Porous scaffolds play a crucial role in bone regeneration. Their morphology facilitates optimum requirements of bone ingrowth at specified locations. The morphological parameters like pore size and porosity of these scaffolds can be customized based on the location of defective areas. In this study, we explored the design and mechanical properties of a Menger-based porous scaffold, intending to mimic the characteristics of natural bone. To achieve this, Menger scaffolds incorporating square and circular pores were designed using the fractal iteration method in Creo software, to optimize both structural integrity and functional performance. Mechanical properties were assessed by finite element method using Ansys structural analysis in the workbench. Based on the optimum requirements of bone ingrowth, the scaffolds were designed with porosities of 59.35

Dielectric properties determine the electromechanical response of electroactive polymer (EAP) actuators and the conversion efficiency of EAP generators. The dielectric constant is especially critical, since it directly governs how effectively such sensors, actuators, and generators perform. The present work compares how frequency, temperature, and mechanical pre-stretch jointly affect the dielectric constants of two candidate elastomers: acrylic VHB 4910 and natural rubber Oppoband 8001. Measurements spanned 1 Hz to 1 MHz across temperatures from − 80℃ to 60℃, with biaxial pre-stretch states ranging from λ 1 × λ 2 = 1 × 2 to 3 × 4. In both elastomers, the dielectric constant fell as frequency rose and as temperature moved away from the optimum, a consequence of dielectric relaxation, and declined steadily with increasing pre-stretch owing to restricted dipole reorientation. VHB 4910 proved considerably more sensitive, its permittivity dropping by 32.53% at 0℃compared with only 14.23% for Oppoband 8001, a difference traceable to the contrasting polarity of the two polymer backbones. Fitting the measurements to the Debye model and to a combined pre-stretch–temperature expression yielded glass transition temperatures of − 42℃ and − 68℃, respectively. These results define operational temperature limits that can inform material selection, particularly for soft robotic applications.

The ongoing climate crisis requires innovative methods to maximize renewable and sustainable energy resources. There have been advancements in harvesting energy from ambient motions such as wind, ocean waves, and human movements. Dielectric elastomer generators (DEGs) are a promising option for energy harvesting due to their high energy density and compatibility with low-frequency oscillations. This review provides an in-depth overview of DEGs, including electroactive materials, electromechanical characterization, electronics for harvesting, interfacing circuits, prototypes, and challenges. DEGs have the potential to play a significant role in decarbonizing energy for both small- and large-scale applications using ambient energy sources.

This study presents a novel 3D printing process for combining two different phases of material: liquid and solid. A closed-cell lattice structure designed for support-free printing, allowing the entrapment of liquid in its empty spaces, thus forming a liquid-entrapped architected structure. The structures are additively manufactured using a simultaneous printing and filling process without any post-processing operation. This is achieved using a hybrid material extrusion (MEX) setup, which has a modified secondary nozzle that dispenses the liquid on demand after the primary nozzle finishes its layer printing process. This simultaneous printing and filling process requires no post-processing operations and greatly reduces fabrication time. These structures are made using thermoplastic polyurethane (TPU) and subsequently filled partially (60%) and fully (100%) with silicone oil. Experimental and numerical quasi-static compression tests are conducted on partially and fully filled global architected structures, and are compared with unfilled structures. A substantial enhancement in effective stiffness and energy absorption (EA) is observed in the post-transition phase. By varying the quantity of liquid, effective stiffness and EA can be passively controlled with precision, to achieve tunable mechanical properties. The ability to tune the mechanical and functional properties holds great potential for a wide range of energy-absorbing applications.

Selective laser sintering (SLS) is one of the prominent methods of polymer additive manufacturing (AM). A low-power laser source is used to directly melt and sinter polymer material into the desired shape. This study focuses on the utilization of the low-power laser SLS system to successfully manufacture metallic components through the development of a metal–polymer composite material. In this study, 17-4 PH stainless powders are used and mixed with polyoxymethylene (POM) and high-density polyethylene (HDPE) to prepare the composite powder material. The polymeric mixture is removed during the thermal degreasing process and subsequent sintering results in a solid metallic component. Sinterit Lisa with a 5 W, 808 nm laser source is used to fabricate the green part. For the printing parameters of 140 °C, laser power of 35.87 mJ/mm2, and layer thickness of 100 μm, the printed samples achieved a maximum density of 3.61 g/cm3 and a complete shape. After sintering at 1310 °C for 180 min, the tensile strength of the shrunk sample is 605.64 MPa, the hardness is HRC 14.8, the average shrinkage rate is 22%, and the density is 7.57 g/cm3, which can reach 97% of the theoretical density. This process allows the use of a wide range of particle sizes that the usual AM technologies have, making it a low-cost, low-energy-consumption, high-speed AM technology.

