3D Printing Technique Research Articles

Fabrication of Biomedical Electrodes Using Printing Approaches

AbstractIn this review, we focus on the fabrication of electrodes, using printing techniques. Generally speaking, electrodes are comprised of a metal conductor with a metal lead (sometimes the same material) for the conduction of electrical current. Different inorganic and organic materials including metal, polymers, carbon, as well as their composites thereof, have been used for electrodes on different substrates. While material-dependent characteristics, including conductivity, optical transparency, corrosion resistance and biocompatibility, determine the choice of material, printing, as the manufacturing method, offers precise control over the geometry and scale of electrodes for selective and sensitive performance. Both 2D- and 3D-printed electrodes have been widely used as sensors for electrochemical applications as well as quantification of biological compounds, establishing contact with biological surfaces and systems, finding application in medical diagnosis, therapy and treatment of various conditions. Costa et al. (Energy Storage Mater 28:216–234, 2020), Mensing et al. (Sustain Mater Technol 25:e00190, 2020) depict the difference between the 2D and 3D printing techniques which can be used for fabrication of 2D and 3D electrodes. The 3D structure of the electrode provides advantages over the 2d electrodes in terms of its catalytic properties through enhancement in its mass transfer process, adsorption efficiency and active exposure sites (Mensing et al. in Sustain Mater Technol 25:e00190, 2020).

A novel pellet-based 3D printing of high stretchable elastomer

Elastomers, known for their high stretchability and flexibility, are widely used in high-tech applications. However, traditional manufacturing methods for elastomeric part production have limitations. 3D printing, particularly fused deposition modeling (FDM), offers a promising alternative by allowing the fabrication of customized elastomers with desired shapes and properties. Conventional filament-based FDM techniques struggle to print elastomers. This article presents a novel approach for 3D printing polyolefin elastomer (POE) using a direct pellet printing technique. A customized pellet printer with a pneumatic pressure feeding system was used that eliminates filament buckling issues commonly associated with conventional filament-based 3D printing methods. The mechanical properties and microstructure of the printed parts were analyzed to evaluate the suitability of the technique for producing high-quality elastomeric components. SEM images indicated a high-quality and accurate printing method; however, there are micro-holes between the raster due to the high shrinkage rate of POE and increasing the nozzle temperature improves the print quality. The mechanical properties of the printed samples exhibited remarkable formability, with elongation reaching up to 1965%. It is also found that as the nozzle temperature increased, the strength, elongation, and bonding between layers improved significantly. This innovative 3D printing technique has the potential for various applications such as soft robotics and wearable electronics.

Gain and Bandwidth Enhancement of 3D-Printed Short Backfire Antennas Using Rim Flaring and Iris Matching.

In this article, we present new design techniques to improve the gain and impedance bandwidth of short backfire antennas. For the gain enhancement procedure, our approach was to flare the rim of the antenna, which simultaneously led to an increase in the impedance bandwidth of the antenna. Parametric studies were carried out to obtain the optimal flaring angle. The peak realized gain was obtained as 17.2 dBi with an impedance bandwidth of 55% (2.4 dB and 28.6% increase in gain and bandwidth, respectively, compared to the unflared antenna). To further enhance the impedance bandwidth, an inductive iris was added to improve impedance matching at the waveguide aperture. We varied the width of the iris to obtain the optimal width that provided the best gain and impedance bandwidth result of 17.1 dBi and 66% (~40% increase compared to the unflared antenna without iris). To experimentally verify the work, prototypes were fabricated and tested. We found good agreement between simulation and measurement. The results of this study indicate that gain and bandwidth can be enhanced through optimized geometrical modification of the SBF structure. Furthermore, our 3D-printed technique demonstrates a mass reduction compared with conventional metallic structures.

3D Printing of a Porous Zn-1Mg-0.1Sr Alloy Scaffold: A Study on Mechanical Properties, Degradability, and Biosafety.

