Piezoelectric ceramic-epoxy lattice structures: a hybrid manufacturing approach for enhanced electro-mechanical performance

Study on isotropic design of triply periodic minimal surface structures under an elastic modulus compensation mechanism

Continuous fiber has been widely used in Additive Manufacturing (AM) to reinforce polymers. However, it has been challenging to 3D print fully dense composites with arbitrary fiber placement. Filling the gaps between fibers is difficult for extrusion‐based processes like fused filament fabrication and Direct Ink Writing (DIW). This study explores the integration of Digital Light Processing (DLP) and Direct Ink Writing technologies to enhance the fabrication of continuous fiber‐reinforced photopolymer (CFRP) composites. The unique combination of these AM techniques aims to improve the mechanical properties of composites by eliminating the gaps between fibers and increasing the interfacial bonding strength. A custom‐built hybrid manufacturing system was employed, allowing for precise control over both DLP and DIW processes. The material composition and curing strategy were explored to improve the printing quality of continuous fibers in photopolymer. Experiments were conducted to assess the mechanical performance of CFRP composites. Results indicate that the integration of DIW and DLP generally improves Young's modulus and flexural modulus of fiber‐reinforced resin, with some cases closely matching theoretical predictions, though certain results show a lower modulus than expected. The fracture surfaces were also investigated. It was found that broken fibers are not uniform, which suggests that the resin infiltration into the fiber bundle can be improved.Highlights Hybrid DLP and DIW system for continuous fiber‐reinforced photopolymer composites. Improved mechanical properties by reducing fiber gaps, stronger interfacial bonding. Higher stiffness and strength achieved, addressing fiber crowding and resin infiltration. Material properties enhanced using nanopowder additives for superior performance. Adaptive UV curing ensures efficient and uniform omnidirectional polymerization.

The challenges of replicating the complex mechanical and structural diversity of natural tissues in vitro by leveraging multi‐material digital light processing (DLP) bioprinting are addressed. This technique utilizes PEGDA‐AAm bio‐ink to develop multi‐component, cell‐laden hydrogel constructs with varying moduli. These constructs not only possess heterogeneous mechanical properties but also feature complex architectures and precisely engineered surface microstructures. The hydrogel microfluidic chips are successfully fabricated with perfusable microchannels, embedding various cell types within the matrix. This approach enables the bioprinting of intricate cell‐laden structures with unique surface topologies, such as spiral grooves and triply periodic minimal surfaces (TPMS), which effectively influence cell alignment, spreading, and migration. By integrating various cell‐laden PA hydrogels, the diverse mechanical moduli of biological tissues, including bone, liver lobules, and vascular networks are replicated. This technique ensures high‐fidelity differentiation between cell types and regions. These findings provide valuable insights into the impact of substrate modulus and structure on cell behavior, underscoring the potential of multi‐component, multi‐modulus hydrogel constructs in creating sophisticated structures with custom‐tailored mechanical properties. This study significantly advances the field by demonstrating the feasibility and effectiveness of multi‐material DLP bioprinting in developing complex, functionally relevant tissue models for tissue engineering and regenerative medicine.

Mechanical and degradation properties of triply periodic minimal surface (TPMS) hydroxyapatite & akermanite scaffolds with functional gradient structure

Recently, triply periodic minimal surface (TPMS) is emerging as an ideal tool to generate porous structures. Yet, most of the current work only focuses on controlling the elastic modulus by the relative density. For special engineering applications, such as porous bone implants or energy absorbers, the generated porous TPMS may still be broken due to anisotropy. In this work, two strategies are proposed to design isotropic TPMS structures. The numerical homogenization theory and finite element analysis methods are utilized to study the relationship between TPMS parameters and the elastic modulus or anisotropy properties. Based on that, a Curvature-Wall thickness (CW) adjustment method is proposed for sheet TPMS structures whose performances are close to isotropy properties. In virtue of the constructed design map, both elastic modulus and anisotropy properties can be controlled. For sheet TPMS structures whose performances are far from the isotropy properties, the TPMS units can be combined to generate composite TPMS, which can be further designed by the proposed Curvature-Wall thickness adjustment method. Experimental results verify the effectiveness and accuracy of the proposed approaches. Appropriate elastic modulus and ideal isotropy properties can be acquired at the same time.

