Print Fidelity Research Articles

An innovative 4D printing approach for fabrication of anisotropic collagen scaffolds

Collagen anisotropy is known to provide the essential topographical cues to guide tissue-specific cell function. Recent work has shown that extrusion-based printing using collagenous inks yield 3D scaffolds with high geometric precision and print fidelity. However, these scaffolds lack collagen anisotropy. In this study, extrusion-based 3D printing was combined with a magnetic alignment approach in an innovative 4D printing scheme to generate 3D collagen scaffolds with high degree of collagen anisotropy. Specifically, the 4D printing process parameters-collagen (Col):xanthan gum (XG) ratio (Col:XG; 1:1, 4:1, 9:1 v/v), streptavidin-coated magnetic particle concentration (SMP; 0, 0.2, 0.4 mg ml-1), and print flow speed (2, 3 mm s-1)-were modulated and the effects of these parameters on rheological properties, print fidelity, and collagen alignment were assessed. Further, the effects of collagen anisotropy on human mesenchymal stem cell (hMSC) morphology, orientation, metabolic activity, and ligamentous differentiation were investigated. Results showed that increasing the XG composition (Col:XG 1:1) enhanced ink viscosity and yielded scaffolds with good print fidelity but poor collagen alignment. On the other hand, use of inks with lower XG composition (Col:XG 4:1 and 9:1) together with 0.4 mg ml-1SMP concentration yielded scaffolds with high degree of collagen alignment albeit with suboptimal print fidelity. Modulating the print flow speed conditions (2 mm s-1) with 4:1 Col:XG inks and 0.4 mg ml-1SMP resulted in improved print fidelity of the collagen scaffolds while retaining high level of collagen anisotropy. Cell studies revealed hMSCs orient uniformly on aligned collagen scaffolds. More importantly, collagen anisotropy was found to trigger tendon or ligament-like differentiation of hMSCs. Together, these results suggest that 4D printing is a viable strategy to generate anisotropic collagen scaffolds with significant potential for use in tendon and ligament tissue engineering applications.

On the Relation between the Viscoelastic Properties of Granular Hydrogels and Their Performance as Support Materials in Embedded Bioprinting.

Granular hydrogels, formed by jamming microgels suspension, are promising materials for three-dimensional bioprinting applications. Despite their extensive use as support materials for embedded bioprinting, the influence of the particle's physical properties on the macroscale viscoelasticity on one hand and on the printing performance on the other hand remains unclear. Herein, we investigate the linear and nonlinear rheology of κ-carrageenan granular hydrogel through small- and large-amplitude oscillatory shear measurements. We tuned the granular hydrogel's properties by changing the stiffness (soft, medium, stiff) and the packing density of the individual microgels. Characterizations in the linear viscoelasticity regime revealed that the storage modulus of granular hydrogels is not a simple function of microgel stiffness and depends on the microgel packing density. At larger strains, increasing the microgel stiffness reduced the energy dissipation of the granular beds and increased the solid-fluid transition point. To understand how the different rheological properties of granular support materials influence embedded bioprinting, we examined the printing fidelity and cellular filament shrinkage within the granular beds. We found that microgels with low packing density diminished the printing quality, while stiff microgels promoted filament roughness. In addition, we found that highly packed stiff microgels significantly reduced the postprinting contraction of cellular filaments. Overall, this work provides a comprehensive knowledge of the rheology of granular hydrogels that can be used to rationally design support beds for bioprinting applications with specific characteristics.

Citrus peel powder alters the rheological properties and 3D printing performance of potato starch gel

Owing to the growing interest in sustainable resource utilization, the current study explores the potential replacement of pectin with citrus peel powder (CP) in starch-based 3D food printing ink formulations. The effect of different concentrations of pectin (1 %, 2 %, 3 %) and CP (1 %, 2 %, 3 %) on the printing fidelity, microstructure, rheological and textural properties of potato starch gel were investigated. The results showed that the 3D printing performance of CP-added inks was higher than that of pectin-added inks at all tested concentrations. The storage modulus of CP-added ink was higher than that of pectin-added ink proving higher printing fidelity of CP-added inks. Additionally, hardness, gumminess, springiness and chewiness of food ink increased with an increase in the concentration of CP while decreased with an increase in concentration of pectin. Interestingly, pectin and CP-added inks displayed similar in vitro digestibility, suggesting an insignificant effect of replacing pectin with CP on in vitro glucose release. Moreover, the antioxidant activity of CP-added ink was higher than pectin-added ink demonstrating the potential applications of CP-added ink in functional ink development. Therefore, this study claims for effective replacement of pectin with CP in starch-based 3D food printing ink formulations as a promising sustainable additive.

