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BACKGROUND: Adrenal insufficiency is usually diagnosed in children who will need lifelong hydrocortisone therapy. However, medicines for pediatrics, in terms of dosage and acceptability, are currently unavailable. RESEARCH DESIGN AND METHODS: Semi-solid extrusion (SSE) 3D printing (3DP) was utilized for manufacturing of personalized and chewable hydrocortisone formulations (printlets) for an upcoming clinical study in children at Vall d'Hebron University Hospital in Barcelona, Spain. The 3DP process was validated using a specific software for dynamic dose modulation. RESULTS: The printlets contained doses ranging from 1 to 6 mg hydrocortisone in three different flavor and color combinations to aid adherence among the pediatric patients. The pharma-ink (mixture of drugs and excipients) was assessed for its rheological behavior to ensure reproducibility of printlets through repeated printing cycles. The printlets showed immediate hydrocortisone release and were stable for 1 month of storage, adequate for prescribing instructions during the clinical trial. CONCLUSIONS: The results confirm the suitability and safety of the developed printlets for use in the clinical trial. The required technical information from The Spanish Medicines Agency for this clinical trial application was compiled to serve as guidelines for healthcare professionals seeking to apply for and conduct clinical trials on 3DP oral dosage forms.

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Nanocellulose hydrogels are promising to replace synthetic ones for direct ink writing (DIW)-based 3D printing biobased applications. However, less gelation strength and low solid content of the hydrogels limit the printability and subsequent fidelity of the dried object. Herein, a biobased, ternary DIW hydrogel ink is developed by one-pot gelation of cellulose nanofibrils (CNF), sodium alginate (SA), and Ca-montmorillonite (Ca-MMT) via in situ ionic crosslinking. The addition of Ca-MMT into CNF/SA formulation simultaneously increases the solid content and gelation strength of the hydrogel. The resultant hydrogels exhibit shape recovery after compression. The optimal CNF concentration in the hydrogel is 1.2 wt%, enabling the highest compressive mechanical performance of the scaffolds. A series of complex, customized shapes with different curvatures and three-dimensional structures (e.g., high-curvature letters, pyramids, human ears, etc.) can be printed with high fidelity before and after drying. This study opens an avenue on preparing nanocellulose-based DIW hydrogel inks using one-pot gelation of the components, which offers a solution to combine DIW-based 3D printing with biobased hydrogel inks, towards diverse biobased applications.

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This research aims to use energy harvested from conductive materials to power microelectronic components. The proposed method involves using vibration-based energy harvesting to increase the natural vibration frequency, reduce the need for battery replacement, and minimise chemical waste. Piezoelectric transduction, known for its high-power density and ease of application, has garnered significant attention. Additionally, graphene, a non-piezoelectric material, exhibits good piezoelectric properties. The research explores a novel method of printing graphene material using 3D printing, specifically Direct Ink Writing (DIW) and fused deposition modelling (FDM). Both simulation and experimental techniques were used to analyse energy harvesting. The experimental technique involved using the cantilever beam-based vibration energy harvesting method. The results showed that the DIW-derived 3D-printed prototype achieved a peak power output of 12.2 µW, surpassing the 6.4 µW output of the FDM-derived 3D-printed prototype. Furthermore, the simulation using COMSOL Multiphysics yielded a harvested output of 0.69 µV.

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Pickering emulsions and foams as well as capillary suspensions are becoming increasingly more popular as inks for 3D printing. However, a lack of understanding of the bulk rheological properties needed for their application in 3D printing is potentially stifling growth in the area, hence the timeliness of this review. Herein, we review the stability and bulk rheology of these materials as well as the applications of their 3D-printed products. By highlighting how the bulk rheology is tuned, and specifically the inks storage modulus, yield stress and critical balance between the two, we present a rheological performance map showing regions where good prints and slumps are observed thus providing clear guidance for future ink formulations. To further advance this field, we also suggest standard experimental protocols for characterizing the bulk rheology of the three types of ink: capillary suspension, Pickering emulsion and Pickering foam for 3D printing by direct ink writing.

