Triply Periodic Minimal Surface Structures Research Articles

Compressive behavior and property prediction of gradient cellular structures fabricated by selective laser melting

Triply periodic minimal surface (TPMS) structures are ideal for applications such as lightweight and bone implantation. Compared with uniform structures, functionally graded cellular materials (FGCMs) are more attractive due to their diverse performance and excellent adaptability to actual requirements. A series of uniform cellular structures including Primitive and Gyroid type are designed and manufactured by selective laser melting (SLM) to understand the morphology, geometry characteristics as well as mechanical properties. Then, the transversely and longitudinally graded cellular structures are proposed to understand its relation to uniform cellular structures. The results show that the actual porosity of cellular structures is slightly lower than the designed, with a small deviation of 2.2%− 3.7%. The elastic modulus and yield strength of uniform cellular structures decrease gradually with increase of porosity. The mechanical properties of uniform cellular structures relative to solid counterparts can be predicted from Gibson-Ashby equations. The porosity gradient TPMS structures are found the mechanical accumulation of uniform cellular substructures. The mechanical properties of gradient TPMS structures can be modelled by composite theories.

TPMS metamaterial structures based on shape memory polymers: Mechanical, thermal and thermomechanical assessment

Triply periodic minimal surfaces (TPMS) are a type of metamaterial that get their unusual properties from the topology of microstructure elements, but they provide non-controllable properties. Utilizing shape memory polymer as a base material, it is possible to control the properties of these structures and create significant and reversible changes in the stiffness, geometry, and performance of metamaterials which could be applicable in many application fields. In this work, the thermal, mechanical, and shape memory behavior of 8 SMP-based TPMS structures has been studied in a wide range of the solid phase volume fractions (i.e., 35–65%). In the thermomechanical analysis, we consider the shape recovery%, the force recovery%, and the shape fixity% as the shape memory properties. For this purpose, the structures were simulated using thermo-visco-hyperelastic constitutive equations. Also, the temperature rate and elastic modulus are considered as the representative thermal and mechanical properties, respectively. Results of this study indicate that the best shape memory and mechanical behaviors belong to the Primitive structure at all different Volume fractions. And the best overall performance for different 8 TPMS structures including the best thermal, mechanical, and thermomechanical behavior accrues at VF = 40% and is sorted as FKS > FRD > Diamond > Diamond-type 2 > Gyroid > IWP > Primitive > Neovious.

Design and mechanical evaluation of additively-manufactured graded TPMS lattices with biodegradable polymer composites

Triply periodic minimal surfaces (TPMS) structures have been extensively promoted for mimicking the tissue scaffolds with interconnected pores and robust mechanical properties. To further optimize the mechanical performance, two kinds of TPMS structures including Schwarz P (P) and Gyroid (G) with uniform and different graded-thickness were designed and proposed in the current work. Biodegradable polymer composites based on poly (butyleneadipate-co-terephthalate) (PBAT) and poly (lactic acid) (PLA) were developed into fused filament fabrication (FFF) filaments. Results showed that PBAT/PLA filaments exhibited good flexibility, thermal and rheological properties and high printability. As for compressive properties, the load-bearing capacity and energy absorption (EA) of TPMS-G were superior to TPMS-P uniform structures. TPMS-G graded samples exhibited better EA capacity, whereas those of graded TPMS-P were inferior to uniform counterparts. The deformation behavior of the internal structure in graded TPMS-G and TPMS-P were examined by computed tomography (CT) scanning and reconstruction. Furthermore, tensile properties of graded and non-graded TPMS were also compared. Under tension load, results demonstrated that non-graded structure of TPMS were both stronger than the graded ones. The proposed biodegradable PBAT/PLA composite and structure design could be applied as biomedical soft scaffolds, wearable devices and resilient absorbing buffers.

