3D Printing of Freestanding MXene Architectures for Current‐Collector‐Free Supercapacitors

Additive manufacturing (AM) technologies appear as a paradigm for scalable manufacture of electrochemical energy storage (EES) devices, where complex 3D architectures are typically required but are hard to achieve using conventional techniques. The combination of these technologies and innovative material formulations that maximize surface area accessibility and ion transport within electrodes while minimizing space are of growing interest. Herein, aqueous inks composed of atomically thin (1–3 nm) 2D Ti₃C₂T_x with large lateral size of about 8 µm possessing ideal viscoelastic properties are formulated for extrusion‐based 3D printing of freestanding, high specific surface area architectures to determine the viability of manufacturing energy storage devices. The 3D‐printed device achieves a high areal capacitance of 2.1 F cm^?2 at 1.7 mA cm^?2 and a gravimetric capacitance of 242.5 F g^?1 at 0.2 A g^?1 with a retention of above 90% capacitance for 10 000 cycles. It also exhibits a high energy density of 0.0244 mWh cm^?2 and a power density of 0.64 mW cm^?2 at 4.3 mA cm^?2. It is anticipated that the sustainable printing and design approach developed in this work can be applied to fabricate high‐performance bespoke multiscale and multidimensional architectures of functional and structural materials for integrated devices in various applications.     

Ink Processing for Thermoelectric Materials and Power‐Generating Devices

The growing concern over the depletion of hydrocarbon resources, and the adverse environmental effects associated with their use, has increased the demand for renewable energy sources. Thermoelectric (TE) power generation from waste heat has emerged as a renewable energy source that does not generate any pollutants. Recently, ink‐based processing for the preparation of TE materials has attracted tremendous attention because of the simplicity in design of power generators and the possibility of cost‐effective manufacturing. In this progress report, recent advances in the development of TE inks, processing techniques, and ink‐fabricated devices are reviewed. A summary of typical formulations of TE materials as inks is included, as well as a discussion on various ink‐based fabrication methods, with several examples of newly designed devices fabricated using these techniques. Finally, the prospects of this field with respect to the industrialization of TE power generation technology are presented.     

Pen‐on‐Paper Approach Toward the Design of Universal Surface Enhanced Raman Scattering Substrates

The translation of a technology from the laboratory into the real world should meet the demand of economic viability and operational simplicity. Inspired by recent advances in conductive ink pens for electronic devices on paper, we present a “pen‐on‐paper” approach for making surface enhanced Raman scattering (SERS) substrates. Through this approach, no professional training is required to create SERS arrays on paper using an ordinary fountain pen filled with plasmonic inks comprising metal nanoparticles of arbitrary shape and size. We demonstrate the use of plasmonic inks made of gold nanospheres, silver nanospheres and gold nanorods, to write SERS arrays that can be used with various excitation wavelengths. The strong SERS activity of these features allowed us to reach detection limits down to 10 attomoles of dye molecules in a sample volume of 10 μL, depending on the excitation wavelength, dye molecule and type of nanoparticles. Furthermore, such simple substrates were applied to pesticide detection down to 20 ppb. This universal approach offers portable, cost effective fabrication of efficient SERS substrates at the point of care. This approach should bring SERS closer to the real world through ink cartridges to be fixed to a pen to create plasmonic sensors at will.     

Self‐Assembly Behavior of Oppositely Charged Inverse Bipatchy Microcolloids

A directed attractive interaction between predefined “patchy” sites on the surfaces of anisotropic microcolloids can provide them with the ability to self‐assemble in a controlled manner to build target structures of increased complexity. An important step toward the controlled formation of a desired superstructure is to identify reversible electrostatic interactions between patches which allow them to align with one another. The formation of bipatchy particles with two oppositely charged patches fabricated using sandwich microcontact printing is reported. These particles spontaneously self‐aggregate in solution, where a diversity of short and long chains of bipatchy particles with different shapes, such as branched, bent, and linear, are formed. Calculations show that chain formation is driven by a combination of attractive electrostatic interactions between oppositely charged patches and the charge‐induced polarization of interacting particles.     

Light‐Induced Buckles Localized by Polymeric Inks Printed on Bilayer Films

Buckling instabilities generate microscale features in thin films in a facile manner. Buckles can form, for example, by heating a metal/polymer film stack on a rigid substrate. Thermal expansion differences of the individual layers generate compressive stress that causes the metal to buckle over the entire surface. The ability to dictate and confine the location of buckle formation can enable patterns with more than one length scale, including hierarchical patterns. Here, sacrificial “ink” patterned on top of the film stack localizes the buckles via two mechanisms. First, stiff inks suppress buckles such that only the non‐inked regions buckle in response to infrared light. The metal in the non‐inked regions absorbs the infrared light and thus gets sufficiently hot to induce buckles. Second, soft inks that absorb light get hot faster than the non‐inked regions and promote buckling when exposed to visible light. The exposed metal in the non‐inked regions reflects the light and thus never get sufficiently hot to induce buckles. This second method works on glass substrates, but not silicon substrates, due to the superior thermal insulation of glass. The patterned ink can be removed, leaving behind hierarchical patterns consisting of regions of buckles among non‐buckled regions.     

