3D Printing by Multiphase Silicone/Water Capillary Inks

3D printing of polymers is accomplished easily with thermoplastics as the extruded hot melt solidifies rapidly during the printing process. Printing with liquid polymer precursors is more challenging due to their longer curing times. One curable liquid polymer of specific interest is polydimethylsiloxane (PDMS). This study demonstrates a new efficient technique for 3D printing with PDMS by using a capillary suspension ink containing PDMS in the form of both precured microbeads and uncured liquid precursor, dispersed in water as continuous medium. The PDMS microbeads are held together in thixotropic granular paste by capillary attraction induced by the liquid precursor. These capillary suspensions possess high storage moduli and yield stresses that are needed for direct ink writing. They could be 3D printed and cured both in air and under water. The resulting PDMS structures are remarkably elastic, flexible, and extensible. As the ink is made of porous, biocompatible silicone that can be printed directly inside aqueous medium, it can be used in 3D printed biomedical products, or in applications such as direct printing of bioscaffolds on live tissue. This study demonstrates a number of examples using the high softness, elasticity, and resilience of these 3D printed structures.     

Organic/polymeric electroluminescent devices processed by hybrid ink-jet printing

Ink-jet printing (IJP) technology is a popular technology for desktop publishing. Since some of the conducting (or conjugated) organic molecules and polymers are solution processable, IJP becomes an ideal method for printing polymer/organic light-emitting diodes with high resolution. In this review article, we present the hybrid ink-jet printing technology (HIJP), which consists of an ink-jet printed layer in conjunction with another uniform spin-coated polymer layer, which serves as a buffer layer to seal the pin holes between the ink droplets. This HIJP technology has been successfully applied to the fabrication of polymer light-emitting logos, multicolor polymer/organic light-emitting diodes, and the built-in shadow mask for the cathode patterning for pixelated polymer LEDs.     

Printing with Satellite Droplets

Despite their specific methodologies, all current noncontact printing techniques such as inkjet printing (IJP), involve the break‐up of a liquid meniscus during the separation of the ink droplet from the bulk ink reservoir. Often, the break‐up of a liquid meniscus results in the formation of one or more satellite droplet whose volumes are several orders of magnitude smaller than the primary droplet. Many attempts are directed to suppress or control the formation of satellite droplets because they blur the printing result. For the first time, a simple mechanism by which a single satellite droplet is exclusively formed and directed to the substrate by a gas stream while the primary droplet remains attached to a metal rod used for controlling the formation and break‐up of the meniscus is reported. High printing resolution is demonstrated by satellite droplets printing (SDP) without the need for small orifices which are prone to clogging. Furthermore, the droplet generation from a large orifice enables SDP to handle viscous inks which has remained challenging for traditional IJP.     

Emerging application of 3D-printing techniques in lithium batteries: From liquid to solid

There is rapid progress in the field of 3D printing technology for the production of electrodes, electrolytes, and packages of batteries due to the technique’s low cost, a wide range of geometries printable, and rapid prototyping speed by combining computer-aided design with advanced manufacturing procedures. The most important part of 3D printing applied in batteries is the printing of electrodes, electrolytes, and packages. These will affect the battery energy/power density. However, there are still several challenges that need to be overcome to print active and stable electrodes/electrolytes for energy storage systems that can rival that of the state-of-the-art. In this review, the printing materials, and methods for batteries from liquid to solid-state batteries are discussed and recent examples of this technique applied in high power/energy batteries are highlighted. This review for batteries will cover 3D printing technologies, printed cathode, and anode in conventional batteries, and printed solid-state electrolytes in solid-state batteries. The working principles, advantages, and limitations for solid-state batteries via the 3D printing method will be discussed before highlighting the printing materials for electrodes and electrolytes. We will then discuss how to modify the electrode and solid-state electrolyte to raise the electrochemical performance of solid-state batteries using 3D printing. Finally, we will give our insights into the future perspectives of this printing technique for fabricating batteries.     

