3D printing of inherently nanoporous polymers via polymerization-induced phase separation

Three-Dimensional Printed Cell-Adaptable Nanocolloidal Hydrogel Induces Endogenous Osteogenesis for Bone Repair

Repairing critical bone defects remains a formidable challenge in regenerative medicine. Scaffolds that can fill defects and facilitate bone regeneration have garnered considerable attention. However, scaffolds struggle to provide an ideal microenvironment for cell growth and differentiation at the interior of the bone defect sites. The scaffold's structure must meet specific requirements to support endogenous bone regeneration. Here, we introduce a novel 3D-printed nanocolloidal gelatin methacryloyl (GelMA) hydrogel, namely, the nG hydrogel, that was derived from the self-assembly of GelMA in the presence of Pluronics F68, emphasizing its osteoinductive capability conferred solely by the specific nanocolloidal structure. The nG hydrogel, exhibiting remarkable pore connectivity and cell-adaptable microscopic structure, induced the infiltration and migration of rat bone mesenchymal stem cells (rBMSCs) into the hydrogel with a large spreading area in vitro. Moreover, the nG hydrogel with interconnected nanospheres promoted the osteogenic differentiation of rBMSCs, leading to up-regulated expression of ALP, RUNX2, COL-1, and OCN, as well as augmented formation of calcium nodules. In the critical-sized rat calvarial defect model, the nG hydrogel demonstrated improved repair of bone defects, with enhanced recruitment of endogenous CD29+ and CD90+ stem cells and increased bone regeneration, as indicated by significantly higher bone mineral density (BMD) in vivo. Mechanistically, the integrin β1/focal adhesion kinase (FAK) mechanotransduction signaling pathway was up-regulated in the nG hydrogel group both in vitro and in vivo, which may partially account for its pronounced osteoinductive capability. In conclusion, the cell-adaptable nG hydrogel shows great potential as a near-future clinical translational strategy for the customized repair of critical-sized bone defects.

The effect of selective surface interaction on polymer phase separation with explicit polydispersity during polymerization

In polymerization-induced phase separation, the impact of polymer-substrate interaction on the dynamics of phase separation for polymer blends is important in determining the final morphology and properties of polymer materials as the surface can act as another driving force for phase separation other than polymerization. We modify the previously-developed polymerizing Cahn-Hilliard (pCH) method by adding a surface potential to model the phase separation behavior of a mixture of two species independently undergoing linear step-growth polymerization in the presence of a surface. In our approach, we explicitly model polydispersity by separately considering different molecular-weight components with their own respective diffusion constants, and with the surface potential preferentially acting on only one species. We first show that the surface potential induces faster phase separation of smaller molecules at early stages before the degree of polymerization becomes large enough to drive bulk phase separation. This model is then used to investigate the degree of anisotropic ordering in a direction perpendicular to the surface over various polymerization rates k̃ and strengths of the potential Ṽ. We find that at low k̃, smaller molecules have sufficient time to diffuse and accumulate at the potential surface, resulting in richer production of heavier polymers at the surface without the need for larger polymers to diffuse on their own toward the surface. Conversely, at high k̃, larger polymers first evenly accumulate throughout the system before undergoing phase separation; the concentration wave initiated from the potential surface then propagates into the bulk, resulting in anisotropic phase separation.

Fabrication of 3D Functional Nanocomposites Through Post-Doping of Two-Photon Microprinted Nanoporous Architectures

Two-photon lithography (TPL) enables the fabrication of complex 3D structures with sub-micrometer precision. Incorporation of new functionalities into TPL-printed structures is key to advance their applications. A prevalent approach to achieve this is by directly adding functional nanomaterials into the photoresist (called "pre-doping"), which has several inherent challenges including material compatibility, light scattering, and nanoparticle agglomeration. Here, a conceptually different "post-doping" strategy is proposed, where the functionality of the TPL-printed architectures is achieved by impregnating functional materials into their nanoporous 3D mimics. Using the principle of polymerization-induced phase separation, TPL printing of complex microarchitectures with well-defined nanoporous structures having pores of ≈420 nm is realized, which allows spontaneous impregnation of functional liquids via capillary effect. Importantly, unlike the "pre-doping" approach that requires printing optimization for each photoresist, this strategy is highly versatile in terms of functionalities possible. As a proof-of-concept, the impregnation of several functional liquids into TPL-printed porous microstructures is demonstrated: a fluorinated-lubricant, an ionic liquid, and three types of fluorescent liquids, conferring the microstructures with slippery, conductive, and localized fluorescence properties, respectively. Such versatility to fabricate complex microstructures with tailorable and localized functionalities is expected to open new possibilities in wide fields including bionics, electronics, and cell biology.

3D printing: trends and approaches toward achieving long-term sustainability in the food industry

Global food security has recently been under serious threat from the rapid rise in the world's population, the problems brought on by climate change, and the appearance of new pandemics. As a result, the need for novel and innovative solutions to solve the existing problems and improve food sustainability has become crucial. 3D printing is expected to play a significant role in providing tangible contributions to the food industry in achieving sustainable development goals. The 3D food printing holds the potential to produce highly customized food in terms of shape, texture, flavor, structure and nutritional value and enable us to create new unique formulations and edible alternatives. The problem of whether the cost of the printed meal and 3D printing itself can be sustainably produced is becoming more and more important due to global concerns. This review intends to provide a comprehensive overview of 3D printed foods with an overview of the current printing methodologies, illustrating the technology's influencing factors, and its applications in personalized nutrition, packaging, value addition, and valorization aspects to fully integrate sustainability concerns thus exploring the potential of 3D food printing.

Self-limiting selective phase separation of graphene oxide and polymer composite solution

Homogeneous mixtures undergo phase separation to generate rich heterogeneous structures as well as enable complex physiological activity and delicate design of artificial materials. Beyond free space, the strong coupling between migrating components and spatial confinement plays a crucial role in determining the essential spatial compartment of phase separation, warranting further continuous exploration. Herein, we report the selective phase separation (SPS) behavior of polymers under a mobile two-dimensional (2D) confinement by graphene oxide (GO) sheets. The selection of a poor solvent triggers the occurrence of SPS in a homogeneous solution of GO and polymers. We reveal that the self-limiting spatial confinement of GO sheets leads to the migration of polymers to form independent and continuous phase in 2D confinement. We examine the quantitative rule of size and continuity of polymer phases in correlation with solvent properties and solute constitutes. The observed SPS allows the facile generation of heterogenous nanostructures in GO/polymer composites. We initiate a SPS wet-spinning to fabricate radial heterogenous fibrous graphene composite fibers with ultrahigh elongation at break and superior flexibility. The observed SPS can inspire more exceptional phase separation behaviors under mobile 2D confinement and offers a facile method to delicately design 2D heterogeneous nanostructured materials.