Mechanical-electromagnetic integration design of Al[formula omitted]/SiO[formula omitted] ceramic cellular materials fabricated by digital light processing

Biomimetic porous silicon oxycarbide ceramics with improved specific strength and efficient thermal insulation

In injection molding, cooling channels are usually manufactured with a straight shape, and thus have low cooling efficiency for a curved mold. Recently, additive manufacturing (AM) was used to fabricate conformal cooling channels that could maintain a consistent distance from the curved surface of the mold. Because this conformal cooling channel was designed to obtain a uniform temperature on the mold surface, it could not efficiently cool locally heated regions (hot spots). This study developed an adaptive conformal cooling method that supports localized-yet-uniform cooling for the heated region by employing micro-cellular cooling structures instead of the typical cooling channels. An injection molding simulation was conducted to predict the locally heated region, and a mold core was designed to include a triply periodic minimal surface (TPMS) structure near the heated region. Two biomimetic TPMS structures, Schwarz-diamond and gyroid structures, were designed and fabricated using a digital light processing (DLP)-type polymer AM process. Various design parameters of the TPMS structures, the TPMS shapes and base coordinates, were investigated in terms of the conformal cooling performance. The mold core with the best TPMS design was fabricated using a powder-bed fusion (PBF)-type metal AM process, and injection molding experiments were conducted using the additively manufactured mold core. The developed mold with TPMS cooling achieved a 15 s cooling time to satisfy the dimensional tolerance, which corresponds to a 40% reduction in comparison with that of the conventional cooling (25 s).

The overarching goal of this research work is to fabricate mechanically robust, dimensionally accurate, and porous dental structures, potentially used for the treatment of dental fractures, anomalies, as well as structural deformities with a focus on oral and maxillofacial surgery applications. In pursuit of this goal, the objective of the work is to investigate the mechanical properties of dental constructs, composed of medical-grade photopolymer resins and fabricated using digital light processing (DLP) process. The fabricated dental constructs not only are porous, but also have complex microstructures imparted by triply periodic minimal surface (TPMS) designs. This study tests the following central hypothesis: the mechanical properties of DLP-fabricated dental structures are significantly affected by photopolymer resin composition. In addition, the following research question is answered in this study: which of the chosen medical-grade photopolymer resins has the most significant impact on the mechanical properties of fabricated dental structures. DLP is a vat-photopolymerization additive manufacturing process, which has emerged as a high-resolution, robust method for the fabrication of a broad range of biological tissues and constructs for oral and dental tissue engineering applications. In the DLP process, the printing process takes place on the basis of radiation-curable resins or liquid photopolymers. Upon exposure to UV light, the resin materials become a solid (via chemical transformation) through a process known as photopolymerization. The DLP process consists of several parameters (such as layer thickness, cure depth, and UV lamp intensity) that significantly influence the functional properties of fabricated dental structures. In spite of the advantages and engendered applications, DLP is inherently complex; the complexity of the DLP process, to a great extent, stems from complex physio-chemical phenomena (such as UV light photopolymerization) in addition to resin (photopolymer)-process interactions, which may adversely affect not only the surface morphology, but also the mechanical properties and ultimately the functional characteristics of the fabricated dental scaffolds. As a result, integrated physics-guided process and material characterization would be required for optimal fabrication of porous and complex dental structures. Particularly in this study, the influence of three medical-grade photopolymer resins on the compression properties as well as the dimensional accuracy of TPMS dental constructs is systematically investigated. The compression properties of the DLP-fabricated dental constructs are measured using a compression testing machine. Furthermore, the dimensional accuracy of the dental constructs is measured via physical measurements and with the aid of a laser scanner. Besides, analysis of variance (ANOVA) is utilized to identify statistically significant photopolymer resin(s). The outcomes of this study pave the way for high-resolution fabrication of complex and porous dental structures with tunable medical and functional properties.