液态金属基油墨的印刷适性调控与可拉伸电子应用

目的 调整液态金属基油墨的印刷适性，用于可拉伸电极的印刷法构建。方法 通过超声破碎法减小液态金属微粒直径，降低其表面张力;探究聚氨酯种类和含量对液态金属微粒的分散性、油墨流变性、电极的印刷适性和可拉伸性的影响。结果 引入PU1185制备的液态金属油墨，丝印电极分辨率达58 µm;印制电极展现了良好的导电性和可拉伸性，预拉伸稳定后的电极在100%的应变下拉伸1 000次，电阻变化不超2倍。结论 液态金属基油墨能够用于高分辨电路的加工，在可拉伸电子领域具有可预见的应用前景。     

Elevated‐Temperature 3D Printing of Hybrid Solid‐State Electrolyte for Li‐Ion Batteries

While 3D printing of rechargeable batteries has received immense interest in advancing the next generation of 3D energy storage devices, challenges with the 3D printing of electrolytes still remain. Additional processing steps such as solvent evaporation were required for earlier studies of electrolyte fabrication, which hindered the simultaneous production of electrode and electrolyte in an all‐3D‐printed battery. Here, a novel method is demonstrated to fabricate hybrid solid‐state electrolytes using an elevated‐temperature direct ink writing technique without any additional processing steps. The hybrid solid‐state electrolyte consists of solid poly(vinylidene fluoride‐hexafluoropropylene) matrices and a Li⁺‐conducting ionic‐liquid electrolyte. The ink is modified by adding nanosized ceramic fillers to achieve the desired rheological properties. The ionic conductivity of the inks is 0.78 × 10 ^?3 S cm^?1. Interestingly, a continuous, thin, and dense layer is discovered to form between the porous electrolyte layer and the electrode, which effectively reduces the interfacial resistance of the solid‐state battery. Compared to the traditional methods of solid‐state battery assembly, the directly printed electrolyte helps to achieve higher capacities and a better rate performance. The direct fabrication of electrolyte from printable inks at an elevated temperature will shed new light on the design of all‐3D‐printed batteries for next‐generation electronic devices.     

用于锂电池包装的铝塑膜印刷封装新工艺

目的研发一种铝塑膜印刷封装的新工艺,提高锂电池包装的生产效率。方法通过对铝塑膜表面先涂布、再印刷、后封装的工艺替代行业内铝塑膜包装锂电池的传统工艺,测试新工艺条件下铝塑印刷膜的耐化学性、耐磨性、附着力及光泽度等指标。结果采用新工艺后,不仅可以拓宽印刷种类,提升生产效率,而且能够实现高精度印刷作业,提高铝塑膜的印刷质量。试验表明,该工艺条件下的铝塑印刷膜耐化学性和耐磨性优良,附着牢度可达100%,平均光泽度为8.4。结论新工艺相比传统工艺具有较强的先进性,可适用于手机锂电池的铝塑膜印刷封装作业。     

Surface‐Embedded Stretchable Electrodes by Direct Printing and their Uses to Fabricate Ultrathin Vibration Sensors and Circuits for 3D Structures

Printing is one of the easy and quick ways to make a stretchable wearable electronics. Conventional printing methods deposit conductive materials “on” or “inside” a rubber substrate. The conductors made by such printing methods cannot be used as device electrodes because of the large surface topology, poor stretchability, or weak adhesion between the substrate and the conducting material. Here, a method is presented by which conductive materials are printed in the way of being surface‐embedded in the rubber substrate; hence, the conductors can be widely used as device electrodes and circuits. The printing process involves a direct printing of a metal precursor solution in a block‐copolymer rubber substrate and chemical reduction of the precursor into metal nanoparticles. The electrical conductivity and sensitivity to the mechanical deformation can be controlled by adjusting the number of printing operations. The fabrication of highly sensitive vibration sensors is thus presented, which can detect weak pulses and sound waves. In addition, this work takes advantage of the viscoelasticity of the composite conductor to fabricate highly conductive stretchable circuits for complicated 3D structures. The printed electrodes are also used to fabricate a stretchable electrochemiluminescence display.     