Recent innovations in interfacial strategies for DLP 3D printing process optimization

Three-dimensional (3D) printing, also known as additive manufacturing, is capable of transforming computer-aided designs into intricate structures directly and on demand. This technology has garnered significant attention in recent years. Among the various approaches, digital light processing (DLP) 3D printing, which utilizes polymers or prepolymers as the ink, has emerged as the leading new technology, driven by high demand across diverse fields such as customized production, healthcare, education, and art design. DLP 3D printing technology employs cured slices as molding units and is recognized for its potential to achieve both high printing speed and resolution. Recent insights into the DLP printing process highlight its inherent interface transformations between liquid and solid states. This review summarizes key aspects of the printing process, speed, precision, and material diversity optimization, from the view of interfacial interactions between solid and liquid phases which are influenced by resin formation, curing surfaces and light source properties. These interactions include those at the liquid resin-UV pattern interface, the cured structure-curing surface interface, the liquid resin-curing surface interface, and the liquid resin-cured structure interface, each contributing to the unique characteristics of the printed results. Finally, this review addresses the current challenges and limitations of DLP 3D printing, providing valuable insights for future improvements and guiding potential innovations in the field.

A Versatile In Situ Precipitation Assisted Direct-Write-3D Printing Strategy for Skinless Hierarchical Porous Polymeric Scaffolds

Skinless, hierarchical porous 3D polymer scaffolds are of critical importance in tissue engineering, enabling improved cell infiltration, nutrient, metabolite and energy exchange, and biomimetic structures, crucial for regenerative medicine, drug delivery, and advanced material applications. However, it is still a great challenge to construct this kind of material with traditional 3D printing techniques. Herein, a novel simple, and versatile in situ precipitation-assisted direct-write-3D printing strategy for skinless, hierarchical porous 3D scaffolds is reported. Homogenous ink containing molecularly dissolved fructose (soluble porogen molecule) and polymer (whether it is hydrophilic, hydrophobic or amphiphilic) is directly extruded into a nonsolvent bath, where simultaneously solidification of the polymer and in situ precipitation of the porogen molecules both on the exterior surface and inside the separated polymer fibers happen. Subsequently, by simply leaching the in situ formed porogen particles, skinless hierarchical porous polymeric 3D scaffolds can be obtained. It is believed that 3D printing, polymer/macromolecule-based scaffolds, especially the skinless hierarchical porous biomaterials, and the tissue engineering market can benefit tremendously from this simple and versatile approach.

Digital Light Processing (DLP) 3D Printing Fabrication of Hydrophobic Meshes Incorporating Fluorinated and Silicone-Based Acrylates Combined with Surface Engineering: Comparison of Their Oil-Water Separation Efficiency

Hydrophobic materials have been fabricated by DLP vat photopolymerization of isobornyl acrylate-based resins with chemical modification and/or surface geometry engineering. Fluorinated and polydimethylsiloxane (PDMS)-based acrylic monomers are used for chemical modification and are incorporated into the printed materials. The water wettability was significantly reduced and plateaued with as low as 5% (w/w) of the auxillary hydrophobic monomer. Regarding surface geometry, meshes with different pore sizes are 3D printed, and the surface hydrophobicity increased with the pore size. We compare the oil-water separation efficiency of the 3D-printed meshes hydrophobized by these three approaches. It was found that the isobornyl acrylate-based resin already demonstrated separation at the optimum pore size. Modification with PDMS showed a further improvement in separation efficiency, whereas no significant increase was observed by use of the fluorinated monomer. This highlights that careful design of surface geometry should be considered to avoid the use of environmentally unfriendly and potentially toxic chemicals when making hydrophobic materials.

3D Printing MXene-Based Electrodes for Supercapacitors

3D printing, as an advanced and promising strategy for processing electrode for energy storage devices, such as supercapacitors and batteries, has garnered considerable interest in recent decades. The interest in 3D printed electrodes stems from its exceptional performance and manufacturing features, including customized sizes and shapes and the layer-by-layer processing principle, etc., especially integrating with MXene which allows the manufacturing of electrodes from different raw materials and possessing desired electrochemical properties. Herculean challenges, such as material compatibility of the printing inks, nondurable interfacial or bulk mechanical strength of the printed electrodes, and sometimes the low capacitance, lead to inferior electrochemical performance and hinder the practical applications of this promising technology. In this review, we firstly summarize the representative 3D printing methods, then, review the MXene-based 3D printing electrodes made from different materials, and last, provide electrochemical performance of 3D printing MXene-based electrodes for supercapacitors. Furthermore, based on a summary on the recent progress, an outlook on these promising electrodes for sustainable energy devices is provided. We anticipate that this review could provide some insights into overcoming the challenges and achieving more remarkable electrochemical performance of 3D printing supercapacitor electrodes and offer perspectives in the future for emerging energy devices.

Scalable Macroscopic Engineering from Polymer-Based Nanoscale Building Blocks: Existing Challenges and Emerging Opportunities

Natural materials exhibit exceptional properties due to their hierarchical structures spanning from the nano- to the macroscale. Replicating these intricate spatial arrangements in synthetic materials presents a significant challenge as it requires precise control of nanometric features within large-scale structures. Addressing this challenge depends on developing methods that integrate assembly techniques across multiple length scales to construct multiscale-structured synthetic materials in practical, bulk forms. Polymers and polymer-hybrid nanoparticles, with their tunable composition and structural versatility, are promising candidates for creating hierarchically organized materials. This review highlights advances in scalable techniques for nanoscale organization of polymer-based building blocks within macroscopic structures, including block copolymer self-assembly with additive manufacturing, polymer brush nanoparticles capable of self-assembling into larger, ordered structures, and direct-write colloidal assembly. These techniques offer promising pathways toward the scalable fabrication of materials with emergent properties suited for advanced applications such as bioelectronic interfaces, artificial muscles, and other biomaterials.

