Fabrication Of Conductors Research Articles

Facile Fabrication of Transparent Conductor of Cu Nanowire-PEDOT:PSS

Facile Fabrication of Transparent Conductor of Cu Nanowire-PEDOT:PSS

Low hysteresis zwitterionic supramolecular polymer ion-conductive elastomers with anti-freezing properties, high stretchability, and self-adhesion for flexible electronic devices.

The fabrication of stretchable ionic conductors with low hysteresis and anti-freezing properties to enhance the durability and reliability of flexible electronics even at low temperatures remains an unmet challenge. Here, we report a facile strategy to fabricate low hysteresis, high stretchability, self-adhesion and anti-freezing zwitterionic supramolecular polymer ion-conductive elastomers (ICEs) by photoinitiated polymerization of aqueous precursor solutions containing a newly designed zwitterionic monomer carboxybetaine ureido acrylate (CBUIA) followed by solvent evaporation. The resultant poly(carboxybetaine ureido acrylate) (PCBUIA) ICEs are highly stretchable and self-adhesive owing to the presence of strong hydrogen bonds between ureido groups and dipole-dipole interactions of zwitterions. The zwitterion groups on the polymer side chains and loaded-lithium chloride endow PCBUIA ICEs with excellent anti-freezing properties, demonstrating mechanical flexibility and ionic transport properties even at a low temperature (-20 °C). Remarkably, the PCBUIA ICEs demonstrate a low hysteresis (≈10%) during cyclic mechanical loading-unloading (≤500%), and are successfully applied as wearable strain sensors and triboelectric nanogenerators (TENGs) for energy harvesting and human motion monitoring. In addition, the PCBUIA ICE-based TENG was used as a wireless sensing terminal for Internet of Things smart devices to enable wireless sensing of finger motion state detection.

Healable Ionic Conductors with Extremely Low-Hysteresis and High Mechanical Strength Enabled by Hydrophobic Domain-Locked Reversible Interactions.

Extremely low hysteresis, high mechanical strength, superior toughness, and excellent healability are essential for stretchable ionic conductors to enhance their reliability and meet for cutting-edge applications. However, the fabrication of stretchable ionic conductors with such mutually exclusive properties remains challenging. Herein, extremely low-hysteresis and healable ionic conductors with a tensile strength of ≈8.9MPa and toughness of ≈23.2MJ m-3 are fabricated through the complexation of 4-carboxybenzaldehyde (CBA) grafted poly(vinyl alcohol) (PVA) (denoted as PVA-CBA) and poly (allylamine hydrochloride) (PAH) followed by acidification and ion-loading steps. The acidification step generates the PVA-CBA/PAH ionic conductors with in situ formed dynamic hydrophobic domains that lock and stabilize noncovalent interactions. This significantly minimizes the energy dissipation of the ionic conductors during cyclic mechanical loading (≤200% strain), resulting in ionic conductors with extremely low hysteresis (≈5%). The fractured ionic conductors can be healed at 60°C to restore their original properties. Because of the extremely low hysteresis, the PVA-CBA/PAH ionic conductors show a highly stable and reproducible electrical response over 5000 uninterrupted loading-unloading cycles at a strain of 200%. The ionic conductor based sensors exhibit a high sensitivity to a wide range of strains (1-500%).

Conductor Qualification and Fabrication for the MACQU Solenoid

A solenoid mock-up called MACQU was designed and tested at CEA Saclay to study the quench propagation in a MADMAX like conductor, i.e. a cable-in-conduit conductor (CICC) with copper conduit cooled at 1.8 K with stagnant superfluid helium. Compared with classic CICCs for fusion magnets, the presence of a cable wrapped by a copper tape and inserted in a copper conduit represented new features from the manufacturing point of view that required a R&D program. In this paper the whole process that led to the final conductor designed for the solenoid MACQU, from strand characterization to the fabrication through the R&D and acceptance phases is described.

Boosting Sensitivity and Durability of Pressure Sensors Based on Compressible Cu Sponges by Strengthening Adhesion of "Rigid-Soft" Interfaces.