3D printing of strontium-enriched biphasic calcium phosphate scaffolds for bone regeneration

Calcium phosphate (CaP) scaffolds doping with therapeutic ions are one of the focuses of recent bone tissue engineering research. Among the therapeutic ions, strontium stands out for its role in bone remodeling. This work reports a simple method to produce Sr-doped 3D-printed CaP scaffolds, using Sr-doping to induce partial phase transformation from β-tricalcium phosphate (β-TCP) to hydroxyapatite (HA), resulting in a doped biphasic calcium phosphate (BCP) scaffold. Strontium carbonate (SrCO3) was incorporated in the formulation of the 3D-printing ink, studying β-TCP:SrO mass ratios of 100:0, 95:5, and 90:10 (named as β-TCP, β-TCP/5-Sr, and β-TCP/10-Sr, respectively). Adding SrCO3 in the 3D-printing ink led to a slight increase in viscosity but did not affect its printability, resulting in scaffolds with a high printing fidelity compared to the computational design. Interestingly, Sr was incorporated into the lattice structure of the scaffolds, forming hydroxyapatite (HA). No residual SrO or SrCO3 were observed in the XRD patterns of any composition, and HA was the majority phase of the β-TCP/10-Sr scaffolds. The addition of Sr increased the compression strength of the scaffolds, with both β-TCP/5-Sr and β-TCP/10-Sr performing better than the β-TCP. Overall, β-TCP/5-Sr presented higher mineralized nodules and mechanical strength, while β-TCP scaffolds presented superior cell viability. The incorporation of SrCO3 in the ink formulation is a viable method to obtain Sr-BCP scaffolds. Thus, this approach could be explored with other CaP scaffolds aiming to optimize their performance and the addition of alternative therapeutic ions.

Rheological characterization and print quality studies of gelatin/collagen I/PEGDA hydrogels

Bioprinting is an up-and-coming technology that uses the basis of additive manufacturing and applies it to the field of tissue engineering. Bioprinting is used to create 3D models of diseased tissue and organs, test cellular responses to drug therapies, and create potentially transplantable organs and vasculature. Bioprinting has gained increasing interest especially in drug discovery, as the traditional 2D cell culture models have been shown to produce results that are not mimicked in animal and human trials. Bioprinters use materials called bioinks, developed from hydrogels which can contain cells and biological factors. While there are commonly used bioinks, there is a need for the development of a diverse range of bioinks for varying applications. In this study, an alternative bioink was developed. The formulations included gelatin, collagen I, and varying amounts of poly (ethylene glycol) diacrylate (PEGDA). These formulations were subject to rheological characterization and print quality analysis. Formulations with higher concentrations of PEGDA had higher degrees of shear-thinning, higher viscosity recovery, lower viscosities, and less dominant gel behavior. The print quality studies showed that the formulations with lower concentrations of PEGDA had better printability, print accuracy, and print fidelity. Formulation P5 had the best overall print quality.

FRESH-based 3D bioprinting of complex biological geometries using chitosan bioink