The role of liquid-liquid phase separation in the disease pathogenesis and drug development

Misfolding and aggregation of specific proteins are associated with liquid-liquid phase separation (LLPS), and these protein aggregates can interfere with normal cellular functions and even lead to cell death, possibly affecting gene expression regulation and cell proliferation. Therefore, understanding the role of LLPS in disease may help to identify new mechanisms or therapeutic targets and provide new strategies for disease treatment. There are several ways to disrupt LLPS, including screening small molecules or small molecule drugs to target the upstream signaling pathways that regulate the LLPS process, selectively dissolve and destroy RNA droplets or protein aggregates, regulate the conformation of mutant protein, activate the protein degradation pathway to remove harmful protein aggregates. Furthermore, harnessing the mechanism of LLPS can improve drug development, including preparing different kinds of drug delivery carriers (microneedles, nanodrugs, imprints), regulating drug internalization and penetration behaviors, screening more drugs to overcome drug resistance and enhance receptor signaling. This review initially explores the correlation between aberrant LLPS and disease, highlighting the pivotal role of LLPS in preparing drug development. Ultimately, a comprehensive investigation into drug-mediated regulation of LLPS processes holds significant scientific promise for disease management.

Localized Ionic Reinforcement of Double Network Granular Hydrogels

Nature produces soft materials with fascinating combinations of mechanical properties. For example, the mussel byssus embodies a combination of stiffness and toughness, a feature that is unmatched by synthetic hydrogels. Key to enabling these excellent mechanical properties are the well-defined structures of natural materials and their compositions controlled on lengths scales down to tens of nanometers. The composition of synthetic materials can be controlled on a micrometer length scale if processed into densely packed microgels. However, these microgels are typically soft. Microgels can be stiffened by enhancing interactions between particles, for example through the formation of covalent bonds between their surfaces or a second interpenetrating hydrogel network. Nonetheless, changes in the composition of these synthetic materials occur on a micrometer length scale. Here, 3D printable load-bearing granular hydrogels are introduced whose composition changes on the tens of nanometer length scale. The hydrogels are composed of jammed microgels encompassing tens of nm-sized ionically reinforced domains that increase the stiffness of double network granular hydrogels up to 18-fold. The printability of the ink and the local reinforcement of the resulting granular hydrogels are leveraged to 3D print a butterfly with composition and structural changes on a tens of nanometer length scale.

Structural Functions of 3D-Printed Polymer Scaffolds in Regulating Cell Fates and Behaviors for Repairing Bone and Nerve Injuries

Tissue repair and regeneration, such as bone and nerve restoration, face significant challenges due to strict regulations within the immune microenvironment, stem cell differentiation, and key cell behaviors. The development of 3D scaffolds is identified as a promising approach to address these issues via the efficiently structural regulations on cell fates and behaviors. In particular, 3D-printed polymer scaffolds with diverse micro-/nanostructures offer a great potential for mimicking the structures of tissue. Consequently, they are foreseen as promissing pathways for regulating cell fates, including cell phenotype, differentiation of stem cells, as well as the migration and the proliferation of key cells, thereby facilitating tissue repairs and regenerations. Herein, the roles of structural functions of 3D-printed polymer scaffolds in regulating the fates and behaviors of numerous cells related to tissue repair and regeneration, along with their specific influences are highlighted. Additionally, the challenges and outlooks associated with 3D-printed polymer scaffolds with various structures for modulating cell fates are also discussed.

Photocurable Foam for Three-Dimensional-Printed Porous Structures

In this research, a foam three-dimensional (3D) printing method using digital light processing (DLP) technology was developed to fabricate 3D-printed porous structures. To address the challenges in preparing DLP precursor foam fluid, we designed a specialized foaming device. This device enables the precursor solution to be blended with air, resulting in a stable foam precursor with an adjustable air/liquid fraction and suitable fluidity, crucially enhancing the gas-liquid contact time for the printing process. By manipulation of fluid flow rates, cycle counts, and gas/liquid ratios, one can easily prepare uniform foams with precise control over the pore size and porosity. To avoid significant volume reduction during ultraviolet (UV) curing, nanoparticle fillers were introduced into the network to prevent collapse of the foam structure. Furthermore, the inclusion of an UV absorber enhanced the quality of the printing process by addressing the limitations associated with particle scattering and reflection. The DLP process can readily fabricate intricate structures, featuring a planar resolution below 30 μm and a printing accuracy of less than 1%. Several examples were also demonstrated to highlight the advantages of this technology and its ability to directly print custom foam structures, thereby saving time and material resources.

3D-printed microrobots for biomedical applications

Microrobots, which can perform tasks in difficult-to-reach parts of the human body under their own or external power supply, are potential tools for biomedical applications, such as drug delivery, microsurgery, imaging and monitoring, tissue engineering, and sensors and actuators. Compared with traditional fabrication methods for microrobots, recent improvements in 3D printers enable them to print high-precision microrobots, breaking through the limitations of traditional micromanufacturing technologies that require high skills for operators and greatly shortening the design-to-production cycle. Here, this review first introduces typical 3D printing technologies used in microrobot manufacturing. Then, the structures of microrobots with different functions and application scenarios are discussed. Next, we summarize the materials (body materials, propulsion materials and intelligent materials) used in 3D microrobot manufacturing to complete body construction and realize biomedical applications (e.g., drug delivery, imaging and monitoring). Finally, the challenges and future prospects of 3D printed microrobots in biomedical applications are discussed in terms of materials, manufacturing and advancement.

A 3D printable near-infrared triggered hydrogel with MoS2 as the crosslink center for tissue repair

Near-infrared (NIR) light, compared with ultraviolet (UV) light, has a stronger tissue penetration ability and is widely used in the medical field. However, few hydrogels can be triggered by NIR. Here, a modular polymer-nanosheet (metal disulfide) (PNS) hydrogel system was proposed, which can be photo-crosslinked through photothermal conversion under NIR light. MoS2, a transition-metal dichalcogenide, was used as a crosslink center in PNS hydrogels. Mo and S (from thiolated polymers), which are essential for gelation, were discovered to have new bonds. Furthermore, 3D printing of NIR-triggered PNS hydrogels was achieved conceptually with masked NIR. Moreover, multiple hydrogels and metal disulfides were applicable in this modular gelation system. This study indicated that these PNS hydrogels have great potential in many smart biomedical applications, including wearable sensors, noninvasive in vivo 3D bioprinting, and tissue repair substitutes.