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OBJECTIVES: To evaluate the dimensional accuracy of occlusal veneers printed using a novel direct ink writing (DIW) system and a clinically approved dental composite. METHODS: A novel three-dimensional printer was developed based on the extrusion-based DIW principle. The printer, constructed primarily with open-source hardware, was calibrated to print with a flowable resin composite (Beautifil Flow Plus). The feasibility of this technology was assessed through an evaluation of the dimensional accuracy of 20 printed occlusal veneers using a laboratory confocal scanner. The precision was determined by pairwise superimposition of the 20 prints, resulting in a set of 190 deviation maps used to evaluate between-sample variations. RESULTS: Without material waste or residuals, the DIW system can print a solid occlusal veneer of a maxillary molar within a 20-minute timeframe. Across all the sampled surface points, the overall unsigned dimensional deviation was 30.1 ± 20.2 µm (mean ± standard deviation), with a median of 24.4 µm (interquartile range of 22.5 µm) and a root mean square value of 36.3 µm. The pairwise superimposition procedure revealed a mean between-sample dimensional deviation of 26.7 ± 4.5 µm (mean ± standard deviation; n = 190 pairs), indicating adequate precision. Visualization of the deviation together with the nonextrusion movements highlights the correlation between high-deviation regions and material stringing. SIGNIFICANCE: This study underscores the potential of using the proposed DIW system to create indirect restorations utilizing clinically approved flowable resin composites. Future optimization holds promise for enhancing the printing accuracy and increasing the printing speed.

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Direct ink writing (DIW) of high-temperature thin-film sensors holds significant potential for monitoring extreme environments. However, existing high-temperature inks face a trade-off between cost and performance. This study proposes a SiCN/RuO2/TiB2 composite ceramic ink. The added TiB2, after annealing in a high-temperature atmospheric environment, forms B2O3 glass, which synergizes with the SiO2 glass phase formed from the SiCN precursor to effectively encapsulate RuO2 particles. This enhances the film's density and adhesion to the substrate, preventing RuO2 volatilization at high temperatures. Additionally, the high conductivity of TiB2 improves the film's overall conductivity. Test results indicate that the SiCN/RuO2/TiB2 film exhibits high linearity from room temperature to 900 °C, high stability (resistance drift rate of 0.1%/h at 800 °C), and high conductivity (4410 S/m). As a proof of concept, temperature sensors and a heat flux sensor were successfully fabricated on a metallic hemispherical surface. Performance tests in extreme environments using high-power lasers and flame guns verified that the conformal thin-film sensor can accurately measure spherical temperature and heat flux, with a heat flux sensor response time of 53 ms. In conclusion, the SiCN/RuO2/TiB2 composite ceramic ink developed in this study offers a high-performance and cost-effective solution for high-temperature conformal thin-film sensors in extreme environments.

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Using three-dimensional (3D) printing technology to fabricate Bi2Te3-based thermoelectric (TE) generators opens a potential way to create shape-conformable devices capable of recovering waste heat from thermal energy sources with diverse surface morphologies. However, pores formed in 3D-printed Bi2Te3-based materials by the removal of the organic ink binder result in unsatisfactory performance compared to the bulk materials, which has limited the widespread application of the ink-based 3D printing process. Furthermore, managing the volatile Se element in the n-type materials poses significant technological challenges compared to the p-type counterparts, resulting in a scarcity of research on 3D printing of n-type Bi2Te3. Here, we synthesized edge-oxidized graphene (EOG)-incorporated Se-free n-type Bi1.7Sb0.3Te3 (BST) using a direct ink writing (DIW) process with a binder-free novel ink. The incorporated EOG provides connectivity between small BST grains separated by pores and induces a bimodal-like grain structure during the DIW and sintering process. The optimal EOG content of 0.1 wt % in 3D-printed n-type BST simultaneously achieved both carrier transport control and active phonon scattering, due to its unique microstructure. A maximum ZT of 0.71 was obtained in the 0.1 wt % EOG/BST materials at 448 K, comparable to commercial bulk n-type Bi2Te3-based materials. Further, a single-element device composed of the EOG-BST material exhibited a 2-fold improvement in performance compared to pure-BST. These results open a technological route for the application of 3D printing technology for ink-based TE materials.

