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

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 × 10⁶ 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.