Tough,Resorbable Polycaprolactone-Based Bimodal Networks for Vat Polymerization 3D Printing

Vat polymerization allows for the accurate and fast fabrication of personalized implants and devices. While the technology advances rapidly and more materials become available, the fabrication of flexible yet tough resorbable materials for biomedical applications remains a challenge. Here, a formulation that can be 3D printed with high accuracy using vat polymerization, yielding materials that are tough, degradable, and non-toxic is presented. This unique combination of properties is obtained by combining a long-chain polycaprolactone macromonomer with a small molecule cross-linker. A wide range of properties is achieved by tuning the ratio of these components. The use of benzyl alcohol as a non-volatile, benign solvent enables fabrication on a low-cost desktop 3D printer, with an exposure time of 8 s per 50-micron layer. The 3D-printed networks are tough and elastic with a tensile strength of 11 MPa at 116% elongation at break. Cells attach and proliferate on the networks with a viability of >91%. The networks are fully degradable to soluble products. This new 3D printable material opens up a range of opportunities in biomedical engineering and personalized medicine.     

Surfactant‐Assisted Emulsion Self‐Assembly of Nanoparticles into Hollow Vesicle‐Like Structures and 2D Plates

The emulsion‐based self‐assembly of nanoparticles into low‐dimensional superparticles of hollow vesicle‐like assemblies is reported. Evaporation of the oil phase at relatively low temperatures from nanoparticle‐containing oil‐in‐water emulsion droplets leads to the formation of stable and uniform sub‐micrometer vesicle‐like assembly structures in water. This result is in contrast with those from many previously reported emulsion‐based self‐assembly methods, which produce solid spherical assemblies. It is found that extra surfactants in both the oil and water phases play a key role in stabilizing nanoscale emulsion droplets and capturing hollow assembly structures. Systematic investigation into what controls the morphology in emulsion self‐assembly is carried out, and the approach is extended to fabricate more complex rattle‐like structures and 2D plates. These results demonstrate that the emulsion‐based assembly is not limited to typical thermodynamic spherical assembly structures and can be used to fabricate various types of interesting low‐dimensional assembly structures.     

Ultraprecise 3D Printed Graphene Aerogel Microlattices on Tape for Micro Sensors and E-Skin

3D printed graphene aerogels hold promise for flexible sensing fields due to their flexibility, low density, conductivity, and piezo-resistivity. However, low printing accuracy/fidelity and stochastic porous networks have hindered both sensing performance and device miniaturization. Here, printable graphene oxide (GO) inks are formulated through modulating oxygen functional groups, which allows printing of self-standing 3D graphene oxide aerogel microlattice (GOAL) with an ultra-high printing resolution of 70 µm. The reduced GOAL (RGOAL) is then stuck onto the adhesive tape as a facile and large-scale strategy to adapt their functionalities into target applications. Benefiting from the printing resolution of 70 µm, RGOAL tape shows better performance and data readability when used as micro sensors and robot e-skin. By adjusting the molecular structure of GO, the research realizes regulation of rheological properties of GO hydrogel and the 3D printing of lightweight and ultra-precision RGOAL, improves the sensing accuracy of graphene aerogel electronic devices and realizes the device miniaturization, expanding the application of graphene aerogel devices to a broader field such as micro robots, which is beyond the reach of previous reports.     

A Review of 3D Printing Technologies for Soft Polymer Materials

Soft polymer materials, which are similar to human tissues, have played critical roles in modern interdisciplinary research. Compared with conventional methods, 3D printing allows rapid prototyping and mass customization and is ideal for processing soft polymer materials. However, 3D printing of soft polymer materials is still in the early stages of development and is facing many challenges including limited printable materials, low printing resolution and speed, and poor functionalities. The present review aims to summarize the ideas to address these challenges. It focuses on three points: 1) how to develop printable materials and make unprintable materials printable, 2) how to choose suitable methods and improve printing resolution, and 3) how to directly construct functional structures/systems with 3D printing. After a brief introduction on this topic, the mainstream 3D printing technologies for printing soft polymer materials are reviewed, with an emphasis on improving printing resolution and speed, choosing suitable printing techniques, developing printable materials, and printing multiple materials. Moreover, the state‐of‐the‐art advancements in multimaterial 3D printing of soft polymer materials are summarized. Furthermore, the revolutions brought about by 3D printing of soft polymer materials for applications similar to biology are highlighted. Finally, viewpoints and future perspectives for this emerging field are discussed.     