Pressure‐Responsive Hierarchical Chiral Photonic Aerogels

Pressure‐responsive chiral photonic aerogels are fabricated by combining liquid crystal self‐assembly and ice‐templating processes. The aerogels have a hierarchical structure in which the primary 2D chiral nematic structured walls of cellulose nanocrystals form ribbons that support a secondary 3D cellular network. Owing to the flexibility of the aerogels in solvent, the 3D structure of the aerogel can easily be transformed to a 2D structure by pressure‐induced rearrangement. The aerogels vary from white in color, which arises from light scattering, to a reflective photonic crystal displaying bright iridescent colors that depend on the immersed solvent. A solvent‐sensitive ink that shows quick color response to different solvents is designed using the pressure‐responsive photonic aerogel. This material demonstrates a new response mechanism for the design of smart and mechanoresponsive photonic materials.     

Building Carbon‐Based Versatile Scaffolds on the Electrode Surface to Boost Capacitive Performance for Fiber Pseudocapacitors

In order to fabricate high performance fiber pseudocapacitors, the trade‐off between high mass loading and high utilization efficiency of pseudocapacitive materials should be carefully addressed. Here, a solution that is to construct a carbon‐based versatile scaffold is reported for loading pseudocapacitive materials on carbonaceous fibers. The scaffold can be easily built by conformally coating commercial pen ink on the fibers without any destruction to the fiber skeleton. Due to the high electrical conductivity and abundant macropore structure, it can provide sufficient loading room and a high ion/electron conductive network for pseudocapacitive materials. Therefore, their loading mass and utilization efficiency can be increased simultaneously, and thus the as‐designed fibrous electrode displays a high areal capacitance of 649 mF cm^?2 (or 122 mF cm^?1 based on length), which is higher than most of the reported fiber pseudocapacitors. The simple and low‐cost strategy opens up a new way to prepare high performance portable/wearable energy storage devices.     

2D Single‐Crystalline Copper Nanoplates as a Conductive Filler for Electronic Ink Applications

Large‐scale 2D single‐crystalline copper nanoplates (Cu NPLs) are synthesized by a simple hydrothermal method. The combination of a mild reductant, stabilizer, and shape modifier allows the dimensional control of the Cu nanocrystals from 1D nanowires (NWs) to 2D nanoplates. High‐resolution transmission electron microscopy (HR‐TEM) reveals that the prepared Cu NPLs have a single‐crystalline structure. From the X‐ray photoelectron spectroscopy (XPS) analysis, it is found that iodine plays an important role in the modification of the copper nanocrystals through the formation of an adlayer on the basal plane of the nanoplates. Cu NPLs with an average edge length of 10 μm are successfully synthesized, and these Cu NPLs are the largest copper 2D crystals synthesized by a solution‐based process so far. The application of the metallic 2D crystals as a semitransparent electrode proves their feasibility as a conductive filler, exhibiting very low sheet resistance (0.4 Ω ?^?1) compared to Cu NWs and a transmittance near 75%. The efficient charge transport is due to the increased contact area between each Cu NPL, i.e., so‐called plane contact (2D electrical contact). In addition, this type of contact enhances the current‐carrying capability of the Cu NPL electrodes, implying that the large‐size Cu NPLs are promising conductive fillers for printable electrode applications.     

Set‐off: Development of a Simulation Press and Analytical Approach to Study the Phenomenon

One type of mass transfer between package and food is through set‐off. This phenomenon is defined as the transfer of components from the external layer (printed surface) of a packaging material to the inner side (surface to come into contact with food) during storage of printed substrates in reels or stacks. The objective of this work was to build up the equipment for set‐off simulation and to assess the extent of benzophenone (BP) transfer. BP is a model photoinitiator used in standard ultraviolet curable inks (non‐low migration inks). For set‐off simulation, the storage conditions (time, temperature and pressure) and the ink film weight are provided by EuPIA Guidelines. Ethanol 50% (v/v) as simulant and contact condition of 40°C/10 days were used. Samples were printed and cured at different speeds. The migrated BP was determined by analysing the extracts using high‐performance liquid chromatography with diode‐array detector. Set‐off phenomenon extent was dependent on the curing. In general, the BP migrations increase as speed increased. Copyright © 2016 John Wiley & Sons, Ltd.     

PUA木器油墨性能与成膜助剂分子结构的相关性

目的 探究不同成膜助剂分子结构对聚氨酯丙烯酸酯（PUA）木器油墨墨膜性能的影响。方法 以成膜助剂作为研究对象,使用PUA作为连接料,与消泡剂等助剂一起制备木器油墨。研究成膜助剂3-甲氧基-3-甲基-1-丁醇、乙二醇丁醚、丙二醇、二乙二醇丁醚和二丙二醇丁醚对PUA木器油墨性能的影响。采用FTIR研究成膜助剂/连接料复合乳液薄膜的化学结构,并对其硬度、附着力、接触角表面性质进行表征。结果 助剂相对分子质量越小,墨膜硬度、附着力越大。当乙二醇丁醚的质量分数为4%时,硬度最大为3H,附着力为最佳等级0;醚键和羟基的相对含量越多则其硬度、附着力和接触角越大,丙二醇质量分数为4%时接触角最大（95.3°）。结论 选择质量分数为4%的丙二醇作为成膜助剂时,综合性能最佳;选择成膜助剂时应优先考虑相对分子质量小、极性基团相对含量多的助剂。