Thin and flexible multilayer polymer composite structures for effective control of microwave electromagnetic absorption

We describe a novel multilayer arrangement of polymer nanocomposites, which is able to very effectively absorb microwave radiation over a broad frequency range or selectively reflect desired wavelengths. The structure is built from alternating films of dielectric polymer and conducting layers. The latter are stacked in a precise gradient of conductivity. The conducting layers consist of either polycarbonate nanocomposite films with carbon nanotubes (CNT) or a very thin CNT coating deposited on insulating polymer from a CNT waterborne ink. In order to ensure good wetting of polycarbonate by the ink and high resulting conductivity of the dry coating, a plasma treatment of the polymer is essential. The stacked multilayer structures are easy to make, modular, and open up new possibilities in the area of microwave management (broadband shielding by absorption or frequency-selective filtering, also called bandgap control). The analytical model developed to simulate the absorbers and filters is in good agreement with experimental characterisation and could be further extended to the design of systems operating in other frequency ranges. (C) 2014 Elsevier Ltd. All rights reserved.