Direct‐Write Assembly of Microperiodic Silk Fibroin Scaffolds for Tissue Engineering Applications

Three–dimensional, microperiodic scaffolds of regenerated silk fibroin have been fabricated for tissue engineering by direct ink writing. The ink, which consisted of silk fibroin solution from the Bombyx mori silkworm, was deposited in a layer‐by‐layer fashion through a fine nozzle to produce a 3D array of silk fibers of diameter 5 µm. The extruded fibers crystallized when deposited into a methanol‐rich reservoir, retaining a pore structure necessary for media transport. The rheological properties of the silk fibroin solutions were investigated and the crystallized silk fibers were characterized for structure and mechanical properties by infrared spectroscopy and nanoindentation, respectively. The scaffolds supported human bone marrow‐derived mesenchymal stem cell (hMSC) adhesion, and growth. Cells cultured under chondrogenic conditions on these scaffolds supported enhanced chondrogenic differentiation based on increased glucosaminoglycan production compared to standard pellet culture. Our results suggest that 3D silk fibroin scaffolds may find potential application as tissue engineering constructs due to the precise control of their scaffold architecture and their biocompatibility.     

3D‐Printable Antimicrobial Composite Resins

3D printing is seen as a game‐changing manufacturing process in many domains, including general medicine and dentistry, but the integration of more complex functions into 3D‐printed materials remains lacking. Here, it is expanded on the repertoire of 3D‐printable materials to include antimicrobial polymer resins, which are essential for development of medical devices due to the high incidence of biomaterial‐associated infections. Monomers containing antimicrobial, positively charged quaternary ammonium groups with an appended alkyl chain are either directly copolymerized with conventional diurethanedimethacrylate/glycerol dimethacrylate (UDMA/GDMA) resin components by photocuring or prepolymerized as a linear chain for incorporation into a semi‐interpenetrating polymer network by light‐induced polymerization. For both strategies, dental 3D‐printed objects fabricated by a stereolithography process kill bacteria on contact when positively charged quaternary ammonium groups are incorporated into the photocurable UDMA/GDMA resins. Leaching of quaternary ammonium monomers copolymerized with UDMA/GDMA resins is limited and without biological consequences within 4–6 d, while biological consequences could be confined to 1 d when prepolymerized quaternary ammonium group containing chains are incorporated in a semi‐interpenetrating polymer network. Routine clinical handling and mechanical properties of the pristine polymer matrix are maintained upon incorporation of quaternary ammonium groups, qualifying the antimicrobially functionalized, 3D‐printable composite resins for clinical use.     

High‐Tensile Strength,Composite Bijels through Microfluidic Twisting

Rope making is a millennia old technique to collectively assemble numerous weak filaments into flexible and high tensile strength bundles. However, delicate soft matter fibers lack the robustness to be twisted into bundles by means of mechanical rope making tools. Here, weak microfibers with tensile strengths of a few kilopascals are combined into ropes via microfluidic twisting. This is demonstrated for recently introduced fibers made of bicontinuous interfacially jammed emulsion gels (bijels). Bijels show promising applications in use as membranes, microreactors, energy and healthcare materials, but their low tensile strength make reinforcement strategies imperative. Hydrodynamic twisting allows to produce continuous bijel fiber bundles of controllable architecture. Modelling the fluid flow field reveals the bundle geometry dependence on a subtle force balance composed of rotational and translational shear stresses. Moreover, combining multiple bijel fibers of different compositions enables the introduction of polymeric support fibers to raise the tensile strength to tens of megapascals, while simultaneously preserving the liquid like properties of the bijel fibers for transport applications. Hydrodynamic twisting shows potentials to enable the combination of a wide range of materials resulting in composites with features greater than the sum of their parts.     

Achieving the Upper Bound of Piezoelectric Response in Tunable,Wearable 3D Printed Nanocomposites

The trade‐off between processability and functional responses presents significant challenges for incorporating piezoelectric materials as potential 3D printable feedstock. Structural compliance and electromechanical coupling sensitivity have been tightly coupled: high piezoelectric responsiveness comes at the cost of low compliance. Here, the formulation and design strategy are presented for a class of a 3D printable, wearable piezoelectric nanocomposite that approaches the upper bound of piezoelectric charge constants while maintaining high compliance. An effective electromechanical interphase model is introduced to elucidate the effects of interfacial functionalization between the highly concentrated perovskite nanoparticulate inclusions (exceeding 74 wt%) and light‐sensitive monomer matrix, shedding light on the significant enhancement of piezoelectric coefficients. It is shown that, through theoretical calculation and experimental validations, maximizing the functionalization level approaches the theoretical upper bound of the piezoelectric constant d₃₃ at any given loading concentration. Based on these findings, their applicability is demonstrated by designing and 3D printing piezoelectric materials that simultaneously achieve high electromechanical sensitivity and structural functionality, as highly sensitive wearables that detect low pressure air (<50 Pa) coming from different directions, as well as wireless, self‐sensing sporting gloves for simultaneous impact absorption and punching force mapping.     