3D‐printed and foamed triply periodic minimal surface lattice structures for energy absorption applications

AbstractStructures currently used for energy absorption include foams, composites, and honeycombs. Recent studies have indicated the potential of triply periodic minimal surfaces (TPMS) for energy absorption applications as well as weight reduction. This study presents three TPMS lattice structures, namely the Gyroid, Fischer‐Koch S, and PMY, which are fabricated in uniform and graded densities. These structures, created in the MSLattice software are 3D printed using polylactic acid. Subsequently, the 3D‐printed structures undergo a gas foaming process to investigate benefits of higher porosity on energy absorption. The structures are then characterized for porosity, compressive properties, energy absorption, and thermal properties. The results show that the uniform and graded density structures have similar energy absorption values as long as the structures have a similar average density with the PMY structure exhibiting the highest energy absorption value, both in unfoamed and foamed conditions, respectively. The foaming process increased the porosity by 50% but did not improve the energy absorption characteristics of any of the structures with the foamed PMY structures exhibiting the least deviation compared to the unfoamed samples. These foamed TPMS structures are suitable for applications in the automotive and aerospace industry that demand lightweight structures for energy absorption.

Numerical analysis of the influence of triply periodic minimal surface structures morphometry on the mechanical response

Background and Objective: Design of bone scaffolds requires a combination of material and geometry to fulfil requirements of mechanical properties, porosity and pore size. Triply Periodic Minimal Surface (TPMS) structures have gained attention due to their similarities to cancellous bone. In this work, we aim at exploring relationships between morphometry and mechanical properties for TPMS configurations.Methods: Eight TPMS structures are defined considering six porosity levels and their morphometry is characterized. The stiffness matrix of each structure is assessed and related to morphometry through a statistical analysis.Results: An orthotropic mechanical behavior has been derived from the numerical homogenization. Properties decay exponentially for decreasing volume fraction. Through volume fraction variation, TPMS mechanical properties can be selected to match bone properties in a range of 0.2% to 70% of the bulk material properties.Conclusions: The comparison between cancellous bone and TPMS morphometry, considering a unit cell size of 1.5 mm, reveals that the configurations analyzed in this work match the requirements of volume fraction, mean thickness and pore size. However, the TPMS studied in this work differ from cancellous bone anisotropy. The results in this paper provide a framework to select the proper TPMS configuration and its geometry for patient-specific applications.

Utilization of triply periodic minimal surfaces for performance enhancement of adsorption cooling systems: Computational fluid dynamics analysis

In this study, triply periodic minimal surface (TPMS) structures have been implemented in adsorber/desorber to improve the performance of adsorption cooling systems (ACSs). The use of metal TPMS-based structures considerably increased the effective thermal conductivity of the porous media/metal composite due to its large surface area to porous media volume. A fully-three-dimensional CFD model was constructed using Ansys Fluent and validated based on relevant previous studies. Five distinct TPMS-based structures, including Gyroid, Diamond, I-graph-wrapped package, Primitive, and Lidinoid were investigated and compared with conventional Fins-based structures under different porosities, constant adsorption times, and optimal adsorption times. The specific surface area and geometric tortuosity of the adopted structures were evaluated using GeoDict software. The results demonstrated that Lidinoid attained the cyclic specific cooling power (SCP) enhancement of 12.4 % compared to Fins-based structures under the constant adsorption time of 500 s and the consistent porosity of 0.5. Meanwhile, when operated at the optimal adsorption time for each structure, Lidinoid improved the cyclic SCP by 17.5 %, while Primitive showed 6.9 % decrease in cyclic SCP compared to Fins-based structure. The cyclic SCP of TPMS structures was better than that of Fins-based structure at medium and higher porosities of 0.5 and 0.8, respectively. However, at lower porosity of 0.2, Fins-based structures outperformed TPMS structures in cyclic SCP. In terms of daily performance, Gyroid, Diamond, and Primitive structures showed faster kinetics and more potential for ACSs applications. The results indicated that Primitive structure achieved 51.6 % increase in cooling capacity per day compared to conventional Fins-based structure. In conclusion, this study has well demonstrated that the exploitation of TPMS opens new avenues for next-generation adsorption cooling applications with superior performance.