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The advantage of low-temperature forming through direct ink writing (DIW) 3D printing is becoming a strategy for the construction of innovative drug delivery systems (DDSs). Optimization of the complex formulation, including factors such as the printing ink, presence of solvents, and potential low mechanical strength, are challenges during process development. This study presents an application of DIW to fabricate water-soluble, high-dose, and sustained-release DDSs. Utilizing poorly compressible metformin hydrochloride as a model drug, a core-shell delivery system was developed, featuring a core composed of 96 % drug powder and 4 % binder, with a shell structure serving as a drug-release barrier. This design aligns with the sustained-release profile of traditional processes, achieving a 25.8 % reduction in volume and enhanced mechanical strength. The strategy facilitates sustained release of high-dose water-soluble formulations for over 12 h, potentially improving patient compliance by reducing formulation size. Process optimization and multi-batch flexibility were also explored in this study. Our findings provide a valuable reference for the development of innovative DDSs and 3D-printed drugs.

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The necessity for orthopedic prostheses, implants, and membranes to treat diseases, trauma, and other disasters has increased as the risk of survive through various factors has intensified exponentially. Considering exponential growth in demand, it has been observed that the traditional technology of grafts and membranes lags to fulfill the demand and effectiveness simultaneously. These challenges in traditional methodologies prompted a revolutionary shift in the biomedical industry when additive manufacturing (AM) emerged as an alternative fabrication technique for medical equipments such as prostheses, implants, and membranes. However these techniques were fast and precise the major attributes of the biomedical materials were the processability, bactericidal nature, biocompatibility, biodegradability, and nontoxicity together with good mechanical properties. Major challenges faced by researchers in the present-day scenario regarding materials are the lack of bactericidal attributes in tailored material, though having better mechanical as well as biocompatible properties, which, on the other hand, are primary critical factors too, in the healthcare sector. Hence considering the advantages of AM and need for membranes with bacteriacidal attributes this present review will highlight the studies based on the manufacturing of membranes with bacteria-resistant properties majorly using direct ink writing and some AM techniques and the reasoning behind the antibacterial attributes of those composite materials.

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Breast cancer is the most frequently diagnosed cancer in women worldwide, and non-adherence to adjuvant hormonotherapy can negatively impact cancer recurrence and relapse. Non-adherence is associated with side effects of hormonotherapy. Pharmacological strategies to mitigate the side effects include coadministration of antidepressants, however patients remain non-adherent. The aim of this work was to develop medicines containing both hormonotherapy, tamoxifen (20 mg), along with anti-depressants, either venlafaxine (37.5 or 75 mg) or duloxetine (30 or 60 mg), to assess the acceptability and efficacy of this personalised approach for mitigating tamoxifen side effects in a clinical trial. A major criterion for the developed medicines was the production rate, specified at minimum 200 dosage units per hour to produce more than 40,000 units required for the clinical trial. A novel capsule filling approach enabled by the pharmaceutical 3D printer M3DIMAKER 2 was developed for this purpose. Firstly, semi-solid extrusion 3D printing enabled the filling of tamoxifen pharma-ink prepared according to French compounding regulation, followed by filling of commercial venlafaxine or duloxetine pellets enabled by the development of an innovative pellet dispensing printhead. The medicines were successfully developed and produced in the clinical pharmacy department of the cancer hospital Gustave Roussy, located in Paris, France. The developed medicines satisfied quality and production rate requirements and were stable for storage up to one year to cover the duration of the trial. This work demonstrates the feasibility of developing and producing combined tamoxifen medicines in a hospital setting through a pharmaceutical 3D printer to enable a clinical trial with a high medicines production rate requirement.