The interface adhesion plays a key role between rigid metal and elastomer in compressible and stretchable conductors. However, the poor interfacial adhesion hinders their wide applications. To strengthen the interface adhesion, herein, a combination strategy of structure interlocking and polymer bridging is designed by introducing a method of subsurface-initiated atom transfer radical polymerization (sSI-ATRP). This method can make polymer brush root in polydimethylsiloxane (PDMS) subsurface, on this basis, metals further grow from subsurface to surface of PDMS via electroless deposition. As a result, the adhesive strength (≈2.5MPa) between metal layer and PDMS elastomer is 4 times higher than that made by common polymer modification. As a demonstration, pressure sensor is constructed by using as-prepared compressible 3D Cu sponge as a top electrode and paper-based interdigited metal electrode as a bottom electrode. The device sensitivity can reach up to 961.2kPa-1 and the durability can arrive at 3000 cycles without degradation. Thus, this proposed interface-enhancement strategy for rigid-soft materials can significantly promote the performance of piezoresistive pressure sensors based on 3D conductive sponge. In the future, it would also be expanded to the fabrication of stretchable conductors and extensively applied in other flexible and wearable electronics.

Design and Fabrication of an Ag Ultrathin Layer-Based Transparent Band Tunable Conductor and Its Thermal Stability.

Transparent conductors (TC) have been widely applied in a wide range of optoelectronic devices. Nevertheless, different transparent spectral bands are always needed for particular applications. In this work, indium tin oxide (ITO)-free TCs with tunable transparent bands based on the film structure of TiO2/Ag/AZO (Al-doped ZnO) were designed by the transfer matrix method and deposited by magnetron sputtering. The transparent spectra and figure-of-merit (FOM) were effectively adjusted by precisely controlling the Ag layer's thickness. The fabricated as-deposited samples exhibited an average optical transmittance larger than 88.3% (400-700 nm), a sheet resistance lower than 7.7 Ω.sq-1, a low surface roughness of about 1.4 nm, and mechanical stability upon 1000 bending cycles. Moreover, the samples were able to hold optical and electrical properties after annealing at 300 °C for 60 min, but failed at 400 °C even for 30 min.

Highly conductive laser-induced graphene through the deposition of liquid metal particles for flexible electronics

The rapid and simple fabrication process of laser-induced graphene (LIG) has enabled the creation of flexible sensors for emerging applications such as wearable electronics and intelligent systems. Although LIG can be designed to be a sensitive strain sensor due to the large change in its resistance under deformation, this property can also limit its use as a printed conductor on flexible substrates. Here, we present a versatile technique to enhance the electrical conductivity and resistive heating ability of LIG for use as flexible conductors in printed electronics. The highly conductive traces are prepared by direct writing of LIG onto a polyimide film using a CO2 laser, upon which the functionalized liquid metal (LM)—eutectic gallium indium (EGaIn)—particles are deposited and activated. This results in a ∼400 times increase in electrical conductivity of LIG traces while maintaining mechanical flexibility and manufacturing scalability without the need for soldering. Electromechanical characterization of the LIG-LM traces shows low resistance change (less than 0.3 Ω) under large bending deformations. At the same time, the enhanced electrical conductivity contributes to the resistive heating performance as it reduces the input voltage requirement by ∼15 times to achieve similar surface temperatures compared to pure LIG traces. By combining EGaIn LM with laser-synthesized graphene, we can fabricate flexible hybrid electronics. We demonstrate the practicality of this technique by fabrication of flexible conductors and heating devices with highly customizable patterns.

Thermally Crosslinked Hole Conductor Enables Stable Inverted Perovskite Solar Cells with 23.9% Efficiency.

Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) represents the state-of-the-art hole transport material (HTM) in inverted perovskite solar cells (PSCs). However, unsatisfied surface properties of PTAA and high energy disorder in the bulk film hinder the further enhancement of device performance. Herein, a simple small molecule 10-(4-(3,6-dimethoxy-9H-carbazol-9-yl)phenyl)-3,7-bis(4-vinylphenyl)-10H-phenoxazine (MCz-VPOZ) is strategically developed for in situ fabrication of polymer hole conductor (CL-MCz) via a facile and low-temperature cross-linking technology. The resulting polymer CL-MCz offers high energy ordering and improved electrical conductivity, as well as appropriate energy-level alignment, enabling efficient charge carrier collection in the devices. Meanwhile, CL-MCz synchronously provides satisfied surface wettability and interfacial functionalization, facilitating the formation of high-quality perovskite films with fewer bulk iodine vacancies and suppressed carrier recombination. Significantly, the device with CL-MCz yields a champion efficiency of 23.9% along with an extremely low energy loss down to 0.41 eV, which represents the highest reported efficiency for non-PTAA-based polymer HTMs in inverted PSCs. Furthermore, the corresponding unencapsulated devices exhibit competitive shelf-life stability under various operational stressors up to 2500 h, reflecting high promises of CL-MCz in the scalable PSC application. This work underscores the promising potential of the cross-linking approach in preparing low-cost, stable, and efficient polymer HTMs toward reliable PSCs.