Architected lattices embedded with phase change materials for thermal management of high-power electronics: A numerical study

• TPMS-PCM based heat sinks under high heat flux were numerically investigated. • The effect of TPMS structure type, PCM type, Applied Heat Flux and Heat Sink Material were studied. • For gallium-TPMS heat sinks, the effect of TPMS structure was not pronounced. For docosane-TPMS heat sinks, the effect of TPMS was considerably significant. • Docosane-TPMS heat sink severely underperformed than gallium-TPMS heat sink in controlling the heat sink base temperature. • An increase in applied heat flux caused faster PCM melting time and higher maximum heat sink temperatures. • Copper based TPMS heat sinks outperformed AlSi10Mg based heat sink owing to superior thermo-physical properties of copper. The boom of additive manufacturing has opened the doors to manufacture complex architectures with ease. The ever-increasing demands of high computational power has garnered a lot of research interest in more advanced and efficient cooling systems. Recently, additively manufactured and mathematically modeled Triply Periodic Minimal Surface (TPMS) based lattices have found widespread attention as thermal conductivity enhancers for phase change materials (PCMs). In this numerical study, architected lattices based on TPMS structures and impregnated with PCM have been studied as heat sinks for potential application in high power electronics cooling application. To authors’ best knowledge, heat sinks based on TPMS structures impregnated with PCM have never been studied for high heat flux/electronics cooling applications. Two TPMS structures i.e., IWP and Primitive have been selected as candidates based on reported work on TPMS-PCM composites performance in thermal energy storage applications. Two materials for architected lattices were considered i.e., Aluminum powder (AlSi10Mg) and Copper. Furthermore, two PCMs are taken into account, one an organic PCM (Docosane) and the other being a metallic PCM (Gallium metal). Besides, three values of applied heat flux replicating to-be-cooled electronic chips were considered i.e., 50 kW/m 2 , 100 kW/m 2 and 150 kW/m 2 . The results indicated that TPMS structures can help in temperature mitigation under high heat flux conditions. In the case of metallic PCM, the performance of both Primitive and IWP structure came out to be nearly identical. Hence, there was no architecture effect noticed in heat transfer performance of the lattices at all the three heat flux values. However, in the case of paraffinic PCM, Primitive structure showed better performance than IWP due to superior natural convection of liquid PCM in Primitive structure. However, paraffinic PCM could not aid in temperature mitigation to a realistic value despite being embedded inside metallic TPMS lattice owing to its inferior thermo-physical characteristics even at the smallest value of the heat flux. Gallium based heat sink outperformed paraffinic PCM as expected for both IWP and Primitive cases. Moreover, Copper based TPMS structures outperformed their AlSi10Mg based counterparts in mitigating the heat sink temperature owing to its superior thermo-physical properties. Therefore, this study offers a perspective of possible utilization and advancement of heat sinks for electronics cooling application.

Dynamic crushing characteristics of bio-inspired minimal surface primitive structures

It has been proven that the triply periodic minimal surface structures (TPMS), a specific type of bio-inspired structures classified as cellular structures with continuous non-self-intersecting surfaces, have excellent energy absorption capability. However, the dynamic crushing characteristics of the TPMS have not been well comprehended. The dynamic response of minimal surface primitive structures under different crushing speeds is numerically investigated in this study. The dynamic crushing stresses of the primitive structure at the loading location and stationary side are measured to investigate the dynamic effect due to the shock wave propagation. Furthermore, the influences of other parameters, i.e., the crushing speed, relative density, and strain rate effect on the crushing stress are also discussed. The obtained results indicate that the plateau stress at the loading location is highly sensitive to the crushing speed while the opposite trend is observed for the plateau stress at the stationary side. It is also found that the primitive structures tend to deform following four distinct mode shapes, i.e., “X” mode, “K” mode, “I1” and “I2” mode, which are dependent on the crushing speed and relative density. Moreover, the energy absorption efficiency is used to define the densification strain, which shows no clear relationship with the relative density. Finally, the empirical models based on the shock wave theory and previous empirical model of honeycomb structures are developed to predict the plateau stress at the loading location and stationary side with/without strain rate effect. The predictions of the proposed analytical models agree well with the numerical results.