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Liquid crystal-based actuators are receiving increased attention for their applications in wearables and biomedical or surgical devices, with selective actuation of individual parts/fingers still being in its infancy. This work presents the design and realization of two gripper devices with four individually addressable liquid-crystal network (LCN) actuators thermally driven via printed graphene-based heating elements. The resistive heat causes the all-organic actuator to bend due to anisotropic volume expansions of the splay-aligned sample. A heat transfer model that includes all relevant interfaces is presented and verified via thermal imaging, which provides good estimates of dimensions, power production, and resistance required to reach the desired temperature for actuation while maintaining safe electrical potentials. The LCN films displace up to 11 mm with a bending force of 1.10 mN upon application of 0-15 V potentials. The robustness of the LCN finger is confirmed by repetitive on/off switching for 500 cycles. Actuators are assembled into two prototypes able to grip and lift objects of small weights (70-100 mg) and perform complex actions by individually controlling one of the device's fingers to grip an additional object. Selective actuation of parts in soft robotic devices will enable more complex motions and actions to be performed.

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Solid polymer electrolytes have been considered as promising candidates for solid-state batteries (SSBs), owing to their excellent interfacial compatibility and high mechanical toughness; however, they suffer from intrinsic low ionic conductivity (lower than 10-6 S/cm) and large thickness (usually surpassed over 100 µm or even 500 µm), which has a negative influence on the interface resistance and ionic migration. In this work, ceria quantum dot (CQD)-modified composite polymer electrolyte (CPE) membranes with a thickness of 20 µm were successfully manufactured via 3D printing technology. The CQD fillers can reduce the crystallinity of the polymer, and the oxygen vacancies on CQDs can facilitate the dissociation of ion pairs in the NaTFSI salt to release more free Na+, improving the ionic conductivity. Meanwhile, tailoring the thickness of the CPE-CQDs membrane via 3D printing can further promote the migration and transport of Na+. Furthermore, the printed NNM//CPE-CQDs//Na SSB exhibited outstanding rate capability and cycling stability. The combination of CQD modification and thickness tailoring through 3D printing paves a new avenue for achieving high performance solid electrolyte membranes for practical application in Na SSBs.

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This paper presents a scalable and straightforward technique for the immediate patterning of liquid metal/polymer composites via multiphase 3D printing. Capitalizing on the polymer's capacity to confine liquid metal (LM) into diverse patterns. The interplay between distinctive fluidic properties of liquid metal and its self-passivating oxide layer within an oxidative environment ensures a resilient interface with the polymer matrix. This study introduces an inventive approach for achieving versatile patterns in eutectic gallium indium (EGaIn), a gallium alloy. The efficacy of pattern formation hinges on nozzle's design and internal geometry, which govern multiphase interaction. The interplay between EGaIn and polymer within the nozzle channels, regulated by variables such as traverse speed and material flow pressure, leads to periodic patterns. These patterns, when encapsulated within a dielectric polymer polyvinyl alcohol (PVA), exhibit an augmented inherent capacitance in capacitor assemblies. This discovery not only unveils the potential for cost-effective and highly sensitive capacitive pressure sensors but also underscores prospective applications of these novel patterns in precise motion detection, including heart rate monitoring, and comprehensive analysis of gait profiles. The amalgamation of advanced materials and intricate patterning techniques presents a transformative prospect in the domains of wearable sensing and comprehensive human motion analysis.

