Room‐Temperature Metallic Fusion‐Induced Layer‐by‐Layer Assembly for Highly Flexible Electrode Applications

To fabricate flexible electrodes, conventional silver (Ag) nanomaterials have been deposited onto flexible substrates, but the formed electrodes display limited electrical conductivity due to residual bulky organic ligands, and thus postsintering processes are required to improve the electrical conductivity. Herein, an entirely different approach is introduced to produce highly flexible electrodes with bulk metal–like electrical conductivity: the room‐temperature metallic fusion of multilayered silver nanoparticles (NPs). Synthesized tetraoctylammonium thiosulfate (TOAS)‐stabilized Ag NPs are deposited onto flexible substrates by layer‐by‐layer assembly involving a perfect ligand‐exchange reaction between bulky TOAS ligands and small tris(2‐aminoethyl)amine linkers. The introduced small linkers substantially reduce the separation distance between neighboring Ag NPs. This shortened interparticle distance, combined with the low cohesive energy of Ag NPs, strongly induces metallic fusion between the close‐packed Ag NPs at room temperature without additional treatments, resulting in a high electrical conductivity of ≈1.60 × 10⁵ S cm^?1 (bulk Ag: ≈6.30 × 10⁵ S cm^?1). Furthermore, depositing the TOAS–Ag NPs onto cellulose papers through this approach can convert the insulating substrates into highly flexible and conductive papers that can be used as 3D current collectors for energy‐storage devices.     

Room‐Temperature Printing of Organic Thin‐Film Transistors with π‐Junction Gold Nanoparticles

Printing semiconductor devices under ambient atmospheric conditions is a promising method for the large‐area, low‐cost fabrication of flexible electronic products. However, processes conducted at temperatures greater than 150 °C are typically used for printed electronics, which prevents the use of common flexible substrates because of the distortion caused by heat. The present report describes a method for the room‐temperature printing of electronics, which allows thin‐film electronic devices to be printed at room temperature without the application of heat. The development of π‐junction gold nanoparticles as the electrode material permits the room‐temperature deposition of a conductive metal layer. Room‐temperature patterning methods are also developed for the Au ink electrodes and an active organic semiconductor layer, which enables the fabrication of organic thin‐film transistors through room‐temperature printing. The transistor devices printed at room temperature exhibit average field‐effect mobilities of 7.9 and 2.5 cm² V^?1 s^?1 on plastic and paper substrates, respectively. These results suggest that this fabrication method is very promising as a core technology for low‐cost and high‐performance printed electronics.     

3D Conformal Printing and Photonic Sintering of High‐Performance Flexible Thermoelectric Films Using 2D Nanoplates

Flexible thermoelectric (TE) devices hold great promise for energy harvesting and cooling applications, with increasing significance to serve as perpetual power sources for flexible electronics and wearable devices. Despite unique and superior TE properties widely reported in nanocrystals, transforming these nanocrystals into flexible and functional forms remains a major challenge. Herein, demonstrated is a transformative 3D conformal aerosol jet printing and rapid photonic sintering process to print and sinter solution‐processed Bi₂Te_2.7Se_0.3 nanoplate inks onto virtually any flexible substrates. Within seconds of photonic sintering, the electrical conductivity of the printed film is dramatically improved from nonconductive to 2.7 × 10⁴ S m^?1. The films demonstrate a room temperature power factor of 730 µW m^?1 K^?2, which is among the highest values reported in flexible TE films. Additionally, the film shows negligible performance changes after 500 bending cycles. The highly scalable and low‐cost fabrication process paves the way for large‐scale manufacturing of flexible devices using a variety of high‐performing nanoparticle inks.     

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.     

