Direct‐Ink‐Writing Printed Stretchable Eutectic Gallium–Indium Antenna for Robust Wireless Communication

Abstract Stretchable antennas represent a pivotal innovation in enhancing wireless interconnection and driving the proliferation of Internet of Things (IoT) applications. Eutectic Gallium–Indium (EGaIn) is an ideal conductor for stretchable antennas. However, the inherent high surface tension and fluidity of EGaIn make the patterning low‐precision, time‐consuming, and failure‐prone. Here a wideband stretchable antenna is presented by direct writing of thermoplastic polyurethane‐modified EGaIn ink and activated by water‐bath ultrasound. The ink exhibits printing‐friendly rheological properties and surface energy, enabling high patterning‐precision printing (10 µm) while preserving excellent conductivity (1.6 × 10 6 S m −1 ). Benefiting from these improvements, the printed antenna achieves a large fractional bandwidth (75%), a high radiation efficiency (76.6%), and an exceptional ultimate strain (> 240%). For a proof‐of‐concept demonstration, the antenna enables a 50‐meter wireless communication, under the case of 240% stretching or conformally wrapped around a drone. This work provides an efficient and universal strategy for manufacturing stretchable antennas, with broad potential in advanced IoTs technologies.