Multimaterial 3D and 4D Bioprinting of Heterogenous Constructs for Tissue Engineering

Additive manufacturing (AM), which is based on the principle of layer-by-layer shaping and stacking of discrete materials, has shown significant benefits in the fabrication of complicated implants for tissue engineering (TE). However, many native tissues exhibit anisotropic heterogenous constructs with diverse components and functions. Consequently, the replication of complicated biomimetic constructs using conventional AM processes based on a single material is challenging. Multimaterial 3D and 4D bioprinting (with time as the fourth dimension) has emerged as a promising solution for constructing multifunctional implants with heterogenous constructs that can mimic the host microenvironment better than single-material alternatives. Notably, 4D-printed multimaterial implants with biomimetic heterogenous architectures can provide a time-dependent programmable dynamic microenvironment that can promote cell activity and tissue regeneration in response to external stimuli. This paper first presents the typical design strategies of biomimetic heterogenous constructs in TE applications. Subsequently, the latest processes in the multimaterial 3D and 4D bioprinting of heterogenous tissue constructs are discussed, along with their advantages and challenges. In particular, the potential of multimaterial 4D bioprinting of smart multifunctional tissue constructs is highlighted. Furthermore, this review provides insights into how multimaterial 3D and 4D bioprinting can facilitate the realization of next-generation TE applications.

Toward Multiscale, Multimaterial 3D Printing

Biological materials and organisms possess the fundamental ability to self-organize, through which different components are assembled from the molecular level up to hierarchical structures with superior mechanical properties and multifunctionalities. These complex composites inspire material scientists to design new engineered materials by integrating multiple ingredients and structures over a wide range. Additive manufacturing, also known as 3D printing, has advantages with respect to fabricating multiscale and multi-material structures. The need for multifunctional materials is driving 3D printing techniques toward arbitrary 3D architectures with the next level of complexity. In this paper, the aim is to highlight key features of those 3D printing techniques that can produce either multiscale or multimaterial structures, including innovations in printing methods, materials processing approaches, and hardware improvements. Several issues and challenges related to current methods are discussed. Ultimately, the authors also provide their perspective on how to realize the combination of multiscale and multimaterial capabilities in 3D printing processes and future directions based on emerging research.

3D Printing and Blue Sustainability: Taking Advantage of Process-Induced Defects for the Metallic Ion Removal from Water

Additive manufacturing (AM), commonly known as 3D printing, allows for the manufacturing of complex systems that are not possible using traditional manufacturing methods. Nevertheless, some disadvantages are attributed to AM technologies. One of the most often referred to is the defects of the produced components, particularly the porosity. One approach to solving this problem is to consider it as a non-problem, i.e., taking advantage of the defects. Commercially, LAY-FOMM®60 polymer was successfully used in AM through a material extrusion process. This filament is a blend of two polymers, one of them soluble in water, allowing, after its removal from the printed components, the increase in porosity. The defects produced were exploited to evaluate the metallic ion removal capacity of manufactured components using non-potable tap water. Two experimental setups, continuous and ultrasound-assisted methods, were compared, concerning their water cleaning capacity. Results revealed that continuous setup presented the highest metallic ion removal capacity (>80%) for the following three studied metallic ions: iron, copper, and zinc. High water swelling capacity (~80%) and the increase in porosity of 3D-printed parts played a significant role in the ion sorption capacity. The developed strategy could be considered a custom and affordable alternative to designing complex filtration/separation systems for environmental and wastewater treatment applications.

Thermal-Rectified Gradient Porous Polymeric Film for Solar-Thermal Regulatory Cooling

Solar-thermal regulation concerning thermal insulation and solar modulation is pivotal for cooling textiles and smart buildings. Nevertheless, a contradiction arises in balancing the demand to prevent external heat infiltration with the efficient dissipation of excess heat from enclosed spaces. Here, a concentration-gradient polymerization strategy is presented for fabricating a gradient porous polymeric film comprising interconnected polymeric microspheres. This method involves establishing an electric field-driven gradient distribution of charged crosslinkers in the precursor solution, followed by subsequent polymerization and freeze-drying processes. The resulting porous film exhibits a significant porosity gradient along its thickness, leading to exceptional unidirectional thermal insulation capabilities with a thermal rectification factor of 21%. The gradient porous film, with its thermal rectification properties, effectively reconciles the conflicting demands of diverse thermal conductivity for cooling unheated and spontaneously heated enclosed spaces. Consequently, the gradient porous film demonstrates remarkable enhancements in solar-thermal management, achieving temperature reductions of 3.0 and 4.1 °C for unheated and spontaneously heated enclosed spaces, respectively, compared to uniform porous films. The developed gradient-structured porous film thus holds promise for the development of thermal-rectified materials tailored to regulate solar-thermal conditions within enclosed environments.

3D printing of reactive macroporous polymers via thiol-ene chemistry and polymerization-induced phase separation

Using thiol-ene chemistry, polymerization-induced phase separation, and DLP 3D printing, we present a method for manufacturing reactive macroporous 3D structures. This approach enables the fabrication of structures with tunable physicochemical properties and compressibility. Moreover, it facilitates post-functionalization through thiol-Michael addition reactions, thereby expanding performance and application potential.

Liquid phase detection in the miniature scale. Microfluidic and capillary scale measurement and separation systems. A tutorial review

Microfluidic and capillary devices are increasingly being used in analytical applications while their overall size keeps decreasing. Detection sensitivity for these microdevices gains more importance as device sizes and consequently, sample volumes, decrease. This paper reviews optical, electrochemical, electrical, and mass spectrometric detection methods that are applicable to capillary scale and microfluidic devices, with brief introduction to the principles in each case. Much of this is considered in the context of separations. We do consider theoretical aspects of separations by open tubular liquid chromatography, arguably the most potentially fertile area of separations that has been left fallow largely because of lack of scale-appropriate detection methods. We also examine the theoretical basis of zone electrophoretic separations. Optical detection methods discussed include UV/Vis absorbance, fluorescence, chemiluminescence and refractometry. Amperometry is essentially the only electrochemical detection method used in microsystems. Suppressed conductance and especially contactless conductivity (admittance) detection are in wide use for the detection of ionic analytes. Microfluidic devices, integrated to various mass spectrometers, including ESI-MS, APCI-MS, and MALDI-MS are discussed. We consider the advantages and disadvantages of each detection method and compare the best reported limits of detection in as uniform a format as the available information allows. While this review pays more attention to recent developments, our primary focus has been on the novelty and ingenuity of the approach, regardless of when it was first proposed, as long as it can be potentially relevant to miniature platforms.

Spongy Ag Foam for Soft and Stretchable Strain Gauges

Strain gauges, particularly for wearable sensing applications, require a high degree of stretchability, softness, sensitivity, selectivity, and linearity. They must also steer clear of challenges such as mechanical and electrical hysteresis, overshoot behavior, and slow response/recovery times. However, current strain gauges face challenges in satisfying all of these requirements at once due to the inevitable trade-offs between these properties. Here, we present an innovative method for creating strain gauges from spongy Ag foam through a steam-etching process. This method simplifies the traditional, more complex, and costly manufacturing techniques, presenting an eco-friendly alternative. Uniquely, the strain gauges crafted from this method achieve an unparalleled gauge factor greater than 8 × 103 at strains exceeding 100%, successfully meeting all required attributes without notable trade-offs. Our work includes systematic investigations that reveal the intricate structure-property-performance relationship of the spongy Ag foam with practical demonstrations in areas such as human motion monitoring and human-robot interaction. These breakthroughs pave the way for highly sensitive and selective strain gauges, showing immediate applicability across a wide range of wearable sensing applications.

