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

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.

Highly Transparent Ka-/W-Band Electromagnetic Shielding Films Based on Double-Layered Metal Meshes

An electromagnetic (EM) wave-shielding film exhibiting high performance in high-frequency bands, such as the Ka- and W-bands, was fabricated by using double-layered metal meshes. The double-layered shielding (DLS) film consists of metallic micromesh and nanomesh electrodes (NMEs) on the upper and lower surfaces of a poly(ethylene terephthalate) (PET) film, respectively. The micromesh electrodes (MMEs) were fabricated such that they possessed a thickness higher than the line width, and they thus exhibited excellent electromagnetic wave-shielding performance in addition to optical transmittance. Moreover, the nanomesh electrodes helped prevent the deterioration of the shielding performance owing to the increase in frequency, which was possible by decreasing the aperture size of the mesh-type electrodes. The shielding effectiveness (SE) of the double-layered metal-mesh film was evaluated by using a shielding measurement system that is optimized for high frequencies. In addition, optical transmittance and flexibility tests were conducted. The results confirm that the double-layered shielding film exhibited a shielding effectiveness of more than 50 dB at an optical transmittance of 90% and a stable bending resistance of up to 5000 cycles at a radius of curvature of 6 mm. Double-layered metal-mesh films with such excellent performance are expected to be widely used in diverse applications such as the automobile, medical, and military industries.

Metallic Micro-Nano Network-Based Soft Transparent Electrodes: Materials, Processes, and Applications

Soft transparent electrodes (TEs) have received tremendous interest from academia and industry due to the rapid development of lightweight, transparent soft electronics. Metallic micro-nano networks (MMNNs) are a class of promising soft TEs that exhibit excellent optical and electrical properties, including low sheet resistance and high optical transmittance, as well as superior mechanical properties such as softness, robustness, and desirable stability. They are genuinely interesting alternatives to conventional conductive metal oxides, which are expensive to fabricate and have limited flexibility on soft surfaces. This review summarizes state-of-the-art research developments in MMNN-based soft TEs in terms of performance specifications, fabrication methods, and application areas. The review describes the implementation of MMNN-based soft TEs in optoelectronics, bioelectronics, tactile sensors, energy storage devices, and other applications. Finally, it presents a perspective on the technical difficulties and potential future possibilities for MMNN-based TE development.

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.

Transparent and high-performance electromagnetic interference shielding composite film based on single-crystal graphene/hexagonal boron nitride heterostructure

The multiple requirements of optical transmittance, high shielding effectiveness, and long-term stability bring considerable challenge to electromagnetic interference (EMI) shielding in the fields of visualization windows, transparent optoelectronic devices, and aerospace equipment. To this end, attempts were hereby made, and based on high-quality single crystal graphene (SCG)/hexagonal boron nitride (h-BN) heterostructure, transparent EMI shielding films with weak secondary reflection, nanoscale ultra-thin thickness and long-term stability were finally realized by a composite structure. In this novel structure, SCG was adopted as the absorption layer, while sliver nanowires (Ag NWs) film acted as the reflection layer. These two layers were placed on different sides of the quartz to form a cavity, which achieved the dual coupling effect, so that the electromagnetic wave was reflected multiple times to form more absorption loss. Among the absorption dominant shielding films, the composite structure in this work demonstrated stronger shielding effectiveness of 28.76 dB with a higher light transmittance of 80.6%. In addition, under the protection of the outermost h-BN layer, the decline range of the shielding performance of the shielding film was extensively reduced after 30 days of exposure to air and maintained long-term stability. Overall, this study provides an outstanding EMI shielding material with great potential for practical applications in electronic devices protection.

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.

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.