The ability of morphing aircraft to adapt their shape in flight hinges on the incredible flexibility of their skins, which have multiple degrees of freedom. This paper presents a compact overview of the latest advancements in polymorphing skins for morphing aircraft, focusing on polymeric skins, electroactive polymers, and shape memory polymers. It examines the critical mechanical properties such as flexibility, durability, and resilience that influence their application in morphing wings. By detailing the synthesis processes, including the use of natural rubber, silicone, acrylic, and fiber-reinforced composites, and exploring various modeling and simulation approaches, the paper highlights the importance of flexible material selection and design principles tailored to morphing aircraft needs. It emphasizes a multidisciplinary strategy integrating polymer material science, mechanical engineering, and aerodynamics to innovate in the morphing aircraft domain. This review aims to serve as an essential resource for researchers and practitioners, paving the way for future developments in aerospace morphing technologies.

This study introduces a new method for fabricating biphasic architectured structures using self-developed hybrid material extrusion (MEX) process. This approach involves filling the voids of closed-cell structures with a powder material in a single process. The architectured structures were 3D printed using thermoplastic polyurethane (TPU) and subsequently filled with polyamide 12 (PA12) powder in two distinct configurations: partially filled (50

Increased usage of selective laser sintering (SLS) for the production of end-use functional components has generated a requirement of developing new materials and process improvements to improve the applicability of this technique. This article discusses a novel process wherein carbon black was applied to the surface of TPU powder to reduce the laser reflectivity during the SLS process. The printing was carried out with a preheating temperature of 75 °C, laser energy density of 0.028 J/mm2, incorporating a 0.4 wt % addition of carbon black to the TPU powder, and controlling the powder layer thickness at 125 μm. The mixed powder, after printing, shows a reflectivity of 13.81%, accompanied by the highest average density of 1.09 g/cm3, hardness of 78 A, tensile strength of 7.9 MPa, and elongation at break was 364.9%. Compared to commercial TPU powder, which lacks the carbon black coating, the reflectance decreased by 1.78%, mechanical properties improved by 33.9%, and there was a notable reduction in the porosity of the sintered product.

The properties of each lattice structure are a function of four basic lattice factors, namely the morphology of the unit cell, its tessellation, relative density, and the material properties. The recent advancements in additive manufacturing (AM) have facilitated the easy manipulation of these factors to obtain desired functionalities. This review attempts to expound on several such strategies to manipulate these lattice factors. Several design-based grading strategies, such as functional grading, with respect to size and density manipulation, multi-morphology, and spatial arrangement strategies, have been discussed and their link to the natural occurrences are highlighted. Furthermore, special emphasis is given to the recently designed tessellation strategies to deliver multi-functional lattice responses. Each tessellation on its own acts as a novel material, thereby tuning the required properties. The subsequent section explores various material processing techniques with respect to multi-material AM to achieve multi-functional properties. The sequential combination of multiple materials generates novel properties that a single material cannot achieve. The last section explores the scope for combining the design and process strategies to obtain unique lattice structures capable of catering to advanced requirements. In addition, the future role of artificial intelligence and machine learning in developing function-specific lattice properties is highlighted.

This work addresses the issues of entrapment of polymer powder and the post-processing powder removal challenges in surface-based lattice structures 3D printed with powder bed-based additive manufacturing (AM) technology. A ventilation design approach has been proposed to enhance the powder removability from the widely researched three-dimensional gyroid and two-dimensional honeycomb lattice structure. The flow characteristics and mechanical behavior of the designed lattices were analyzed using computational fluid dynamics (CFD) and finite element analysis (FEA), respectively, followed by experimental powder flow and compression testing. HP jet fusion 4200® industrial 3D printer was used for printing the lattice structures for experimental validation. The results showed a 65–85

