Ultra-low-profile and high-gain liquid metal antenna fabricated through synergistic strategy of thermal activation and interface modification

As the internet of everything (IoE) advances, flexible ultra-low-profile and high-gain liquid metal (LM) radio frequency antennas represent a pivotal innovation for wireless communication in dynamic deformation scenarios, yet remain limited by the insulating oxide skin of LM materials and dielectric-conductor interfacial challenges in LM-based antennas. Herein, we pioneer a synergistic strategy of thermal activation and interface modification to fabricate flexible ultrathin eutectic gallium-indium (EGaIn) LM films for ultra-low-profile and high-gain antennas. Low-surface-tension LM inks (39.2 mN m−1) containing acetic acid (HAc) and high-surface-energy polydopamine-modified commercial dielectric substrates (45 mJ m−2) establish energy-matched printing interfaces, in which the work of adhesion reaches up to 71.6 mJ m−2, thereby fabricating uniform dense EGaIn films with robust film-substrate adhesion. Thermal evaporation activation of HAc in situ removes the insulating Ga2O3 skin and induces particle fusion for highly conductive dense film. Based on this synergistic strategy, the conductive LM structures (5.5 μm) can be precisely printed achieving high electrical conductivity (1.6 × 106 S m−1), without additional encapsulation or mechanical/chemical activation. The resulting elliptical loop antenna achieves an ultra-low profile (0.278 mm, 0.005λ0), high gain (4.7 dBi) and excellent mechanical resilience that maintains stable S11 and negligible gain variation (±0.08 dBi) over 5000 bending cycles. They can replace rigid antennas in commercial wireless image transmission systems, achieving stable low-latency image transmission over distances exceeding 150 m while maintaining reliable performance under diverse dynamic deformation conditions.