Study on fabricating transparent, stretchable, and self-healing ionic conductive elastomers from biomass molecules through solvent-free synthesis

We propose a simple and effective strategy for increasing the conductivity of polyTA by copolymerization reactions, and a series of autonomously self-healing, transparent, liquid-free ionic conductors was prepared.

Dynamic self-assembly of small molecules enables the spontaneous fabrication of hole conductors at perovskite/electrode interfaces for over 22% stable inverted perovskite solar cells.

The bottom hole transport layers (HTLs) are of paramount importance in determining both the efficiency and stability of inverted perovskite solar cells (PSCs), however, their surface nature and properties strongly interfere with the upper perovskite crystallization kinetics and also influence interfacial carrier dynamics. In this work, we strategically develop a simple, facile and spontaneous fabrication method of the HTL at the perovskite/electrode interface by dynamic self-assembly (DSA) of small molecules during perovskite crystallization. Different from the traditional layer-by-layer approach, this DSA strategy involves a bilateral movement of self-assembled molecules (SAMs) from perovskite solution, realizing simultaneous fabrication of the HTL and perovskite surface passivation. We design a multifunctional molecule, (4-(7H-benzo[c]carbazol-7-yl)butyl)phosphonic acid (BCB-C4PA), for the DSA process, to optimize both self-assembly ability and interfacial energy alignment. Benefitting from this unconventional DSA approach and BCB-C4PA, a champion PCE of 22.2% is achieved along with remarkable long-term environmental stability for over 2750 h, which is among the highest reported efficiencies for SAM-based PSCs. This investigation provides a creative, unique and effective molecular approach for preparing reliable charge transport layers, opening up new avenues for the further development of efficient interfacial contacts for PSCs.

Liquid-Free Ion-Conducting Elastomer with Environmental Stability for Soft Sensing and Thermoelectric Generating.

Ionic conductors are promising candidates for fabricating soft electronics, but currently applied ionic hydrogels and organogels suffer from liquid leakage and evaporation issues. Herein, we fabricated a free-liquid ionic conducting elastomer (LFICE) with dry lithium bis(trifluoromethane sulfonimide) and elastomeric waterborne polyurethane. The resultant versatile LFICE exhibits superior tensile strength (∼4.5 MPa), satisfactory stretchability (>900%), excellent ionic conductivity (8.32 × 10-4 S m-1 at 25 °C), and sensitive strain (3.21) and temperature (2.22% °C-1) response. The LFICE also presents durable environmental stability due to the all-solid-state feature. In the exploration of application prospects, the as-assembled LFICE sensor can precisely and repeatedly detect human motion and temperature changes, demonstrating its potentials in digital medical diagnosis and monitoring; the as-assembled LFICE thermoelectric generator (TEG) shows a high ionic thermovoltage of 4.41 mV K-1, paving a bright path for the advent of self-powered soft electronics. It is believed that this research boosts the facile fabrication of environmental stable stretchable ionic conductors holding great promise in next-generation soft electronics integrated with dual thermo- and strain-response and energy harvesting.

Stretchable Ionic Conductors for Soft Electronics.

With the rapid development of soft electronics in the era of Internet of Everything (IoE), electrical conductors with stretchability, the indispensable components of soft electronics, have gained new opportunities and also faced increasing challenges. According to the principles of electrical conductivity, stretchable electrical conductors can be divided into electronic conductors and ionic conductors. Different from the stretchable electronic conductors derived from stretchable polymeric matrices integrated with electronically conductive fillers, stretchable ionic conductors are constructed by embedding mobile ions into the crosslinked polymer networks. Therefore, stretchable ionic conductors have received extensive attention and in-depth research in the past decade, thanks to their intrinsic stretchability and electrical conductivity. This review systematically summarizes the achievements on the different categories of stretchable ionic conductors (e.g., hydrogels, ionogels, and liquid-free ion-conductive elastomers), in terms of their design, fabrication, properties, and applications. The advantages and limitations of the different types of stretchable ionic conductors are discussed. Outlooks are also provided to envision the remaining challenges for the further development and practical applications of stretchable ionic conductors. It is expected to arouse inspirations for the design and fabrication of new and high-performance stretchable ionic conductors and advanced soft electronics for the IoE era.

