Strain-Invariant Stretchable Antennas via Radical Surface Current Redistributions: Theory, Design, and Experiments

Abstract

Stretchable and flexible antennas are pivotal in wearable electronics and soft robotics, but achieving consistent resonant frequency under mechanical strain is a fundamental problem that remains to be solved. This paper introduces, for the first time, a strain-invariant patch antenna fabricated with a liquid metal conductor, EGaIn, and a soft elastomeric substrate, Ecoflex 00-30, with overall dimensions of 90 × 90 × 1.5 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>. By strategically employing slot-induced surface current redistribution and leveraging Poisson’s effect, the proposed design achieves an exceptional level of frequency stability. Experimental results demonstrate a maximum frequency shift of only 0.8% under strains up to 58.8%, significantly outperforming existing straininvariant stretchable antennas, which typically exhibit significant frequency shifts for strains higher than 30%. Unlike conventional approaches that rely on specialized materials or complex 3D structures, our planar antenna offers remarkable scalability and versatility, presenting a transformative solution for next-generation wireless communication and sensing systems for soft electronics.