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Cellulose nanofibrils (CNFs) are derived from biomass and have significant potential as fossil-based plastic alternatives used in disposable electronics. Controlling the nanostructure of fibrils is the key to obtaining strong mechanical properties and high optical transparency. Vacuum filtration is usually used to prepare the CNFs film in the literature; however, such a process cannot control the structure of the CNFs film, which limits the transparency and mechanical strength of the film. Here, direct ink writing (DIW), a pressure-controlled extrusion process, is proposed to fabricate the CNFs film, which can significantly harness the alignment of fibrils by exerting shear stress force on the filaments. The printed films by DIW have a compact structure, and the degree of fibril alignment quantified by the small angle X-ray diffraction (SAXS) increases by 24 % compared to the vacuum filtration process. Such a process favors the establishment of the chemical bond (or interaction) between molecules, therefore leading to considerably high tensile strength (245 ± 8 MPa), elongation at break (2.2 ± 0.5 %), and good transparency. Thus, proposed DIW provides a new strategy for fabricating aligned CNFs films in a controlled manner with tunable macroscale properties. Moreover, this work provides theoretical guidance for employing CNFs as structural and reinforcing materials to design disposable electronics.

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BACKGROUND: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful tool for microanalysis of solid materials. Nevertheless, one limitation of the method is the lack of well-characterized homogeneous reference materials (RMs), such as BaF2 crystal and BaCO3 ceramics samples, making direct quantification difficult. This work presents a novel Direct Ink Writing (DIW) method to produce RMs for microanalysis. The Mg, Cr, Fe, Co, Ni, Cu, Y, Mo, Pr, Gd, Dy, Ho, Er, Tm, Yb, and Lu solutions were gravimetrically doped into BaCO3 by mixing with the dispersant and then cured with DIW techniques. (94) RESULTS: BaCO3 powder was combined with a dopant analyte to produce a printable slurry, aided by the use of a dispersant and cellulose. The resulting mixture was then printed using DIW equipment. The retention rates of the doped elements were investigated by internal and external standard method, and the results showed that they were completely dispersed in the solid material. After further optimization, it was found that there was no significant heterogeneity among the printed samples. LA-ICP-MS was used to analyze printed samples, to evaluate micro-scale homogeneity. The mass concentration of the doped element was determined by ICP-MS, verify its move closer to nominal value. Compared with the traditional reference materials preparation methods, the DIW technology greatly increased the sample homogeneity and the accuracy of the desired concentration. (132) SIGNIFICANCE: As far as we know, there are few reports on the application of DIW method to prepare calibration standards. In brief, it is proved that the proposed method of preparing calibration standard by DIW technique to quantify analytes is valid and robust. This procedure provides great potential for LA-ICP-MS in-situ analysis in the field of well-prepared products, such as ceramic and crystal samples.(63).

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MXene inks offer a promising avenue for the scalable production and customization of printing electronics. However, simultaneously achieving a low solid content and printability of MXene inks, as well as mechanical flexibility and environmental stability of printed objects, remains a challenge. In this study, we overcame these challenges by employing high-viscosity aramid nanofibers (ANFs) to optimize the rheology of low-concentration MXene inks. The abundant entangled networks and hydrogen bonds formed between MXene and ANF significantly increase the viscosity and yield stress up to 103 Pa·s and 200 Pa, respectively. This optimization allows the use of MXene/ANF (MA) inks at low concentrations in direct ink writing and other high-viscosity processing techniques. The printable MXene/ANF inks with a high conductivity of 883.5 S/cm were used to print shields with customized structures, achieving a tunable electromagnetic interference shielding effectiveness (EMI SE) in the 0.2-48.2 dB range. Furthermore, the MA inks exhibited adjustable infrared (IR) emissivity by changing the ANF ratio combined with printing design, demonstrating the application for infrared anticounterfeiting. Notably, the printed MXene/ANF objects possess outstanding mechanical flexibility and environmental stability, which are attributed to the reinforcement and protection of ANF. Therefore, these findings have significant practical implications as versatile MXene/ANF inks can be used for customizable, scalable, and cost-effective production of flexible printed electronics.

