Electromagnetic shielding using Anderson localization in nanoparticle–biopolymer composites

Electromagnetic shielding is a critical function in various technologies, which is ideally achieved using a metal that reflects all incident radiation below its plasma frequency. Using high-resolution finite difference frequency domain simulations at microwave/RF frequencies, we show that the same efficacy can be achieved using a disordered collection of metal nanoparticles embedded in a flexible material. The mechanism underlying the reflection in the composite material is wave localization, disallowing the propagation of radiation up to the plasma frequency of the metal that constitutes the particles. We realize such a biopolymer composite using DNA–CTMA (deoxyribonucleic acid–cetyltrimethylammonium complex) as a support structure for Ag nanoparticles. This biopolymer composite exhibits an extremely high shielding effectiveness, close to that of a metal slab, because of Anderson localization of the electromagnetic waves.