Multilayer Stretchable Conductors on Polymer Substrates for Conformal and Reconfigurable Antennas

Multilayer stretchable conductors (SCs) are demonstrated for the first time as an alternative cost-effective method for implementing conformal and reconfigurable antennas over flexible substrates. Structurally, these SCs are realized on polydimethylsiloxane (PDMS) substrate via single or double copper layers deposited around a commercially available conductive rubber. The dc measurements demonstrate the stretchability of the multilayer SCs up to 25% and 22.5 times larger conductivity as compared to the standalone conductive rubber. The RF performance of these multilayer SCs is first characterized in the 1-5-GHz range by measuring the insertion loss in 50-Ω microstrip lines. As compared to a standalone conductive rubber, the triple-layer SC has shown 58% less insertion loss. To demonstrate their use in reconfigurable and flexible conformal antennas, an aperture-coupled patch antenna is designed, fabricated, and tested. Specifically, it is shown that the antenna can be tuned from 2.97 to 2.69 GHz when stretched by 9%. Additionally, the patch antenna implemented from the multilayer SC exhibits 6.18 dB realized gain. This gain is 3.71 dB better than that of a patch antenna implemented from a standalone conductive rubber layer, and only 0.4 dB lower than that of a conventional patch.