目的 针对高频电磁波应用红外探测领域的需求,采用纳米材料增强吸收飞秒激光还原沉积技术制备柔性电磁屏蔽金属网栅,获得工艺窗口,测试金属网栅的耐弯曲导电性、界面结合性能、红外透过率及电磁屏蔽性能。方法 在聚酰亚胺（PI）薄膜表面预置前驱体油墨,飞秒激光聚焦于PI薄膜和前驱体油墨的界面处,通过调控激光参数实现作用区域的金属Cu离子还原并沉积在PI薄膜表面;采用光学显微镜、激光共聚焦显微镜、扫描电子显微镜、X射线衍射分析仪、拉曼光谱仪进行沉积层形貌和成分分析;采用数字万用表和四探针电阻测试仪测试Cu线电阻;依据ASTM D3359-09附着性能测试标准评估Cu与PI基材之间的附着性能;采用傅里叶变换红外光谱仪测试Cu网栅在中红外波段的透过率;采用矢量网络分析仪测试Cu网栅的电磁屏蔽性能。结果 随峰值功率密度的增加和扫描速度的降低,Cu线线宽、线高随之增大;物相中Cu2O减少,Cu相增多;当峰值功率密度过大且扫描速度过低时,Cu线中心发生烧蚀去除,PI基底发生分解与碳化。Cu线电阻率最低为2.25×10-6 Ω·m。金属Cu网栅在中红外波段相对透过率达73.0%~98.7%,在8~12 GHz范围内电磁屏蔽性能为14~34 dB,附着性能达ASTM 5B等级,弯折10 000次后电阻变化率小于0.56。结论 飞秒激光还原沉积技术在红外光学窗口、高频电磁防护等器件的金属功能图案制造中展现出应用潜力。
Abstract
With the rapid development of 5G communication, wearable devices, and military stealth technologies, there is an urgent demand for flexible electromagnetic shielding (EMS) materials that simultaneously exhibit high infrared transparency and robust shielding effectiveness (SE). Conventional solutions, such as indium tin oxide (ITO) coatings and metal nanowires face significant challenges, including high fabrication costs, brittleness, complex post-processing, and poor interfacial adhesion. To address these limitations, the work aims to propose an innovative femtosecond laser reduction deposition (FLRD) technique for fabricating flexible copper (Cu) mesh on polyimide (PI) substrates. This approach integrates nanomaterial-enhanced absorption, precision laser processing, and structural design to achieve synergistic optimization of infrared transparency and electromagnetic shielding performance.
The research begins by addressing the shortcomings of existing manufacturing methods, such as photolithography and laser ablation. While photolithography offers high resolution, its multi-step process, material incompatibility, and high cost hinder scalability. Laser ablation, though cost-effective, risks damaging polymer substrates due to excessive thermal effects. In contrast, the FLRD method leverages femtosecond laser pulses (1 035 nm wavelength, 305 fs pulse duration) to selectively reduce Cu2+ ions in a precursor ink composed of copper nitrate trihydrate, ethylene glycol, and graphene nanosheets. The graphene enhances localized light absorption, enabling precise control over the photothermal reduction process without inducing substrate ablation. Systematic optimization of laser parameters, including peak power density (4.2×108 to 12.8×108 W/cm2), scanning speed (5-60 mm/s), and repetition cycles, ensures the formation of continuous, high-conductivity Cu lines with minimal resistivity (2.25×10-6 Ω·m) and sub-30 μm line width.
Key findings demonstrate the exceptional performance of the fabricated Cu mesh. By varying the mesh period (200/400/600 μm), the relative transmittance in the mid-infrared range (2 500-25 000 nm) reaches 73.0%-98.7%, surpassing theoretical predictions due to surface plasmon effects. Concurrently, the EMS performance in the 8-12 GHz frequency band achieves 14-34 dB, with sheet resistance values ranging from 18 to 45 Ω/sq. The interplay between geometric parameters and performance metrics is thoroughly analyzed: smaller mesh periods enhance SE at the expense of transmittance, while larger periods prioritize optical transparency. Remarkably, the Cu/PI interface exhibits outstanding adhesion (ASTM class:5B), and the mesh retains mechanical stability after 10 000 bending cycles (radius: 3 mm, angle: 150°), with a resistance change rate below 0.56.
A scalable and versatile platform is established for manufacturing high-performance infrared-transparent EMS materials. The FLRD technique eliminates the need for vacuum systems, masks, or post-processing, significantly reducing production costs and complexity. By decoupling optical and electrical properties through tunable mesh architectures, the technology offers unprecedented design flexibility for applications in infrared optical windows, flexible electronics, and high-frequency electromagnetic protection. Future work could hybrid nanostructures to further optimize performance across broader spectral ranges. Overall, this research advances the frontier of multifunctional material engineering, providing a viable pathway that meets the escalating demands of next-generation optoelectronic and communication systems.
关键词
激光制造 /
飞秒激光还原沉积技术 /
红外透明薄膜 /
电磁屏蔽 /
金属网栅
Key words
laser manufacturing /
femtosecond laser reduction deposition /
infrared transparent film /
electromagnetic shielding /
metal mesh
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基金
北京市自然科学基金青年项目（2244087）
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