Traditional three-dimensional (3D) bioprinting has always been associated with the challenge of print fidelity of complex geometries due to the gel-like nature of the bioinks. Embedded 3D bioprinting has emerged as a potential solution to print complex geometries using proteins and polysaccharides-based bioinks. This study demonstrated the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) 3D bioprinting method of chitosan bioink to 3D bioprint complex geometries. 4.5% chitosan was dissolved in an alkali solvent to prepare the bioink. Rheological evaluation of the bioink described its shear-thinning nature. The power law equation was fitted to the shear rate-viscosity plot. The flow index value was found to be less than 1, categorizing the material as pseudo-plastic. The chitosan bioink was extruded into another medium, a thermo-responsive 4.5% gelatin hydrogel. This hydrogel supports the growing print structures while printing. After this, the 3D bioprinted structure was crosslinked with hot water to stabilize the structure. Using this method, we have 3D bioprinted complex biological structures like the human tri-leaflet heart valve, a section of a human right coronary arterial tree, a scale-down outer structure of the human kidney, and a human ear. Additionally, we have shown the mechanical tunability and suturability of the 3D bioprinted structures. This study demonstrates the capability of the chitosan bioink and FRESH method for 3D bioprinting of complex biological models for biomedical applications.

Construct functional PEGDA/CSMA/CuII photosensitive ink for SLA 3D printing of blood contact appliance

Stereolithography (SLA) is an emerging technology in three-dimensional printing that has garnered significant attention in the biomedical field due to its high printing fidelity, good biocompatibility, and high spatial resolution. Polyethylene glycol diacrylate (PEGDA) is commonly used as a photosensitive printing ink in SLA, and it possesses excellent biocompatibility, photosensitivity, processability, water solubility, and biomechanical tunability. Additionally, PEGDA exhibits unique anti-protein, platelet, and cell adhesion possibilities, making it a promising material for blood contact applications. However, cross-linking PEGDA using chain growth photopolymerization results in a high concentration of reactive functional groups, leading to high print volume shrinkage, decreased precision of the finished product, warping, deformation, and cracking. This study introduces a chemically modified methacryloylated chitosan (CSMA) as a cross-linking agent into the PEGDA ink. This strategy effectively reduces the volume shrinkage of the ink and imparts antimicrobial properties to the final product. The dual anticoagulation properties of PEGDA were achieved by loading divalent copper ion (CuII) into the ink, which better addresses the antimicrobial and anticoagulant needs in the physiological environment of blood. The results show that SLA printable inks based on PEGDA/CSMA/CuII have low swelling, high print fidelity, high stability, and good cell compatibility. Furthermore, by verifying the functionality of PEGDA/CSMA/CuII, the research shows that the bioprinting ink exhibits excellent antibacterial and anticoagulant properties, making it a promising material candidate for SLA 3D printing of blood purification, central venous catheter, and other semi-implanted blood materials. This study provides new ideas for developing multifunctional photosensitive inks in biomedical engineering.

Granular Biphasic Colloidal Hydrogels for 3D Bioprinting.

Granular hydrogels composed of hydrogel microparticles are promising candidates for 3D bioprinting due to their ability to protect encapsulated cells. However, to achieve high print fidelity, hydrogel microparticles need to jam to exhibit shear-thinning characteristics, which is crucial for 3D printing. Unfortunately, this overpacking can significantly impact cell viability, thereby negating the primary advantage of using hydrogel microparticles to shield cells from shear forces. To overcome this challenge, a novel solution: a biphasic, granular colloidal bioink designed to optimize cell viability and printing fidelity is introduced. The biphasic ink consists of cell-laden polyethylene glycol (PEG) hydrogel microparticles embedded in a continuous gelatin methacryloyl (GelMA)-nanosilicate colloidal network. Here, it is demonstrated that this biphasic bioink offers outstanding rheological properties, print fidelity, and structural stability. Furthermore, its utility for engineering complex tissues with multiple cell types and heterogeneous microenvironments is demonstrated, by incorporating β-islet cells into the PEG microparticles and endothelial cells in the GelMA-nanosilicate colloidal network. Using this approach, it is possible to induce cell patterning, enhance vascularization, and direct cellular function. The proposed biphasic bioink holds significant potential for numerous emerging biomedical applications, including tissue engineering and disease modeling.

Dissecting the Interplay Mechanism among Process Parameters toward the Biofabrication of High-Quality Shapes in Embedded Bioprinting.

