Freeze-casting Technique Research Articles

Biomimetic structural aerogel derived from green tide enteromorpha-prolifera: Multi-sided unidirectional freeze casting and solar-driven viscous oil spill remediation

The development of environmental remediation materials from renewable biowaste, especially for the cleanup of viscous oil spills in an eco-friendly manner, marks a substantial advancement in functional materials. This study proposes a biomass aerogel (M−MCEP) transformed from Enteromorpha prolifera (EP) in green tides for solar-driven recovery of high-viscosity oil spills. Inspired by the lamella-bridge architecture of Thalia dealbata stems, a biomimetic structure with multi-domain, long-range aligned lamella-bridge interconnections is constructed by a multi-sided unidirectional freeze-casting technique. Multi-scale interface optimization between rigid photothermal fillers and soft lamellar layers achieves multiple reinforcements, providing aerogel with a perfect balance of elasticity and strength. The multidomain low tortuosity channels and photothermal effects enhance M−MCEP’s photothermal conversion (95.2 %) and thermal conductivity (0.3517 W/m·K), reducing oil flow resistance and achieving high oil retention efficiency (>92 %). Under 1 sun irradiation, M−MCEP rapidly heats to 67.3 °C, effectively reducing the viscosity of crude oil in situ, with a crude oil adsorption rate of 1843 mL/m2 within 30 s. Moreover, M−MCEP captures emulsified oil in oil-in-water emulsions through high-speed repeated oscillations, achieving a separation efficiency of 96.42–99.21 %. Renewable resources and unique structural designs provided by nature drive the development of advanced biomimetic aerogels for efficiently remedying catastrophic oil spills.

Enhancing mechanical and thermal properties of polyvinyl alcohol/curdlan composite hydrogels and aerogels via freeze-casting technique

This study introduces a novel approach to fabricating polyvinyl alcohol (PVA)/curdlan (CURD) composite aerogels by employing the freeze-casting technique to achieve exceptional mechanical and thermal properties. Our research demonstrated that the formation of dual-network structure that combines the mechanical strength of PVA with the thermal stability of CURD. Scanning electron microscopy revealed a unique honeycomb-like cross-sectional morphology in the PVA/CURD aerogels. Notably, the PVA/CURD composite hydrogel demonstrated consistent compressive stress performance even after 50 compression cycles and exhibited minimal swelling (only 4%) when immersed in distilled water for 24hours. Furthermore, the aerogels exhibited varying swelling ratios in different pH environments, with a significant increase observed in acidic conditions. Thermal analysis confirmed the enhanced thermal stability of the composite aerogels, attributed to the incorporation of CURD. These findings suggest that PVA/CURD composite aerogels have promising applications in fields that require materials with robust mechanical and thermal endurance.

Advanced Bioceramics: Properties, Fabrication and Applications

Bioceramics are engineered materials that achieve their applications in the medical field. Bioceramics are promising inorganic materials to create scaffolds for bone regeneration due to their desirable properties, such as biocompatibility, osteoconduction, and their similarity with bone composition. Bioceramics can operate as tissue replacement and can be used for coating metal implants to increase their biocompatibility. Bioceramics are classified into three types: bioinert ceramics, bioactive bioceramics, and biodegradable ceramics. There are different methods for the fabrication of bioceramics, they can be prepared by conventional powder processing methods or by some new unconventional methods. Bioceramics can be fabricated by a sintering process, which takes place through the hardening of the green bodies at a relatively high temperature lower than their melting point. Nowadays, microwave sintering is excellent in both heating efficiency, saving energy and time, and the concomitant processing cost. There are other methods used to obtain bioceramics; such as sol-gel, gas-foaming, gel-casting, and freeze-casting techniques. Recently, the CAD/CAM technique (computer-aided design/manufacture) was used in the fabrication of bioceramics and is applied in the dentistry field. The application of bioceramics connects to the repair of the skeletal system, which consists of joints, bones, and teeth, as well as both soft and hard tissues. Bioceramics can be used to replace parts of the cardiovascular system, especially heart valves.

