Paper with Power: Engraving 2D Materials on 3D Structures for Printed,High‐Performance,Binder‐Free,and All‐Solid‐State Supercapacitors

The prevalence of the Internet of Things (IoT) and wearable electronics create an unprecedented demand for new power sources which are low cost, high performance, and flexible in many application settings. In this paper, a strategy for the scalable fabrication of high‐performance, all‐solid‐state supercapacitors (SCs) is demonstrated using conventional paper and an inkjet printer. Emerging printed electronics technology and low‐cost chemical engraving methods are bridged for the first time to construct Cu_xO nanosheets, in situ, on the 3D metallized fiber structures. Benefitting from both the “2D Materials on 3D Structures” design and the binder‐free nature of the fabricated electrodes, substantial improvements to electrical conductivity, aerial capacitance, and electrochemical performance of the resulting SCs are observed. With the proposed strategy, the fabricated SCs can be seamlessly integrated into any printed circuit, sensors, or artwork; the properties of these SCs can be easily tuned by simple pattern design, fulfilling the increasing demand of highly customized power systems in the IoT and flexible/wearable electronics industries.     

Highly Luminescent and Stable Green Quasi‐2D Perovskite‐Embedded Polymer Sheets by Inkjet Printing

Perovskite materials serve as promising candidates for display and lighting due to their excellent optical properties, including tunable bandgaps and efficient luminescence. However, their efficiency and stability must be improved for further application. In this work, quasi‐two‐dimensional (quasi‐2D) perovskites embedded in different polymers are prepared by inkjet printing to construct any luminescent patterns/pictures on the polymer substrates. The optimized quantum yield reaches over 65% by polyvinyl‐chloride‐based quasi‐2D perovskite composites. In addition, as‐fabricated perovskite?polymer composites with patterns show excellent resistance to abrasion, moisture, light irradiation, and chemical erosion by various solvents. Both quantum yield and lifetime are superior to those reported to date. These achievements are attributed to the introduction of the PEA⁺ cations to improve the luminance and stability of perovskite. This patterned composite can be useful for color‐conversion films with low cost and large‐scale fabrication.     

Inkjet Printing of Latex‐Based High‐Energy Microcapacitors

Microenergy storage devices are appealing and highly demanded for diverse miniaturized electronic devices, ranging from microelectromechanical system, robotics, to sensing microsystems and wearable electronics. However, making high‐energy microcapacitors with currently available printing technologies remains challenging. Herein, the possibility to use latex polyvinylidene fluoride (PVDF) as aqueous ink for making dielectric capacitors at the microscale is shown. The dielectric properties of printed microcapacitors can be optimized based on a novel approach, i.e., mixing PVDF latex with polyvinyl alcohol (PVA) to realize dielectric organic nanocomposites. The PVA prevents the coalescence of PVDF nanoparticles and serves as a continuous matrix phase with high dielectric breakdown strength. While the well‐dispersed PVDF nanoparticles serve as highly polarizable and isolated domains, providing large electric displacement under high fields. Consequently, a high discharged energy density of 12 J cm^?3 is achieved at 550 MV m^?1. These printed microcapacitors demonstrate mechanical robustness and dielectric stability over time.     

Inkjet Printing of Self‐Assembled 2D Titanium Carbide and Protein Electrodes for Stimuli‐Responsive Electromagnetic Shielding

2D titanium carbides (MXene) possess significant characteristics including high conductivity and electromagnetic interference shielding efficiency (EMI SE) that are important for applications in printed and flexible electronics. However, MXene‐based ink formulations are yet to be demonstrated for proper inkjet printing of MXene patterns. Here, tandem repeat synthetic proteins based on squid ring teeth (SRT) are employed as templates of molecular self‐assembly to engineer MXene inks that can be printed as stimuli‐responsive electrodes on various substrates including cellulose paper, glass, and flexible polyethylene terephthalate (PET). MXene electrodes printed on PET substrates are able to display electrical conductivity values as high as 1080 ± 175 S cm^?1, which significantly exceeds electrical conductivity values of state‐of‐the‐art inkjet‐printed electrodes composed of other 2D materials including graphene (250 S cm^?1) and reduced graphene oxide (340 S cm^?1). Furthermore, this high electrical conductivity is sustained under excessive bending deformation. These flexible electrodes also exhibit effective EMI SE values reaching 50 dB at films with thicknesses of 1.35 µm, which mainly originate from their high electrical conductivity and layered structure.     

