Flexible substrates have been increasingly studied in recent years. This paper proposes natural rubber as a new substrate material for flexible antennas. In our work, prototype antennas were built using rubber formulated with different filler contents. Carbon black was used as the filler where its amount was varied to yield different dielectric properties. Prototype inset-feed microstrip patch antennas with outer dimensions 7.52 mm × 10.607 mm × 1.7 mm and copper as its conducting material were fabricated to operate at 2.45 GHz. The prototypes were measured and their performance analyzed in terms of the effects of filler content on Q, return loss and bending effects on their gain and radiation characteristics. The return loss and gain were found to be comparable to those built on existing synthetic substrates, but these new antennas offer an added feature of frequency-tunability by varying the filler content. Under bending conditions, these new antennas were also found to perform better than existing designs, showing less changes in their gain, frequency shift and beamwidth, in addition to less impedance mismatch when bent.
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