Switchable Multi-Spectral Electromagnetic Defense in the Ultraviolet, Visible, Infrared, Gigahertz, and Terahertz Bands Using a Magnetically-Controllable Soft Actuator.

Traditional passive single-spectrum electromagnetic defense materials are inadequate to defend against complex multispectral electromagnetic threats. Herein, a bilayer heterofilm (BLH film)-based magnetically controllable soft actuator (MCSA), comprising a defense unit and a drive unit, is constructed. The defense unit offers multispectral electromagnetic protection, while the drive unit enables active defense via magnetic actuation. The synergy allows the MCSA to provide intelligent, switchable electromagnetic defense from ultraviolet to terahertz spectra. The BLH film exhibits the lowest infrared emissivity of 0.04 at 14 μm and an average of 0.16 at 8-14 μm, outperforming comparable composites while integrating radiation energy management for enhanced overall protection. It also demonstrates complete blocking of ultraviolet and visible light (320-780 nm), demonstrating zero transmission. Furthermore, the MCSA can be modulated between open and closed states by applying a magnetic field, facilitating a seamless transition between full-band transparency and full-band defense modes. To expand electromagnetic defense applications, a multilayer gradient impedance matching (M-BLH-300) absorber based on the BLH film is fabricated for stealth in microwave bands, achieving a strong reflection loss of -26.7 dB with an effective absorption bandwidth of 4.85 GHz. Notably, the M-BLH-300 absorber retains excellent performance when extended to the terahertz frequency range and further demonstrates its suitability for multispectrum (from ultraviolet to terahertz) defense. In short, this innovative design concept of combining multispectral defense with intelligent switches will guide the development of next-generation advanced electromagnetic defense systems.