In recent years, the use of zinc (Zn) alloys as degradable metal materials has attracted considerable attention in the field of biomedical bone implant materials. This study investigates the fabrication of porous scaffolds using a Zn-1Mg-0.1Sr alloy through a three-dimensional (3D) printing technique, selective laser melting (SLM). The results showed that the porous Zn-1Mg-0.1Sr alloy scaffold featured a microporous structure and exhibited a compressive strength (CS) of 33.71 ± 2.51 MPa, a yield strength (YS) of 27.88 ± 1.58 MPa, and an elastic modulus (E) of 2.3 ± 0.8 GPa. During the immersion experiments, the immersion solution showed a concentration of 2.14 ± 0.82 mg/L for Zn2+ and 0.34 ± 0.14 mg/L for Sr2+, with an average pH of 7.61 ± 0.09. The porous Zn-1Mg-0.1Sr alloy demonstrated a weight loss of 12.82 ± 0.55% and a corrosion degradation rate of 0.36 ± 0.01 mm/year in 14 days. The Cell Counting Kit-8 (CCK-8) assay was used to check the viability of the cells. The results showed that the 10% and 20% extracts significantly increased the activity of osteoblast precursor cells (MC3T3-E1), with a cytotoxicity grade of 0, which indicates safety and non-toxicity. In summary, the porous Zn-1Mg-0.1Sr alloy scaffold exhibits outstanding mechanical properties, an appropriate degradation rate, and favorable biosafety, making it an ideal candidate for degradable metal bone implants.

3D-printed bioinspired spicules: Strengthening and toughening via stereolithography

Recently, the replication of biological microstructures has garnered significant attention due to their superior flexural strength and toughness, coupled with lightweight structures. Among the most intriguing biological microstructures renowned for their flexural strength are those found in the Euplectella Aspergillum (EA) marine sponges. The remarkable strength of this sponge is attributed to its complex microstructure, which consists of concentric cylindrical layers known as spicules with organic interlayers. These features effectively impede large crack propagation, imparting extraordinary mechanical properties. However, there have been limited studies aimed at mimicking the spicule microstructure. In this study, structures inspired by spicules were designed and fabricated using the stereolithography (SLA) 3D printing technique. The mechanical properties of concentric cylindrical structures (CCSs) inspired by the spicule microstructure were evaluated, considering factors such as the wall thickness of the cylinders, the number of layers, and core diameter, all of which significantly affect the mechanical response. These results were compared with those obtained from solid rods used as solid samples. The findings indicated that CCSs with five layers or fewer exhibited a flexural strength close to or higher than that of solid rods. Particularly, samples with 4 and 5 cylindrical layers displayed architecture similar to natural spicules. Moreover, in all CCSs, the absorbed energy was at least 3–4 times higher than solid rods. Conversely, CCSs with a cylinder wall thickness of 0.65 mm exhibited a more brittle behavior under the 3-point bending test than those with 0.35 mm and 0.5 mm wall thicknesses. CCSs demonstrated greater resistance to failure, displaying different crack propagation patterns and shear stress distributions under the bending test compared to solid rods. These results underscore that replicating the structure of spicules and producing structures with concentric cylindrical layers can transform a brittle structure into a more flexible one, particularly in load-bearing applications.

3D printing of hybrid solid–liquid structures

Abstract3D printing is a versatile technology for creating objects with custom geometries and compositions and is increasingly employed for fabricating hybrid solid–liquid composites (SLCs). These composites, comprising solid matrices with integrated liquid components, showcase unique properties such as enhanced flexibility and improved thermal and electrical conductivities. This review focuses on methods to fabricate SLCs directly by different 3D printing techniques, e.g. without needing to backfill or impregnate a porous matrix. The techniques of extrusion, vat photopolymerization and material jetting combined with microfluidics, inkjet printing, vacuum filling and ultraviolet light curing to produce SLCs are emphasized. We also discuss the development of feedstocks, focusing on emulsions and polymer capsules as fillers, and analyze current literature to highlight their significance. The review culminates in a perspective on new directions, highlighting the potential of bicontinuous interfacially jammed emulsion gels (bijels) to facilitate the printing of continuous liquid pathways, alongside the importance of understanding ink formulation and stability. Concluding with future perspectives, we underline the transformative impact of 3D‐printed SLCs in diverse applications, signaling a significant advancement in the field. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Coated Microneedle System for Delivery of Clotrimazole in Deep-Skin Mycoses.

