High-performance composite Ag-Ni mesh based flexible transparent conductive film as multifunctional devices

Flexible Embedded Metal Meshes by Sputter-Free Crack Lithography for Transparent Electrodes and Electromagnetic Interference Shielding

A facile and novel fabrication method is demonstrated for creating flexible poly(ethylene terephthalate) (PET)-embedded silver meshes using crack lithography, reactive ion etching (RIE), and reactive silver ink. The crack width and spacing in a waterborne acrylic emulsion polymer are controlled by the thickness of the polymer and the applied stress due to heating and evaporation. Our innovative fabrication technique eliminates the need for sputtering and ensures stronger adhesion of the metal meshes to the PET substrate. Crack trench depths over 5 μm and line widths under 5 μm have been achieved. As a transparent electrode, our flexible embedded Ag meshes exhibit a visible transmission of 91.3% and sheet resistance of 0.54 Ω/sq as well as 93.7% and 1.4 Ω/sq. This performance corresponds to figures of merit (σDC/σOP) of 7500 and 4070, respectively. For transparent electromagnetic interference (EMI) shielding, the metal meshes achieve a shielding efficiency (SE) of 42 dB with 91.3% visible transmission and an EMI SE of 37.4 dB with 93.7% visible transmission. We demonstrate the highest transparent electrode performance of crack lithography approaches in the literature and the highest flexible transparent EMI shielding performance of all fabrication approaches in the literature. These metal meshes may have applications in transparent electrodes, EMI shielding, solar cells, and organic light-emitting diodes.

Flexible, Transparent and Conductive Metal Mesh Films with Ultra-High FoM for Stretchable Heating and Electromagnetic Interference Shielding

Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference (EMI) shielding, achieving a flexible EMI shielding film, while maintaining a high transmittance remains a significant challenge. Herein, a flexible, transparent, and conductive copper (Cu) metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique. The Cu mesh film shows an ultra-low sheet resistance (0.18 Ω □-1), high transmittance (85.8%@550 nm), and ultra-high figure of merit (> 13,000). It also has satisfactory stretchability and mechanical stability, with a resistance increases of only 1.3% after 1,000 bending cycles. As a stretchable heater (ε > 30%), the saturation temperature of the film can reach over 110 °C within 60 s at 1.00 V applied voltage. Moreover, the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5 μm. As a demonstration, it is used as a transparent window for shielding the wireless communication electromagnetic waves. Therefore, the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.

Electrical conductivity of crack-template-based transparent conductive films: A computational point of view

Crack-template-based transparent conductive films (TCFs) are promising kinds of junction-free, metallic network electrodes that can be used, e.g., for transparent electromagnetic interference shielding. Using image processing of published photos of TCFs, we have analyzed the topological and geometrical properties of such crack templates. Additionally, we analyzed the topological and geometrical properties of some computer-generated networks. We computed the electrical conductance of such networks against the number density of their cracks. Comparison of these computations with predictions of the two analytical approaches revealed the proportionality of the electrical conductance to the square root of the number density of the cracks was found, this being consistent with the theoretical predictions.

Honeycomb-ring hybrid random mesh design with electromagnetic interference (EMI) shielding for low stray light

A honeycomb-ring hybrid random mesh structure is designed to achieve low stray light performance. The honeycomb-ring hybrid random mesh comprises the random honeycomb and random ring, achieving two random superpositions in the structure distribution. The stray light distribution is very low by the combination design with different random hybrid structures. In order to illustrate the advantages of the hybrid random structure, we design a random honeycomb network by randomly offsetting vertices. At the same time, for the random honeycomb structure, we replace each vertex with the ring structure with the size of the ring randomly controlled. Thus, the corresponding honeycomb-ring hybrid random structure is obtained. Compared with the random honeycomb, the maximal normalized high-order diffraction energy of the honeycomb-ring hybrid random mesh is about a 62.85% drop, and the shielding performance is increased by about 50%. At the same time, the optical transmittance remains nearly unchanged. Due to the enjoyable property of the designed honeycomb-ring hybrid random mesh, a sample was prepared for performance verification. The measurement results show that it achieves eminent diffraction pattern distribution with the maximal normalized high-order diffraction energy of about -31.8 dB. At the same time, the average optical transmittance exceeds 86%, and the electromagnetic shielding effectiveness (SE) in the Ku band is greater than 26 dB. Based on the fine photoelectric performance of the honeycomb-ring hybrid random mesh structure, it has great application potential for high-quality optical windows.

