Cranial reconstruction, cranioplasty, is conducted to repair skull defects caused by craniectomy following traumatic brain injury, stroke, or postoperative infection. Complications requiring implant removal occur in 10-20% of cases as the optimal cranioplasty material is not known. We describe the Cambridge University Hospital's (CUH) multidisciplinary cranial reparation service and aim to assess the safety of the workflow compared with existing technologies. We retrospectively analyzed the medical records of all patients who underwent cranioplasty via the CUH cranioplasty pathway with cranioplasty implants manufactured utilizing grade 23 Ti-6Al-4V powder bed fusion (PBF) between December 2017 and December 2021. The primary and secondary outcomes were implant removal and the occurrence of cranioplasty infections, respectively. We identified 107 cranioplasty procedures performed in 105 patients, who were followed for a median time of 34.9 months (interquartile range 46.7-17.7, range 2 days to 60.2 months). Twenty-four (22%) patients had at least one complication, and 11 (10%) cranioplasties had been removed because of complications. Thirteen (12%) patients had surgical site infections, but only eight (7%) cranioplasties had to be removed because of infections. Placement of a cerebrospinal fluid shunt (hazard ratio [HR] 8.57, 95% confidence interval [CI] 2.36-31.12) and high American Society of Anesthesiologists grade (HR 6.87, 95% CI 1.66-28.39) predicted shorter cranioplasty survival. We demonstrated the largest currently published series of titanium cranioplasties produced using PBF-the overall complication and removal rates (22% and 10%, respectively) were comparable with those reported in the literature. We have embedded the key steps and skills in the cranioplasty process in an academic setting allowing for tailored surgery and flexibility to develop further service innovations in the future. Patients with cerebrospinal fluid shunts and those in poor general condition were at increased risk of infections and subsequent cranioplasty failure.

Additive manufacturing, particularly 3D-printing, has emerged as a crucial method for creating prototypes and specialized components in various scientific fields. This study investigates the biocompatibility and performance of 3D-printed materials, with focus on cyclic olefin copolymer (COC) in comparison with traditional materials such as polylactic acid (PLA) and COC combined with glass (Glass + COC) inlays. Biocompatibility is especially critical for cell-based research and millifluidic applications, impacting cell culture experiments and the interaction of 3D-printed structures with reactive substances. To investigate material influence, experiments were conducted using rat cardiomyocyte (H9c2) and human embryonal kidney (HEK293) cell lines, with comprehensive assays including lactate, lactate dehydrogenase (LDH), and thiazolyl blue tetrazolium bromide assays assessing metabolic activity, cell stress, and cell viability. Results demonstrated that Glass + COC exhibited increased metabolic activity and cell viability compared with standard polystyrene (PS) culture dishes, with COC and PLA materials showing comparable viability with standard PS dishes, although with slight differences favoring COC. Lactate assays revealed subtle increases in lactate secretion, notably in Glass + COC cultures, suggesting a correlation with cell viability. LDH assays provided insights into potential material-associated toxicity. Microscopy experiments visually confirmed cell growth and distribution within culture vials, using various transparent materials, including PLA foil, COC foil, standard microscope glass slides, and Glass + COC. Furthermore, atomic force microscopy (AFM) examined surface roughness and differences between the upper and lower surfaces of 3D-printed PLA and COC parts, contributing to the understanding of material surface characteristics. In conclusion, this study highlights the biocompatibility of 3D-printed materials for cell-based research, emphasizing the potential of COC and Glass + COC manufactured via 3D-printing for such applications. The interplay among cell viability, metabolic activity, and lactate levels underscores the importance of material selection. Microscopy and AFM analyses enhance the comprehension of cell growth behavior and surface properties, advancing the selection of 3D-printed materials for biocompatible applications.

To meet the growing requirement of spinal interbody fusion caused by trauma and disease, 3D printed porous titanium alloy scaffolds were applied as intervertebral cages to achieve structural reconstruction of bone defects. However, the biological inert of the titanium alloy hindered firm bonding between the bone and porous scaffold. Surface roughness that resulted from sandblasting treatment with alumina sand grains could endow the titanium alloy scaffold with bioactivity. Minimum and maximum-type cervical and posterior lumbar cages were used to optimize the sandblasting process, achieving an adequate and uniform sandblasting effect. The optimized sandblasting process parameters were as follows: alumina sand grains of 100 mesh, sandblasting distance of 10 cm, sandblasting pressure of 0.4-0.5 MPa, and sandblasting time of 15-20 s.