Mycoses of the skin are infectious diseases caused by fungal microorganisms that are generally treated with topical agents. However, such therapy is often ineffective and has to be supported by oral use of active substances, which, in turn, can cause many side effects. A good alternative for the treatment of deep-skin mycoses seems to be microneedles (MNs). The aim of this research was to fabricate and evaluate the properties of innovative MNs coated with a hydrogel as potential carriers for clotrimazole (CLO) in the treatment of deep fungal skin infections. A 3D printing technique using a photo-curable resin was employed to produce MNs, which were coated with hydrogels using a dip-coating method. Hydrogels were prepared with carbopol EZ-3 Polymer (Lubrizol) in addition to glycerol and triisopropanolamine. Clotrimazole was introduced into the gel as the solution in ethanol or was suspended. In the first step of the investigation, a texture analysis of hydrogels was prepared with a texture analyzer, and the drug release studies were conducted with the use of automatic Franz diffusion cells. Next, the release profiles of CLO for coated MNs were checked. The last part of the investigation was the evaluation of the antifungal activity of the prepared systems, and the inhibition of the growth of Candida albicans was checked with the diffusion and suspended-plate methods. The texture profile analysis (TPA) for the tested hydrogels showed that the addition of ethanol significantly affects the following studied parameters: hardness, adhesiveness and gumminess, causing a decrease in their values. On the other hand, for the gels with suspended CLO, better spreadability was seen compared to gels with dissolved CLO. The presence of the active substance did not significantly affect the values of the tested parameters. In the dissolution study, the results showed that higher amounts of CLO were released for MNs coated with a hydrogel containing dissolved CLO. Also, microbiological tests proved its efficacy against fungal cultures. Qualitative tests carried out using the diffusion method showed that circular zones of inhibition of fungal growth on the plate were obtained, confirming the hypothesis of effectiveness. The suspension-plate technique confirmed the inhibitory effect of applied CLO on the growth of Candida albicans. From the analysis of the data, the MNs coated with CLO dissolved in hydrogel showed better antifungal activity. All received results seem to be helpful in developing further studies for MNs as carriers of antifungal substances.

Custom orthotic insoles with gradual variable stiffness using 3D printed spacer technique

ABSTRACT 3D-printing enables fabricating insoles with locally variable mechanical properties that can better redistribute plantar pressure by altering the mechanical structure. However, current approaches have limitations in terms of speed, strand thickness, and gradual stiffness transitions. To address this, our research proposes utilising the 3D-printed Spacer technique. Our approach involves 3D-printing the insole on their lateral side, with gradual stiffness transitions achieved by modulating the feed speed and material extrusion, enabling strands thinner than the nozzle diameter, while eliminating travel movements. We present a workflow for customisation and fabrication of insole geometry utilising 3D foot scans and automatic g-code generation directly from our design tool. Additionally, we introduce a novel automated support removal process using a hot-wire cutter mounted on a 6-axis robotic arm. We evaluated the printed structures’ mechanical properties and durability through compression tests and assessed the insoles’ performance using a user wear test that included pressure distribution analysis.