Structural and Electrochemical Investigation of Anode‐Supported Proton‐Conducting Solid Oxide Fuel Cell Fabricated by the Freeze Casting Process

ABSTRACTHierarchically oriented macroporous NiO–BaZr0.1Ce0.7Y0.2O3−δ (BZCY7) anode‐supporting layer (ASL) was developed using the freeze casting technique. The resulting freeze‐cast structure was analyzed through scanning electron microscopy and X‐ray computed tomography. A thin layer of BZCY7 was utilized as a proton‐conducting electrolyte, whereas La1.9Sr0.1Ni0.7Cu0.3O3−δ –gadolinium‐doped ceria 10% Gd (LSNC–GDC10) was employed and evaluated as cathode layer. The performance of the cell was assessed by means of electrochemical impedance spectroscopy and I–V–P curves at various temperatures. Furthermore, as a point of comparison, a cell with an ASL was prepared using the dry pressing method, incorporating 20 wt.% graphite as a pore‐forming agent. The freeze‐cast anode‐supported cell demonstrated a polarization resistance of 1.45 Ω cm2 at 550°C and 0.29 Ω cm2 at 750°C. Maximum achieved power densities were 0.189 and 0.429 W cm−2 at 550 and 750°C, respectively. For the cell fabricated by the dry pressing method, the maximum power densities were 0.158 and 0.397 W cm−2 at 550 and 750°C, respectively. Additionally, the tortuosity factor of the anode layer and the gas diffusion streamline in the direction of solidification were determined by using 3D X‐ray tomography imaging and subsequent image processing.

Simulation Analysis of the Freezing Process For Achieving Bidirectional Freezing Coating Via the Freeze-Casting Technique

To delve deeper into the shapes and positions of the solidification front, as well as the detailed temperature distributions under various solidification conditions, this study employed the commercial software ANSYS FLUENT to conduct a meticulous numerical simulation of the two-dimensional solidification process in freeze casting. As part of the research, the enthalpy-porous media solidification/melting model was chosen as the core theoretical framework, and the accuracy of the numerical calculations was verified by comparing them with locally measured temperature changes from experiments. Subsequently, we further examined the influence mechanisms of factors such as cold source temperature, solid content, mold depth, and mold thermal conductivity on the speed of the solidification front. This is crucial because, in the freeze casting process, the speed of the solidification front directly determines the formation and evolution of macropore structures. The results of the simulation analysis indicate that an increase in mold thermal conductivity, a decrease in cold source temperature, a shallower mold depth, and a higher solid content all lead to a corresponding increase in the movement speed of the solidification front. These simulation outcomes not only provide strong theoretical support for optimizing the process parameters of freeze casting but also aid in achieving more precise control over the microstructure of materials, thus enabling a more efficient and accurate material preparation process.

Fabrication of 3D aligned porous nanocellulose-based aerogel for enrichment of the histidine-containing polypeptides

The high-throughput immobilized metal affinity chromatography (IMAC) material is urgently required to improve the efficiency of separation and purification of tagged peptides in related biomedical applications. Herein, the amino-thiourea-modified nanocellulose (S-TOCN) -polyvinyl alcohol (PVA) composite aerogel with aligned pores was prepared by a directional freeze-casting technique and then used to immobilize metal ions (M2+) for the selective separation and purification of histidine-containing peptides from protein hydrolysates. The obtained S-TOCN-PVA materials with an oriented porous structure exhibited excellent mechanical properties, good adsorption performance, and reusability under optimal conditions. The adsorption capacity of the S-TOCN-PVA aerogel for metal ions was as follows: Cu2+>Ni2+>Zn2+>Co2+, and the higher metal ion chelating amount of the S-TOCN-PVA composite aerogel for Cu2+ and Ni2+ reached 87.21 mg/g at pH=7 and 83.66 mg/g at pH=6 in the 2 h incubation period, respectively. The enrichment effects of Cu2+/S-TOCN-PVA and Ni2+/S-TOCN-PVA aerogels with the selectivity of His-containing peptides from apricot kernel protein hydrolysates were up to 3.99 folds and 4.81 folds, respectively, for one cycle. Furthermore, after 5cycles, the Ni2+/S-TOCN-PVA aerogels remained at 87.5% of their initial adsorption capacity (848 mg/g), and the concentration increased by 39.05-fold. Molecular docking simulations show that the oxygen of the carboxyl group (-C-O and -CO) and the hydrogen of the imidazole group on the His molecule are mainly bonded to the hydrogen of the amino groups and the oxygen of the carboxyl group (C-O-C) in the structure of M2+/S-TOCN-PVA aerogels. The fabricated metal ion-immobilized 3D-aligned porous nanocellulose-based aerogels are promising IMAC materials for efficient separation and purification of the histidine-containing polypeptides from complicated biological samples.