Multi-objective Bayesian optimization accelerated design of TPMS structures

Triply periodic minimal surface (TPMS) is an effective filling architecture in porous ceramic artificial bone for its great bionic characteristics and self-supporting properties. However, design optimization of TPMS architecture remains a huge challenge due to the convoluted multi parameter-property relationship. In this study, optimization of TPMS structure for composite titania ceramic is accelerated by using the multi-objective optimization algorithm guided finite element method (FEM) simulation. According to the FEM analysis on thickness (Pt), array number (Pa) and constant number (Pc) as verified by compression testing and fluid experiment, Pt and Pa in TPMS structures are the key factors to force reaction, while Pa mainly determined the pressure drop. With Pc increasing, the pressure drops initially increased and decreasing after Pc=0. Bayesian optimization (BO) method is used to optimize both strength and permeability iteratively, in which the optimal Pareto frontier converges in less than 10 iterations. The parameter combination (Pt=0.28, Pc=-0.49, Pa=3.5) in best performing TPMS structure yields suitable modulus and permeability required for practical bone filling application, with 1.21 GPa in strength and 4.03 × 10−9 m−2 in permeability.

Mechanical properties of triply periodic minimal surface (TPMS) scaffolds: considering the influence of spatial angle and surface curvature.

Triply periodic minimal surface (TPMS) has a promising application in the design of bone scaffolds due to its relevance in bone structure. Notably, the mechanical properties of TPMS scaffolds can be affected by many factors, including the spatial angle and surface curvature, which, however, remain to be discovered. This paper illustrates our study on the mechanical properties of tissue scaffolds consisting of TPMS structures (Primitive and I-WP) by considering the influence of spatial angle and surface curvature. Also, the development of a novel model representative of the mechanical properties of scaffolds based on the entropy weight fuzzy comprehensive evaluation method is also presented. For experimental investigation and validation, we employed the selective laser melting technology to manufacture scaffolds with varying structures from AlSi10Mg powder and then performed mechanical testing on the scaffolds. Our results show that for a given porosity, the Gaussian curvature of the stretched TPMS structures is more concentrated and have a higher elastic modulus and fatigue life. At the spatial angle θ = 27°, the shear modulus of the primitive unit reaches its largest value; the shear modulus of the I-WP unit is positively correlated with the spatial angle. Additionally, it is found that the comprehensive mechanical properties of TPMS structures can be significantly improved after changing the surface curvature. Taken together, the identified influence of spatial angle and surface curvature and the developed models of scaffold mechanical properties would be of significant advance and guidance for the design and development of bone scaffolds.

3D printed flexible wearable sensors based on triply periodic minimal surface structures for biomonitoring applications

Soft piezoresistive wearable conductors have led to a paradigm shift in the monitoring of human bodily motions. Cellular additively manufactured conductors are promising piezoresistive components as they offer mechanical tunability and provide controllable percolation pathways. In the present study, we engineer high surface-area cellular structures with the triply periodic minimal surface (TPMS)-based architectures to tailor their piezoresistive response for use in wearable devices. A simple and economical fabrication process is proposed, wherein a fused deposition modeling 3D printing technique is utilized to fabricate flexible thermoplastic polyurethane (TPU) cellular structures. Interconnectivity of TPMS designs enables the coating of a continuous graphene layer over the TPU internal surfaces via a facile dip-coating process. The effects of pore shape on piezoresistivity are studied in four different TPMS structures (i.e. Primitive, Diamond, Gyroid, and I-WP). Mechanical properties of sensors are evaluated through experimental procedures and computation methods using finite element analysis of the Mooney–Rivlin hyperelastic model. The piezoresistive performance of sensors exhibits durability under cyclic compression loading. Finally, we conclude that the Primitive structure offers suitable piezoresistive characteristics for sensing of walking, whereas the Diamond structure presents favorable results for respiration monitoring.