Optimizing polymer composite dielectric properties via digital light processing 3D printing of ordered barium titanate skeleton

Through construction of a three-dimensional continuous ceramic network, the dielectric performance of polymer composites can be enhanced with a reduced amount of ceramic loading. However, the commonly employed methods, such as freeze casting or sacrificial template, fail to precisely control the structure of the ceramic skeleton, leading to significant randomness in content control. In this work, a Digital Light Processing (DLP) 3D printing technique is utilized to precisely fabricate ordered three-dimensional ceramic structures, which are further sintered at high temperatures to obtain a continuous barium titanate (BT) skeleton (BTS). This is then compounded with cyanate ester based polymers (CP) to prepare BTS/CP composites. Results show that when the content of BT is 61.2 vol%, the dielectric constant of the composite is 657 at 100 Hz, which is about 173 times higher than CP, while maintaining a lower dielectric loss of 0.026. Interestingly, the distribution of BTS in the composites has a significant impact on the dielectric performance of the composite. When the BT content is about 50 vol%, the dielectric constant of the “fine and dense” skeleton composite is 2.1 times higher than that of the “coarse and sparse” skeleton composite. This study proposes a novel strategy for building a structurally and compositionally controllable three-dimensional barium titanate (BT) network within polymers, demonstrating the noteworthy influence of macrostructure on the dielectric performance of polymer composites. This offers a fresh approach to the mass application of ordered three-dimensional ceramic skeleton enhanced polymer composites in the fields of electronics and electricity.

Solid Isotropic Material with Penalization-Based Topology Optimization of Three-Dimensional Magnetic Circuits with Mechanical Constraints

Topology optimization is currently enjoying renewed interest thanks to the recent development of 3D printing techniques, which offer the possibility of producing these new complex designs. One of the difficulties encountered in manufacturing topologically optimized magnetostatic structures is that they are not necessarily mechanically stable. In order to take this mechanical constraint into account, we have developed a SIMP-based topology optimization algorithm which relies on numerical simulations of both the mechanical deformation and the magnetostatic behavior of the structure. Two variants are described in this paper, respectively taking into account the compliance or the von Mises constraint. By comparing the designs obtained with those from magnetostatic optimization alone, our approach proves effective in obtaining efficient and robust designs.

The 3D-printed shell complete denture technique: Simplifying prosthodontic diagnosis prior to implant planning.

Traditionally, artificial teeth arrangements or the definitive complete dentures are used to establish important prosthodontic parameters such as the occlusal plane orientation, vertical dimension, and the incisal edge position. The relationship of these elements with the underlying bony structures is commonly evaluated using advanced planning protocols such as the dual scan technique. This technique article presents an uncomplicated alternative approach to establish these parameters intraorally using a 3D-printed shell complete denture generated from a 3D scan of the patient's existing complete denture.

Photo-Curable 3D Printing of Circularly Polarized Afterglow Metal-Organic Framework Monoliths.

Developing coordination complexes (such as metal-organic frameworks, MOFs) with circularly polarized luminescence (CPL) is currently attracting tremendous attention and remains a significant challenge in achieving MOF with circularly polarized afterglow. Herein, MOFs-based circularly polarized afterglow is first reported by combining the chiral induction approach and tuning the afterglow times by using the auxiliary ligands regulation strategy. The obtained chiral R/S-ZnIDC, R/S-ZnIDC(bpy), and R/S-ZnIDC(bpe)(IDC = 1H-Imidazole-4,5-dicarboxylate, bpy = 4,4'-Bipyridine, bpe = trans-1,2-Bis(4-pyridyl) ethylene) containing a similar structure unit display different afterglow times with 3, 1, and <0.1s respectively which attribute to that the longer auxiliary ligand hinders the energy transfer through the hydrogen bonding. The obtained chiral complexes reveal a strong chiral signal, obvious photoluminescence afterglow feature, and strong CPL performance (glum up to 3.7×10-2). Furthermore, the photo-curing 3D printing method is first proposed to prepare various chiral MOFs based monoliths from 2D patterns to 3D scaffolds for anti-counterfeiting and information encryption applications. This work not only develops chiral complexes monoliths by photo-curing 3D printing technique but opens a new strategy to achieve tunable CPL afterglow in optical applications.

Printable Block Molecular Assemblies with Controlled Exciton Dynamics.