印刷法制备功能芯片的研究进展

目的概述印刷芯片的制备方法和研究现状,开拓印刷技术的研究思路和应用场景,为印刷芯片的发展提供参考。方法从印刷材料、印刷方法和芯片应用3个方面介绍近年来印刷芯片的研究进展,重点对比各种印刷方法的关键科学问题及特点,并且指出芯片印刷的发展方向。结果基于印刷方法在大面积制备、材料兼容性、绿色环保等方面的优势,印刷芯片在显示、能源、生物、智能包装等诸多方面快速发展,不过仍然面临高精度、规模化、功能集成方面的挑战。结论通过更好地调控印刷过程中液滴成型,构筑功能材料精细微纳结构,实现高精度器件与芯片全印刷制造。未来在实现智能、自动、互联化功能芯片制造的同时,发展绿色可持续印刷新策略。     

Electro‐Assisted Bioprinting of Low‐Concentration GelMA Microdroplets

Low‐concentration gelatin methacryloyl (GelMA) has excellent biocompatibility to cell‐laden structures. However, it is still a big challenge to stably fabricate organoids (even microdroplets) using this material due to its extremely low viscosity. Here, a promising electro‐assisted bioprinting method is developed, which can print low‐concentration pure GelMA microdroplets with low cost, low cell damage, and high efficiency. With the help of electrostatic attraction, uniform GelMA microdroplets measuring about 100 μm are rapidly printed. Due to the application of lower external forces to separate the droplets, cell damage during printing is negligible, which often happens in piezoelectric or thermal inkjet bioprinting. Different printing states and effects of printing parameters (voltages, gas pressure, nozzle size, etc.) on microdroplet diameter are also investigated. The fundamental properties of low‐concentration GelMA microspheres are subsequently studied. The results show that the printed microspheres with 5% w/v GelMA can provide a suitable microenvironment for laden bone marrow stem cells. Finally, it is demonstrated that the printed microdroplets can be used in building microspheroidal organoids, in drug controlled release, and in 3D bioprinting as biobricks. This method shows great potential use in cell therapy, drug delivery, and organoid building.     

Inkjet‐Printed High‐Performance Flexible Micro‐Supercapacitors with Porous Nanofiber‐Like Electrode Structures

Flexible planar micro‐supercapacitors (MSCs) with unique loose and porous nanofiber‐like electrode structures are fabricated by combining electrochemical deposition with inkjet printing. Benefiting from the resulting porous nanofiber‐like structures, the areal capacitance of the inkjet‐printed flexible planar MSCs is obviously enhanced to 46.6 mF cm^?2, which is among the highest values ever reported for MSCs. The complicated fabrication process is successfully averted as compared with previously reported best‐performing planar MSCs. Besides excellent electrochemical performance, the resultant MSCs also show superior mechanical flexibility. The as‐fabricated MSCs can be highly bent to 180° 1000 times with the capacitance retention still up to 86.8%. Intriguingly, because of the remarkable patterning capability of inkjet printing, various modular MSCs in serial and in parallel can be directly and facilely inkjet‐printed without using external metal interconnects and tedious procedures. As a consequence, the electrochemical performance can be largely enhanced to better meet the demands of practical applications. Additionally, flexible serial MSCs with exquisite and aesthetic patterns are also inkjet‐printed, showing great potential in fashionable wearable electronics. The results suggest a feasible strategy for the facile and cost‐effective fabrication of high‐performance flexible MSCs via inkjet printing.     