In this work, a novel dual-phase metamaterial, named as "hybrid lattice metamaterial (HLM)," are designed and fabricated by combining reentrant and sea-urchin (SU) based surface-lattice (SL) structure with polyamide12 (PA12) material via material extrusion (MEX) process. Four different designs with varying reentrant truss thicknesses of 0.8 mm (H1), 1.0 mm (H2), 1.2 mm (H3), and 1.5 mm (H4) have been modified to assemble seamlessly with the empty spaces within the SL structure. Quasistatic compression tests were conducted to evaluate the deformation modes and compression characteristics. The findings from quasistatic experiments were subsequently validated using numerical simulations. The H4 metamaterial exhibited superior structural properties, with 42 % increase in stiffness and 35 % enhancement in specific energy absorption compared to only SL structure. Additionally, dynamic sinusoidal compression tests were conducted to evaluate the dynamic elastic ratio (DER), hysteresis work and viscoelastic properties using the tan delta. The H4 metamaterial outperformed the SL in all dynamic properties, with a 50 % increase in elastic modulus and 36 % increase in hysteresis work. This study shows metamaterial properties can be tailored for specific requirements. SL structure facilitate elastic recovery, while H4 metamaterials offer superior energy absorption and stability, making it well-suited for protective equipment and impact-resistant components.

The quest to make additive manufacturing of large-sized products viable will increasingly involve latticing the parts with large mesoscale lattice structures. Latticing with large-scale surface based lattice structures will result in a lightweight, economic component with high mass-specific strength, and faster fabrication, compared to truss lattices. However, due to the large size, and an internal void, the surface lattice structures exhibit instability. To address this issue, along with enhancing their properties, the hybrid lattice structures known as 'nested lattice structures (NLS)' have been designed in this study. The NLS consists of large surface-based sea urchin (SU) unit cells nesting truss lattices within. Three different trusses: BCC (bending-dominated), fluorite (bending-dominated), and octet (stretch-dominated) have been modified to accommodate the void space of the SU lattice structure. The designed NLS have been additively manufactured with the HP - Multi Jet Fusion (MJF) process. The overall properties of the fabricated structures are then evaluated through experimental uniaxial compression and finite element analysis. The obtained properties of the NLS are then compared with an empty SU lattice structure. The results reveal that the SU+ nested octet (N-Octet) delivers the highest load-bearing properties; having elastic modulus and compressive strength increased by 35.5% and 6% respectively, compared to the empty SU lattice structure. On the other hand, SU+ nested BCC (N-BCC) NLS reduces the dropping plateau slope of the empty SU lattice by 92%, thereby imparting a smoother deformation. Moreover, it also improves the crushing force efficiency by 16%. Furthermore, the mutual volumetric composition of NLS that would deliver the best properties is identified to be: 40% SU - 60% BCC (SU+N-BCC), 40-50% SU - 50-60% fluorite (SU+NFluorite), and 50% SU - 50% octet (SU+N-Octet). This study also highlights the improved stability of NLS under different static strain rates. The designed NLS would likely find diverse application in the latticing of large additive manufactured components.

The quest for obtaining lattice structures with mutually exclusive properties through morphological innovations has been rapidly increasing. Nowadays, lattice structures are not only meant for achieving lightweight compo-nents but also to deliver unique hybrid functionalities. In this context, the concept of tessellation is recently developed to obtain specific paths of stimulus (load, heat, fluid, vibration, etc.) transfer based on the required responses. The mechanical and functional properties of the lattice structures can be governed and manipulated by changing the path of stimulus transfer in it. In this study, the uniaxial load is considered as a stimulus to examine the load transfer mechanism and various properties of non-edge-to-edge tessellations. These tessellations were designed based on the principles of metallic crystal stacking systems. The designed tessellations were fabricated using HP multi-jet powder bed fusion technology. The deformation behavior, load transfer via stress contours, and equivalent plastic strain (PEEQ) were investigated using experimental compression and numerical analysis. The study reveals unique mechanical properties with changes in structural behavior upon changing the load transfer mechanism (i.e. tessellations). The study reveals radial, zig-zag, and S-shaped patterns of load transfers in BCC, FCC, and HCP tessellated lattice structures. As a result, both the BCC and FCC tessellated lattice structures are known for their load-bearing properties. FCC tessellation demonstrates the highest strength and specific energy absorption capacity. The PEEQ analysis shows extreme plastic deformation in many regions which is cross-validated by cracks in the experimental samples. Contrary to that, HCP is the only structure that shows a constant positive plateau slope until densification. The quasi-static crash force efficiency of the HCP structure outperforms its other counterparts. Moreover, the HCP lattice structure also shows very few locations of plastic deformation with a PEEQ value not exceeding 25%. These properties make HCP a suitable choice for generating cushioning effect. The real-time applications of these structures are presented in protective helmets which need high-strength strength outer covering and high cushioning inner liner. Similarly, the advantageous properties can also be exploited in customized athletic shoes.