Simplified Large‐Area Manufacturing of Organic Electrochemical Transistors Combining Printing and a Self‐Aligning Laser Ablation Step

A hybrid manufacturing approach for organic electrochemical transistors (OECTs) on flexible substrates is reported. The technology is based on conventional and digital printing (screen and inkjet printing), laser processing, and post‐press technologies. A careful selection of the conductive, dielectric, and semiconductor materials with respect to their optical properties enables a self‐aligning pattern formation which results in a significant reduction of the usual registration problems during manufacturing. For the prototype OECTs, based on this technology, on/off ratios up to 600 and switching times of 100 milliseconds at gate voltages in the range of 1 V were obtained.     

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.     

Accelerating the Screening of Perovskite Compositions for Photovoltaic Applications through High‐Throughput Inkjet Printing

The exploration and optimization of numerous mixed perovskite compositions are causing a strong demand for high‐throughput synthesis. Nevertheless high‐throughput fabrication of perovskite films with representative film properties, which can efficiently screen the perovskite compositions for photovoltaic applications, has rarely been explored. A high‐throughput inkjet printing approach that can automatically fabricate perovskite films with various compositions with high reproducibility and high speed is developed. The automatic sequential printing of four precursors forms 25 mixed films in a fast and reproducible manner. The obtained bandgaps, photoluminescence (PL) peak positions, and PL lifetimes allow for the efficient screening of perovskite compositions for photovoltaic applications. To exemplify this concept, among 25 tested films, two compositions CH₃NH₃PbBr_0.75I_2.25 (MA) and (HC(NH₂)₂)_0.75(CH₃NH₃)_0.25PbBr_0.75I_2.25 (FA_0.75MA_0.25) with a long (237 ns) and short (49.0 ns) PL lifetime, respectively, are screened out for device investigations. As expected, the MA‐based device exhibits a much higher efficiency (19.0%) than that (15.3%) of the FA_0.75MA_0.25 counterpart. This efficiency improvement is mainly ascribed to a smaller dark saturate current density, a lower level of energetic disorder, more efficient charge transfer and decreased charge recombination losses, which are consistent with the much longer PL lifetime in the database.     

Flexible RFID Tag Metal Antenna on Paper‐Based Substrate by Inkjet Printing Technology

A reliable and low‐cost solution‐processing procedure to synthesize a highly adhesive flexible metal antenna with low resistivity for radio‐frequency identification device (RFID) tags on paper substrates via inkjet printing combined with surface modification and electroless deposition (ELD) is demonstrated in this paper. Through the surface modification of colloidal solution of hydrolyzed stannous chloride and chitosan solution, the paper‐based substrate is able to reduce the penetration rate of ink and further increase the adsorption amount of silver ions, which could create a catalytic activating layer to catalyze the subsequent ELD of a conductive deposited metal antenna. The resulting metal antenna for RFID tags presents good adhesive strength and low resistivity of 2.58 × 10^?8 Ω·m after 40 min of ELD, and maintains a reliable reading range of RFID tags even after over 1000 times of bending and mechanical stress. Consequently, the developed technology proposed allows for cheap, efficient, and massive production of metal antenna for paper‐based RFID tags with excellent mechanical and electrical properties. Furthermore, this process is especially advantageous for the fabrication of next‐generation flexible electronic devices based on paper substrates.     

Textured Tubular Nanoparticle Structures: Precursor‐Templated Synthesis of GaN Sub‐micrometer Sized Tubes

Porous and sub‐micrometer tubes made of textured GaN nanoparticles have been synthesized by an in situ chemical reaction and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) and Raman spectroscopies. The in situ reaction involves thermal decomposition and nitridation of 1D gallium oxyhydroxide (GaOOH) at temperatures in the range of 700–900 °C. The 1D shape of the precursor GaOOH is maintained in the resultant GaN tubes. The GaN nanocrystals (estimated to be about 15 nm in size) are found to be highly oriented with respect to each other in the tube structure, with the [110] GaN direction parallel to the tube axis. The growth mechanism of the tube structure has also been studied. β‐Ga₂O₃ is found to be an intermediate phase between the starting GaOOH precursor and the final GaN product. The growth mechanism involves decomposition of GaOOH, which produces β‐Ga₂O₃ tubes with hollow interiors, and nitridation of β‐Ga₂O₃, which leads to growth of textured GaN nanocrystals. Based on the growth mechanism, tubular structures with either quasi‐circular or rectangular cross section are selectively synthesized by controlling the heating rate and calcination temperature. This in situ chemical reaction method provides a new route for synthesizing 1D hollow nanostructures.     