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

Mechanical-electromagnetic integrated design has great potential in the development of electromagnetic shielding equipment for military use. In this study, Al2O3/SiO 2 ceramics with triply periodic minimal surfaces (TPMSs) were fabricated using digital light processing (DLP) technology. The preparation of SiO 2 and Al2O3 powders is vital for DLP because minimal aggregates or sedimentation in the ceramic paste is required. Debinding and sintering programs were developed to prevent defects in the designed microstructure. The interfacial characterization demonstrated that the surfaces of the sintered ceramics were compact and smooth. The compression strength of the TPMS ceramic with a volume fraction of 50% was 24 MPa, which is relatively good among additively manufactured cellular ceramics. The TPMS structures also exhibited significant electromagnetic interference (EMI) shielding effectiveness in the X-band (2 to 18 GHz), and the shielding performance was adequate to meet the demands of electromagnetic shielding materials. Additive manufacturing of Al2O3/SiO2 ceramic with TPMS architectures was successfully achieved by considering the mechanical-electromagnetic integration.

Gyroid minimal surface-based composite porous structure with superior mechanical property via triangular grid design and stress distribution optimization

Triply periodic minimal surface structures (TPMS) possess excellent printability during additive manufacturing processing and mechanical properties. However, for TPMS shell structure due to the single connected regions, the porosity and connectivity become limited on the premise of mechanical property. In this study, triangular grid-based design of Gyroid composite porous structure (CPS) and optimized CPS through assigning diameter based on stress distribution were proposed for obtaining higher porosity and improved mechanical properties, following the analysis of curvature distribution characteristics. Afterwards, finite element simulation and quasi-static compression tests were performed for studying the stress distribution and mechanical responses. The results showed that the designed Gyroid CPS with high porosity did not obviously destroy the original curvature characteristic, while strength, modulus and specific energy absorption were enhanced simultaneously. It is expected to provide beneficial inspiration for the design and application of TPMS-based porous structures with the integration of high porosity and mechanical property.

Dynamic Load Mitigation of 3D-printed Triply Periodic Minimal Surface Structures

Three types of triply periodic minimal surface (TPMS) structures are chosen to investigate the quasi-static and dynamic compressive behaviors in this paper. All the TPMS lattices (Primitive, Gyroid, IWP) have the same relative density of 37.5%, and the samples are fabricated by the 3D printing of selective laser melting technique using AlSi10Mg powder. The energy absorption performance and dynamic load mitigation of the 3D printed TPMS structures under three different impact velocities are compared, and the corresponding engineering strain rates are 143 s −1, 286 s −1, and 571 s −1, respectively. The results of numerical simulation indicate that the IWP structure has the highest specific energy absorption (SEA) and plateau stress, followed by the Gyroid structure, and finally the Primitive structure. The SEA of Primitive and Gyroid structures increases with the impact velocity and decreases for IWP structure.