3D Laser Nanoprinting of Functional Materials

3D laser nanoprinting represents a revolutionary manufacturing approach as it allows maskless fabrication of 3D nanostructures at a resolution beyond the optical diffraction limit. Specifically, it endows the printed structures novel physical, chemical, or mechanical properties not observed at macroscopic scale. However, 3D laser nanoprinting typically relies on the photopolymerization process, indicating its limitation on the printable materials and functionalities. The capability to print diverse functional materials beyond polymer will enable a lot of new device applications in nanophotonics, microelectronics, and so on. One of the strategies is to use the 3D-printed polymer structures as skeletons for functional material deposition, while another is to mix the functional components with the photocurable molecules and print the nanocomposites. More recently, several laser nanoprinting techniques beyond photopolymerization are also developed. In this review, the cutting-edge technical innovation is summarized and a couple of examples are highlighted showing exciting applications of the printed structures in magnetic microrobots, photonics, and optoelectronics. Finally, the vision for existing challenges and future development in this field is shared.     

Particle‐Free Emulsions for 3D Printing Elastomers

3D printing is a rapidly growing field that requires the development of yield‐stress fluids that can be used in postprinting transformation processes. There is a limited number of yield‐stress fluids currently available with the desired rheological properties for building structures with small filaments (≤l00 µm) with high shape‐retention. A printing‐centric approach for 3D printing particle‐free silicone oil‐in‐water emulsions with a polymer additive, poly(ethylene oxide) is presented. This particular material structure and formulation is used to build 3D structure and to pattern at filament diameters below that of any other known material in this class. Increasing the molecular weight of poly(ethylene oxide) drastically increases the extensibility of the material without significantly affecting shear flow properties (shear yield stress and linear viscoelastic moduli). Higher extensibility of the emulsion correlates to the ability of filaments to span relatively large gaps (greater than 6 mm) when extruded at large tip diameters (330 µm) and the ability to extrude filaments at high print rates (20 mm s^?1). 3D printed structures with these extensible particle‐free emulsions undergo postprinting transformation, which converts them into elastomers. These elastomers can buckle and recover from extreme compressive strain with no permanent deformation, a characteristic not native to the emulsion.     

三维LDV/APV系统在AF1喷嘴雾化特性研究中的应用

AF1喷嘴是一种气水雾化加湿喷嘴,它具有雾场均匀、不易堵塞、不会漏水等优点,既可用在一些特殊的无中央空调的工作环境中,又可对有中央空调的环境进行补充加湿。对该类喷嘴的结构及雾化特性进行研究,以推进该类喷嘴的国产化进程,指导其应用,具有重要的现实意义。本文以压缩空气、水为工质,使用三维LDV/APV系统对该喷嘴的雾化特性进行了实验研究,测量了不同水、气压力条件下,雾场颗粒的粒径和三维速度,讨论了相关参数改变后,对喷嘴雾化效果的影响。     

Nonflammable and Magnetic Sponge Decorated with Polydimethylsiloxane Brush for Multitasking and Highly Efficient Oil–Water Separation

Developing sponge materials integrating excellent flame retardancy, multitasking separation performance, and efficient emulsion‐breaking ability is significant but challenging for the remediation of oil spills causing fires and environmental damages. Herein, a superhydrophobic oil–water separation sponge material, containing a melamine‐formaldehyde (MF) sponge substrate, magnetic polydopamine (PDA) coating, and branched polydimethylsiloxane (PDMS) brush, through dopamine‐mediated surface initiated atom transfer radical polymerization (SI‐ATRP) is fabricated. The synergistic flame resistance of the MF substrate and PDMS brush significantly improves its adaptability in fire. More importantly, the decorated PDMS brushes can effectively overcome the size mismatch between sponge macropores and tiny emulsified droplets, while remaining the intrinsic macroporous characteristic. When treating W/O emulsions, the PDMS brushes stretch up to act as “interface‐breaking blades” to accelerate the coalescence of emulsified water droplets. Meanwhile, such PDMS brushes can serve as “oil‐trapping tentacles” to efficiently capture oil droplets when treating O/W emulsions. Such material design synergistically contributes to satisfactory separation efficiency (98.7%) and ultrahigh permeation flux (up to 1.35 × 10⁵ L m^?2 h^?1), even for treating high viscosity emulsions. Besides, the reported sponge also inherits robust durability, superior recyclability, and convenient magnetic collection. These features make the sponge promising for multitasking and highly efficient oil–water separation.     