The electromechanical performance of a dielectric elastomer (DE) is greatly influenced by the dielectric strength of the elastomeric materials. The dielectric strength of an elastomer profoundly depends on the state of mechanical stretch. In this work, the stretch-dependent dielectric strength for DE is measured for all possible modes of stretches using compliant electrodes. Dielectric breakdown measurement using compliant electrodes considers voltage-induced deformation, which reflects the actual working condition energy transduction. Hence, the measured strength is for a meaningful value of a working DE. Capacitive extensometry and optical method are the two leading methods for the same. We compare the extensometry and optical methods in estimating the true value of dielectric breakdown strength of DEs at high prestretches. Furthermore, we propose a modified thickness stretch-based power law for the dielectric breakdown strength. Using the capacitive extensometry method, we verify the model on comprehensive experimental data on three types of elastomers, i.e., acrylic, silicone, and natural rubber. This work proposes a general framework for estimating the meaningful stretch-dependent dielectric strength of DEs.

Fused filament fabrication (FFF), commercially known as fused deposition modelling (FDM), is a widespread 3D printing process that builds up components by depositing a continuous filament of material, typically a thermoplastic, along a determined path. The mechanical performance of such parts is promising, even if strongly influenced by the deposition process. In this work, the mechanical behaviour of a specific lattice structure printed in acrylonitrile butadiene styrene (ABS) is studied and a model of lattice behaviour up to the damage regime is developed, with emphasis on the resulting anisotropy. The investigation starts with the analysis of the anisotropy of simple prismatic samples printed with various filament orientations. Deformation and damage of the lattice structure under compressive loading is observed at the meso- and micro-scales. An anisotropic model is then developed within the ABAQUS© environment to reproduce the elasto-plastic behaviour, incorporating onset and evolution of inter- and intra-layer damage. Good agreement is observed between the modelled and experimental response.

Additive manufacturing (AM) entails manufacturing complex lightweight structures based on the principle of layer-wise material deposition. However, this principle also results in high mechanical anisotropy in all directions. The process of material extrusion (MEX) is severely affected by mechanical properties owing to its processing conditions. Mechanical anisotropy can result in sudden failures when loaded multidirectionally; its effect is more predominant in lattice structures. This study was conducted to reduce mechanical anisotropy in MEX-fabricated lattice structures by mimicking the internal architecture of the human tooth. The human tooth is prone to mechanical anisotropy because the hard enamel, meant to withstand extreme mechanical forces, consists of microscopic enamel prisms (perpendicular rods). Soft dentin imbues the enamel with the necessary toughness when loaded multidirectionally. This natural design principle was bio-mimicked in this study to reduce the mechanical anisotropy in additively manufactured lattice structures. The lattice structure was printed using an elastic-plastic material (hard) that was similar to the enamel via a MEX process and toughened by an underlying soft polyurethane foam, similar to the dentin in the human tooth. Global close-sea urchin lattice structures were used to entrap the soft materials within the lattice structure. This bioinspired architecture was named the architectured lattice structure. It was 3D printed through a hybrid MEX process. The reduction of mechanical anisotropy in the printed parts was evaluated using the 3D printing of the architectured lattice structure in 0°, 45°, and 90° orientations to the loading direction. Crash force analysis reveals that the architectured lattice structures outperformed their counterpart in terms of energy absorption and crash force efficiency. The scanned electron microscope analysis of both designs revealed that interlayer delamination was the primary failure mechanism. Mechanical anisotropy was almost eliminated owing to the print direction and the load versus deformation curve exhibited similar mechanical behavior for all print directions. Finally, the effect of the underlying foam inside the lattice structure, which exhibited near-isotropic behavior, was evaluated via numerical analysis. The proposed bioinspired architectured lattice structures can be utilized for lightweight additively manufactured structures with high strength, toughness, and uniform mechanical properties in all directions.