Microfluidic 3D Printing Responsive Scaffolds with Biomimetic Enrichment Channels for Bone Regeneration

Tissue-engineered scaffolds have been extensively explored for treating bone defects; however, slow and insufficient vascularization throughout the scaffolds remains a key challenge for further application. Herein, a versatile microfluidic 3D printing strategy to fabricate black phosphorus (BP) incorporated fibrous scaffolds with photothermal responsive channels for improving vascularization and bone regeneration is proposed. The thermal channeled scaffolds display reversible shrinkage and swelling behavior controlled by near-infrared irradiation, which facilitates the penetration of suspended cells into the scaffold channels and promotes the prevascularization. Furthermore, the embedded BP nanosheets exhibit intrinsic properties for in situ biomineralization and improve in vitro cell proliferation and osteogenic differentiation. Following transplantation in vivo, these channels also promote host vessel infiltration deep into the scaffolds and effectively accelerate the healing process of bone defects. Thus, it is believed that these near-infrared responsive channeled scaffolds are promising candidates for tissue/vascular ingrowth in diverse tissue engineering applications.     

Inkjet Printing of a Highly Loaded Palladium Ink for Integrated,Low‐Cost pH Sensors

An inkjet printing process for depositing palladium (Pd) thin films from a highly loaded ink (>14 wt%) is reported. The viscosity and surface tension of a Pd‐organic precursor solution is adjusted using toluene to form a printable and stable ink. A two‐step thermolysis process is developed to convert the printed ink to continuous and uniform Pd films with good adhesion to different substrates. Using only one printing pass, a low electrical resistivity of 2.6 μΩ m of the Pd film is obtained. To demonstrate the electrochemical pH sensing application, the surfaces of the printed Pd films are oxidized for ion‐to‐electron transduction and the underlying layer is left for electron conduction. Then, solid‐state reference electrodes are integrated beside the bifunctional Pd electrodes by inkjet printing. These potentiometric sensors have sensitivities of 60.6 ± 0.1 and 57 ± 0.6 mV pH^?1 on glass and polyimide substrates, and short response times of 11 and 6 s, respectively. Also, accurate pH values of real water samples are obtained by using the printed sensors with a low‐cost multimeter. These results indicate that the facile and cost‐effective inkjet printing and integration techniques may be applied in fabricating future electrochemical monitoring systems for environmental parameters and human health conditions.     

Low‐Temperature‐Processed Printed Metal Oxide Transistors Based on Pure Aqueous Inks

Additive patterning of transparent conducting metal oxides at low temperatures is a critical step in realizing low‐cost transparent electronics for display technology and photovoltaics. In this work, inkjet‐printed metal oxide transistors based on pure aqueous chemistries are presented. These inks readily convert to functional thin films at lower processing temperatures (T ≤ 250 °C) relative to organic solvent‐based oxide inks, facilitating the fabrication of high‐performance transistors with both inkjet‐printed transparent electrodes of aluminum‐doped cadmium oxide (ACO) and semiconductor (InO_x ). The intrinsic fluid properties of these water‐based solutions enable the printing of fine features with coffee‐ring free line profiles and smoother line edges than those formed from organic solvent‐based inks. The influence of low‐temperature annealing on the optical, electrical, and crystallographic properties of the ACO electrodes is investigated, as well as the role of aluminum doping in improving these properties. Finally, the all‐aqueous‐printed thin film transistors (TFTs) with inkjet‐patterned semiconductor (InO_x ) and source/drain (ACO) layers are characterized, which show ideal low contact resistance (R _c < 160 Ω cm) and competitive transistor performance (µ _lin up to 19 cm² V^?1 s^?1, Subthreshold Slope (SS) ≤150 mV dec^?1) with only low‐temperature processing (T ≤ 250 °C).     

Conformal Printing of Graphene for Single‐ and Multilayered Devices onto Arbitrarily Shaped 3D Surfaces

Printing has drawn a lot of attention as a means of low per‐unit cost and high throughput patterning of graphene inks for scaled‐up thin‐form factor device manufacturing. However, traditional printing processes require a flat surface and are incapable of achieving patterning onto 3D objects. Here, a conformal printing method is presented to achieve functional graphene‐based patterns onto arbitrarily shaped surfaces. Using experimental design, a water‐insoluble graphene ink with optimum conductivity is formulated. Then single‐ and multilayered electrically functional structures are printed onto a sacrificial layer using conventional screen printing. The print is then floated on water, allowing the dissolution of the sacrificial layer, while retaining the functional patterns. The single‐ and multilayer patterns can then be directly transferred onto arbitrarily shaped 3D objects without requiring any postdeposition processing. Using this technique, conformal printing of single‐ and multilayer functional devices that include joule heaters, resistive deformation sensors, and proximity sensors on hard, flexible, and soft substrates, such as glass, latex, thermoplastics, textiles, and even candies and marshmallows, is demonstrated. This simple strategy promises to add new device and sensing functionalities to previously inert 3D surfaces.     

