Theoretical Design and Experimental Evaluation of Structural Randomized Transparent Conductive Metal Mesh （Invited）

The rapid proliferation of modern electronic devices has made Electromagnetic Interference （EMI） a crucial challenge， impacting the reliability of optical systems and human health. Transparent optical windows， ubiquitous in aerospace， medical imaging， defense， and communication systems， require materials exhibiting simultaneously high optical transparency， robust EMI shielding， and minimal higher-order diffraction energy. While conventional periodic metal meshes provide effective EMI shielding， their regular structures generate orthogonal array diffraction patterns that compromise the resolution and performance of imaging systems. Alternative transparent EMI shielding materials， including Transparent Conductive Oxides （TCOs）， carbon-based materials， two-dimensional transition metal carbides/nitrides （MXenes）， conductive polymers， and metal nanowires， typically exhibit limitations in simultaneously achieving high optical transparency and robust broadband EMI Shielding Effectiveness （SE）. To overcome these limitations， this study introduces a fabrication technique for structurally randomized metal meshes based on a random crack-template method， integrated with comprehensive theoretical modeling. This strategy optimizes optical and electromagnetic performance while suppressing and homogenizing higher-order diffraction energy.Fabrication of the structurally randomized metal meshes commenced with the synthesis of an acrylic resin crack-template precursor featuring tunable physical properties. This precursor was spin-coated onto a quartz substrate to generate a random crack template （~6.5 µm depth）. Copper was subsequently deposited into the crack grooves via electron-beam-assisted evaporation. Finally， the crack template was removed using an organic solvent. Scanning Electron Microscopy （SEM） and energy dispersive X-Ray Spectroscopy （EDX） analyses confirmed the formation of a random copper mesh characterized by uniform metal line thickness （~300 nm） and high connectivity. A multiphysics-coupled framework integrating structural parameters， optical performance， and electromagnetic performance was developed to evaluate the random copper mesh. Optical performance was assessed through transmittance （Topt） and total reflectance （Rtotal）， incorporating the effects of metal line coverage， surface roughness （modeled using the Beckmann scattering formulation）， and multipath interference. Diffraction analysis employs Fraunhofer theory to quantify the suppression of higher-order diffraction energy by structural randomization. The electromagnetic shielding model establishes quantitative correlations between geometric parameters， electrical properties （sheet resistance Rs）， and total shielding effectiveness （SEtotal=SER+SEA+SEM）.Experimental results demonstrate an average visible-light transmittance （380~760 nm） of 85.5% with a 7.6% loss relative to the quartz substrate， and an average reflectivity of 10.3% is tested at a 6° incidence. Bidirectional Reflectance/Transmittance Distribution Function （BRDF/BTDF） measurements indicated that the random copper mesh optical window exhibited predominantly specular reflection， with scattered light intensity as low as 10-4 1/sr， demonstrating excellent optical uniformity. The He-Ne laser diffraction testing revealed a uniform diffraction pattern. The fabricated random copper mesh demonstrated favorable electrical conductivity， exhibiting a sheet resistance of 14.38 Ω/sq. This measured value slightly exceeded the theoretical prediction （11.69 Ω/sq）， primarily due to imperfect connectivity within the mesh structure， manifested as isolated metal lines. Furthermore， the random copper mesh achieved an average EMI SE of 24.56 dB across the 1~18 GHz frequency band， as independently verified by Vector Network Analyzer （VNA） measurements and CST Microwave Studio simulations. The inherent structural randomness of the crack-template method effectively suppressed the orthogonal array stray light. Critically， the developed coupled optical-electromagnetic performance model establishes quantitative relationships between structural parameters and functional metrics， facilitating scalable industrial production. This innovation successfully resolves the inherent trade-off between EMI shielding and optical transparency， offering significant promise for precision imaging applications in environments with high EMI. Future investigations will explore advanced materials （such as silver and graphene） and hybrid architectures to extend performance across broader electromagnetic spectral ranges.