Creating hierarchical molecular block heterostructures, with the control over size, shape, optical, and electronic properties of each nanostructured building block can help develop functional applications, such as information storage, nanowire spectrometry, and photonic computing. However, achieving precise control over the position of molecular assemblies, and the dynamics of excitons in each block, remains a challenge. In the present work, the first fabrication of molecular heterostructures with the control of exciton dynamics in each block, is demonstrated. Additionally, these heterostructures are printable and can be precisely positioned using Direct Ink Writing-based (DIW) 3D printing technique, resulting in programable patterns. Singlet excitons with emission lifetimes on nanosecond or microsecond timescales and triplet excitons with emission lifetimes on millisecond timescales appear simultaneously in different building blocks, with an efficient energy transfer process in the heterojunction. These organic materials also exhibit stimuli-responsive emission by changing the power or wavelength of the excitation laser. Potential applications of these organic heterostructures in integrated photonics, where the versatility of fluorescence, phosphorescence, efficient energy transfer, printability, and stimulus sensitivity co-exist in a single nanowire, are foreseen.

Recent advances in 3D printing for in vitro cancer models

3D printing techniques allow for the precise placement of living cells, biological substances, and biochemical components, establishing themselves as a promising approach in bioengineering. Recently, 3D printing has been applied to develop human-relevant in vitro cancer models with highly controlled complexity and as a potential method for drug screening and disease modeling. Compared to 2D culture, 3D-printed in vitro cancer models more closely replicate the in vivo microenvironment. Additionally, they offer a reduction in the complexity and ethical issues associated with using in vivo animal models. This focused review discusses the relevance of 3D printing technologies and the applied cells and materials used in cutting-edge in vitro cancer models and microfluidic device systems. Future prospective solutions were discussed to establish 3D-printed in vitro models as reliable tools for drug screening and understanding cancer disease mechanisms.

3D printed phantom with 12 000 submillimeter lesions to improve efficiency in CT detectability assessment.

The detectability performance of a CT scanner is difficult to precisely quantify when nonlinearities are present in reconstruction. An efficient detectability assessment method that is sensitive to small effects of dose and scanner settings is desirable. We previously proposed a method using a search challenge instrument: a phantom is embedded with hundreds of lesions at random locations, and a model observer is used to detect lesions. Preliminary tests in simulation and a prototype showed promising results. In this work, we fabricated a full-size search challenge phantom with design updates, including changes to lesion size, contrast, and number, and studied our implementation by comparing the lesion detectability from a nonprewhitening (NPW) model observer between different reconstructions at different exposure levels, and by estimating the instrument sensitivity to detect changes in dose. Designed to fit into QRM anthropomorphic phantoms, our search challenge phantom is a cylindrical insert 10cm wide and 4cm thick, embedded with 12 000 lesions (nominal width of 0.6mm, height of 0.8mm, and contrast of -350 HU), and was fabricated using PixelPrint, a 3D printing technique. The insert was scanned alone at a high dose to assess printing accuracy. To evaluate lesion detectability, the insert was placed in a QRM thorax phantom and scanned from 50 to 625 mAs with increments of 25 mAs, once per exposure level, and the average of all exposure levels was used as high-dose reference. Scans were reconstructed with three different settings: filtered-backprojection (FBP) with Br40 and Br59, and Sinogram Affirmed Iterative Reconstruction (SAFIRE) with strength level 5 and Br59 kernel. An NPW model observer was used to search for lesions, and detection performance of different settings were compared using area under the exponential transform of free response ROC curve (AUC). Using propagation of uncertainty, the sensitivity to changes in dose was estimated by the percent change in exposure due to one standard deviation of AUC, measured from 5 repeat scans at 100, 200, 300, and 400 mAs. The printed insert lesions had an average position error of 0.20mm compared to printing reference. As the exposure level increases from 50 mAs to 625 mAs, the lesion detectability AUCs increase from 0.38 to 0.92, 0.42 to 0.98, and 0.41 to 0.97 for FBP Br40, FBP Br59, and SAFIRE Br59, respectively, with a lower rate of increase at higher exposure level. FBP Br59 performed best with AUC 0.01 higher than SAFIRE Br59 on average and 0.07 higher than FBP Br40 (all P<0.001). The standard deviation of AUC was less than 0.006, and the sensitivity to detect changes in mAs was within 2% for FBP Br59. Our 3D-printed search challenge phantom with 12 000 submillimeter lesions, together with an NPW model observer, provide an efficient CT detectability assessment method that is sensitive to subtle effects in reconstruction and is sensitive to small changes in dose.