Subscale HTS Fusion Conductor Fabrication and Testing in High Magnetic Background Field

In actual or future fusion machines like ITER, JT-60SA, W7-X or the present EU-DEMO design, low temperature superconductor (LTS) cables are used or planned to be used in the magnet system to create the strong magnetic field necessary for plasma confinement. High temperature superconductors (HTS) offer the potential to increase the magnetic field strength in fusion magnet systems even further, allowing to build more compact fusion machines or to realize higher flux swings in central solenoids. In this work, two HTS conductors were fabricated and characterized by high current testing at 77 K in self-field conditions and at 4.2 K with an external magnetic field up to 12 T. Both samples offer the same amount of superconducting HTS tapes but differ in the assembly process and termination type. These tests were intended to validate the current KIT design of a HTS CroCo triplet conductor and to qualify a low degradation cable manufacturing process.

Phosphinate MOFs Formed from Tetratopic Ligands as Proton-Conductive Materials.

Metal-organic frameworks (MOFs) are attracting attention as potential proton conductors. There are two main advantages of MOFs in this application: the possibility of rational design and tuning of the properties and clear conduction pathways given by their crystalline structure. We hereby present two new MOF structures, ICR-10 and ICR-11, based on tetratopic phosphinate ligands. The structures of both MOFs were determined by 3D electron diffraction. They both crystallize in the P3̅ space group and contain arrays of parallel linear pores lined with hydrophilic noncoordinated phosphinate groups. This, together with the adsorbed water molecules, facilitates proton transfer via the Grotthuss mechanism, leading to a proton conductivity of up to 4.26 × 10-4 S cm-1 for ICR-11. The presented study demonstrates the high potential of phosphinate MOFs for the fabrication of proton conductors.

Switched Proton Conduction in Metal-Organic Frameworks.

Stimuli-responsive materials can respond to external effects, and proton transport is widespread and plays a key role in living systems, making stimuli-responsive proton transport in artificial materials of particular interest to researchers due to its desirable application prospects. On the basis of the rapid growth of proton-conducting porous metal–organic frameworks (MOFs), switched proton-conducting MOFs have also begun to attract attention. MOFs have advantages in crystallinity, porosity, functionalization, and structural designability, and they can facilitate the fabrication of novel switchable proton conductors and promote an understanding of the comprehensive mechanisms. In this Perspective, we highlight the current progress in the rational design and fabrication of stimuli-responsive proton-conducting MOFs and their applications. The dynamic structural change of proton transfer pathways and the role of trigger molecules are discussed to elucidate the stimuli-responsive mechanisms. Subsequently, we also discuss the challenges and propose new research opportunities for further development.

A Waterproof Ion‐Conducting Fluorinated Elastomer with 6000% Stretchability, Superior Ionic Conductivity, and Harsh Environment Tolerance

AbstractThe development of ionic conductors with extreme stretchability, superior ionic conductivity, and harsh‐environment resistance is urgent while challenging because the tailoring of these performances is mutually exclusive. Herein, a hydrophobicity‐constrained association strategy is presented for fabricating a liquid‐free ion‐conducting fluorinated elastomer (ICFE) with microphase‐separated structures. Hydrophilic nanodomains with long‐range ordering and selectively enriched Li ions provided high‐efficient conductive pathways, yielding impressive room‐temperature ionic conductivity of 3.5 × 10–3 S m–1. Hydrophobic nanodomains with abundant and reversible hydrogen bonds endow the ICFE with superior damage‐tolerant performances including ultrastretchability (>6000%), large toughness (17.1 MJ m–3) with notch insensitivity, antifatigue ability, and high‐efficiency self‐healability. Due to its liquid‐free characteristic and surface‐enriched hydrophobic nanodomains, the ICFE demonstrates an extreme temperature tolerance (−20 to 300 °C) and unique underwater resistance. The resultant ICFE is assembled into a proof‐of‐concept skin‐inspired sensor, showing impressive capacitive sensing performance with high sensitivity and wide‐strain‐range linearity (gauge factor to 1.0 in a strain range of 0–350%), excellent durability (>1000 cycles), and unique waterproofness in monitoring of complex human motions. It is believed that the hydrophobicity‐constrained association method boosts the fabrication of stretchable ionic conductors holding a great promise in skin‐inspired ionotronics with harsh‐environment tolerance.