A Review of Recent Investigations on Flow and Heat Transfer Enhancement in Cooling Channels Embedded with Triply Periodic Minimal Surfaces (TPMS)

Triply periodic minimal surfaces (TPMS) have shown better mechanical performance, mass transfer, and thermal conductivity than conventional and strut-based structures, which have been employed in different disciplines. Most of the literature investigates different TPMS topologies in cooling channels to enhance thermal performance due to the smooth curvature and large surface area. However, a deeper investigation of the effects of TPMS design variables and the thermal performance advantages of cooling channels is required. This review details the effects of TPMS design variables, i.e., porosity, wall thickness, and unit cell size, on flow and heat transfer enhancement. It is found that varying the design variables significantly changes the flow and heat transfer characteristics. Also, by comparing TPMS and conventional cooling structures, it is found that most TPMS structures show better thermal performance than other strategies. Moreover, different fabrication methods for TPMS-based cooling channels in recent investigations are collected and discussed. In light of the reviewed literature, recommendations for future research suggest that more experimental and numerical studies on the flow and heat transfer for different cooling applications are needed. Therefore, this review serves as a reference tool to guide future studies on the flow and heat transfer of TPMS-based cooling channels.

Surface Morphology, Compressive Behavior, and Energy Absorption of Graded Triply Periodic Minimal Surface 316L Steel Cellular Structures Fabricated by Laser Powder Bed Fusion

Laser powder bed fusion (LPBF) is an emerging technique for the fabrication of triply periodic minimal surface (TPMS) structures in metals. In this work, different TPMS structures such as Diamond, Gyroid, Primitive, Neovius, and Fisher-Koch S with graded relative densities are fabricated from 316L steel using LPBF. The graded TPMS samples are subjected to sandblasting to improve the surface finish before mechanical testing. Quasi-static compression tests are performed to study the deformation behavior and energy absorption capacity of TPMS structures. The results reveal superior stiffness and energy absorption capabilities for the graded TPMS samples compared to the uniform TPMS structures. The Fisher-Koch S and Primitive samples show higher strength whereas the Fisher-Koch S and Neovius samples exhibit higher elastic modulus. The Neovius type structure shows the highest energy absorption up to 50% strain among all the TPMS structures. The Gibson-Ashby coefficients are calculated for the TPMS structures, and it is found that the C2 values are in the range suggested by Gibson and Ashby while C1 values differ from the proposed range.

Laser Powder Bed Fusion-built Ti6Al4V Bone Scaffolds Composed of Sheet and Strut-based Porous Structures: Morphology, Mechanical Properties, and Biocompatibility

Laser powder bed fusion (L-PBF)-built triply periodic minimal surface (TPMS) structures are designed by implicit functions and are endowed with superior characteristics, such as adjustable mechanical properties and light-weight features for bone repairing; thus, they are considered as potential candidates for bone scaffolds. Unfortunately, previous studies have mainly focused on different TPMS structures. The fundamental understanding of the differences between strut and sheet-based structures remains exclusive, where both were designed by one formula. This consequently hinders their practical applications. Herein, we compared the morphology, mechanical properties, and biocompatibility of sheet and strut-based structures. In particular, the different properties and in vivo bone repair effects of the two structures are uncovered. First, the morphology characteristics demonstrate that the manufacturing errors of sheet-based structures with diverse porosities are comparable, and semi-melting powders as well as the ball phenomenon are observed; in comparison, strut-based samples exhibit cracks and thickness shrinking. Second, the mechanical properties indicate that the sheet-based structures have a greater elastic modulus, energy absorption, and better repeatability compared to strut-based structures. Furthermore, layer-by-layer fracturing and diagonal shear failure modes are observed in strut-based and sheet-based structures, respectively. The in vivo experiment demonstrates enhanced bone tissues in the strut-based scaffold. This study significantly enriches our understanding of TPMS structures and provides significant insights in the design of bone scaffolds under various bone damaging conditions.