The Emerging Trends of 3d Printing Techniques in Pharma Sector

Technology involving 3-dimensional printing has begun to revolutionize several fields, including pharmacy. In pharmacy, it offers a reliable avenue for precision medicine, dosage forms and drug delivery systems. The creation of complex drug structures with precise control over composition, shape and release kinetics, catering to individual patient needs has been possible with the intervention of this method. One significant utilization in pharmacy is the customization of dosage forms. Traditional manufacturing methods often struggle to produce tailored medications for patients with unique requirements, such as paediatric or geriatric populations. With 3D printing, pharmacists can create personalized medication with appropriate dosages, structures, and release kinetics, improving patient adherence and beneficial results. Moreover, sophisticated medication delivery systems may be created thanks to 3D printing. For instance, multi- layered tablets can be designed to release multiple drugs at different rates, optimizing treatment regimens for conditions requiring combination therapies. Furthermore, intricate structures like porous scaffolds or micro needle arrays can facilitate targeted drug delivery, enhancing bioavailability and minimizing side effects. Additionally, 3D printing facilitates the rapid prototyping of pharmaceutical formulations, accelerating the drug development process. Researchers can efficiently iterate through various designs, optimizing formulations for efficacy, stability and manufacturability. Despite its promise, challenges remain in integrating 3D printing into mainstream pharmacy practice, including regulatory hurdles, material selection and scalability issues. However, ongoing advancements in technology and collaborations between academia, industry and regulatory agencies are driving progress in overcoming these barriers. In conclusion, 3D printing technology holds immense potential to transform pharmacy by enabling personalized medicine, new dosage formulations and cutting-edge medication delivery technologies. As research and development in this field continue, the prospect of tailored pharmaceuticals tailored to individual patient needs becomes increasingly attainable.

Negative Printing for the Reinforcement of In Situ Tissue-Engineered Cartilage.

In the realm of in situ cartilage engineering, the targeted delivery of both cells and hydrogel materials to the site of a defect serves to directly stimulate chondral repair. Although the in situ application of stem cell-laden soft hydrogels to tissue defects holds great promise for cartilage regeneration, a significant challenge lies in overcoming the inherent limitation of these soft hydrogels, which must attain mechanical properties akin to the native tissue to withstand physiological loading. We therefore developed a system where a gelatin methacryloyl hydrogel laden with human adipose-derived mesenchymal stem cells is combined with a secondary structure to provide bulk mechanical reinforcement. In this study, we used the negative embodied sacrificial template 3D printing technique to generate eight different lattice-based reinforcement structures made of polycaprolactone, which ranged in porosity from 80% to 90% with stiffnesses from 28 ± 5 kPa to 2853 ± 236 kPa. The most promising of these designs, the hex prism edge, was combined with the cellular hydrogel and retained a stable stiffness over 41 days of chondrogenic differentiation. There was no significant difference between the hydrogel-only and hydrogel scaffold group in the sulfated glycosaminoglycan production (340.46 ± 13.32 µg and 338.92 ± 47.33 µg, respectively) or Type II Collagen gene expression. As such, the use of negative printing represents a promising solution for the integration of bulk reinforcement without losing the ability to produce new chondrogenic matrix.