In recent decades, titanium (Ti)-based materials have emerged as paramount contenders for biomedical applications. This study presents a comprehensive examination of the advancements in Ti alloys and composites tailored for biomedical applications through laser-based additive manufacturing (AM) processes. Specifically, we delve into prominent laser-based AM methods such as (1) selective laser sintering, (2) selective laser melting, (3) direct metal laser sintering, and (4) laser-engineered net shaping. Moreover, we elucidate the incorporation of these state-of-the-art AM systems in the synthesis of Ti alloys and composites. Conclusively, the pivotal nuances demanding rigorous exploration to enhance the properties of Ti-based materials in the biomedical realm are highlighted.

The ability to customize products with additive manufacturing allows manufacturers to meet the unique requirements and functionality for individual applications. By printing dissolvable materials as a matrix material, the release of active agents over time can be tailored on a per part basis by varying both geometry and printed material properties. Direct printing of actives via filament material extrusion is challenging because many active agents become inactive at the elevated temperatures found in the melt-based process. This limitation is circumvented by embedding the active agents into designed voids of a printed water-soluble capsule. In this work, this process is demonstrated by the deposition of liquids and powders into thin-walled, water-soluble, printed structures. The authors demonstrate the ability to tune dissolution time by varying the thickness of a printed part's walls in order to create a delay in release and by creating parts with multiple chambers to initiate a multistaged release. This ability provides opportunities for creating customized containers for the prescribed release of liquid and powdered active agents.

Materials based on the hydroxypropyl methylcellulose mixed with different biopolymers (BioP; 5 w% of chitosan, sodium alginate, apple pectin, or citrus pectin) were processed by hot-melt extrusion and 3D printing to produce capsules intended for controlled drug release. Microscopic analyses confirmed significant impact of BioP on the processing temperatures and quality of the 3D printing. The capsules' chemical composition had a more significant impact on the dissolution profiles in acidic and neutral media, which are a robust function of the intermolecular bonds and swelling characteristics of the particular BioP (as indicated by the combined results of Raman spectroscopy, differential scanning calorimetry [DSC], and thermogravimetry). The capsules of all tested compositions retained the model drug for 120 min in pH 1.2, i.e., fulfilled the condition of targeting the small intestine. The presence of the particular BioP was found to be particularly beneficial in the development of personalized capsules for oral administration. The addition of both pectins led to a relatively fast pH-independent release of the model drug and has the potential applications in the targeting of the duodenum or jejunum. The capsules containing alginate and chitosan exhibited later initial release in pH 1.2, guaranteeing an unaltered passage through the stomach environment.

Electrohydrodynamic (EHD) technology is renowned for its significant advantages in high resolution and micro-nanoscale printing, demonstrating an immense potential in the development of micro-nano devices. During the printing process, it is inevitably influenced by different interferences, which result in printing errors that influence its printing precision. This article summarizes several research topics on printing errors of EHD printing technology, involving the sources, and correction of different types of printing errors. First, the induced factors of printing errors are summarized in details, which are used to categorize the error correction methods. Then, the existing correction methods are comprehensively summarized and analyzed according to the types of printing errors. Finally, the conclusions are provided, involving some potential research topics.

An colon model, particularly one suited to high throughput screening, has the potential to enhance understanding of cellular mechanisms and functions important in intestinal health and can be used for drug testing and drug permeation studies. While extensively studied, traditional monolayered cultures using immortalized colon cancer cell lines on transwell plates fail to accurately replicate the native intestinal epithelium's complex architecture. To address this limitation, we have developed a novel, facile photopolymerization technique to fabricate scaffolds that closely resemble colon crypts. We have further developed a method using screen printing to be able to coat these scaffolds while preserving the crypt architecture in order to vary the surface chemistry of these systems. This paper focuses on the development of three-dimensional crypt models that can be made with simple equipment and with chemical precursors that are commercially available to make building tissue models more accessible to the broader research community.

The application of additive manufacturing techniques has increased over the years in almost all production fields, thanks to the possibility of creating objects from scratch and with the desired shape, with no need for molds or complex machinery typical of subtractive manufacturing. This success has concerned the biomedical world as well, where melt-based methods represent the golden standard to produce scaffolds for hard-tissue engineering. Despite the large number of studies present in the literature on scaffold production, the fabrication process is still affected by drawbacks and limitations, which hinders the standardization and upscaling to the industrial level. In this review, we briefly present the history of additive manufacturing and the reasons of its success, with particular reference to the tissue engineering and regenerative medicine world. We then proceed to highlight the current factors limiting the straightforwardness of the production process and affecting the quality and the performance of the manufactured scaffolds. Eventually, we suggest potential strategies to increase the level of control during manufacturing and to improve the biomimicry of the fabricated constructs, with the goal of obtaining a more optimal workflow.