3D printed 0–3 type piezoelectric composites with high voltage sensitivity

Triply Periodic Minimal Surface (TPMS)-based aluminium–alumina Interpenetrating Phase Composites (IPCs) manufactured through the combination of Additive Manufacturing (AM) and investment casting are explored in this study. Multiple alumina TPMS structures (Gyroid, Diamond, and Primitive) with different geometries and volume fractions were designed and fabricated using Digital Light Processing (DLP) AM technology. Afterwards, these ceramic structures were filled with an aluminium alloy via investment casting, uncovering an aluminium–alumina IPCs. A global characterization was performed, including ceramics shrinkage and mass loss; specimens’ morphology; chemical and crystalline characterization; density analysis and mechanical testing. Overall, DLP technology was found effective for producing these highly complex ceramic structures, with high surface quality. The sintered alumina structures presented a relative density of ca. 76.3% and a pseudo-ductile layer-by-layer failure behaviour, with Diamond-based TPMS exhibiting the highest compressive strength. Regarding the IPCs, the addition of aluminium significantly changed the compressive behaviour of the samples, presenting an energy absorption behaviour. The integration of the alumina phase into the aluminium alloy led to an improvement on the compressive offset stress of approximately 6% when compared to the aluminium alloy used. Diamond and Gyroid IPCs demonstrated similar mechanical behaviour and the highest mechanical performance.Graphical

Natural bone is a naturally mineralized material with a non-homogeneous porous structure, which is difficult to construct using conventional manufacturing methods. Triply periodic minimal surfaces (TPMS) have emerged as an excellent solution in recent years for constructing porous artificial bone structures, characterized by smooth surfaces, highly interconnected porous structures, and mathematically controllable geometries. In this work, digital light processing (DLP) printing technology was used to construct a non-homogeneous TPMS structure with strontium-doping 13-93 bioactive glass (Sr@BG) prepared by fusion method. The heterogeneous scaffolds were obtained by integrating high-strength I-wrapped package (I) and high-permeability Gyroid (G) units behaving a sufficient compressive strength of 5.8±0.6 MPa, a porosity of ∼63% and a permeability of 0.97 × 10−8 m2, which matched the microstructural parameters of cancellous bone. Meanwhile, the biomimetic structure and Sr doping could cooperatively promote the adhesion, proliferation and differentiation of bone mesenchymal stem cells (BMSCs). In addition, the osteogenic ability of IG scaffolds was verified in rabbit’s femoral condylar defect. In general, heterogeneous IG scaffolds possess desirable bioactivity and mechanical property which meet the functional and structural requirements of bone regeneration

Next-generation finely controlled graded porous antibacterial bioceramics for high-efficiency vascularization in orbital reconstruction

Shape-memory polymer metamaterials based on triply periodic minimal surfaces

Bone scaffolds require both good bioactivity and mechanical properties to keep shape and promote bone repair. In this work, T-ZnOw enhanced biphasic calcium phosphate (BCP) scaffolds with triply periodic minimal surface (TPMS)-based double-layer porous structure were fabricated by digital light processing (DLP) with high precision. Property of suspension was first discussed to obtain better printing quality. After sintering, T-ZnOw reacts with β-tricalcium phosphate (β-TCP) to form Ca19Zn2(PO4)14, and inhibits the phase transition to α-TCP. With the content of T-ZnOw increasing from 0 to 2 wt%, the flexural strength increases from 40.9 to 68.5 MPa because the four-needle whiskers can disperse stress, and have the effect of pulling out as well as fracture toughening. However, excessive whiskers will reduce the cure depth, and cause more printing defects, thus reducing the mechanical strength. Besides, T-ZnOw accelerates the deposition of apatite, and the sample with 2 wt% T-ZnOw shows the fastest mineralization rate. The good biocompatibility has been proved by cell proliferation test. Results confirmed that doping T-ZnOw can improve the mechanical strength of BCP scaffolds, and keep good biological property, which provides a new strategy for better bone repair.