Miniaturized reconfigurable three dimensional printed frequency selective surface based microwave absorbers

ABSTRACT A unique strategy for the design of reconfigurable microwave absorbers based on the frequency selective surface (FSS) concept is presented in this paper. Three different topologies are considered (namely, Structure A, B, and C), and their resonance frequencies are varied by increasing the height and subsequently changing the capacitance value, with the help of a modular interlocking block system. This reconfigurability further reduces the electrical size of the absorber structures, thereby leading to miniaturization. Structure A has an absorption frequency switching from 4.89 GHz to 2.26 GHz (with a 53.7% miniaturization). Similarly, Structure B has a frequency range between 2.98 and 1.89 GHz, leading to a size reduction of 36.5%, whereas the frequency shift is observed in Structure C from 2.25 GHz to 1.79 GHz (with a shift of 20.4%). The absorptivity curves in L, S, and C bands for various structures are unaltered by variation in polarization and incident angle (up to 30 degrees), indicating polarization-insensitive and angularly stable responses. Impedance responses (real and imaginary) are also evaluated to justify the absorption characteristics. The proposed structures are fabricated using the three-dimensional (3D) printing technique, and their test results are consistent with the simulated responses.

A comprehensive review on surface modifications of polymer‐based 3D‐printed structures: Metal coating prospects and challenges

AbstractThe production of complex structures out of a variety of materials has undergone a revolution due to the rapid development of additive manufacturing (AM) technology. Initially confined to applications such as magnetic actuators and two‐dimensional electric or electronic circuits, the convergence of 3D printing and metallization methods has emerged as a revolutionary approach. This synergy facilitates the creation of functional and customizable metal‐polymer hybrid structures characterized by high strength, lightweight properties, intricate geometric designs, and superior surface finish. These structures also exhibit enhanced electrical and thermal conductivity, as well as optical reflectivity. This paper reviews techniques to improve the effectiveness of 3D‐printed polymer antennas and structures by using various techniques of metallization. The metallization processes are examined, and a classification based on the materials employed is presented to facilitate comparisons that highlight the optimal utilization of materials for the fabrication of 3D‐printed polymer structures. The main emphasis here is on the effectiveness of different processes in terms of deposition, bonding strength, electrical conductivity, and various characteristics of metallic coatings developed on polymers. This review contributes an in‐depth analysis of the latest developments in 3D printing and metallization techniques specifically applied to polymer antennas and structures. The exploration extends to potential applications, challenges encountered, and future prospects within this dynamic field. As AM and metallization continue to evolve, this study aims to provide a comprehensive understanding of the state‐of‐the‐art methodologies and their implications for the future of polymer‐based structures and antennas.

3D printing of hydrogels for flexible micro‐supercapacitors

AbstractAdvances in hydrogel technology have paved the way for novel and valuable capabilities that are being applied to a diverse spectrum of energy storage applications. Hydrogels, originally renowned for their biomedical applications, are now finding translation into the energy storage domain. These versatile materials exhibit promising potential for various energy‐related applications, including but not limited to acting as highly flexible electrolytes, facilitating the development of flexible supercapacitors, and contributing to advancements in energy conversion devices. The tunable properties of hydrogels, their high ion accessibility, and desirable mechanical characteristics position them as promising candidates for enhancing the performance and efficiency of energy storage systems. In this review, we emphasize the integration of hydrogels into flexible micro‐supercapacitors through 3D printing technology, unraveling the charge transport mechanisms inherent in hydrogels. We discuss methods for developing hydrogels with enhanced physicochemical properties, such as improved mechanical strength, flexibility, and charge transport, offering new prospects for next‐generation energy storage devices. With a deeper understanding of gelation chemistry, we showcase significant progress in fabricating stimuli‐responsive, self‐healing, and highly stretchable hydrogels. Furthermore, we present compelling examples highlighting the versatility of hydrogels, including tailorable architectures, conductive nanostructures, 3D frameworks, and multifunctionalities. The application of innovative 3D printing techniques in hydrogel design is poised to yield materials with immense potential in the realm of energy storage.