Functionally Gradient Macroporous Polymers: Emulsion Templating Offers Control over Density, Pore Morphology, and Composition

Gradient macroporous polymers were produced by polymerization of emulsion templates comprising a continuous monomer phase and an internal aqueous template phase. To produce macroporous polymers with gradient composition, pore size, and foam density, we varied the template formulation, droplet size, and internal phase ratio of emulsion templates continuously and stacked those prior to polymerization. Using the outlined approach, it is possible to vary one property along the resulting macroporous polymer while retaining the other properties. The elastic moduli and crush strengths change along the gradient of the macroporous polymers; their mechanical properties are dominated by those of the weakest layers in the gradient. Macroporous polymers with gradient chemical composition and thus stiffness provide both high impact load and energy adsorption, rendering the gradient foam suitable for impact protective applications. We show that dual-dispensing and simultaneous blending of two different emulsion formulations in various ratios results in a fine, bidirectional change of the template composition, enabling the production of true gradient macroporous polymers with a high degree of design freedom.

Intelligent Biomaterialomics: Molecular Design, Manufacturing, and Biomedical Applications

Materialomics integrates experiment, theory, and computation in a high-throughput manner, and has changed the paradigm for the research and development of new functional materials. Recently, with the rapid development of high-throughput characterization and machine-learning technologies, the establishment of biomaterialomics that tackles complex physiological behaviors has become accessible. Breakthroughs in the clinical translation of nanoparticle-based therapeutics and vaccines have been observed. Herein, recent advances in biomaterials, including polymers, lipid-like materials, and peptides/proteins, discovered through high-throughput screening or machine learning-assisted methods, are summarized. The molecular design of structure-diversified libraries; high-throughput characterization, screening, and preparation; and, their applications in drug delivery and clinical translation are discussed in detail. Furthermore, the prospects and main challenges in future biomaterialomics and high-throughput screening development are highlighted.

A review of the recent achievements and future trends on 3D printed microfluidic devices for bioanalytical applications

3D printing has revolutionized the manufacturing process of microanalytical devices by enabling the automated production of customized objects. This technology promises to become a fundamental tool, accelerating investigations in critical areas of health, food, and environmental sciences. This microfabrication technology can be easily disseminated among users to produce further and provide analytical data to an interconnected network towards the Internet of Things, as 3D printers enable automated, reproducible, low-cost, and easy fabrication of microanalytical devices in a single step. New functional materials are being investigated for one-step fabrication of highly complex 3D printed parts using photocurable resins. However, they are not yet widely used to fabricate microfluidic devices. This is likely the critical step towards easy and automated fabrication of sophisticated, complex, and functional 3D-printed microchips. Accordingly, this review covers recent advances in the development of 3D-printed microfluidic devices for point-of-care (POC) or bioanalytical applications such as nucleic acid amplification assays, immunoassays, cell and biomarker analysis and organs-on-a-chip. Finally, we discuss the future implications of this technology and highlight the challenges in researching and developing appropriate materials and manufacturing techniques to enable the production of 3D-printed microfluidic analytical devices in a single step.

Purification of monoclonal antibodies using novel 3D printed ordered stationary phases

3D printing offers the unprecedented ability to fabricate chromatography stationary phases with bespoke 3D morphology as opposed to traditional packed beds of spherical beads. The restricted range of printable materials compatible with chromatography is considered a setback for its industrial implementation. Recently, we proposed a novel ink that exhibits favourable printing performance (printing time ∼100 mL/h, resolution ∼200 µm) and broadens the possibilities for a range of chromatography applications thanks to its customisable surface chemistry. In this work, this ink was used to fabricate 3D printed ordered columns with 300 µm channels for the capture and polishing of therapeutic monoclonal antibodies. The columns were initially assessed for leachables and extractables, revealing no material propensity for leaching. Columns were then functionalised with protein A and SO3 ligands to obtain affinity and strong cation exchangers, respectively. 3D printed protein A columns showed >85 % IgG recovery from harvested cell culture fluid with purities above 98 %. Column reusability was evaluated over 20 cycles showing unaffected performance. Eluate samples were analysed for co-eluted protein A fragments, host cell protein and aggregates. Results demonstrate excellent HCP clearance (logarithmic reduction value of > 2.5) and protein A leakage in the range of commercial affinity resins (<100 ng/mg). SO3 functionalised columns employed for polishing achieved removal of leaked Protein A (down to 10 ng/mg) to meet regulatory expectations of product purity. This work is the first implementation of 3D printed columns for mAb purification and provides strong evidence for their potential in industrial bioseparations.

Solid-state, liquid-free ion-conducting elastomers: rising-star platforms for flexible intelligent devices

Soft ionic conductors have emerged as a powerful toolkit to engineer transparent flexible intelligent devices that go beyond their conventional counterparts. Particularly, due to their superior capacities of eliminating the evaporation, freezing and leakage issues of the liquid phase encountered with hydrogels, organohydrogels and ionogels, the emerging solid-state, liquid-free ion-conducting elastomers have been largely recognized as ideal candidates for intelligent flexible devices. However, despite their extensive development, a comprehensive and timely review in this emerging field is lacking, particularly from the perspective of design principles, advanced manufacturing, and distinctive applications. Herein, we present (1) the design principles and intriguing merits of solid-state, liquid-free ion-conducting elastomers; (2) the methods to manufacture solid-state, liquid-free ion-conducting elastomers with preferential architectures and functions using advanced technologies such as 3D printing; (3) how to leverage solid-state, liquid-free ion-conducting elastomers in exploiting advanced applications, especially in the fields of flexible wearable sensors, bioelectronics and energy harvesting; (4) what are the unsolved scientific and technical challenges and future opportunities in this multidisciplinary field. We envision that this review will provide a paradigm shift to trigger insightful thinking and innovation in the development of intelligent flexible devices and beyond.