Silver nanowire bridged graphene framework for encapsulating phase change materials with high thermal conductivity and solar-to-heat conversion ability

To construct a high-efficiency thermally conductive graphene nanoplate (GNP) framework, ball-milling technique and silver nanowires (AgNW) bridging strategy were employed to improve the compatibility of GNP and the interfacial thermal resistance (ITR) in GNP skeletons, respectively. By using unidirectionally freeze casting technique, long range ordered GNP frameworks containing a small amount of AgNW as “bridge” were obtained, which were used to encapsulation phase change material (PCM). As a result, the honeycomb-like micropores of the framework with strong capillary effect give PCM anti-leakage and shape stability. The vertically aligned and AgNW bridged GNP skeletons form high-speed heat transfer paths endowith low ITR, thus significantly improve thermal conductivity to 7.24 W/mK. More importantly, GNP framework with strong light absorption ability endows PCM with well solar-to-heat conversion and storage ability. Therefore, AgNW bridged GNP framework endowing PCM with comprehensive thermal management ability exhibits a high potential in addressing the thermal problems of electronics.

General Semi-Solid Freeze Casting for Uniform Large-Scale Isotropic Porous Scaffolds: An Application for Extensive Oral Mucosal Reconstruction.

Ice-templated porous biomaterials possess transformative potential in regenerative medicine; yet, scaling up ice-templating processes for broader applications-owing to inconsistent pore formation-remains challenging. This study reports an innovative semi-solid freeze-casting technique that draws inspiration from semi-solid metal processing (SSMP) combined with ice cream-production routines. This versatile approach allows for the large-scale assembly of various materials, from polymers to inorganic particles, into isotropic 3D scaffolds featuring uniformly equiaxed pores throughout the centimeter scale. Through (cryo-)electron microscopy, X-ray tomography, and finite element modeling, the structural evolution of ice grains/pores is elucidated, demonstrating how the method increases the initial ice nucleus density by pre-fabricating a semi-frozen slurry, which facilitates a transition from columnar to equiaxed grain structures. For a practical demonstration, as-prepared scaffolds are integrated into a bilayer tissue patch using biodegradable waterborne polyurethane (WPU) for large-scale oral mucosal reconstruction in minipigs. Systematic analyses, including histology and RNA sequencing, prove that the patch modulates the healing process toward near-scarless mucosal remodeling via innate and adaptive immunomodulation and activation of pro-healing genes converging on matrix synthesis and epithelialization. This study not only advances the field of ice-templating fabrication but sets a promising precedent for scaffold-based large-scaletissue regeneration.

Three-dimensional freeze-casting solar evaporator for highly efficient water evaporation and high salinity desalination

The escalating global freshwater crisis demands sustainable water management strategies, such as solar-driven interfacial steam generation (SISG). Three-dimensional (3D) photothermal evaporators emerge as a promising solution due to significantly higher evaporation rates compared to two-dimensional (2D) counterparts. This study described the design and fabrication of M-shaped 3D evaporators using the freeze-casting technique with graphite nanopowder (GNP) and polyvinylidene fluoride (PVDF). Under 1.0 kW m−2 solar irradiation and 4 m s-1 convective flow, a high evaporation rate of up to 10.5 kg m−2 h−1 in pure water was achieved. The M-shaped 3D evaporators demonstrated excellent performance in solar desalination and wastewater treatment, maintaining stability even in a 20 wt% sodium chloride (NaCl) solution at 1.0 kW m−2 solar irradiation and 2 m s−1 convective flow, with a rate of approximately 3.8 kg m−2 h−1. These findings highlight the significant potential for leveraging the synergistic interplay between solar energy and convective flow, which can be harnessed through the fabrication of customized 3D evaporators via freeze-casting. This innovative approach offers a scalable and cost-effective solution, contributing to both efficient water evaporation and environmentally sustainable high salinity desalination for future water treatment.

Engineered Microchannel Scaffolds with Instructive Niches Reinforce Endogenous Bone Regeneration by Regulating CSF-1/CSF-1R Pathway.

Structural and physiological cues provide guidance for the directional migration and spatial organization of endogenous cells. Here, a microchannel scaffold with instructive niches is developed using a circumferential freeze-casting technique with an alkaline salting-out strategy. Thereinto, polydopamine-coated nano-hydroxyapatite is employed as a functional inorganic linker to participate in the entanglement and crystallization of chitosan molecules. This scaffold orchestrates the advantage of an oriented porous structure for rapid cell infiltration and satisfactory immunomodulatory capacity to promote stem cell recruitment, retention, and subsequent osteogenic differentiation. Transcriptomic analysis as well as its in vitro and in vivo verification demonstrates that essential colony-stimulating factor-1 (CSF-1) factor is induced by this scaffold, and effectively bound to the target colony-stimulating factor-1 receptor (CSF-1R) on the macrophage surface to activate the M2 phenotype, achieving substantial endogenous bone regeneration. This strategy provides a simple and efficient approach for engineering inducible bone regenerative biomaterials.