Thermo-spun reaction encapsulation fabrication of environment-stable and knittable fibrous ionic conductors with large elasticity and high fatigue resistance

The development of knittable fibrous ionic conductors with a wide temperature tolerance, high fatigue resistance and wearing comfort is crucial yet challenging for the emerging wearable skin sensors. Herein, a thermo-spun reaction encapsulation strategy is presented for fabricating a low-temperature tolerant and high fatigue-resistant fibrous ionic conductor. The fibrous ionic conductor demonstrates a core-sheath structure that consists of hydrogen-bonded poly(ionic liquid)-backboned ionogel (HB-PILI) and thermoplastic elastomer (TPE) as the core and sheath, respectively. Due to the combination of the ionic conductive core and highly elastic sheath, the resultant HB-PILI@TPE fiber exhibits high stretchability (>100%), wide temperature resistance (−50 ∼ 50 °C), and excellent fatigue resistance (maximum stress retention of 74.3% after 5000 stretching-releasing cycles). As a result, fibrous strain sensors based on the resultant HB-PILI@TPE fiber demonstrate fast response time (less than100 ms), high-yet-linear sensitivity (gauge factor of 1.05), and excellent cyclic stability (>3000 cycles). Importantly, the fibrous sensor also shows stable responses to various strains (0 ∼ 100% strain) and frequencies (0.01 ∼ 0.2 Hz). Moreover, the HB-PILI@TPE fiber is capable of being easily weaved into a fabric that could maintain high mechanical elasticity in a wide temperature range. As a proof of concept, the as-assembled fibrous ionic sensor is capable of being attached to human skin and monitoring the movements of large and facet joints in real-time, showing high wearing comfort, large sensitivity and wide detecting range. Therefore, the developed fibrous ionic conductors that are fabricated by the thermo-spun reaction encapsulation method are promising for fabricating high-performance wearable skin sensors with excellent wearing comfort and high environmental tolerance.

Solution-based, additive fabrication of flush metal conductors in plastic substrates by printing and plating in two-level capillary channels

A strategy to control the structure of electroless copper deposition in confined features was developed for applications in printed electronic devices and interconnects. This work builds on and refines a previous process of additively manufacturing metal conductors using a combined imprint, print, and plate strategy. A two-level imprinted channel geometry, consisting of inner, parallel capillary channels running along the base surface of a main channel, was designed to control electroless copper deposition. The inner capillary channels contain and precisely position the silver ink seed layer, and the main channel confines the electroless copper as it deposits from the seed layer, resulting in flat copper surfaces that are flush with the surface of the substrate or at a controlled depth. This process produces metal conductors with aspect ratios (height/width) up to ≈2 and low edge roughnesses as defined by the imprinting process. The resistance of the final conductors varies linearly with the length and inversely with the width of the main channel, suggesting high uniformity throughout. Conductive lines with a width of 40 μm and depth of 10 µm had low resistance per unit length (≈1Ω cm−1) and retained their performance with repeated mechanical flexing. The methods described here to confine the growth of electroless plated copper are adaptable to form conductors for numerous applications in flexible electronics.

2D metal patterns transformed from 3D printed stamps for flexible Zn//MnO2 in-plane micro-batteries

Patterned 2D metal conductors have been frequently employed as interconnectors and electrodes in flexible and wearable electronics due to their high conductivity and low cost. However, many patterned technologies have shortcomings including conventional photolithography and emerging printing technologies (inkjet, screen, microcontact printing, et al.). Herein, a new alternative printing strategy, transform printing, is put forward to print metal patterns and construct Zn//MnO2 in-plane micro-batteries (IMBs) by combining 3D printing with stamping of metal films. As printed metal patterns on paper show very high-precision (<2% diffusion) and low sheet-resistance (75.0 mΩ/□). Using these metal patterns, Zn//MnO2 IMBs are constructed based on aqueous and gel electrolytes. The devices display an outstanding energy density (168 μWh cm−2, corresponding to 336 mAh g−1)/power density (4.5 mW cm−2) outperforming the flexible and rechargeable Zn//MnO2 IMBs previously reported and most of the micro-supercapacitors, show long-term cycle stability (84.3% of capacity retention after 2000 cycles at 5 A g−1) and excellent mechanical flexibility. Owing to the simple, rapid, and low-cost fabrication of metal conductors and MBs with excellent properties, this printing strategy provides a new idea for the exploration of next-generation flexible and wearable electronics.

One-Step Fabrication of Low-Resistance Conductors on 3D-Printed Structures by Laser-Induced Graphene

One-Step Fabrication of Low-Resistance Conductors on 3D-Printed Structures by Laser-Induced Graphene