3D printing has emerged as a groundbreaking technology with transformative applications in various health care domains. In drug delivery, it enables the precise fabrication of customized dosage forms, offering controlled release patterns and stimulus-triggered release capabilities. In addition, 3D printing plays a pivotal role in tissue engineering, facilitating the creation of complex structures with biomimetic properties. The impact of 3D printing technology extends to personalized medicine, allowing for the production of patient-specific medications tailored to individual needs. In the realm of regenerative medicine, 3D printing contributes to the fabrication of intricate scaffolds and bioprinted tissues, fostering advancements in the regeneration of damaged or diseased tissues. The versatility and precision of 3D printing make it a powerful tool across these domains, promising innovative solutions and personalized approaches in the field of health care. A comprehensive review of scholarly literature spanning from 1980 to the present was conducted across prominent databases such as PubMed, Wiley Online Library, Multidisciplinary Digital Publishing Institute, Kosmet, Science Direct, and Scopus. The present review offers a comprehensive examination of 3D printing in the biomedical and pharmaceutical sectors, shedding light on its historical progression while envisioning a future where regenerative and customized medicines become commonplace.

A printed layer of silica-enforced poly(dimethylsiloxane)-co-(diphenylsiloxane) is modeled as a two-phase system consisting of air and polymer with an interface set up during the printing process. The structural geometry changes mostly due to the action of surface tension, while all material properties are strongly temperature dependent. Polymer flow is described using equations of the extended Herschel-Bulkley model, with parameters strongly dependent on temperature and degree of curing. Parameters of the model are determined using flow sweep measurements and separate experiments with vertical structure sagging at different temperatures. The curing process is modeled using dependencies between the curing rate, degree of curing, and temperature obtained in studies by differential scanning calorimetry. The developed model is used for simulations of printed structure deformations with different initial and boundary conditions.

The manufacturing of parts with medium complexity using wire-arc directed energy deposition (waDED) gets constantly improved by the development of tailored alloys and improvements in the generation of welding paths. In this study, both aspects are considered by proposing a novel aluminum alloy based on Al-Mg-Zn, which is then used for the waDED manufacturing of a car rim. The alloy was characterized in small-scale samples, in which no hot cracks and only a few gas porosities were found. In addition, the high quality of the alloy was verified by tensile tests of the heat-treated samples. The determined yield strength was >365 MPa, the ultimate tensile strength was >450 MPa, and the fracture strain was at least 3.9%. To put the new alloy to use, a standard aluminum car rim model was modified for the needs of waDED. Difficulties due to the steep overhang of the outer ring in the intersecting area with the spokes could be resolved by utilizing and adapting the collision avoidance of the path generation tool in the critical area. The optimization of the welding paths was simplified by first planning the paths using a section of the rim model. The rim geometry was manufactured successfully, and valuable findings regarding the waDED process of parts with medium complexity could be derived.

In addition to the well-documented resource efficiency and geometrical freedom, Digital Fabrication (DFAB) revolutionizes architecture by integrating functionalities into building elements, unlocking untapped potential from the micro- to the macroscales. This study uses binder-jet printed sand for a DFAB prototype-Fireplace2-tailored for indoor heating. Named after its traditional counterpart, Fireplace2 showcases DFAB's prowess in crafting precise microclimates for heightened thermal comfort. Our research, tuning mechanical and thermal properties across micro and meso scales, illustrates DFAB's utility in architects' hands for crafting tailored microclimates. This approach manipulates the effective thermal conductivity and macroscale topology for stability against toppling (0.8 kN). A vertical infill porosity gradient establishes a surface temperature gradient, countering ventilation-induced thermal gradients. With a minimal operational temperature vertical gradient (+0.2°C), complying with international comfort standards (Predicted Mean Vote -0.23, People Dissatisfied 6%), Fireplace2 stands testament to DFAB's microclimate-shaping capabilities despite challenges like foot-level ventilation. The study propels DFAB into a sustainable paradigm, aligning occupant comfort with environmental consciousness, thereby fostering more efficient and enjoyable indoor spaces.