Towards an Ideal Energy Absorber: Relating Failure Mechanisms and Energy Absorption Metrics in Additively Manufactured AlSi10Mg Cellular Structures under Quasistatic Compression

A designer of metallic energy absorption structures using additively manufactured cellular materials must address the question of which of a multitude of cell shapes to select from, the majority of which are classified as either honeycomb, beam-lattice, or Triply Periodic Minimal Surface (TPMS) structures. Furthermore, there is more than one criterion that needs to be assessed to make this selection. In this work, six cellular structures (hexagonal honeycomb, auxetic and Voronoi lattice, and diamond, gyroid, and Schwarz-P TPMS) spanning all three types were studied under quasistatic compression and compared to each other in the context of the energy absorption metrics of most relevance to a designer. These shapes were also separately studied with tubes enclosing them. All of the structures were fabricated out of AlSi10Mg with the laser powder bed fusion (PBF-LB. or LPBF) process. Experimental results were assessed in the context of four criteria: the relationship between the specific energy absorption (SEA) and maximum transmitted stress, the undulation of the stress plateau, the densification efficiency, and the design tunability of the shapes tested—the latter two are proposed here for the first time. Failure mechanisms were studied in depth to relate them to the observed mechanical response. The results reveal that auxetic and Voronoi lattice structures have low SEA relative to maximum transmitted stresses, and low densification efficiencies, but are highly tunable. TPMS structures on the other hand, in particular the diamond and gyroid shapes, had the best overall performance, with the honeycomb structures between the two groups. Enclosing cellular structures in tubes increased peak stress while also increasing plateau stress undulations.

Analysis on the convective heat transfer process and performance evaluation of Triply Periodic Minimal Surface (TPMS) based on Diamond, Gyroid and Iwp

Heat dissipation capacity is one of the bottlenecks in developing high heat release devices such as electronic chips and laser generators. TPMS exhibits good thermophysical properties and is expected to provide better heat dissipation solutions for high heat-releasing devices. However, studies on the convective heat transfer properties of TPMS structures are still insufficient. In this manuscript, research focuses on evaluating the convective heat transfer performance of several representative TPMS structures and elucidating their mechanism of enhanced heat transfer. The TPMS studied in this paper include Gyroid, Diamond, and Iwp, and their convective heat transfer performance is compared with that of Fins-structure. In addition, an experiment was carried out to verify the accuracy of the numerical simulation. The results showed that the numerical simulation results were in good agreement with the experiment, with an error of less than 6%. In the numerical simulation, the lattice size of the three TPMS is 20 × 20 × 20 mm3, the fluid is air, the heating surface is heated at a constant wall temperature of 373.15 K, and the Reynolds number is in the range of 166–940. Compared with the Fins-structure model, the Nusselt number of TPMS-Diamond is increased by 9–196%, that of TPMS-Gyroid is increased by 5.8–149%, while the TPMS-Iwp is increased by 6.8–43.5%. Among the three TPMS structures, the convective heat transfer performance of TPMS-Dimond is the best, which can be attributed to its geometric structures without the “through-holes,” which leads to a more substantial disturbance of the wall to the fluid, thereby enhancing the heat transfer.

Processing Vat Polymerized Triply Periodic Minimal Surface Scaffolds of Hydroxyapatite

Vat polymerization of ceramic slurries offers a means for producing triply periodic minimal surface (TPMS) structures, which are candidates for artificial trabecular bone replacement therapy. However, structures with relevant pore sizes below 500 μm and porosities above 80% push the limits of current ceramic additive manufacturing capabilities. Herein, printing and postprocessing of TPMS structures with features relevant to bone, specifically, pore sizes from 400 to 1,265 μm, porosities over 75%, and wall thicknesses below 200 μm are addressed. The resolution of several key fundamental challenges includes: (a) adhesion to the build plate by starting the first layer with the highest surface area slice, (b) cleaning complex designs with two centrifugation cycles consistently removing 100% of residual slurry, (c) elimination of contamination from heating elements by sintering hydroxyapatite in a tube furnace, and (d) determining differences in firing shrinkage between designs to allow for targeting specified sintered dimensions. The outcome of this work enables the consistent fabrication of hydroxyapatite TPMS scaffolds (gyroid, trifurcating, clover) with high agreement between the computer‐aided design (CAD), printed, and fired designs in 5 mm cubes and cylinder with 8 mm diameter and 20 mm length.