Advanced Nanomaterials in Medical 3D Printing

3D printing is now recognized as a significant tool for medical research and clinical practice, leading to the emergence of medical 3D printing technology. It is essential to improve the properties of 3D-printed products to meet the demand for medical use. The core of generating qualified 3D printing products is to develop advanced materials and processes. Taking advantage of nanomaterials with tunable and distinct physical, chemical, and biological properties, integrating nanotechnology into 3D printing creates new opportunities for advancing medical 3D printing field. Recently, some attempts are made to improve medical 3D printing through nanotechnology, providing new insights into developing advanced medical 3D printing technology. With high-resolution 3D printing technology, nano-structures can be directly fabricated for medical applications. Incorporating nanomaterials into the 3D printing material system can improve the properties of the 3D-printed medical products. At the same time, nanomaterials can be used to expand novel medical 3D printing technologies. This review introduced the strategies and progresses of improving medical 3D printing through nanotechnology and discussed challenges in clinical translation.

3D-Printed Porous Supramolecular Sorbents for Cobalt Recycling

Electronic waste recycling is a recognized global challenge that requires new strategies to bind and release critical materials selectively, such as cobalt present in lithium-ion batteries. To address this challenge, hierarchical 3D-printed porous polymer scaffolds bearing supramolecular receptors were prepared using vat photopolymerization and their cobalt binding profiles were examined as a function of matrix polarity. By combining high-resolution digital light processing (DLP) with polymerization-induced phase separation (PIPS), functional acrylic copolymer networks with micrometer-level precision of geometry and nanometer-level pores were generated. Covalent integration of a methacrylate-functionalized bisdicyclohexyl acetamide (BDCA-MA) receptor enabled binding and release of cobalt(II) chloride (CoCl2) via a solvent polarity switch mechanism involving a change in solvent from ethanol to water. The present structures proved reusable as shown by sustained high binding efficiency over five bind and release cycles. This platform represents a "green" and energy conscious method for future electronic waste recycling.

Modeling the competition between phase separation and polymerization under explicit polydispersity

The dynamics of phase separation for polymer blends is important in determining the final morphology and properties of polymer materials; in practical applications, this phase separation can be controlled by coupling to polymerization reaction kinetics via a process called 'polymerization-induced phase separation'. We develop a phase-field model for a polymer melt blend using a polymerizing Cahn-Hilliard (pCH) formalism to understand the fundamental processes underlying phase separation behavior of a mixture of two species independently undergoing linear step-growth polymerization. In our method, we explicitly model polydispersity in these systems to consider different molecular-weight components that will diffuse at different rates. We first show that this pCH model predicts results consistent with the Carothers predictions for step-growth polymerization kinetics, the Flory-Huggins theory of polymer mixing, and the classical predictions of spinodal decomposition in symmetric polymer blends. The model is then used to characterize (i) the competition between phase separation dynamics and polymerization kinetics, and (ii) the effect of unequal reaction rates between species. For large incompatibility between the species (i.e. high χ), our pCH model demonstrates that the strength for phase separation directly corresponds to the kinetics of phase separation. We find that increasing the reaction rate k̃, first induces faster phase separation but this trend reverses as we further increase k̃ due to the competition between molecular diffusion and polymerization. In this case, phase separation is delayed for faster polymerization rates due to the rapid accumulation of slow-moving, high molecular weight components.

Robust Superhydrophobicity through Surface Defects from Laser Powder Bed Fusion Additive Manufacturing

The robustness of superhydrophobic objects conflicts with both the inevitable introduction of fragile micro/nanoscale surfaces and three-dimensional (3D) complex structures. The popular metal 3D printing technology can manufacture robust metal 3D complex components, but the hydrophily and mass surface defects restrict its diverse application. Herein, we proposed a strategy that takes the inherent ridges and grooves' surface defects from laser powder bed fusion additive manufacturing (LPBF-AM), a metal 3D printing process, as storage spaces for hydrophobic silica (HS) nanoparticles to obtain superhydrophobic capacity and superior robustness. The HS nanoparticles stored in the grooves among the laser-melted tracks serve as the hydrophobic guests, while the ridges' metal network provides the mechanical strength, leading to robust superhydrophobic objects with desired 3D structures. Moreover, HS nanoparticles coated on the LPBF-AM-printed surface can inhibit corrosion behavior caused by surface defects. It was found that LPBF-AM-printed objects with HS nanoparticles retained superior hydrophobicity after 150 abrasion cycles (~12.5 KPa) or 50 cycles (~37.5 KPa). Furthermore, LPBF-AM-printed ships with superhydrophobic coating maintained great water repellency even after 10,000 cycles of seawater swashing, preventing dynamic corrosion upon surfaces. Our proposed strategy, therefore, provides a low-cost, highly efficient, and robust superhydrophobic coating, which is applicable to metal 3D architectures toward corrosion-resistant requirements.

Effect of Macromolecular Structure on Phase Separation Regime in 3D Printed Materials

In this study, the fabrication of 3D-printed polymer materials with controlled phase separation using polymerization induced microphase separation (PIMS) via photoinduced 3D printing is demonstrated. While many parameters affecting the nanostructuration in PIMS processes are extensively investigated, the influence of the chain transfer agent (CTA) end group, i.e., Z-group, of macromolecular chain transfer agent (macroCTA) remains unclear as previous research has exclusively employed trithiocarbonate as the CTA end group. Herein, the effect of macroCTAs containing four different Z-groups on the formation of nanostructure of 3D printed materials is explored. The results show that the different Z-groups lead to distinct network formation and phase separation behaviors between the resins, influencing both the 3D printing process and the resulting material properties. Specifically, less reactive macroCTAs toward acrylic radical addition, such as O-alkyl xanthate and N-alkyl-N-aryl dithiocarbamate, result in translucent and brittle materials with macrophase separation morphology. In contrast, more reactive macroCTAs such as S-alkyl trithiocarbonate and 4-chloro-3,5-dimethylpyrazo dithiocarbamate produce transparent and rigid materials with nano-scale morphology. Findings of this study provide a novel approach to manipulate the nanostructure and properties of 3D printed PIMS materials, which can have important implications for materials science and engineering.

Rapid Electrohydrodynamic-Driven Pattern Replication over a Large Area via Ultrahigh Voltage Pulses

Despite the prospects of electrohydrodynamic instability patterning (EHIP), poor process parameter controllability is a significant challenge in uniform large-scale nanopatterning. Herein, we introduce a EHIP process using an ultrahigh electric field (>108 V/m) to effectively accelerate the pattern growth evolution. Owing to the strong dependence on a temporal parameter (1/τm) of the field strength, our method not only reduces the completion time of pattern growth but also overcomes critical parametric restrictions on the pattern replication, thereby enhancing the replicated pattern quality in three dimensions. The pattern can be uniformly replicated over the entire film surface even without a perfectly uniform air gap, which has been severely difficult in the conventional method. To further demonstrate how straightforward yet versatile our approach is, we applied our EHIP approach to successfully replicate the densely packed nanostructures of cicada wings.