Freeform,Reconfigurable Embedded Printing of All‐Aqueous 3D Architectures

Aqueous microstructures are challenging to create, handle, and preserve since their surfaces tend to shrink into spherical shapes with minimum surface areas. The creation of freeform aqueous architectures will significantly advance the bioprinting of complex tissue‐like constructs, such as arteries, urinary catheters, and tracheae. The generation of complex, freeform, three‐dimensional (3D) all‐liquid architectures using formulated aqueous two‐phase systems (ATPSs) is demonstrated. These all‐liquid microconstructs are formed by printing aqueous bioinks in an immiscible aqueous environment, which functions as a biocompatible support and pregel solution. By exploiting the hydrogen bonding interaction between polymers in ATPS, the printed aqueous‐in‐aqueous reconfigurable 3D architectures can be stabilized for weeks by the noncovalent membrane at the interface. Different cells can be separately combined with compartmentalized bioinks and matrices to obtain tailor‐designed microconstructs with perfusable vascular networks. The freeform, reconfigurable embedded printing of all‐liquid architectures by ATPSs offers unique opportunities and powerful tools since limitless formulations can be designed from among a breadth of natural and synthetic hydrophilic polymers to mimic tissues. This printing approach may be useful to engineer biomimetic, dynamic tissue‐like constructs for potential applications in drug screening, in vitro tissue models, and regenerative medicine.     

Rewritable phosphorescent paper by the control of competing kinetic and thermodynamic self-assembling events

Security inks have become of increasing importance. They are composed of invisible substances that provide printed images that are not able to be photocopied, and are readable only under special environments. Here we report a novel photoluminescent ink for rewritable media that dichroically emits phosphorescence due to a structural bistability of the self-assembled luminophor. Long-lasting images have been developed by using conventional thermal printers, which are readable only on exposure to ultraviolet light, and more importantly, are thermally erasable for rewriting. Although thermally rewritable printing media have already been developed using visible dyes and cholesteric liquid crystals, security inks that allow rewriting of invisible printed images are unprecedented. We realized this unique feature by the control of kinetic and thermodynamic processes that compete with one another in the self-assembly of the luminophor. This strategy can provide an important step towards the next-generation security technology for information handling.     

Microscale Electro‐Hydrodynamic Cell Printing with High Viability

Cell printing has gained extensive attentions for the controlled fabrication of living cellular constructs in vitro. Various cell printing techniques are now being explored and developed for improved cell viability and printing resolution. Here an electro‐hydrodynamic cell printing strategy is developed with microscale resolution (<100 µm) and high cellular viability (>95%). Unlike the existing electro‐hydrodynamic cell jetting or printing explorations, insulating substrate is used to replace conventional semiconductive substrate as the collecting surface which significantly reduces the electrical current in the electro‐hydrodynamic printing process from milliamperes (>0.5 mA) to microamperes (<10 µA). Additionally, the nozzle‐to‐collector distance is fixed as small as 100 µm for better control over filament deposition. These features ensure high cellular viability and normal postproliferative capability of the electro‐hydrodynamically printed cells. The smallest width of the electro‐hydrodynamically printed hydrogel filament is 82.4 ± 14.3 µm by optimizing process parameters. Multiple hydrogels or multilayer cell‐laden constructs can be flexibly printed under cell‐friendly conditions. The printed cells in multilayer hydrogels kept alive and gradually spread during 7‐days culture in vitro. This exploration offers a novel and promising cell printing strategy which might benefit future biomedical innovations such as microscale tissue engineering, organ‐on‐a‐chip systems, and nanomedicine.     

Exit morphology and mechanical property of FDM printed PLA: influence of hot melt extrusion process

In order to study the hot melt extrusion process in fused deposition modeling (FDM), this study mainly explores the effects of printing temperature, heated block length, feeding speed on the exit morphology and mechanical properties of FDM printed Polylactic acid (PLA) samples. High-speed camera is used to capture the exit morphology of molten PLA just extruded to the nozzle. According to exit morphology, the outlet states of extruded molten material can be divided into four categories, namely, bubbled state, coherent state, expanding state, and unstable state. Tensile test results show that printing temperature, heated block length and printing speed have significant influence on tensile properties and fracture mode of FDM printed samples. When the heated block length is 15 mm and 30 mm, there is a ductile-brittle transition in fracture mode with the increase of printing speed. The printing process window under different heated block lengths and printing temperatures has been figured out and the distribution of printing process window under different printing speeds has been discussed. There is a maximum printing process window under the heated block length of 30 mm. This finding provides a frame work for performance prediction of FDM printed parts and theoretical guidance for expanding the scope of printing process window. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00405-1     