Embedded bioprinting overcomes the barriers associated with the conventional extrusion-based bioprinting process as it enables the direct deposition of bioinks in 3D inside a support bath by providing in situ self-support for deposited bioinks during bioprinting to prevent their collapse and deformation. Embedded bioprinting improves the shape quality of bioprinted constructs made up of soft materials and low-viscosity bioinks, leading to a promising strategy for better anatomical mimicry of tissues or organs. Herein, the interplay mechanism among the printing process parameters toward improved shape quality is critically reviewed. The impact of material properties of the support bath and bioink, printing conditions, cross-linking mechanisms, and post-printing treatment methods, on the printing fidelity, stability, and resolution of the structures is meticulously dissected and thoroughly discussed. Further, the potential scope and applications of this technology in the fields of bioprinting and regenerative medicine are presented. Finally, outstanding challenges and opportunities of embedded bioprinting as well as its promise for fabricating functional solid organs in the future are discussed.

Optimising printing fidelity of the single-nozzle based multimaterial direct ink writing for 3D food printing

ABSTRACT Single-nozzle based multimaterial direct ink writing enables voxel-based fabrication with superior printing efficiency than multi-nozzle protocol. This is attractive for food 3D printing process where efficiency matters for its application. However, for single-nozzle based process, the presence of residual material in the shared channel can affect its printing fidelity. In this study, we propose a path planning algorithm that can address this issue by incorporating (i) advance distance to compensate the extrusion delay when switching materials, and (ii) in-process printhead motion adjustments to stabilise the extrusion process. Our approach demonstrated a substantial improvement in printing fidelity, where the switching point offset was reduced to ±0.5 mm. Similarly, the unstable extrusion behaviours (bulging and necking) during switching materials were suppressed, where the printing fidelity was improved by 27 ± 5% (bulging) and 19 ± 3% (necking) respectively. Additionally, we provide an open-source slicing programme that empowers users to implement the above two algorithms.

Microfluidic human physiomimetic liver model as a screening platform for drug induced liver injury

The pre-clinical animal models often fail to predict intrinsic and idiosyncratic drug induced liver injury (DILI), thus contributing to drug failures in clinical trials, black box warnings and withdrawal of marketed drugs. This suggests a critical need for human-relevant in vitro models to predict diverse DILI phenotypes. In this study, a porcine liver extracellular matrix (ECM) based biomaterial ink with high printing fidelity, biocompatibility and tunable rheological and mechanical properties is formulated for supporting both parenchymal and non-parenchymal cells. Further, we applied 3D printing and microfluidic technology to bioengineer a human physiomimetic liver acinus model (HPLAM), recapitulating the radial hepatic cord-like structure with functional sinusoidal microvasculature network, biochemical and biophysical properties of native liver acinus. Intriguingly, the human derived hepatic cells incorporated HPLAM cultured under physiologically relevant microenvironment, acts as metabolic biofactories manifesting enhanced hepatic functionality, secretome levels and biomarkers expression over several weeks. We also report that the matured HPLAM reproduces dose- and time-dependent hepatotoxic response of human clinical relevance to drugs typically recognized for inducing diverse DILI phenotypes as compared to conventional static culture. Overall, the developed HPLAM emulates in vivo like functions and may provide a useful platform for DILI risk assessment to better determine safety and human risk.

Advective Assembler‐Enhanced Support Bath Rotational Direct Ink Writing

AbstractManufacturing intricately controlled, hierarchically distributed structures poses significant fabrication challenges, but is crucial for enhancing functionality in synthetic systems. A 3D printing technique combining advective assembly with rotational direct ink writing is developed and exploited to build topologically complex, multimaterial structures with high precision. A modular advective assembler printhead is fabricated and employed in the process. This flow‐structuring device is designed with a complex network of internal channels that patterns flowing hydrogel‐based inks, creating multi‐layered filaments whose structures go well beyond conventional nozzle shape and size limitations. The composite filaments are extruded into a rotating support bath of Polyacrylic acid microgels. The rheology of the inks and support bath are critical to maintain print fidelity and integrity, and are characterized by linear and nonlinear bulk rheometry. Optimization of the materials creates a platform where curvilinear, multimaterial architectures are constructed without being constrained to slicing across X, Y, and Z axes. The versatility of this manufacturing platform is demonstrated by printing helical structures that undergo swelling‐induced actuation. This processing method has the potential to significantly enhance additive manufacturing by enabling the production of intricate, multiscale composite structures with broad applicability in fields such as bioengineering, soft robotics, and functional composite materials.

