Flexible, conductive Cu-x@CNT films for ultra-broadband electromagnetic interference shielding and low-voltage electrothermal heating

Abstract

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