Highly Robust Indium‐Free Transparent Conductive Electrodes Based on Composites of Silver Nanowires and Conductive Metal Oxides

A hybrid approach for the realization of In‐free transparent conductive layers based on a composite of a mesh of silver nanowires (NWs) and a conductive metal‐oxide is demonstrated. As metal‐oxide room‐temperature‐processed sol–gel SnO_x or Al:ZnO prepared by low‐temperature (100 °C) atomic layer deposition is used, respectively. In this concept, the metal‐oxide is intended to fuse the wires together and also to “glue” them to the substrate. As a result, a low sheet resistance down to 5.2 Ω sq^‐1 is achieved with a concomitant average transmission of 87%. The adhesion of the NWs to the substrate is significantly improved and the resulting composites withstand adhesion tests without loss in conductivity. Owing to the low processing temperatures, this concept allows highly robust, highly conductive, and transparent coatings even on top of temperature sensitive objects, for example, polymer foils, organic devices. These Indium‐ and PEDOT:PSS‐free hybrid layers are successfully implemented as transparent top‐electrodes in efficient all‐solution‐processed semitransparent organic solar cells. It is obvious that this approach is not limited to organic solar cells but will generally be applicable in devices which require transparent electrodes.     

Inkjet‐Printed Flexible Gold Electrode Arrays for Bioelectronic Interfaces

Bioelectronic interfaces require electrodes that are mechanically flexible and chemically inert. Flexibility allows pristine electrode contact to skin and tissue, and chemical inertness prevents electrodes from reacting with biological fluids and living tissues. Therefore, flexible gold electrodes are ideal for bioimpedance and biopotential measurements such as bioimpedance tomography, electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). However, a manufacturing process to fabricate gold electrode arrays on plastic substrates is still elusive. In this work, a fabrication and low‐temperature sintering (≈200 °C) technique is demonstrated to fabricate gold electrodes. At low‐temperature sintering conditions, lines of different widths demonstrate different sintering speeds. Therefore, the sintering condition is targeted toward the widest feature in the design layout. Manufactured electrodes show minimum feature size of 62 μm and conductivity values of 5 × 10 ⁶ S m^?1. Utilizing the versatility of printing and plastic electronic processes, electrode arrays consisting of 31 electrodes with electrode‐to‐electrode spacing ranging from 2 to 7 mm are fabricated and used for impedance mapping of conformal surfaces at 15 kHz. Overall, the fabrication process of an inkjet‐printed gold electrode array that is electrically reproducible, mechanically robust, and promising for bioimpedance and biopotential measurements is demonstrated.     

Cover Picture: Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non‐Planar Electronic and Lab‐on‐a‐Chip Device Patterning (Adv. Funct. Mater. 4/2005)

A composite image is shown that highlights examples of device architectures that either incorporate or exploit polymer‐embedded metallic microstructures. In work reported by Nuzzo and co‐workers on p. 557, new applications of soft lithography, in conjunction with advanced forms of multilayer metallization, are used to construct these exceptionally durable structures. They are suitable for use in non‐planar lithographic patterning, and as device components finding applications ranging from microelectronics to Lab‐on‐a‐Chip analytical systems. This article describes the fabrication of durable metallic patterns that are embedded in poly(dimethylsiloxane) (PDMS) and demonstrates their use in several representative applications. The method involves the transfer and subsequent embedding of micrometer‐scale gold (and other thin‐film material) patterns into PDMS via adhesion chemistries mediated by silane coupling agents. We demonstrate the process as a suitable method for patterning stable functional metallization structures on PDMS, ones with limiting feature sizes less than 5 μm, and their subsequent utilization as structures suitable for use in applications ranging from soft‐lithographic patterning, non‐planar electronics, and microfluidic (lab‐on‐a‐chip, LOC) analytical systems. We demonstrate specifically that metal patterns embedded in both planar and spherically curved PDMS substrates can be used as compliant contact photomasks for conventional photolithographic processes. The non‐planar photomask fabricated with this technique has the same surface shape as the substrate, and thus facilitates the registration of structures in multilevel devices. This quality was specifically tested in a model demonstration in which an array of one hundred metal oxide semiconductor field‐effect transistor (MOSFET) devices was fabricated on a spherically curved Si single‐crystalline lens. The most significant opportunities for the processes reported here, however, appear to reside in applications in analytical chemistry that exploit devices fabricated using the methods of soft lithography. Toward this end, we demonstrate durably bonded metal patterns on PDMS that are appropriate for use in microfluidic, microanalytical, and microelectromechanical systems. We describe a multilayer metal‐electrode fabrication scheme (multilaminate metal–insulator–metal (MIM) structures that substantially enhance performance and stability) and use it to enable the construction of PDMS LOC devices using electrochemical detection. A polymer‐based microelectrochemical analytical system, one incorporating an electrode array for cyclic voltammetry and a microfluidic system for the electrophoretic separation of dopamine and catechol with amperometric detection, is demonstrated.     