All-atmospheric fabrication of Ag-Cu core-shell nanowire transparent electrodes with Haacke figure of merit >600 × 10-3 Ω-1

Transparent conducting electrodes (TCEs) are essential components in devices such as touch screens, smart windows, and photovoltaics. Metal nanowire networks are promising next-generation TCEs, but best-performing examples rely on expensive metal catalysts (palladium or platinum), vacuum processing, or transfer processes that cannot be scaled. This work demonstrates a metal nanowire TCE fabrication process that focuses on high performance and simple fabrication. Here we combined direct and plating metallization processes on electrospun nanowires. We first directly metallize silver nanowires using reactive silver ink. The silver catalyzes subsequent copper plating to produce Ag-Cu core-shell nanowires and eliminates nanowire junction resistances. The process allows for tunable transmission and sheet resistance properties by adjusting electrospinning and plating time. We demonstrate state-of-the-art, low-haze TCEs using an all-atmospheric process with sheet resistances of 0.33 Ω sq^-1 and visible light transmittances of 86% (including the substrate), leading to a Haacke figure of merit of 652 × 10^-3 Ω^-1. The core-shell nanowire electrode also demonstrates high chemical and bending durability.

Crack-Templated Wire-Like Semitransparent Electrodes with Unique Irregular Patterns

The development of novel methods of producing transparent electrodes is important because of their ever-evolving applications and thus the additional parameters they must meet. In this work, we present a method of manufacturing semitransparent silver electrodes. This technique involves cracking the polyvinylpyrrolidone layer in the presence of a colloidal nanodispersion of zinc oxide. The resulting cracked polymer layer serves as the disposable mask for metal deposition. The whole procedure is valuable due to the fast and easy step of cracks formation caused by the elevated temperature and reduced pressure. The obtained electrodes have high transparency (82.4%) in a wide spectral range, which is only limited by the transparency of the applied substrate, and low resistivity (27.3 × 10^-7 Ωm). The presence of unique patterns suggests new ideas for the applications of such electrodes, such as coding, security, and antiplagiarism protection.

Low Cost Embedded Copper Mesh Based on Cracked Template for Highly Durability Transparent EMI Shielding Films

Embedded copper mesh coatings with low sheet resistance and high transparency were formed using a low-cost Cu seed mesh obtained with a magnetron sputtering on a cracked template, and subsequent operations electroplating and embedding in a photocurable resin layer. The influence of the mesh size on the optoelectric characteristics and the electromagnetic shielding efficiency in a wide frequency range is considered. In optimizing the coating properties, a shielding efficiency of 49.38 dB at a frequency of 1 GHz, with integral optical transparency in the visible range of 84.3%, was obtained. Embedded Cu meshes have been shown to be highly bending stable and have excellent adhesion strength. The combination of properties and economic costs for the formation of coatings indicates their high prospects for practical use in shielding transparent objects, such as windows and computer monitors.

Freestanding "core-shell" AgNWs/metallic hybrid mesh electrodes for a highly efficient transparent electromagnetic interference shielding film

We fabricated the freestanding "core-shell" AgNWs/ Ni mesh electrodes by employing AgNWs solution onto the freestanding Ni-mesh. The combination of AgNWs and Ni mesh resulted in higher electrical conductivity, thereby enhancing the electromagnetic interference (EMI) shielding effectiveness (SE). The hybrid freestanding electrode created highly effective transparent and flexible EMI shielding films, featuring an ultrathin thickness (3 µm), the high optical transparency of 93% at 550 nm, and a SE of 41.5 dB in the X-band, which exceeds that of 30 dB for a freestanding Ni-mesh (94%). We showed that the hybrid freestanding AgNWs/Ni-mesh film is a promising high-performance transparent and flexible EMI shielding material that satisfies the requirements for optoelectronic devices.

Templateless, Plating-Free Fabrication of Flexible Transparent Electrodes with Embedded Silver Mesh by Electric-Field-Driven Microscale 3D Printing and Hybrid Hot Embossing

Flexible transparent electrodes (FTEs) with an embedded metal mesh are considered a promising alternative to traditional indium tin oxide (ITO) due to their excellent photoelectric performance, surface roughness, and mechanical and environmental stability. However, great challenges remain for achieving simple, cost-effective, and environmentally friendly manufacturing of high-performance FTEs with embedded metal mesh. Herein, a maskless, templateless, and plating-free fabrication technique is proposed for FTEs with embedded silver mesh by combining an electric-field-driven (EFD) microscale 3D printing technique and a newly developed hybrid hot-embossing process. The final fabricated FTE exhibits superior optoelectronic properties with a transmittance of 85.79%, a sheet resistance of 0.75 Ω sq^-1 , a smooth surface of silver mesh (R_a  ≈ 18.8 nm) without any polishing treatment, and remarkable mechanical stability and environmental adaptability with a negligible increase in sheet resistance under diverse cyclic tests and harsh working conditions (1000 bending cycles, 80 adhesion tests, 120 scratch tests, 100 min ultrasonic test, and 72 h chemical attack). The practical viability of this FTE is successfully demonstrated with a flexible transparent heater applied to deicing. The technique proposed offers a promising fabrication strategy with a cost-effective and environmentally friendly process for high-performance FTE.