Enhancing the 3D printing fidelity of vat photopolymerization with machine learning-driven boundary prediction

Like many pixel-based additive manufacturing (AM) techniques, digital light processing (DLP) based vat photopolymerization faces the challenge that the square pixel based processing strategy can lead to zigzag edges especially when feature sizes come close to single-pixel levels. Introducing greyscale pixels has been a strategy to smoothen such edges, but it is a challenging task to understand which of the many permutations of projected pixels would give the optimal 3D printing performance. To address this challenge, a novel data acquisition strategy based on machine learning (ML) principles is proposed, and a training routine is implemented to reproduce the smallest shape of an intended 3D printed object. Through this approach, a chessboard patterning strategy is developed along with an automated data refining and augmentation workflow, demonstrating its efficiency and effectiveness by reducing the deviation by around 30%.

Abstract 4217: An engineered breast tumor microenvironment model, with single-cell spatial resolution, to assess spatial dynamics of tumor evolution

Abstract Cellular heterogeneity is a prominent feature of the tumor microenvironment, and the organization of these cells has been linked to clinical outcomes such as disease progression and drug resistance. While retrospective analysis of patient tumors has produced a myriad of insights, samples are limited and highly complex making it challenging to validate causality. Here we present an engineered breast tumor microenvironment model, with single cell spatial resolution, to systematically identify which cell phenotypes and their spatial arrangements may be driving ductal carcinoma in situ disease progression. A microfluidic dispenser (Biopixlar, Fluicell) was optimized to enable the spatial patterning of single cells to replicate native histology. To demonstrate the high spatial precision of our method, we first replicated an annotated 2D section of a breast tumor biopsy region of interest (ROI) using MCF10A, MDA-MB-231, primary mammary fibroblasts, THP-1 derived macrophages, and primary mesenchymal stem cells. The XY coordinate of each cell was identified to create a print map matching the original biopsy. Deposited cells adhered to their intended target with an average print fidelity of 2.4 µm. Next, the stromal compartment of the ROI was altered to include phenotypes associated with tumor promoting microenvironments (i.e. cancer associated fibroblasts, M2 macrophages) and the core of the MCF10A ring filled with MDA-MB-231. Each deposited cell contained a fluorescent tag corresponding with its cell type to facilitate real time spatial tracking and annotation. The tumor microenvironments were live cell imaged for 24 hours at 5 minute intervals. MCF10A cells spread to form their junctions and create a cohesive ring, MDA-MB-231 cells proliferated and rapidly moved around within the confined space, and the cells of the stromal compartment spread to create a dense tissue like structure. The microenvironments were cultured for an additional 2-6 days, fixed, and stained for markers of proliferation, phenotype shifts, cell-cell junctions, and morphology. Unlocking the relative contributions of the specific cell types in ductal carcinoma in situ tumor microenvironment to the overall evolution of invasive breast cancer may hold the answer for many questions in early detection, treatment, and cancer avatar models. Citation Format: Haylie R. Helms, Kody A. Oyama, Alexander E. Davies, Ellen M. Langer, Luiz E. Bertassoni. An engineered breast tumor microenvironment model, with single-cell spatial resolution, to assess spatial dynamics of tumor evolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4217.

The effect of triglycerol diacrylate on the printability and properties of UV curable, bio-based nanohydroxyapatite composites