React‐on‐Demand (RoD) Fabrication of Highly Conductive Metal–Polymer Hybrid Structure for Flexible Electronics via One‐Step Direct Writing or Printing

As a fast prototyping technique, direct writing of flexible electronics is gaining popularity for its low‐cost, simplicity, ultrahigh portability, and ease of use. However, the latest handwritten circuits reported either have relative low conductivity or require additional post‐treatment, keeping this emerging technology away from end‐users. Here, a one‐step react‐on‐demand (RoD) method for fabricating flexible circuits with ultralow sheet resistance, enhanced safety, and durability is proposed. With the special functionalized substrate, a real‐time 3D synthesis of silver plates in microscale is triggered on‐demand right beneath the tip in the water‐swelled polyvinyl alcohol (PVA) coating, forming a 3D metal–polymer hybrid structure of ≈7 µm with one single stroke. The as‐fabricated silver traces show an enhanced durability and ultralow sheet resistance down to 4 mΩ sq^?1 which is by far the lowest sheet resistance reported in literatures achieved by direct writing. Meanwhile, PVA seal small particles inside the film, adding additional safety to this technology. Since neither nanomaterials nor a harsh fabrication environment are required, the proposed method remains low cost, user friendly, and accessible to end users. With little effort, the RoD approach can be extended to various printing systems, offering a particle‐free, sintering‐free solution for high‐resolution, high‐speed production of flexible electronics.     

Rational Design of a Printable,Highly Conductive Silicone‐based Electrically Conductive Adhesive for Stretchable Radio‐Frequency Antennas

Stretchable radio‐frequency electronics are gaining popularity as a result of the increased functionality they gain through their flexible nature, impossible within the confines of rigid and planar substrates. One approach to fabricating stretchable antennas is to embed stretchable or flowable conductive materials, such as conductive polymers, conductive polymer composites, and liquid metal alloys as stretchable conduction lines. However, these conductive materials face many challenges, such as low electrical conductivity under mechanical deformation and delamination from substrates. In the present study, a silicone‐based electrically conductive adhesive (silo‐ECA) is developed that have a conductivity of 1.51 × 10⁴ S cm^?1 and can maintain conductivity above 1.11 × 10³ S cm^?1, even at a large stain of 240%. By using the stretchable silo‐ECAs as a conductor pattern and pure silicone elastomers as a base substrate, stretchable antennas can be fabricated by stencil printing or soft‐lithography. The resulting antenna's resonant frequency is tunable over a wide range by mechanical modulation. This fabrication method is low‐cost, can support large‐scale production, has high reliability over a wide temperature range, and eliminates the concerns of leaking or delamination between conductor and substrate experienced in previously reported micro‐fluidic antennas.     

Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non‐Planar Electronic and Lab‐on‐a‐Chip Device Patterning

This article describes the fabrication of durable metallic patterns that are embedded in poly(dimethylsiloxane) (PDMS) and demonstrates their use in several representative applications. The method involves the transfer and subsequent embedding of micrometer‐scale gold (and other thin‐film material) patterns into PDMS via adhesion chemistries mediated by silane coupling agents. We demonstrate the process as a suitable method for patterning stable functional metallization structures on PDMS, ones with limiting feature sizes less than 5 μm, and their subsequent utilization as structures suitable for use in applications ranging from soft‐lithographic patterning, non‐planar electronics, and microfluidic (lab‐on‐a‐chip, LOC) analytical systems. We demonstrate specifically that metal patterns embedded in both planar and spherically curved PDMS substrates can be used as compliant contact photomasks for conventional photolithographic processes. The non‐planar photomask fabricated with this technique has the same surface shape as the substrate, and thus facilitates the registration of structures in multilevel devices. This quality was specifically tested in a model demonstration in which an array of one hundred metal oxide semiconductor field‐effect transistor (MOSFET) devices was fabricated on a spherically curved Si single‐crystalline lens. The most significant opportunities for the processes reported here, however, appear to reside in applications in analytical chemistry that exploit devices fabricated using the methods of soft lithography. Toward this end, we demonstrate durably bonded metal patterns on PDMS that are appropriate for use in microfluidic, microanalytical, and microelectromechanical systems. We describe a multilayer metal‐electrode fabrication scheme (multilaminate metal–insulator–metal (MIM) structures that substantially enhance performance and stability) and use it to enable the construction of PDMS LOC devices using electrochemical detection. A polymer‐based microelectrochemical analytical system, one incorporating an electrode array for cyclic voltammetry and a microfluidic system for the electrophoretic separation of dopamine and catechol with amperometric detection, is demonstrated.     

Anhydride‐Assisted Spontaneous Room Temperature Sintering of Printed Bioresorbable Electronics

Bioresorbable electronic devices are promising replacements for conventional build‐to‐last electronics in implantable biomedical systems and consumer electronics. However, bioresorbable devices are typically achieved by complex complementary metal oxide semiconductor fabrication processes that minimize exposure to humidity. Emerging printable techniques for bioresorbable electronics demand further improvement in electrical conductivity and mechanical robustness. This paper presents a room‐temperature spontaneous sintering method of bioresorbable inks that contain zinc nanoparticles and anhydride. The entire process can be conducted in atmosphere environment under 90% humidity within 300 min. It has minimum requirement for external heating and special ambient conditions, allowing humidity to trigger the surface chemistry of zinc nanoparticles and spontaneous welding between neighboring nanoparticles. The resulting bioresorbable patterns are highly conductive (σ = 72 400 S m^?1) and mechanically robust (>1500 bending cycles) to enable practical applications. A radio circuit achieved through the above method can operate stably over 14 days in air and disappear in water for less than 30 min. The spontaneous room‐temperature sintering represents a rapid and energy‐efficient approach to achieve high‐performance bioresorbable electronics with improved mechanical robustness and electrical performance, leading to broader impacts in the areas of healthcare, information security, and consumer electronics.     

Metallic Architectures from 3D‐Printed Powder‐Based Liquid Inks

A new method for complex metallic architecture fabrication is presented, through synthesis and 3D‐printing of a new class of 3D‐inks into green‐body structures followed by thermochemical transformation into sintered metallic counterparts. Small and large volumes of metal‐oxide, metal, and metal compound 3D‐printable inks are synthesized through simple mixing of solvent, powder, and the biomedical elastomer, polylactic‐co‐glycolic acid (PLGA). These inks can be 3D‐printed under ambient conditions via simple extrusion at speeds upwards of 150 mm s^–1 into millimeter‐ and centimeter‐scale thin, thick, high aspect ratio, hollow and enclosed, and multi‐material architectures. The resulting 3D‐printed green‐bodies can be handled immediately, are remarkably robust, and may be further manipulated prior to metallic transformation. Green‐bodies are transformed into metallic counterparts without warping or cracking through reduction and sintering in a H₂ atmosphere at elevated temperatures. It is shown that primary metal and binary alloy structures can be created from inks comprised of single and mixed oxide powders, and the versatility of the process is illustrated through its extension to more than two dozen additional metal‐based materials. A potential application of this new system is briefly demonstrated through cyclic reduction and oxidation of 3D‐printed iron oxide constructs, which remain intact through numerous redox cycles.     