Control of pore morphology and mechanical strength of alumina ceramics produced by freeze-casting

In this work, unidirectional and bidirectional freeze-casting techniques were employed to fabricate alumina monoliths using camphene as solvent. Monolith samples with aligned porosity were produced in unprecedented molds designed using materials with different thermal conductivities (technyl and copper) and varying the alumina monoliths concentrations (15, 20 and 25 % of solid load). The total porosity of the produced monoliths ranged within 50–70 % and it was observed that the different molds did not influence the total porosity of the material. The SEM images showed that the samples produced in the technyl/copper mold presented a change on the perpendicular alignment of the pores in the transition region from copper to technyl. The copper side exhibited more aligned structures forming continuous channels, that become less noticeable when closer to the transition region, reaching the technyl region where the dendrites were not well aligned. The monoliths prepared in the technyl mold showed a better mechanical resistance with values of 19.6; 23.34 and 34.2 MPa for 15, 20 and 25 % of the solid load, respectively.

Solvent volume expansion inhibition during freeze casting and its application in composite solid lithium electrolytes

Composite solid electrolytes hold the promise to enable all-solid-state lithium-ion batteries to be practicable. One critical issue is the construction of uniform porous ceramic framework. The work proposed an innovative freeze casting-based technology to construct porous ceramic framework of Li1+xAlxGe2−x(PO4)3 (LAGP), which was further composited with polymeric electrolytes to assemble full cells. The pore structure of the ceramic framework was effectively tuned by the ratio of mixed water-ethanol solvents, which could offset the volume expansion of water during freeze casting, benefit powder compact and sintering, and thus improved the quality of the composite solid electrolytes. The unique solvent composition design strategy provided ample opportunity for microstructural modification and the suppression of short-circuiting lithium dendrites, as demonstrated by the improvement of critical current density and phase field modeling. This work offers new perspectives on creating different pore structure free of residual stress or volume expansion once freeze casting technique is adopted.

Biomimetic Nacre-like Hydroxyapatite/Polymer Composites for Bone Implants.

One of the most ambitious goals for bone implants is to improve bioactivity, incapability, and mechanical properties; to reduce the need for further surgery; and increase efficiency. Hydroxyapatite (HA), the main inorganic component of bones and teeth, has high biocompatibility but is weak and brittle material. Cortical bone is composed of 70% calcium phosphate (CaP) and 30% collagen and forms a complex hierarchical structure with anisotropic and lamellar microstructure (osteons) which makes bone a light, strong, tough, and durable material that can support large loads. However, imitation of concentric lamellar structure of osteons is difficult to achieve in fabrication. Nacre from mollusk shells with layered structures has now become the archetype of the natural "model" for bio-inspired materials. Incorporating a nacre-like layered structure into bone implants can enhance their mechanical strength, toughness, and durability, reducing the risk of implant catastrophic failure or fracture. The layered structure of nacre-like HA/polymer composites possess high strength, toughness, and tunable stiffness which matches that of bone. The nacre-like HA/polymer composites should also possess excellent biocompatibility and bioactivity which facilitate the bonding of the implant with the surrounding bone, leading to improved implant stability and long-term success. To achieve this, a bi-directional freeze-casting technique was used to produce elongated lamellar HA were further densified and infiltrated with polymer to produce nacre-like HA/polymer composites with high strength and fracture toughness. Mechanical characterization shows that increasing the ceramic fractions in the composite increases the density of the mineral bridges, resulting in higher flexural and compressive strength. The nacre-like HA/(methyl methacrylate (MMA) + 5 wt.% acrylic acid (AA)) composites with a ceramic fraction of 80 vol.% showed a flexural strength of 158 ± 7.02 MPa and a Young's modulus of 24 ± 4.34 GPa, compared with 130 ± 5.82 MPa and 19.75 ± 2.38 GPa, in the composite of HA/PMMA, due to the higher strength of the polymer and the interface of the composite. The fracture toughness in the composition of 5 wt.% PAA to PMMA improves from 3.023 ± 0.98 MPa·m1/2 to 5.27 ± 1.033 MPa·m1/2 by increasing the ceramic fraction from 70 vol.% to 80 vol.%, respectively.

