simulation and clinical reality presents a significant challenge, potentially increasing the operation time and complications. Moreover, the psychological aspect of handling biological tissues is often overlooked. In this study, we address these limitations by developing a customized 3D-printed fixture for the Lübecker Toolbox that allows for training suturing on ex-vivo porcine feet. Shapr3D CAD software was used to design a fixture that securely positions porcine feet within the Lübecker Toolbox. One challenge of including biological tissue into surgical training is to allow for a fair performance comparison across the variety of porcine feet. Thus, we propose to perform several cuts of fixed length at standardized locations of the foot. To this end, we designed a 3D-printed stencil to ensure reproducible cuts. The fixture and stencil were manufactured using a Bambu 3D printer with PLA. Three surgical trainees evaluated the integrated system via questionnaires. Feedback from all surgical trainees confirmed the successful integration of the 3D-printed fixture with the Lübecker Toolbox, providing a stable training setup. The proposed design maintained consistent positioning relative to the simulator's integrated camera. Moreover, the use of biological tissue offered more authentic tactile feedback compared to artificial materials and the 3D-printed stencil enabled standardized tissue cutting for suturing practice. This study demonstrates that 3D-printed fixtures can effectively incorporate real tissue into surgical simulation, enhancing training authenticity and standardization. Our approach offers a cost-efficient, reproducible solution that can be integrated into existing simulators. Future work will expand on this concept by testing additional tissue types and evaluating the impact on clinical skill transfer.
Printed Anatomy for Planning, Training, and Phantoms for Quality Assurance
Copyright (c) 2025 Sami Beirami; Nazila Esmaeili, Jannis Hagenah https://creativecommons.org/licenses/by/4.0
3D printed coil array for spherical harmonic spatial encoding in magnetic particle imaging
Magnetic particle imaging is a promising method of noninvasive diagnostics that is being consistently developed for future implementation in clinical routine. The method is based on measuring the magnetic response of superparamagnetic nanoparticles using a set of drive, gradient, and receive coils. One of the major technical obstacles to translating the method to the human scale is the large amount of energy required to establish gradient fields of sufficient levels. In this work, we propose a novel approach to spatial encoding of the volumetric distribution of superparamagnetic nanoparticles by using only a drive field and an array of receive coils. The coils have a complex structure designed using numerical optimization algorithms, and only additive manufacturing methods provide the necessary freedom to translate this concept into the working prototype we demonstrate.
Copyright (c) 2025 Egor Kretov; Dennis Wendt, Matthias Graeser https://creativecommons.org/licenses/by/4.0
Hybrid manufacturing approach for multi-scale bio-inspired blood contacting membrane designs
Extracorporeal membrane oxygenation is an effective treatment option for patients with severe respiratory diseases. Here, the blood is supplied with oxygen while carbon dioxide is removed inside an artificial lung (AL), outside of the human body. This process currently makes use of hollow fiber membranes (HFM). However, suboptimal blood flow conditions exist within the HFM structures which lead to reduced gas transfer efficiency and increased thrombosis-risk reducing device durability. Additively manufacturing enables the creation of tailored blood flow channels for improved hemocompatibility. However, additive AL fabrication remains challenging due to the wide range of feature sizes and limited material options. In this study, we propose a novel concept for ALs that are based on custom designed, bio-inspired 3D membrane structures. The structures were fabricated with a hybrid additive-conventional process. For the creation of functional, miniaturized prototypes, we utilized high precision stereolithography to fabricate a sacrificial tool geometry. Afterwards, the membrane structure was formed in a dip-coating process step. After etching of the sacrificial part, only the 3D membrane structure was preserved that is made from a biocompatible, gas permeable siloxane. The manufacturing results were characterized concerning overall built quality, surface roughness and membrane thicknesses using optical- and scanning electron microscopy. Finally, we carried out in-vitro performance testing concerning gas transfer rates and pressure drops according to ISO 7199 with porcine blood. Using our hybrid manufacturing strategy, watertight 3D membrane structures were successfully fabricated with membrane thicknesses around 100 µm across a total structural length of 50 cm. In-vitro tests demonstrated gas transfer rates of up to 2 ml/min and low pressure drops (<20 mmHg per l/min). The size of the laboratory prototypes as well as their gas transfer performance are still below clinical applicability. However, once scaled, this approach may lead to next-generation ALs with higher durability and lower complication rates. Moreover, regulatory admission can be simplified, as already approved membrane materials can be used within the manufacturing process.