This study introduces a novel design and additive manufacturing of technical textiles to achieve tunable mechanical properties through the tessellations of a singular material. The design of these chainmail fabrics was inspired by overlapping tessellation strategies found in biological structures. Two types of chainmail fabrics —BCC and FCC were designed to exhibit high flexibility and stretchability with two-dimensional degrees of freedom. The fabrics were designed to bend along two orthogonal axes and drape around curved surfaces. Furthermore, the relative placement of the unit cells was adjusted to selectively arrest the degrees of freedom, resulting in chainmail fabrics with tunable flexibilities and mechanical properties. Four fabrics for each design Fabric-A, Fabric-B, Fabric-C, and Fabric-D were developed with varying degrees of freedom. All the designed chainmail fabrics were additively manufactured using HP-MJF powder bed fusion technology with a polyamide-12 material. The mechanical properties of the fabricated samples were evaluated through experimental tension tests and numerical simulations. The fabricated BCC and FCC chainmail fabrics exhibited a stress-free zone, followed by an elastoplastic zone, with different mechanical properties observed at different orientations. The FCC fabrics outperformed the BCC fabrics with 45° orientation, exhibiting excellent load-bearing properties, and the 0° orientation showed superior energy absorption capacity. The numerical simulations accurately predicted the mechanical properties and failure locations. Fabric-A was highly flexible but had compromised load-bearing and energy-absorption abilities, whereas Fabric-D acted as a rigid lattice structure with exceptional load-bearing and energy-absorbing properties. FCC fabrics are easier to manufacture using various polymer additive processes owing to their supportless nature. Tunable technical fabrics such as these have potential applications in lightweight and adaptive spinal posture-correcting braces as well as in protective equipment.

Additive manufacturing of metamaterial composites allows for lightweight structures with tunable mechanical and functional properties. This study achieves this using a Hybrid fused filament fabrication process where PU foam is injected inside the supportless closed cell lattice structure made of thermoplastic polyurethane (TPU). The process is based on the direct digital manufacturing concept, eliminating the need for post-processing. The resulting structures exhibited improved mechanical properties, including stiffness, energy dissipation, and damping capacity. Functionally grading the lattice structures further enhanced their properties, making them highly customizable for energy-absorbing and damping products such as protective and sporting goods.

The laborious work of post-processing powder removal from lattice structures made by polymer powder-based additive manufacturing (AM) process is still a major challenge and requires in-depth study. Here, a novel 3D honeycomb shaped lattice structure with ventilated holes bio-inspired from polyhedral plant cells has been designed to eliminate powder entrapment in constricted inter-cellular regions of surface-based lattice structure. The ventilation enables cross flow of powder within the lattice structure, resulting in easy and complete removal of entrapped powder. The computational fluid dynamics (CFD) method was used to understand the flow paths in various surface based lattice structures. An experimental setup was also designed to calculate the powder flowability from these lattices. The Finite Element Analysis (FEA) method and compression tests of various lattice structures were done to benchmark the strength of newly designed lattice structure. This innovative lattice structure can be used in biomedical, heat-exchanger, food and drug delivery systems and light-weighting applications.

Natural structures use many different two-dimensional or three-dimensional architectures in their designs, which can be extremely optimized, light-weight, and adaptable to their surrounding conditions. Taking inspiration from nature and applying their design principles would make optimized engineering solutions in a future sustainable world. In this study, the potential of edge-to-edge tessellation based materials is examined for their ability to deliver multi-functional properties through a single bulk material. The characteristics of nature and natural phenomena are closely examined and mimicked while designing these materials. The tessellation-backed, bio-mimicked materials are named ' Advanced Functional Architectured Materials (AFAMs)'. In this study, the structural and functional properties of each AFAM were evaluated under experimental and numerical analysis. Moreover, the properties of the AFAMs were benchmarked against existing designs of truss-based and surface-based materials. The study reveals that each AFAM behaves uniquely, almost as different material, in terms of its load-bearing and cushioning abilities. All the AFAMs are designed in such a way that they can be interlocked with minimum interfacial dissimilarities to deliver multi-material properties. The interfacial strength was evaluated to examine the possibility of delamination. The study reveals that the interfacial strengths of interlocked AFAMs are similar to individual AFAM.