Boosting transparent electromagnetic interference shielding by multi-cavity resonances

We propose a multi-cavity resonant architecture that is established by employing two opposing ultrathin silver-based films to form a Fabry-Pérot (F-P) cavity and inserting one or two metallic mesh layers in between. Compared with the single F-P cavity, the multi-cavity architecture with one metallic mesh layer experimentally exhibits a ∼37% improvement in the average shielding effectiveness and maintains a transmittance over 80% at 550 nm. A more significant improvement of ∼108% in shielding effectiveness (SE) can be achieved by inserting two metallic mesh layers. The proposed multi-cavity architecture provides a strategy for removal of the hindrance to transparent electromagnetic interference shielding.

Multifunctional Electromagnetic Interference Shielding Ternary Alloy (Ni-W-P) Decorated Fabric with Wide-Operating-Range Joule Heating Performances

Flexible electromagnetic interference (EMI) shielding textiles with wide-operating-range Joule heating performances are urgently indispensable in the application of artificial intelligence, communication industry, and wearable electronics. Herein, a simple and cost-effective approach is proposed to construct multifunctional textiles by electroless depositing a nickel-tungsten-phosphorus (Ni-W-P) ternary alloy on a polyamide (PA) fabric. The resultant fabric with a thickness of ∼117 μm exhibits a favorable EMI shielding effectiveness (SE) of 43.6 dB within 2-12.5 GHz. Particularly, finite difference time domain (FDTD) simulation was introduced to investigate the effects of the PA fabric mesh number and Ni-W ratio on the EMI SE value, which was validated by experimental results. In addition, the conductive fabric demonstrates excellent heating efficiency (up to 140 °C under 2 V within 60 s), a wide operating range (from 40 to 140 °C), and simultaneously, satisfactory reproducibility by undergoing dozens of heating and cooling cycles. Notably, EMI SE of the multifunctional fabric remains unchanged even after a series of durability measurements including 180 °C heating, ultrasonication treatment, and repetitive peeling tests, respectively. Therefore, the prepared Ni-W-P coated PA fabric with prominent chemical stability and mechanical robustness endows enormous potential in multi-scene applications.

Embedded flexible and transparent double-layer nickel-mesh for high shielding efficiency

An efficient approach to obtain high shielding effectiveness (SE) in transparent shielding in an optical window field is proposed and demonstrated by fabricating an embedded double-layer metallic mesh (DLMM) comprised of randomly structured Ni meshes on both sides of a flexible substrate, employing a facile and low-cost double-sided nanoimprinting method. The unique nonperiodic random structure contributes to uniform diffraction and eliminates the Moiré fringe generated by double-layer periodic meshes, ensuring high imaging quality for optical applications. The designed DLMM films simultaneously achieve strong shielding in the X-band and high transmittance in the visible spectrum, demonstrating a high transmittance of 88.7% at the 550-nm wavelength and a SE of 46.9 dB at a frequency of 8.2 GHz. An ultra-high SE of 80 dB is achieved at 64.2% transmittance, which reveals the highest reported SE over a metallic mesh for transparent shielding, indicating the high potential for this transparent electromagnetic interference shielding material for practical optical applications.

Reduced Graphene Oxide Conformally Wrapped Silver Nanowire Networks for Flexible Transparent Heating and Electromagnetic Interference Shielding

Metal nanowire networks (MNNs) are promising as transparent electrode materials for a diverse range of optoelectronic devices and also work as active materials for electrical heating and electromagnetic interference (EMI) shielding applications. However, the relatively low performance and poor durability of MNNs are limiting the practical application of the resulting devices. Here, we report a controllable approach to enhance the conductivity and the stability of MNNs with their transmittance remaining unchanged, in which reduced graphene oxide conformally wrapped silver nanowire networks (AgNW@rGO networks) are synthesized by selective electrodeposition of GO nanosheets on AgNWs followed by a pulsed laser irradiation treatment. Experimental characterizations and finite-difference time-domain simulations indicate that pulsed laser irradiation at a specific wavelength not only reduces the GO but also welds the AgNWs together through a surface plasmon resonance process. As a result, the AgNW@rGO networks exhibit low sheet resistance of 3.3 Ω/□, average transmittance of 91.1%, and good flexibility. Wrapping with rGO improves the maximum electrical heating temperature of the AgNW network transparent heaters due to the effective suppression of the oxidation and the migration of surface silver atoms. In addition, excellent EMI shielding effectiveness of up to 35.5 dB in the 8.2-12.4 GHz frequency range is obtained as a consequence of the combined effects of dual reflection, conduction loss, and multiple dielectric polarization relaxation processes.