3D Printing Hierarchically Nano-Ordered Structures

Natural materials are composed of a limited number of molecular building blocks and their exceptional properties are governed by their hierarchical structure. However, this level of precision is unattainable with current state-of-the-art materials for 3D printing. Herein, new self-assembled printable materials based on block copolymers (BCPs) enabling precise control of the nanostructure in 3D are presented. In particular, well-defined BCPs consisting of poly(styrene) (PS) and a polymethacrylate-based copolymer decorated with printable units are selected as suitable self-assembled materials and synthesized using controlled radical polymerization. The synthesized library of BCPs are utilized as printable formulations for the fabrication of complex 3D microstructures using two-photon laser printing. By fine-tuning the BCP composition and solvent in the formulations, the fabrication of precise 3D nano-ordered structures is demonstrated for the first time. A key point of this work is the achievement of controlled nano-order within the entire 3D structures. Thus, imaging of the cross-sections of the 3D printed samples is performed, enabling the visualization also from the inside. The presented versatile approach is expected to create new avenues for the precise design of functional polymer materials suitable for high-resolution 3D printing exhibiting tailor-made nanostructures.

3D Printed Customizable Microsampling Devices for Neuroscience Applications

Multifunctional devices that incorporate chemical or physical measurements combined with ways to manipulate brain tissue via drug delivery, electrical stimulation, or light for optogenetics are desired by neuroscientists. The next generation in vivo brain devices will likely utilize the extensive flexibility and rapid processing of 3D printing. This Perspective demonstrates how close we are to this reality for advanced neuroscience measurements. 3D printing provides the opportunity to improve microsampling-based devices in ways that have not been previously available. Not only can 3D printing be used for actual device creation, but it can also allow printing of peripheral objects necessary to assemble functional devices. The most probable 3D printing set up for microsampling devices with appropriate nm to μm feature size will likely require 2-photon polymerization-based printers. This Perspective describes the advantages and challenges for 3D printing of microsampling devices as an initial step to meet the next generation device needs of neuroscientists.

Sequence-Encoded Differences in Phase Separation Enable Formation of Resilin-like Polypeptide-Based Microstructured Hydrogels

Microstructured hydrogels are promising platforms to mimic structural and compositional heterogeneities of the native extracellular matrix (ECM). The current state-of-the-art soft matter patterning techniques for generating ECM mimics can be limited owing to their reliance on specialized equipment and multiple time- and energy-intensive steps. Here, a photocross-linking methodology that traps various morphologies of phase-separated multicomponent formulations of compositionally distinct resilin-like polypeptides (RLPs) is reported. Turbidimetry and quantitative 1H NMR spectroscopy were utilized to investigate the sequence-dependent liquid-liquid phase separation of multicomponent solutions of RLPs. Differences between the intermolecular interactions of two different photocross-linkable RLPs and a phase-separating templating RLP were exploited for producing microstructured hydrogels with tunable control over pore diameters (ranging from 1.5 to 150 μm) and shear storage moduli (ranging from 0.2 to 5 kPa). The culture of human mesenchymal stem cells demonstrated high viability and attachment on microstructured hydrogels, suggesting their potential for developing customizable platforms for regenerative medicine applications.

Biomimetic scaffolds using triply periodic minimal surface-based porous structures for biomedical applications

The design of biomimetic porous scaffolds has been gaining attention in the biomedical sector lately. Shells, marine sponges, shark teeth, cancellous bone, sea urchin spine, and the armadillo armor structure are examples of biological systems that have already been studied to drive the design of innovative, porous, and multifunctional structures. Among these, triply periodic minimal surfaces (TPMSs) have attracted the attention of scientists for the fabrication of biomimetic porous scaffolds. The interest stems from their outstanding properties, which include mathematical controllable geometry features, highly interconnected porous architectures, high surface area to volume ratio, less stress concentration, tunable mechanical properties, and increased permeability. All these distinguishing features enable better cell adhesion, optimal integration to the surrounding tissue avoiding stress shieldings, a good permeability of fluid media and oxygen, and the possibility of vascularization. However, the sophisticated geometry of these TPMS-based structures has proven challenging to fabricate by conventional methods. The emergence of additive manufacturing (AM) and the enhanced manufacturing freedoms and flexibility it guarantees could solve some of the bottlenecks, thus leading to a surge of interest in designing and fabricating such structures in this field. Also, the feasibility of using AM technologies allows for obtaining size programmable TPMS printable in various materials, from polymers to metal alloys. Here, a comprehensive overview of 3D-printed TPMS porous structures is provided from a design for additive manufacturing (DfAM) and application perspective. First, design strategies, geometry design algorithms, and related topological optimization are introduced according to diverse requirements. Based on that, the performance control of TPMS and the pros and cons of the different AM processes for fabricating TPMS scaffolds are summarized. Lastly, practical applications of 3D-printed biomimetic TPMS porous structures for the biomedical field are presented to clarify the advantages and potential of such structures.

Interfacial Regulation for 3D Printing based on Slice-Based Photopolymerization

3D printing, also known as additive manufacturing, can turn computer-aided designs into delicate structures directly and on demand by eliminating expensive molds, dies, or lithographic masks. Among the various technical forms, light-based 3D printing mainly involved the control of polymer-based matter fabrication and realized a field of manufacturing with high tunability of printing format, speed, and precision. Emerging slice- and light-based 3D-printing methods have prosperously advanced in recent years but still present challenges to the versatility of printing continuity, printing process, and printing details control. Herein, the field of slice- and light-based 3D printing is discussed and summarized from the view of interfacial regulation strategies to improve the printing continuity, printing process control, and the character of printed results, and several potential strategies to construct complex 3D structures of distinct characteristics with extra external fields, which are favorable for the further improvement and development of 3D printing, are proposed.