基于太赫兹技术的熔融沉积3D打印误差分析

熔融沉积(FDM)技术是目前市售3D打印机应用最广泛的材料成型技术,基于这一技术的3D打印机精确度评价与打印试件的误差分析还没有十分完善的标准化方法。FDM 3D打印常用的聚合物材料在太赫兹波段存在明显吸收。基于太赫兹时域光谱(THz-TDS),通过缝隙注水的方式放大试件非实体部分的太赫兹响应,使得太赫兹技术可同时监测3D打印试件实体部分与非实体部分的打印精确度。通过分析试件的太赫兹光谱,能够分辨与原始设计相差0.96%的微米级误差,补充了3D打印误差的分析方法。     

Mechanical Properties Tailoring of 3D Printed Photoresponsive Nanocellulose Composites

3D printing technologies allow control over the alignment of building blocks in synthetic materials, but compositional changes often require complex multimaterial printing steps. Here, 3D printable materials showing locally tunable mechanical properties are produced in a single printing step of Direct Ink Writing. These new inks consist of a polymer matrix bearing biocompatible photoreactive cinnamate derivatives and up to 30 wt% of anisotropic cellulose nanocrystals. The printed materials are mechanically versatile and can undergo further crosslinking upon illumination. When illuminating the material and controlling the irradiation doses, the Young's moduli can be adjusted between 15 and 75 MPa. Moreover, spatially controlled illumination allows patterning stiff geometries, resulting in 3D printed structures with segments of different mechanical properties tailoring the mechanical behavior under compression. The high design freedom implemented by 3D printing and photopatternability opens the venue to rapid manufacturing of devices for applications such as prosthetics or soft robotics where the 3D shapes and mechanical properties must be tailored for personalized load cases.     

Designing Semipermeable Hydrogel Shells with Controlled Thickness through Internal Osmosis in Triple-Emulsion Droplets

Hydrogel shells that compartmentalize the water core from the aqueous surrounding provide molecular selectivity on size and charge in transmembrane transport. It is highly demanding to produce thin hydrogel shells to minimize diffusion length and maximize core volume. Here, internal osmosis in water-in-oil-in-water-in-oil (W/O/W/O) triple-emulsion droplets is used to produce thin hydrogel shells enclosing a large water core. The triple-emulsion droplets are prepared to have an ultrathin middle oil layer using a capillary microfluidic device. The innermost water droplet has a higher osmolarity than the outer water layer containing photopolymerizable hydrogel precursors, which pumps water from the outer layer to the core through the ultrathin oil layer by the osmosis. Therefore, the outer layer gets thinner and hydrogel precursors are enriched while the size of the triple-emulsion droplets remains unchanged. Through photopolymerization of precursors and phase transfer from oil to water, hydrogel shells enclosing water core are produced in the water environment; the oil layer is ruptured for molecular exchange through the shells. The thickness and composition of the hydrogel shells are precisely controllable by the osmotic conditions. The shells show a high permeation rate due to the thinness as well as controlled cut-off threshold of permeation for neutral and charged molecules.     

Diels–Alder Reversible Thermoset 3D Printing: Isotropic Thermoset Polymers via Fused Filament Fabrication

This study presents a new 3D printing process, the Diels–Alder reversible thermoset (DART) process, and a first generation of printable DART resins, which exhibit thermoset properties at use temperatures, ultralow melt viscosity at print temperatures, smooth part surface finish, and as‐printed isotropic mechanical properties. This study utilizes dynamic covalent chemistry based on reversible furan‐maleimide Diels–Alder linkages in the polymers, which can be decrosslinked and melt‐processed during printing between 90 and 150 °C, and recrosslinked at lower temperatures to their entropically favored state. This study compares the first generation of DART materials to commonly 3D printed high‐toughness thermoplastics. Parts printed from typical fused filament fabrication compatible materials exhibit anisotropy of more than 50% and sometimes upward of 98% in toughness when deformed along the build direction, while the first generation of DART materials exhibit less than 4% toughness reduction when deformed along the build direction. At room temperature, the toughest DART materials exhibit baseline toughness of 18.59 ± 0.91 and 18.36 ± 0.57 MJ m^?3 perpendicular and parallel to the build direction, respectively. DART printing will enable chemists, polymer engineers, materials scientists, and industrial designers to translate new robust materials possessing targeted thermomechanical properties, multiaxial toughness, smooth surface finish, and low anisotropy.     