3D printable biopolymer nanocomposites composed of hydroxyapatite nanoparticles and functionalized plant-based monomers demonstrate potential as sustainable and structural biomaterials. To increase this potential, their printability and performance must be improved. For extrusion-based 3D printing, such as Direct Ink Writing (DIW), printability is important for print fidelity. In this work, triglycerol diacrylate (TGDA) was added to an acrylated epoxidized soybean oil:polyethylene glycol diacrylate resin to increase hydrogen bonding. Greater hydrogen bonding was hypothesized to improve printability by increasing the ink's shear yield strength, and therefore shape holding after deposition. The effects of this additive on material and mechanical properties were quantified. Increased hydrogen bonding due to TGDA content increased the ink's shear yield stress and viscosity by 916% and 27.6%, respectively. This resulted in improved printability, with best performance at 3 vol% TGDA. This composition achieved an ultimate tensile strength (UTS) of 32.4 ± 2.1 MPa and elastic modulus of 1.15 ± 0.21 GPa. These were increased from the 0 vol% TGDA composite, which had an UTS of 24.8 ± 1.8 MPa and a modulus of 0.88 ± 0.06 GPa. This study demonstrates the development of bio-based additive manufacturing feedstocks for potential uses in sustainable manufacturing, rapid prototyping, and biomaterial applications.

Suitability of Gelatin Methacrylate and Hydroxyapatite Hydrogels for 3D-Bioprinted Bone Tissue.

Complex bone defects are challenging to treat. Autografting is the gold standard for regenerating bone defects; however, its limitations include donor-site morbidity and increased surgical complexity. Advancements in 3D bioprinting (3DBP) offer a promising alternative for viable bone grafts. In this experiment, gels composed of varying levels of gelatin methacrylate (GelMA) and hydroxyapatite (HA) and gelatin concentrations are explored. The objective was to increase the hydroxyapatite content and find the upper limit before the printability was compromised and determine its effect on the mechanical properties and cell viability. Design of Experiments (DoE) was used to design 13 hydrogel bioinks of various GelMA/HA concentrations. These bioinks were assessed in terms of their pipettability and equilibrium modulus. An optimal bioink was designed using the DoE data to produce the greatest stiffness while still being pipettable. Three bioinks, one with the DoE-designed maximal stiffness, one with the experimentally defined maximal stiffness, and a literature-based control, were then printed using a 3D bioprinter and assessed for print fidelity. The resulting hydrogels were combined with human bone-marrow-derived mesenchymal stromal cells (hMSCs) and evaluated for cell viability. The DoE ANOVA analysis indicated that the augmented three-level factorial design model used was a good fit (p < 0.0001). Using the model, DoE correctly predicted that a composite hydrogel consisting of 12.3% GelMA, 15.7% HA, and 2% gelatin would produce the maximum equilibrium modulus while still being pipettable. The hydrogel with the most optimal print fidelity was 10% GelMA, 2% HA, and 5% gelatin. There were no significant differences in the cell viability within the hydrogels from day 2 to day 7 (p > 0.05). There was, however, a significantly lower cell viability in the gel composed of 12.3% GelMA, 15.7% HA, and 2% gelatin compared to the other gels with a lower HA concentration (p < 0.05), showing that a higher HA content or print pressure may be cytotoxic within hydrogels. Extrusion-based 3DBP offers significant advantages for bone-tissue implants due to its high customizability. This study demonstrates that it is possible to create printable bone-like grafts from GelMA and HA with an increased HA content, favorable mechanical properties (145 kPa), and a greater than 80% cell viability.

Predictive modeling for online in-plane shape deviation inspection and compensation of additive manufacturing

PurposeLimited geometric accuracy is one of the major challenges that hinder the wider application of additive manufacturing (AM). This paper aims to predict in-plane shape deviation for online inspection and compensation to prevent error accumulation and improve shape fidelity in AM.Design/methodology/approachA sequence-to-sequence model with an attention mechanism (Seq2Seq+Attention) is proposed and implemented to predict subsequent layers or the occluded toolpath deviations after the multiresolution alignment. A shape compensation plan can be performed for the large deviation predicted.FindingsThe proposed Seq2Seq+Attention model is able to provide consistent prediction accuracy. The compensation plan proposed based on the predicted deviation can significantly improve the printing fidelity for those layers detected with large deviations.Practical implicationsBased on the experiments conducted on the knee joint samples, the proposed method outperforms the other three machine learning methods for both subsequent layer and occluded toolpath deviation prediction.Originality/valueThis work fills a research gap for predicting in-plane deviation not only for subsequent layers but also for occluded paths due to the missing scanning measurements. It is also combined with the multiresolution alignment and change point detection to determine the necessity of a compensation plan with updated G-code.