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Advancement in additive manufacturing (AM) allows the production of nanocomposites with complex and custom geometries not typically allowable with conventional manufacturing techniques. The benefits of AM have led to recent interest in producing multifunctional materials capable of being printed with current AM technologies. In this article, piezoresistive composites realized by AM and the matrices and fillers utilized to make such devices are introduced and discussed. Carbon-based nanoparticles (Carbon Nanotubes, Graphene/Graphite, and Carbon Black) are often the filler choice of most researchers and are heavily discussed throughout this review in combination with extrusion AM methods. Piezoresistive applications such as physiological and wearable sensors, structural health monitoring, and soft robotics are presented with an emphasis on material and AM selection to meet the demands of such applications.

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The emergence of additive manufacturing technologies for fiber-reinforced thermoset composites has greatly bolstered their utilization, particularly within the aerospace industry. However, the ability to precisely measure the interface strength between the fiber and thermoset matrix in additively manufactured composites has been constrained by the cumbersome nature of single-fiber pull-out experiments and the need for costly instrumentation. This study aims to introduce a novel methodology for conducting single-fiber pull-out tests aimed at quantifying interface shear strength in additively manufactured thermoset composites. Our findings substantiate the viability of this approach, showcasing successful fiber embedding within composite test specimens and precise characterization of fiber pull-out strength using a conventional mechanical testing system. The test outcome revealed an average interfacial strength value of 2.4 MPa between carbon fiber and the thermoset epoxy matrix, aligning with similar studies in the existing literature. The outcome of this study offers an affordable and versatile test methodology to revolutionize composite material fabrication for superior mechanical performance.

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Inkjet printing is of great interest in the preparation of optoelectronic and microelectronic devices due to its low cost, low process temperature, versatile material compatibility, and ability to precisely manufacture multi-layer devices on demand. However, interlayer solvent erosion is a typical problem that limits the printing of organic semiconductor devices with multi-layer structures. In this study, we proposed a solution to address this erosion problem by designing polystyrene-block-poly(4-vinyl pyridine)-grafted Au nanoparticles (Au@PS-b-P4VP NPs). With a colloidal ink containing the Au@PS-b-P4VP NPs, we obtained a uniform monolayer of Au nano-crystal floating gates (NCFGs) embedded in the PS-b-P4VP tunneling dielectric (TD) layer using direct-ink-writing (DIW). Significantly, PS-b-P4VP has high erosion resistance against the semiconductor ink solvent, which enables multi-layer printing. An active layer of semiconductor crystals with high crystallinity and well-orientation was obtained by DIW. Moreover, we developed a strategy to improve the quality of the TD/semiconductor interface by introducing a polystyrene intermediate layer. We show that the NCFG memory devices exhibit a low threshold voltage (<3 V), large memory window (66 V), stable endurance (>100 cycles), and long-term retention (>10 years). This study provides universal guidance for printing functional coatings and multi-layer devices.

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Soft actuators with stimuli-responsive and reversible deformations have shown great promise in soft robotics. However, some challenges remain in existing actuators, such as the materials involved derived from nonrenewable resources, complex and nonscalable preparation methods, and incapability of complex and programmable deformation. Here, a biobased ink based on cuttlefish ink nanoparticles (CINPs) and cellulose nanofibers (CNFs) was developed, allowing for the preparation of biodegradable patterned actuators by direct ink writing technology. The hybrid CNF/CINP ink displays good rheological properties, allowing it to be accurately printed on a variety of flexible substrates. A bilayer actuator was developed by printing an ink layer on a biodegradable poly(lactic acid) film using extrusion-based 3D printing technology, which exhibits reversible and large bending behavior under the stimuli of humidity and light. Furthermore, programmable and reversible folding and coiling deformations in response to stimuli have been achieved by adjusting the ink patterns. This work offers a fast, scalable, and cost-effective strategy for the development of biodegradable patterned actuators with programmable shape-morphing.