Fully Printed Flexible Smart Hybrid Hydrogels

A printable hybrid hydrogel is fabricated by embedding poly(N‐isopropylacrylamide) (PNIPAm) microparticles within a water‐rich silica‐alumina(Si/Al)‐based gel matrix. The hybrid gel holds water content of up to 70 wt%, due to its unique Si/Al matrix. The hybrid hydrogel can respond to both heat and electrical stimuli, and can be directly printed layer‐by‐layer using a commercial 3‐dimensional printer, without requiring any curing. The hybrid ink is printed onto a transparent, flexible conductive electrode composed of silver nanoparticles and sustains bending angles of up to 180°, which enables patterning of various flexible devices such as smart windows and a 3D optical waveguide valve.     

A Tailorable Family of Elastomeric‐to‐Rigid, 3D Printable,Interbonding Polymer Networks

Soft materials with widely tailorable mechanical properties throughout the material's volume can shape the future of soft robotics and wearable electronics, impacting both consumer and defense sectors. Herein, a platform of 3D printable soft polymer networks with unprecedented tunability of stiffness of nearly three orders of magnitude (MPa to GPa) and an inherent capability to interbond is reported. The materials are based on dynamic covalent polymer networks with variable density of crosslinkers attached to prepolymer backbones via a temperature‐reversible Diels–Alder (DA) reaction. Inherent flexibility of the prepolymer chains and controllable crosslinking density enable 3D printed networks with glass transition temperatures ranging from just a few degrees to several tens of degrees Celsius. Materials with an elastomeric network demonstrate a fast and spontaneous self‐healing behavior at room temperature both in air and under water—a behavior difficult to achieve with other crosslinked materials. Reversible dissociation of DA networks at temperatures exceeding ≈120 °C allows for reprintability, while control of the stereochemistry of DA attachments enables reprogrammable shape memory behavior. The introduced platform addresses current major challenges including control of polymer interbonding, enhanced mechanical performance of printed parts, and reprocessability of 3D‐printed crosslinked materials in the absence of solvent.     

3D Printed Supercapacitor: Techniques,Materials, Designs,and Applications

Supercapacitors (SCs) offer broad possibilities in the rising domain of military and civilian owing to their intrinsic properties of superior power density, long lifetime, and safety features. Despite of low-cost, facile manufacture, and time-saving, 3D printing technology unleashes the potential of SCs in terms of achieving desirable capacitance with high mass loading, fabrication of well-designed complicated structures, and direct construction of on-chip integration systems. In this review, first, the representative printing technologies for SCs and advanced printable materials are scrutinized for SCs and advanced printable materials. Then the structure design principles of electrodes and devices are respectively highlighted and reported cases are systematically summarized. Next, configurations of the SCs and their applications in various areas are described in detail. Finally, the promising research directions for the future are discussed. The perspectives reviewed here are expected to provide a comprehensive understanding of 3D-printed SCs and guidance in realizing their promise in various applications.     

A new cymbal-shaped high power microactuator for nebulizer application

Inhalation therapy is being applied in the home care field to a gradually increasing degree, and therefore two issues of great importance are the convenience and portability of medical devices. Hence, this paper presents a novel cymbal-shaped high power microactuator (CHPM) that includes a ring-type piezoelectric ceramics and a cymbal-shaped micro nozzle plate. The latter can focus energy on the center of the nozzle plate and induce a large force, which provides the cymbal-shaped microactuator with high power to spray medical solutions of high-viscosity produce ultra-fine droplets and increase the atomization rate. In this research, the CHPM can reduce liquids to droplets of an ultra-fine size distribution (Mass Median Aerodynamic Diameter, MMAD), increasing the nebulizing rate and enabling the spraying of high-viscosity fluids (lavender oil, cP > 3.5). The ultra-fine droplets were of a MMAD of less than 4.07 μm at 127.89 kHz and the atomization rate was 0.5 mL/min. The drive voltage of CHPM was only 3 V, and the power consumption only one-tenth that of ultrasonic atomizers at 1.2 W. The simulation and experiments carried out in this study proved that the droplets are much smaller than those produced by current conventional devices. Therefore, the CHPM is suitable for use in the development of a convenient and portable inhalation therapy device.