Evaluation of 3D printability of blueberry powder gel system under ultrasound pretreatment

To achieve the personalized food of 3D manufacturing of blueberry powder (BP) with high nutritional value, the potato starch (PS) and low methoxy pectin (LMP) were selected as matrix material carrying BP to prepare the gels for 3D printing. The 3D printability of the ultrasound-treated gels was evaluated in terms of flow and forming properties. The results indicated that the addition of PS improved the flowability and support stability of the gels due to the non-covalent bonding interaction between the components of the additives and BP via hydrogen bonding. The ultrasound treatment of the gels can cause the cross-linking of PS and LMP to form a uniform and compact structure, which improves the 3D printing fidelity. A Principal Component Analysis-Multiple Linear Regression (PCA-MLR) model is developed to evaluate the 3D printability of BP gels as a function of the flow and thermal properties of the gels, and the texture of the 3D printed food system. The research results may provide a new method for the 3D printing of food powders such as BP.

Nodo-Tie: an innovative, 3-D printed simulator for surgical knot-tying skills development

IntroductionClinical simulators are an important resource for medical students seeking to improve their fundamental surgical skills. Three-dimensional (3-D) printing offers an innovative method to create simulators due to its low production costs and reliable printing fidelity. We aimed to validate a 3-D printed knot-tying simulator named Nodo-Tie. MethodsWe designed a 3-D printed knot-tying simulator integrated with a series of knot-tying challenges and a designated video curriculum made accessible via a quick-response (QR) code. The Nodo-Tie, which costs less than $1 to print and assemble, was distributed to second-year medical students starting their surgical clerkship. Participants were asked to complete a survey gauging the simulator's usability and educational utility. The time between simulator distribution and survey completion was eight weeks. ResultsStudents perceived the Nodo-Tie as easy-to-use (4.6 ± 0.8) and agreed it increased both their motor skills (4.5 ± 0.9) and confidence (4.5 ± 0.8) for tying surgical knots in the clinical setting. Many students agreed the Nodo-Tie provided a stable, durable surface for knot-tying practice (83.7%, n = 41) and that they would continue to use it beyond their participation in the study period (91.7%, n = 44). DiscussionMedical students found this interactive, 3-D printed knot-tying simulator to be an effective tool to use for self-directed development of their knot-tying skills. Given the Nodo-Tie's low cost, students were able to keep the Nodo-Tie for use beyond the study period. This increases the opportunity for students to engage in the longitudinal practice necessary to master knot-tying as they progress through their medical education. Key messagesClinical simulators provide proactive learners with reliable, stress-free environments to engage in self-directed surgical skills development. The Nodo-Tie, a 3-D printed simulator, serves as a cost-effective, interactive tool for medical students to develop their knot-tying abilities beyond the clinical setting.

The synergistic effect of κ-carrageenan and l-lysine on the 3D printability of yellow flesh peach gels: The importance of material elasticity in the printing process

This study investigated the effect of κ-carrageenan and l-lysine on the physical, chemical and textural properties of yellow flesh peaches and their suitability for 3D printing. The addition of κ-carrageenan and l-lysine was found to improve the apparent viscosity, elasticity, gel strength, and Young's modulus of the yellow flesh peach with κ-carrageenan and l-lysine gels (PCLG) and increase the minimum piston pressure required for 3D printing, thereby improving the printing performance.Optimum levels of κ-carrageenan and l-lysine (0.1 mmol/mL and 3.42 × 10−2 mmol/mL, respectively) were found to enhance mechanical strength, viscoelasticity and print fidelity. On the other hand, when the addition of κ-carrageenan is 0.1 mmol/mL, the addition of l-lysine causes an increase in the G0 value and a decrease in the η0 value of the PCLG according to Burger's model, indicating a transition from viscosity to elasticity and an increase in maximum extrusion force, while the apparent viscosity does not change significantly. The results of 3D printing showed that when the addition of κ-carrageenan and l-lysine reached 0.1 mmol/mL and 6.84 × 10−2 mmol/mL, respectively, the PCLG could not be smoothly extruded, indicating that elasticity also plays an important role during the extrusion process of the mixed gel.