Record-High Transparent Electromagnetic Interference Shielding Achieved by Simultaneous Microwave Fabry-Pérot Interference and Optical Antireflection

As a potential risk to human and environmental health, radio frequency (RF) radiation should be studied due to the higher frequencies and larger bandwidths that may be employed. Electromagnetic interference (EMI) shielding materials can prevent exposure to RF radiation, but most of them are visibly opaque. In this work, we propose and fabricate visibly transparent EMI shielding materials using an ultrathin silver layer sandwiched by oxides (SLSO) as building blocks. The samples with a double-sided SLSO (D-SLSO) structure exhibit the highest EMI shielding effectiveness (SE) of 70 dB at 27.6 GHz (>62 dB on average at 4-40 GHz) and a transmittance close to 90% at a visible wavelength of 550 nm, which is comparable with those of polyethylene terephthalate (PET) and glass substrates. The D-SLSO structure plays a dual role: it suppresses optical reflections as antireflection coatings and enhances EMI shielding via Fabry-Pérot interference. In addition, we discuss the origin of the extraordinary frequency dependence of SE, which monotonically increases, contrary to that of conventional metallic mesh. This report describes SLSO-based transparent EMI shielding materials with record-high SE and visible transmittance that provide optoelectronic applications with robust safety and reliability under RF radiation with high and broad frequencies.

Multi-layer silver nanowire/polyethylene terephthalate mesh structure for highly efficient transparent electromagnetic interference shielding

Electromagnetic interference protection in optoelectronic devices is challenging because of the dual requirements of optical transmittance and high shielding effectiveness (SE). Herein, we propose a novel silver nanowire (AgNW)/polyethylene terephthalate (PET) multi-layer mesh pattern structure for transparent electromagnetic shielding obtained via laser marking and transfer printing. A three-layer composite shielding film with an optical transmittance of 67.8% exhibits a SE of 44 dB at 10 GHz, which is superior to most of the reported transparent shielding films composed of AgNWs to date. The newly designed multi-layer composite structure can enhance the transparent shielding properties of the shielding film via optimization of the AgNW distribution and the shielding film structure. It is expected that this multi-layer mesh composite structure will have splendid application prospects in electromagnetic shielding films, which require both light transmittance and high SE.

Review of Polymer Composites with Diverse Nanofillers for Electromagnetic Interference Shielding

Polymer matrix composites have generated a great deal of attention in recent decades in various fields due to numerous advantages polymer offer. The advancement of technology has led to stringent requirements in shielding materials as more and more electronic devices are known to cause electromagnetic interference (EMI) in other devices. The drive to fabricate alternative materials is generated by the shortcomings of the existing metallic panels. While polymers are more economical, easy to fabricate, and corrosion resistant, they are known to be inherent electrical insulators. Since high electrical conductivity is a sought after property of EMI shielding materials, polymers with fillers to increase their electrical conductivity are commonly investigated for EMI shielding. Recently, composites with nanofillers also have attracted attention due to the superior properties they provide compared to their micro counterparts. In this review polymer composites with various types of fillers have been analysed to assess the EMI shielding properties generated by each. Apart from the properties, the manufacturing processes and morphological properties of composites have been analysed in this review to find the best polymer matrix composites for EMI shielding.

Ultrathin, lightweight, and freestanding metallic mesh for transparent electromagnetic interference shielding

A unique freestanding nickel (Ni) metallic mesh-based electromagnetic interference shielding film has been fabricated though the direct-writing technique and a subsequent selective metal electrodeposited process. The structured freestanding Ni mesh film demonstrates a series of advantages, including ultrathin thickness (2.5-6.0 μm) and ultralight weight (0.23 mg cm^-2), extraordinary optoelectronic performance (sheet resistance about 0.24-0.7 Ω sq^-1 with transparency of 92%-93%), high figure of merit (18000) and outstanding flexibility as it can withstand folding, rolling and crumpling into various shapes while keeping the conductivity constant. Furthermore, by using this high-performance Ni mesh, an ultrathin, lightweight, freestanding and transparent electromagnetic interference shielding (EMI) film with extraordinary optoelectronic properties (shielding effectiveness about 40 dB with transparency of 92%) is demonstrated in X-band, with no performance attenuation observed even in bending state. This freestanding metallic mesh-structured electrode can be further explored or applied in various potential applications, such as conformal microwave antennas, transparent EMI windows, and wearable electronics.