Flexible and tunable microwave absorption structures using carbonyl iron@polydimethylsiloxane pillar arrays

Abstract

Abstract Flexible absorbers with artificially engineered micro-structures are promising microwave-shielding materials for use with flexible electronic devices. However, deformation of such flexible absorbers has a great impact on their microwave absorption properties, and this requires more intensive research. Herein, flexible absorbers comprising periodically arrayed polydimethylsiloxane pillars mixed with carbonyl iron particles (CIPs) were fabricated via a template-casting method and deformed by vertically applied forces. As the bending angles of the pillars increased from 0° to 70° the frequencies of the absorption peaks exhibited a linear redshift from 11.69 to 10.53 GHz. The shifting rates were −0.00543, −0.00235 and −0.00681 GHz per degree for the 2 mm period arrays and −0.00432, −0.00324 and −0.00412 GHz per degree for the 3 mm period arrays, when the CIP mass ratios were 40%, 50% and 60%, respectively. The shift of the peaks results from the increased imaginary part of permeability and permittivity when the pillars bend, giving rise to an increase in the propagation constant in the effective medium and enhancement of the first-order Fabry–Perot resonance. The results demonstrate a simple and feasible pathway for manipulating microwave absorption dynamically through deformation.