A Review of Freeze Casting: Preparation Process, Modified Methods, and Development Tendency

Abstract: Fabricating materials with nacre-like structure have received considerable attention as it shows an excellent combination of mechanical strength and toughness. A considerable number of researchers have reported the preparation method of bionic structure, such as layer-by-layer assembly, vacuum filtration, coextrusion assembly, electrophoresis deposition, water-evaporation-induced assembly, 3D printing, and freeze casting. Compared with other techniques, freeze casting, known as ice templating, is an environmentally friendly, prolongable, and potential method, so it has been rapidly developing and widely researched in recent decades. In this review, the front six methods with their benefits and limitations are briefly introduced. Then, the freeze casting technique with the preparation process and modified technique is emphatically analyzed. Finally, the future tendencies of materials application and technique application are discussed. Freeze casting consists of suspension preparation, solidification, sublimation, and post-treatment processes. The mechanism and influence of parameters during suspension preparation and solidification processes are principally discussed. It must be pointed out that the performance and structure of samples are closely related to the model and external force. Besides, the adjustable process parameters of freezing casting are a strong guarantee of obtaining the target product. The purpose of this review is to promote freeze casting workers to understand the influence of parameters and enlighten them in new experimental designs.

Oriented Porous NASICON 3D Framework via Freeze-Casting for Sodium-Metal Batteries.

Sodium-metal batteries are promising candidates for low-cost, large-format energy storage systems. However, sodium-metal batteries suffer from high interfacial resistance between the electrodes and the solid electrolyte, leading to poor electrochemical performance. We demonstrate a sodium superionic conductor (NASICON) with an oriented porous framework of sodium aluminum titanium phosphate (NATP) fabricated by the freeze-casting technique, which shows excellent properties as a solid electrolyte. Using X-ray computed tomography, we confirm the uniform low-tortuosity channels present along the thickness of the scaffold. We infiltrated the porous NATP scaffolds with sodium vanadium phosphate (NVP) cathode nanoparticles achieving mass loadings of ∼3-4 mg cm-2, which enables short sodium ion diffusion path lengths. For the resulting hybrid cell, we achieved a capacity of ∼90 mAh g-1 at a specific current of 50 mA g-1 (∼300 Wh kg-1) for over 100 cycles with ∼94% capacity retention. Our study offers valuable insights for the design of hybrid solid electrolyte-cathode active material structures to achieve improved electrochemical performance through low-tortuosity ion transport networks.

Flexible three-dimensional interconnected PZT skeleton based piezoelectric nanogenerator for energy harvesting

Flexible piezoelectric nanogenerator (PENG) has attracted extensive attention due to the capability of energy collection and charging low-power microelectronic devices. Herein, PZT ceramic skeleton with three-dimensional (3D) interconnected network structure was fabricated via freeze casting technique. PZT/PDMS composites were prepared by introducing PDMS to the aligned pores of both green and sintered PZT skeletons. This special network structure enabled stress not to be buffered by PDMS. PENG composed of sintered PZT skeleton exhibited distinctly superior electrical output performance to that of the green one due to the effective stress transfer resulting from the direct contact between PZT particles. The maximum output voltage and output current of PENG based on 40 vol% sintered-PZT/PDMS composite reached 174 V and 28.2 μA, which were 19 V and 4.7 μA higher than those of green-PZT/PDMS composite, respectively. Thereby, this work provided a referable thought for the further development of PENG in the prospective market.

Multifunctional SiC aerogel reinforced with nanofibers and nanowires for high-efficiency electromagnetic wave absorption

Ceramic aerogels with recoverable compressibility, super-insulation capacity, and remarkable thermal and chemical stability are fascinating for use in the field of high-level electromagnetic wave (EMW) absorption. However, integrating multiple functions into a monolithic ceramic aerogel using presently available fabrication techniques remains a challenge. Therefore, we employed a novel strategy to successfully synthesize a multifunctional and monolithic SiC ceramic aerogel using a simple freeze casting technique with a subsequent carbonation and calcination process. The as-synthesized SiC aerogel-2 exhibits ultralow density, fire resistance, high-temperature chemical and thermal stability, and excellent insulating properties. Notably, the one-dimensional SiC nanofibers and nanowires inside the SiC aerogel-2 act as a reinforcement to ensure the presence of a stable porous structure. The sample exhibits excellent mechanical performance and also achieves ideal impedance matching to present high-efficiency EMW-absorbing properties, including a minimum reflection loss (RLmin) of − 61.56 dB and a maximum effective absorption bandwidth (EABmax) of 9.82 GHz. Thus, the successful fabrication of multifunctional SiC aerogels will pave the way for the development and widespread application of high-level EMW absorption materials in aviation and aerospace fields.