Robust Electrostatically Interactive Hydrogel Coatings for Macroscopic Supramolecular Assembly via Rapid Wet Adhesion

A macroscopic supramolecular assembly (MSA) refers to non-covalent interactions between building blocks over a micrometer scale, which provides insights into bio-/wet adhesion, self-healing, and so on and new fabrication strategies to heterogeneous structures and bio-scaffolds. The key to realize the MSA of rigid materials is pre-modifying a compliant coating known as a "flexible spacing coating" beneath the interactive moieties. However, available coatings are limited to polyelectrolyte multilayers with shortcomings of tedious fabrication, weak adhesion to substrates, susceptibility to external reagents, and so on. Here, we develop a facile method to induce a new "flexible spacing coating" of a poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel with electrostatic interactions to achieve MSA of diverse rigid materials (quartz, metal, rubber, and plastics). Selective self-assembly of positive-negative charged surfaces is observed by the naked eye under 3 min of shaking in water, providing strategies to rapid wet adhesion. The interfacial binding force between positive-negative interacted surfaces is 1018.1 ± 299.2 N/m², which is over two magnitudes larger than that of control groups, that is, positive-positive (24.4 ± 10.0 N/m²) and negative-negative (67.5 ± 16.7 N/m²) interacted surfaces. In situ force measurements and control experiments of identically charged building blocks have strongly supported the improved binding strength and chemical selectivity between interactive building blocks. The coating is advantageous with a simple fabrication, strong adhesion to materials, robust solvent tolerance to assembly solutions, and feasibility of photo-patterning. We envision that the above strategy would broaden the material choices of flexible spacing coatings for efficient MSA and new methods for rapid interfacial adhesion.

Photocurable 3D-Printable Systems with Controlled Porosity towards CO2 Air Filtering Applications

Porous organic polymers are versatile platforms, easily adaptable to a wide range of applications, from air filtering to energy devices. Their fabrication via vat photopolymerization enables them to control the geometry on a multiscale level, obtaining hierarchical porosity with enhanced surface-to-volume ratio. In this work, a photocurable ink based on 1,6 Hexanediol diacrylate and containing a high internal phase emulsion (HIPE) is presented, employing PLURONIC F-127 as a surfactant to generate stable micelles. Different parameters were studied to assess the effects on the morphology of the pores, the printability and the mechanical properties. The tests performed demonstrates that only water-in-oil emulsions were suitable for 3D printing. Afterwards, 3D complex porous objects were printed with a Digital Light Processing (DLP) system. Structures with large, interconnected, homogeneous porosity were fabricated with high printing precision (300 µm) and shape fidelity, due to the addition of a Radical Scavenger and a UV Absorber that improved the 3D printing process. The formulations were then used to build scaffolds with complex architecture to test its application as a filter for CO₂ absorption and trapping from environmental air. This was obtained by surface decoration with NaOH nanoparticles. Depending on the surface coverage, tested specimens demonstrated long-lasting absorption efficiency.

Current State-of-the-Art in Membrane Formation from Ultra-High Molecular Weight Polyethylene

One of the materials that attracts attention as a potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). One potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). The present review summarizes the results of studies carried out over the last 30 years in the field of preparation, modification and structure and property control of membranes made from ultrahigh molecular weight polyethylene. The review also presents a classification of the methods of membrane formation from this polymer and analyzes the conventional (based on the analysis of incomplete phase diagrams) and alternative (based on the analysis of phase diagrams supplemented by a boundary line reflecting the polymer swelling degree dependence on temperature) physicochemical concepts of the thermally induced phase separation (TIPS) method used to prepare UHMWPE membranes. It also considers the main ways to control the structure and properties of UHMWPE membranes obtained by TIPS and the original variations of this method. This review discusses the current challenges in UHMWPE membrane formation, such as the preparation of a homogeneous solution and membrane shrinkage. Finally, the article speculates about the modification and application of UHMWPE membranes and further development prospects. Thus, this paper summarizes the achievements in all aspects of UHMWPE membrane studies.

Superrepellent Porous Polymer Surfaces by Replication from Wrinkled Polydimethylsiloxane/Parylene F

Superrepellent surfaces, such as micro/nanostructured surfaces, are of key importance in both academia and industry for emerging applications in areas such as self-cleaning, drag reduction, and oil repellence. Engineering these surfaces is achieved through the combination of the required surface topography, such as porosity, with low-surface-energy materials. The surface topography is crucial for achieving high liquid repellence and low roll-off angles. In general, the combination of micro- and nanostructures is most promising in achieving high repellence. In this work, we report the enhancement of wetting properties of porous polymers by replication from wrinkled Parylene F (PF)-coated polydimethylsiloxane (PDMS). Fluorinated polymer foam “Fluoropor” serves as the low-surface-energy polymer. The wrinkled molds are achieved via the deposition of a thin PF layer onto the soft PDMS substrates. Through consecutive supercritical drying, superrepellent surfaces with a high surface porosity and a high water contact angle (CA) of >165° are achieved. The replicated surfaces show low roll-off angles (ROA) <10° for water and <21° for ethylene glycol. Moreover, the introduction of the micro-wrinkles to Fluoropor not only enhances its liquid repellence for water and ethylene glycol but also for liquids with low surface tension, such as n-hexadecane.

Low-Temperature Printed Hierarchically Porous Induced-Biomineralization Polyaryletherketone Scaffold for Bone Tissue Engineering

Polyetheretherketone (PEEK) as a popular orthopaedic implant is usually fabricated into a hierarchically porous structure for improving osteogenic activity. However, the applications are limited due to the excessively high processing temperature and uncontrollably tedious modification routes. Here, an amorphous polyaryletherketone with carboxyl groups (PAEK-COOH) is synthesized and fabricated to the hierarchically controllable porous scaffolds via a low-temperature 3D-printing process. The prepared PAEK-COOH scaffolds present controllable porous structures ranging from nano- to micro-scale, and their mechanical strengths are comparable to that of trabecular bone. More importantly, the in vitro experiments show that the nanoporous surface is conducive to promoting cellular adhesion, and carboxyl groups can induce hydroxyapatite mineralization via electrostatic interaction. The in vivo experiments demonstrate that the PAEK-COOH scaffolds offer much better osseointegration without additional active ingredients, compared to that of PEEK. Therefore, this work will not only develop a promising candidate for bone tissue engineering, but provide a viable method to design PAEK biomaterials.

Designing Nanostructured 3D Printed Materials by Controlling Macromolecular Architecture

Nanostructured polymeric materials play important roles in many advanced applications, however, controlling the morphologies of polymeric thermosets remains a challenge. This work uses multi-arm macroCTAs to mediate polymerization-induced microphase separation (PIMS) and prepare nanostructured materials via photoinduced 3D printing. The characteristic length scale of microphase-separated domains is determined by the macroCTA arm length, while nanoscale morphologies are controlled by the macroCTA architecture. Specifically, using 2- and 4- arm macroCTAs provides materials with different morphologies compared to analogous monofunctional linear macroCTAs at similar compositions. The mechanical properties of these nanostructured thermosets can also be tuned while maintaining the desired morphologies. Using multi-arm macroCTAs can thus broaden the scope of accessible nanostructures for extended applications, including the fabrication of actuators and potential drug delivery devices.