Flexible, Conductive Cu@CNT Films for Ultra-Broadband Electromagnetic Interference Shielding and Low-voltage Electrothermal Heating

Abstract

The prosperous outdoor exercise activities have raised higher performance and multi-functional requirements for the films used in clothing and equipment. However, developing films that have multi-functions such as comfortable, flexible, high-performance electromagnetic interference (EMI) shielding and exceptional electrothermal heating capabilities remains a significant challenge. Herein, a flexible, highly conductive Cu@CNT film was fabricated using the strategy of copper particles bridging conductive nanotubes and polymer fixing conductive networks. The two-step strategy remarkably enhanced the CNT-based conductive network and improved the electrical conductivity of Cu-2.0@CNT film to 22,051 S/m. The resulting Cu@CNT film demonstrated an outstanding average EMI shielding effectiveness (SE) of 57.8 dB across 5-40 GHz, and a remarkable average EMI SE more than 60 dB in 0.2-1.6 THz at the film thickness of 100 μm. The film also exhibited a normalized EMI SE (SE/t) of 578 dB mm-1, which exceeds most reported film materials. Additionally, the Cu@CNT film exhibited impressive electrothermal heating properties, including a high saturated temperature (over 160 ℃ at 3.5 V), a high heating rate (＞ 10 ℃/s at 3.5 V), a controllable thermal response (＜ 15 s) and a stable and uniform heating distribution. Additionally, as a demonstration, it is used as a flexible electromagnetic wave isolation film and flexible heaters. Therefore, the flexible composite film with multiple protective functions proposed in this work provides a competitive material for the next-generation outdoor clothing and equipment applications.