3D-printed concrete (3DPC) technology based on layer-by-layer stacking has received increasing attention owing to its ability to produce customized formwork-free products. In this study, basalt-derived manufactured sand (MS) was used as a replacement for natural sand in 3DPC mixtures. Tests on printability, green strength at varying curing times, hardened mechanical properties, and characterization of the microstructure were conducted. The results demonstrate that the incorporation of MS into 3DPC produces an increase in fluidity and a reduction in unconfined compressive strength. Incorporation of MS enhanced the flexural strength of 3DPC along the printing direction, that is, the interlayer bonding strength, while decreasing its compressive anisotropy from 0.81 to 0.29. This partially compensates for interlayer defects in 3DPC, thereby benefiting for overall performance improvement of structures.

The use of plant fibers instead of commercial fibers in building materials is environmentally sustainable. Here in this work, the alkalized straw fibers were introduced into the 3D printed cementitious composite to investigate their effect on the properties of the printed composite. The flowability, buildability, and mechanical strengths of the printed composite were tested, and the internal pore distribution was analyzed by X-ray computed tomography. In addition, the straw fibers and printed specimens were tested by X-ray diffraction and scanning electron microscopy. Results showed that, with the increase of straw-fiber content, the flowability of the composites gradually decreased, and the buildability and mechanical strengths first decreased and then increased. Alkaline treatment can improve the crystallinity of cellulose in straw fibers, reduce water absorption, and enhance the bonding performance with the mortar interface. Therefore, compared with the natural-straw-fiber group, the flowability, buildability, and mechanical properties of the alkalized-straw-fiber composites were improved. Specifically, when the content of alkalized straw fiber was 0.4%, the 28 days flexural strength of the fiber alkalized group increased by about 12.6% compared with the natural-straw-fiber group. Microscopically, alkaline straw fibers have better energy absorption and load transfer capabilities inside the composite material, enhancing the toughness of the specimen. Overall, the incorporation of alkalized straw fibers into 3D printed cementitious composites showed better printing, mechanical, and environmental benefits.

In this research, the design and implementation of a novel chopped fiber deposition system for the laser sintering (LS) process is discussed. The system allows deposition of chopped fibers with different lengths and of multiple fiber types in a commercial LS machine. A weight percentage of 5% (2 vol%) glass fibers can be implemented without disturbing the LS process. LS specimens both with and without fibers can be produced during the same job as the setup only deposits fibers on half the powder bed. This is to reach an in-depth understanding of the influence of fibers on the produced specimens as the comparison can be made with the matrix material built in the same job. The setup was developed to answer the increasing demand for additively manufactured polymer composites with optimized mechanical properties currently manifesting in industries such as aerospace, biomedical, and automotive. To reach successful stress transfer from fiber to polymer, fibers need to have a certain critical length dependent on the combination of fiber and matrix material. For most material combinations, this length is longer than what is obtained with the fillers reported in literature. The development of the deposition system successfully allows the deposition of chopped fibers with longer lengths (to reach successful stress transfer) during the LS process, overcoming previously reported difficulties. The setup consists of six main components and can be connected to the recoating roller or blade present in every LS machine. With a test sieve, the vibrating system and a four-blade mixer are the most important for the functioning of the system. After preliminary testing, a profound optimization of the setup was conducted after which LS specimens with chopped fibers were successfully produced. X-ray computed tomography imaging of the produced specimens with fibers, showed a successful integration of chopped fibers in different random directions throughout the layers.

Numerical modeling of additive manufacturing processes is often conducted to predict both thermal and mechanical effects such as distortions, residual stresses, and phase distributions. The prediction accuracy is highly dependent on an accurate representation of thermal field, especially heat sources. In this study, response surface methodology (RSM) is serially utilized and mutually mapped to understand the relationships between process parameters and heat source coefficients. First, the effects of process factors and heat source model coefficients on experimental and numerical bead geometry are, respectively, identified through analysis of variance on central composite designs. With influences mathematically quantified, heat source coefficients in accordance with experimental conditions are inversely solved using nonlinear least square method, followed by correlation with process factors. The results show that both the effects of process parameters and heat source coefficients on bead geometry characteristics can be modeled using quadratic polynomials. The connections between heat source coefficients and process variables can also be modeled using quadratic or lower polynomial functions with good accuracy. It is proven that the proposed RSM mapping method is feasible for heat process correlation. The research outcome provides a convenient and reliable method of heat source calibration for laser additive manufacturing.

