Electromagnetic interference shielding in soft, lightweight, and flexible conducting polymer-based sponges

Abstract Developing highly efficient, low-density, and mechanically flexible electromagnetic interference (EMI) shielding materials based on conducting polymers has gained significant momentum for suppressing electromagnetic pollution. In our work, we investigated the EMI shielding behavior of uniaxially compressible sponges using the conducting polymer poly(3,4-ethylenedixoythiophene) polystyrene sulfonate (PEDOT:PSS) in the X-band frequency range of 8–12.4 GHz. Two types of PEDOT:PSS sponges, type-I with glycerol and (3-glycidyloxypropyl) trimethoxy silane and type-II containing glycerol and polyethylene glycol, were prepared by freeze-drying method. Both sponges exhibited a rapid decrease in resistance for the initial compressive strain of less than 20%, which stabilized at higher compressive strains. This behavior was likely due to the complex 3D porous structures of the sponges and was linked to the creation of new electrical contacts due to pore collapse under compressive strain. The enhanced electrical conductivity, porous structure, large surface area, and many internal surfaces resulted in exceptional EMI shielding for PEDOT:PSS sponges, achieving shielding values as high as 44 dB and 72 dB, respectively. The EMI shielding in these materials was primarily dominated by the reflection process. This work contributes to developing flexible and high-efficiency EMI shielding materials for flexible electronic applications in the future.