Efficient recovery of highly viscous crude oil spill by superhydrophobic ocean biomass-based aerogel assisted with solar energy

The crude oil spills is one of the crucial ocean environmental disaster. The low fluidity of high-viscosity crude oil poses significant challenges for its penetration into conventional porous adsorption materials. Fortunatelly, the viscosity of crude oil is especially temperature-sensitive, leading to the extensive research on porous materials that utilize solar heat for heat generation. In this work, we propose a biodegradable marine bio-based aerogel (PDMS-Ink@CS) with aligned channel structure via directional freeze casting technique, primarily composed of chitosan and cuttlefish ink. The PDMS-Ink@CS demonstrates excellent photothermal conversion and oil adsorption performance. We systematically investigated the effects of sunlight intensity and pore structure on the viscosity-reduction and adsorption rate of crude oil. Under simulated sunlight intensity of 1 kW m−2, the surface temperature of PDMS-Ink@CS aerogel reaches approximately 70 ℃ within 60 s, allowing to absorb crude oil 18 times its weight and recover via extrusion. When combined with a vacuum pump device, the PDMS-Ink@CS aerogel realizes the continuous recovery of crude oil from the seawater surface. Moreover, the separation efficiency of PDMS-Ink@CS aerogel for W/O emulsions can reach 99 %, which greatly broadens its range of applications. Particularly noteworthy is the fact that the PDMS-Ink@CS aerogel biodegrades within 30 days without causing environmental pollution. Thus, this super-hydrophobic ocean biomass-based chitosan aerogel exhibits vast potential for oil spill recovery applications.

Bioinspired Self-Standing, Self-Floating 3D Solar Evaporators Breaking the Trade-Off between Salt Cycle and Heat Localization for Continuous Seawater Desalination.

Facing the global water shortage challenge, solar-driven desalination is considered a sustainable technology to obtain freshwater from seawater. However, the trade-off between the salt cycle and heat localization of existing solar evaporators (SE) hinders its further practical applications. Here, inspired by water hyacinth, a self-standing and self-floating 3D SE with adiabatic foam particles and aligned water channels is built through a continuous directional freeze-casting technique. With the help of the heat insulation effect of foam particles and the efficient water transport of aligned water channels, this new SE can cut off the heat transfer from the top photothermal area to the bulk water without affecting the water supply, breaking the long-standing trade-off between salt cycle and heat localization of traditional SEs. Additionally, its self-standing and self-floating features can reduce human maintenance. Its large exposure height can increase evaporation area and collect environmental energy, breaking the long-standing limitation of solar-to-vapor efficiency of conventional SEs. With the novel structure employed, an evaporation flux of 2.25kgm-2 h-1 , and apparent solar-to-vapor efficiency of 136.7% are achieved under 1sun illumination. This work demonstrates a new evaporator structure, and also provides a key insight into the structural design of next-generation salt-tolerant and high-efficiency SEs.

Investigation on the Compressive Behavior of Hybrid Polyurethane(PU)-Foam-Filled Hyperbolic Chiral Lattice Metamaterial.

In this study, a novel hybrid metamaterial has been developed via fulfilling hyperbolic chiral lattice with polyurethane (PU) foam. Initially, both the hyperbolic and typical body-centered cubic (BCC) lattices are fabricated by 3D printing technique. These lattices are infiltrated in a thermoplastic polyurethane (TPU) solution dissolved in 1,4-Dioxane, and then freeze casting technique is applied to achieve the PU-foam-filling. Intermediate (IM) layers possessing irregular pores, are formed neighboring to the lattice-foam interface. While, the foam far from the lattice exhibits a multi-layered structure. The mechanical behavior of the hybrid lattice metamaterials has been investigated by monotonic and cyclic compressive tests. The experimental monotonic tests indicate that, the filling foam is able to soften the BCC lattice but to stiffen the hyperbolic one, further to raise the stress plateau and to accelerate the densification for both lattices. The foam hybridization also benefits the hyperbolic lattice to prohibit the property degradation under the cyclic compression. Furthermore, the failure modes of the hybrid hyperbolic lattice are identified as the interface splitting and foam collapse via microscopic analysis. Finally, a parametric study has been performed to reveal the effects of different parameters on the compressive properties of the hybrid hyperbolic lattice metamaterial.