Sample Target Substrates with Reduced Spot Size for MALDI‐TOF Mass Spectrometry Based on Patterned Self‐Assembled Monolayers

The wetting properties of structured self‐assembled monolayers are used to fabricate sample target substrates for MALDI‐TOF mass spectrometry. Combining the advantages of a hydrophobic‐hydrophilic surface pattern and the possibility of obtaining micrometer patterns allows an increase in the sensitivity of MALDI‐TOF mass spectrometry analysis and a reduction in the traceable concentration down to fmol µL^?1. This easy, cheap and fast patterning process provides substrates that allow sensitive, high‐resolution mass spectrometry of dilute solutions.     

Fabrication of Biofunctionalized Quasi‐Three‐Dimensional Microstructures of a Nonfouling Comb Polymer Using Soft Lithography

This paper describes a simple set of patterning methods that are applicable to diverse substrates and allow the routine and rapid fabrication of protein patterns embedded within a background that consists of quasi‐three‐dimensional microstructures of a cell‐resistant polymer. The ensemble of methods reported here utilizes three components to create topographically nonfouling polymeric structures that present cell‐adhesive protein patterns in the regions between the microstructures: the first component is an amphiphilic comb polymer that is comprised of a methyl methacrylate backbone and pendant oligo(ethylene glycol) moieties along the side chain, physically deposited films of which are protein‐ and cell‐resistant. The second component of the fabrication methodology involves the use of different variants of soft lithography, such as microcontact printing to create nonfouling topographical features of the comb polymer that demarcate cell‐adhesive regions of the third component: a cell‐adhesive extracellular protein or peptide. The ensemble of methods reported in this paper was used to fabricate quasi‐three‐dimensional patterns that present topographical and biochemical cues on a variety of substrates, and was shown to successfully maintain cellular patterns for up to two months in serum‐containing medium. We believe that this, and other such methods under development that allow independent and systematic control of chemistry, topography and substrate compliance will provide versatile “test‐beds” for fundamental studies in cell biology as well as allow the discovery of rational design principles for the development of biomaterials and tissue‐engineering scaffolds.     

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.     

Tunable Room‐Temperature Synthesis of ReS2 Bicatalyst on 3D‐ and 2D‐Printed Electrodes for Photo‐ and Electrochemical Energy Applications

The advancement in 3D‐printing technologies conveniently offers boundless opportunities for the customization of a practical substrate or electrode for diverse functionalities. ReS₂ is an attractive transition metal dichalcogenide (TMD), showing strong photoelectrochemical activities. Two advanced systems are merged for the next step in electrochemistry—the limits of the prevailing synthesis techniques of TMDs operating at high temperature or low pressure, which are not compatible with 3D‐printed polymer electrodes that can withstand only comparatively low temperatures, are overcome. A unique NH₄ReS₄ precursor is separately prepared to conduct subsequent ReS₂ electrodeposition at room temperature on 3D‐printed carbon and 2D‐printed carbon electrodes. The deposited ReS₂ is investigated as a dual‐functional electro‐ and photocatalyst in hydrogen evolution reaction and photoelectrochemical oxidation of water. Moreover, the electrodeposition conditions can be adjusted to optimize the catalytic activities. These encouraging outcomes demonstrate the simplicity yet versatility of TMDs based on electrodeposition technique on a rationally designed conductive platform, which creates numerous possibilities for other TMDs and on other low‐temperature substrates for electrochemical energy devices.     