3D printed fashion products have become a trend. This article explains use of fused deposition modeling technology for 3D printing of fabrics with thermoplastic polyurethane flexible filament. A total of 15 structures of fabric were designed and printed for fabric performance tests. The fabric structures were "woven-like." Those fabrics were printed by 0.8, 1.0, and 1.5 mm nozzles, separately. Meanwhile, the fabrics had various layer heights, but total thickness of the fabric was fixed at 0.6 mm. The strongest fabric could resist up to 460 N in ball burst test. In tensile test, the strongest fabric was broken at 230 N and maximum elongation was 647% at break. Besides, the failure performance was analyzed, recovery ability of fabric was also evaluated. The least deformation of the fabric was 2.5% after stretching with 60 N and releasing for five cycles. These results of the fabric performance could be a database and a reference for designing the structure of an apparel or a garment.

Finite element analysis (FEA) of fused deposition modeling (FDM) has recently been recognized in additive manufacturing (AM) for predictions in temperature and displacement. These predictions can be invaluable for making corrections to the printing process to improve quality of printed components. However, FEA has limitations that discourage manufacturers from using it. For example, the fine mesh model takes considerably long computational times (although it yields more accurate results than those of a coarse mesh model). In this work, an innovative deep learning (DL)-based super-resolution (SR) approach is proposed to improve the result accuracy of a coarse mesh model to the higher accuracy level of a fine mesh model and reduce the computational time. The element in the FEA is treated as the physical pixel in an image, so the grid from fine mesh model and coarse mesh model in the FEA is analogous to high resolution (HR) images and low resolution (LR) images, respectively. The results show that the difference value between HR and reconstructed SR is much lower than the difference value between HR and interpolated LR, which demonstrate that our modified super resolution residual network SR reconstruction algorithm is effective to improve the interpolated LR in temperature and displacement. In addition, both the increased peak signal-to-noise ratio (PSNR) value and structural similarity index measure (SSIM) value indicated that the quality of both temperature and displacement images is improved through the learned SR model. In addition, the results confirm that mapping between fine mesh model and coarse mesh model in a temperature field is varied from the one in displacement field.

3D printing technology has made fabrication of electronics and sensors a cost-effective and customisable approach. Fabrication of 3D-printed strain gauges through fused deposition modeling technology offers compatibility and flexibility in adopting different substrate and conductive materials. The performance of a 3D-printed strain sensor depends on the selection of the conductive and substrate materials. This work focuses on the effects of substrate material variations and sensor geometrical variations on sensitivity, accuracy, stability, and working range of conductive polylactic acid (CPLA)-based 3D-printed strain sensor. Four variants of thermoplastic polyurethane (TPU) materials with different shore hardness values such as thermoplastic elastomer (TPE) 70A, eLastic TPE 83A, eFlex TPU 87A, and eTPU 95A have been chosen as the substrate materials. Strain sensors are 3D printed with all TPU substrate variants with CPLA in five different configurations, namely linear, serpentine, square, triangular, and trapezoidal. The resistance change ratios of the printed sensors, gauge factor, strain limits, and hysteresis error are computed by loading the sensor over various strain values under multiple cycles. Results revealed that the CPLA-eTPU 95A in triangular configuration outperforms other TPU variants in terms of gauge factor and hysteresis error. The gauge factor and hysteresis error exhibited by the CPLA-eTPU 95A in triangular configuration are 18.63% higher and 18.37% lower than that of CPLA-eFlex TPU 87A sensor, respectively. This happens due to high elastic modulus and shape recovery characteristics of eTPU 95A substrate; whereas the stretching limit of eTPU 95A is 25% lower than the eFlex TPU 87A substrate. Finally, by changing the vertical distance between the surface layers of the sensing element and the substrate material as 0.1 mm, a significant increase of 54% in the working range of CPLA-eTPU 95A strain sensor was observed.

Triply periodic minimal surface (TPMS) has been widely used in biology due to its excellent biological, controllable mechanical, and material transport properties. In this study, four types of TPMS structures with silicon nitride (SiN) ceramic were successfully prepared using digital light processing (DLP) with different minimal surface equations. The influence of different TPMS structures on the mechanical and biological properties of SiN ceramic was systematically investigated. Results indicated a better cell proliferation ability in the D structure compared with three other structures, with favorable compressive strength and Young's modulus of 51.84 ± 8.85 MPa and 3.33 ± 0.08 GPa, respectively.