“Invisible” Silver Tracks Produced by Combining Hot‐Embossing and Inkjet Printing

Hot‐embossed features are prepared by pushing customized and standard silicon calibration gratings, known as masters, into either polystyrene or polycarbonate, which are kept above their glass transition temperatures. droplet of a silver nanoparticle ink is then dispensed over one of these as‐formed grooves using an inkjet printer. The ink fills the grooves as a consequence of capillary forces and is observed to form tracks with a uniform width. The tracks are described as ‘invisible’ on account of having widths ranging from 5 to 15 µm. Wider tracks can be produced by dispensing more droplets and tracks with different morphologies can be produced by using different masters. Several as‐prepared features are thermally treated to produce conductive silver tracks. The conductivity of the tracks is found to be ～20% that of bulk silver.     

Fast‐Response,Stiffness‐Tunable Soft Actuator by Hybrid Multimaterial 3D Printing

Soft robots have the appealing advantages of being highly flexible and adaptive to complex environments. However, the low‐stiffness nature of the constituent materials makes soft robotic systems incompetent in tasks requiring relatively high load capacity. Despite recent attempts to develop stiffness‐tunable soft actuators by employing variable stiffness materials and structures, the reported stiffness‐tunable actuators generally suffer from limitations including slow responses, small deformations, and difficulties in fabrication with microfeatures. This work presents a paradigm to design and manufacture fast‐response, stiffness‐tunable (FRST) soft actuators via hybrid multimaterial 3D printing. The integration of a shape memory polymer layer into the fully printed actuator body enhances its stiffness by up to 120 times without sacrificing flexibility and adaptivity. The printed Joule‐heating circuit and fluidic cooling microchannel enable fast heating and cooling rates and allow the FRST actuator to complete a softening–stiffening cycle within 32 s. Numerical simulations are used to optimize the load capacity and thermal rates. The high load capacity and shape adaptivity of the FRST actuator are finally demonstrated by a robotic gripper with three FRST actuators that can grasp and lift objects with arbitrary shapes and various weights spanning from less than 10 g to up to 1.5 kg.     

Simultaneous Immobilization of Bioactives During 3D Powder Printing of Bioceramic Drug‐Release Matrices

The combination of a degradable bioceramic scaffold and a drug‐delivery system in a single low temperature fabrication step is attractive for the reconstruction of bone defects. The production of calcium phosphate scaffolds by a multijet 3D printing system enables localized deposition of biologically active drugs and proteins with a spatial resolution of approximately 300 µm. In addition, homogeneous or localized polymer incorporation during printing with HPMC or chitosan hydrochloride allows the drug release kinetics to be retarded from first to zero order over a period of 3–4 days with release rates in the range 0.68%–0.96% h^?1. The reduction in biological activity of vancomycin, heparin, and rhBMP‐2 following spraying through the ink jet nozzles is between 1% and 18%. For vancomycin, a further loss of biological activity following incorporation into a cement and subsequent in vitro release is 11%. While previously acknowledged as theoretically feasible, is its shown for the first time that bone grafts with simultaneous geometry, localized organic bioactive loading, and localized diffusion control are a physical reality. This breakthrough offers a new future for patients by providing the required material function to match patient bone health status, site of repair, and age.     

Textile‐Based Flexible Electroluminescent Devices

Flexible and transparent textile‐based conductors are developed by inkjet printing poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) onto polyethylene terephthalate (PET) mesh fabrics. The conductivity–transparency relationship is determined for textile‐based conductors with different thicknesses of the printed PEDOT:PSS film. The function of these textile‐based conductors is studied in the alternating current powder electroluminescent (ACPEL) devices and compared with indium tin oxide (ITO) glass in an ACPEL device of the same configuration. Textiles coated with conducting polymers are a potential alternative to coated polymer films for flexible, transparent conductors.     

Fabrication,Characterization, and Printing of Conductive Ink Based on Multi Core–Shell Nanoparticles Synthesized by RAPET

In the current research, conductive patterns are deposited on different substrates by direct inkjet printing of conductive inks based on metal@carbon and bimetal@carbon core–shell nanoparticles synthesized by the RAPET (reaction under autogenic pressure at elevated temperatures) technique. Various co‐solvents and additives are examined for production of stable conductive ink. The morphology of the deposited layers is characterized by optical and scanning electron microscopy measurements. The stability of the prepared inks is examined by dynamic light scattering measurements. The electrical resistivity is measured by a four‐point probe system and calculated using the geometric dimensions. The results obtained are very promising and indicate that the conductivity of the deposited layers is close to that of bulk metals and higher than most results published so far. Moreover, the importance and advantages of the protective carbon layer that prevents metal oxidation is demonstrated.     

加速开发和推广应用喷墨打印技术

文章指出,在PCB中采用喷墨打印技术的重要性。