Inkjet printed electronics using copper nanoparticle ink

Inkjet printing of electrode using copper nanoparticle ink is presented. Electrode was printed on a flexible glass epoxy composite substrate using drop on demand piezoelectric dispenser and was sintered at 200 °C of low temperature in N₂ gas condition. The printed electrodes were made with various widths and thickness. In order to control the thickness of the printed electrode, number of printing was varied. Resistivity of printed electrode was calculated from the cross-sectional area measured by a profilometer and resistance measured by a digital multimeter. Surface morphology of electrode was analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM). From the study, it was found that 10 times printed electrode has the most stable grain structure and low resistivity of 36.7 nΩ m.     

3D Printing Hierarchical Silver Nanowire Aerogel with Highly Compressive Resilience and Tensile Elongation through Tunable Poisson's Ratio

Metallic aerogels have attracted intense attention due to their superior properties, such as high electrical conductivity, ultralow densities, and large specific surface area. The preparation of metal aerogels with high efficiency and controllability remains challenge. A 3D freeze assembling printing technique integrated with drop‐on‐demand inkjet printing and freeze casting are proposed for metallic aerogels preparation. This technique enables tailoring both the macrostructure and microstructure of silver nanowire aerogels (SNWAs) by integrating programmable 3D printing and freeze casting, respectively. The density of the printed SNWAs is controllable, which can be down to 1.3 mg cm^?3. The ultralight SNWAs reach high electrical conductivity of 1.3 S cm^?1 and exhibit excellent compressive resilience under 50% compressive strain. Remarkably, the printing methodology also enables tuning aerogel architectures with designed Poisson's ratio (from negative to positive). Moreover, these aerogel architechtures with tunable Poisson's ratio present highly electromechanical stability under high compressive and tensile strain (both strain up to 20% with fully recovery).     

纸张性能对纸张呈现色彩能力的影响

主要是进行纸张的传统印刷色域实验和数字印刷色域实验,并进一步分析纸张性能在传统印刷和数字印刷中对纸张色域的影响.这样印刷厂可以根据印刷品的质量要求尽快的确定适合目标印刷品的纸张.     

Programmable Microfluidics Enabled by 3D Printed Bionic Janus Porous Matrics for Microfluidic Logic Chips

Numerous structures have been functionally optimized for directional liquid transport in nature. Inspired by lush trees’ xylem that enable liquid directional transportation from rhizomes to the tip of trees, a new kind of programmable microfluidic porous matrices using projection micro-stereolithography (PµSL) based 3D printing technique is fabricated. Structural matrices with internal superhydrophilicity and external hydrophobicity are assembled for ultra-fast liquid rising enabled by capillary force. Moreover, the unidirectional microfluidic performance of the bionic porous matrices can be theoretically optimized by adjusting its geometric parameters. Most significantly, the successive programmable flow of liquid in a preferred direction inside the bionic porous matrices with tailored wettability is achieved, validating by a precisely printed liquid displayer and a microfluidic logic chip. The programmable and functional microfluidic matrices promise applications of patterned liquid flow, displayer, logic chip, cell screening, gas–liquid separation, and so on.     

Inkjet printed acrylic formulations based on UV-reduced graphene oxide nanocomposites

This work reports the formulation of water-based graphene oxide/acrylic nanocomposite inks, and the structural and electrical characterization of test patterns obtained by inkjet direct printing through a commercial piezoelectric micro-fabrication device. Due to the presence of heavily oxygenated functional groups, graphene oxide is strongly hydrophilic and can be readily dispersed in water. Through a process driven by UV irradiation, graphene oxide contained in the inks was reduced to graphene during photo-curing of the polymeric matrix. Printed samples of the nanocomposite material showed a decrease of resistivity with respect to the polymeric matrix. The analysis of the influence of printed layer thickness on resistivity showed that thin layers were less resistive than thick layers. This was explained by the reduced UV penetration depth in thick layers due to shielding effect, resulting in a less effective photo-reduction of graphene oxide.