Seriography‐Guided Reduction of Graphene Oxide Biopapers for Wearable Sensory Electronics

Novel nacre‐mimic bio‐nanocomposites, such as graphene‐based laminates, are pushing the boundaries of strength and toughness as flexible engineering materials. Translating these material advances to functional flexible electronics requires methods for generating print‐scalable microcircuits (conductive elements surrounded by dielectric) into these strong, tough, lightweight bio‐nanocomposites. Here, a new paradigm for printing flexible electronics by employing facile, eco‐friendly seriography to confine the reduction of graphene oxide biopapers reinforced by silk interlayers is presented. Well‐defined, micropatterned regions on the biopaper are chemically reduced, generating a 10⁶ increase in conductivity (up to 10⁴ S m^?1). Flexible, robust graphene‐silk circuits are showcased in diverse applications such as resistive moisture sensors and capacitive proximity sensors. Unlike conductive (i.e., graphene‐ or Ag nanoparticle‐loaded) inks printed onto substrates, seriography‐guided reduction does not create mechanically weak interfaces between dissimilar materials and does not require the judicious formation of ink. The unimpaired functionality of printed‐in graphene‐silk microcircuits after thousands of punitive folding cycles and chemical attack by harsh solvents is demonstrated. This novel approach provides a low‐cost, portable solution for printing micrometer‐scale conductive features uniformly across large areas (>hundreds of cm²) in layered composites for applications including wearable health monitors, electronic skin, rollable antennas, and conformable displays.     

Inkjet Process for Conductive Patterning on Textiles: Maintaining Inherent Stretchability and Breathability in Knit Structures

In this work, a novel technique of inkjet printing e‐textiles with particle free reactive silver inks on knit structures is developed. The inkjet‐printed e‐textiles are highly conductive, with a sheet resistance of 0.09 Ω sq^‐1, by means of controlling the number of print passes, annealing process, and textile structures. It is notable that the inkjet process allows textiles to maintain its inherent properties, including stretchability, flexibility, breathability, and fabric hand after printing process. This is achieved by formation of ultrathin silver layers surrounding individual fibers. The silver layers coated on fibers range from 250 nm to 2.5 µm, maintaining the size of interstices and flexibility of fibers. The annealing process, structure of fibers, and printed layers significantly influence the electrical conductivity of the patterned structures on textiles. Outstanding electrical conductivity and durability are demonstrated by optimizing print passes, controlling textile structures, and incorporating an in situ annealing process. The electrical resistance dependence on the strain rate of the textiles is examined, showing the ability to maintain electrical conductivity to retain light‐emitting diode use, stable more than 500 consecutive strain cycles. Most importantly, inkjet‐printed e‐textiles maintain their characteristic washability, breathability, and fabric hands for applications in wearable technology.     

High‐Performance Solid Polymer Electrolytes Filled with Vertically Aligned 2D Materials

Solid state lithium metal batteries are the most promising next‐generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due to the excellent flexibility, manufacturability, lightweight, and low‐cost processing. However, fatal drawbacks of the SPE such as the insufficient ionic conductivity and Li⁺ transference number at room temperature restrict their practical application. Here vertically aligned 2D sheets are demonstrated as an advanced filler for SPE with enhanced ionic conductivity, Li⁺ transference number, mechanical modulus, and electrochemical stability, using vermiculite nanosheets as an example. The vertically aligned vermiculite sheets (VAVS), prepared by the temperature gradient freezing, provide aligned, continuous, run‐through polymer‐filler interfaces after infiltrating with polyethylene oxide (PEO)‐based SPE. As a result, ionic conductivity as high as 1.89 × 10^?4 S cm^?1 at 25 °C is achieved with Li⁺ transference number close to 0.5. Along with their enhanced mechanical strength, Li|Li symmetric cells using VAVS–CSPE are stable over 1300 h with a low overpotential. LiFePO₄ in all‐solid‐state lithium metal batteries with VAVS–CSPE could deliver a specific capacity of 167 mAh g^?1 at 0.1 C at 35 °C and 82% capacity retention after 200 cycles at 0.5 C.     

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.