Copyright (c) 2025 Kai Barbian, Ulrich Steinseifer, Sebastian Jansen https://creativecommons.org/licenses/by/4.0
Investigating inter-layer crosslinking of alginate-gelatine hydrogels to modify layer adhesion
Alginate-gelatin hydrogels are commonly utilized as bioink components in bioprinting. To improve the structural integrity of bioprinted objects made from these hydrogels, ionic crosslinking is typically conducted using calcium chloride, usually after the entire object has been printed. This study investigates the effects of inter-layer crosslinking applied between the deposition of successive printing layers on layer adhesion. The primary research questions are: Does inter-layer crosslinking enhance or diminish layer adhesion? Can these effects be modulated by adjusting inter-layer crosslinking parameters, such as the duration of crosslinking before the deposition of the next layer? To address these questions, test structures are printed using a commercial bioprinter (CELLINK BIO X6, CELLINK, Gothenburg, Sweden). The test structures consist of two-layer rectangular shapes measuring 30 mm by 30 mm. After extruding the first layer of hydrogel, calcium chloride is applied as a crosslinker using drop-on-demand printing. Subsequently, the second layer of hydrogel is extruded using a pneumatic printhead. The central parameters varied include calcium chloride concentration, extrusion volume of calcium chloride, and the time interval between crosslinker application and the extrusion of the second layer. Preliminary findings indicate that inter-layer crosslinking can enhance the overall structural integrity of the object, while reduced layer adhesion may facilitate object separation, such as detaching the target object from support structures.
Copyright (c) 2025 André Behrends, Lea Evers, Annika Dell, Roman Leonov, Dennis Wendt, Thomas Friedrich, Thorsten Buzug https://creativecommons.org/licenses/by/4.0
Sinter-joined bioceramics for hybrid bone implants
Artificial bone implants are used when a bone defect exceeds a critical size, and autografts or allografts are not an option due to insufficient quality or limited availability. Implants must be biocompatible, osteoconductive, ideally bioresorbable, and resistant to mechanical stress during handling and healing [1]. Natural bone is not a homogeneous material but consists of several hierarchically structured phases that cannot necessarily be imitated by one single material. Our approach was therefore to combine two bioceramic materials in one hybrid implant. We used yttria-stabilized zirconia for phases with high mechanical strength and hydroxyapatite for phases that require osteointegration. As a manufacturing process, we used lithography-based ceramic manufacturing to produce the individual green parts (composite material consisting of photopolymer matrix and ceramic powder) which were combined in a sinter-joining process during thermal post-processing. The sinter-joining concept involves inducing a press-fit between the two parts by precisely controlling the shrinking behavior [2]. To establish process control, we started with a simple ring-in-ring design and progressed to biaxial bending plates to quantify mechanical resistance. We found a significant increase in the maximal measured force in the piston-on-three-balls test set-up from (72 ± 53) N to (366 ± 88) N for a 5% and 10% press-fit, respectively. For further evaluation, we created micrographs and assessed shrinking behavior and deformation. As final step, we designed more complex structures to demonstrate the successful sinter-joining. [3] This study demonstrated a proof-of-concept for sinter-joining different bioceramics to create hybrid implants that mimic the multi-phase composition of natural bone by combining bioactive with mechanically strong materials. We have published this study in the Open Ceramics Journal [3]. References [1] V. Campana et al., “Bone substitutes in orthopaedic surgery: from basic science to clinical practice,” J Mater Sci: Mater Med, vol. 25, no. 10, pp. 2445–2461, Oct. 2014, doi: 10.1007/s10856-014-5240-2. [2] J. Schubert, Y. End, V. Schulze, and F. Zanger, “Exploring the Applicability of Sinterjoining to Combine Additively Manufactured Ceramic Components,” Procedia CIRP, vol. 115, pp. 18–23, 2022, doi: 10.1016/j.procir.2022.10.043. [3] S. Nistler, C. Hofstetter, S. Baudis, M. Schwentenwein, and J. Stampfl, “Sinter-joining of two different bioceramic materials,” Open Ceramics, vol. 22, p. 100759, Jun. 2025, doi: 10.1016/j.oceram.2025.100759.
Copyright (c) 2025 Sarah Nistler; Christoph Hofstetter, Stefan Baudis, Martin Schwentenwein, Jürgen Stampfl https://creativecommons.org/licenses/by/4.0