Liquid Crystal Elastomer Bistable Metastructures for Zero-Holding-Power Beam-Steering Antennas

Antennas on rotorcraft and unmanned aerial vehicles must redirect their beams as the airframe attitude changes, yet conventional steering—mechanical gimbals or powered phase shifters—adds mass and draws continuous power, both of which erode payload and endurance. Bistable structures, which switch rapidly and retain the switched configuration without continuous holding power, offer a route past this trade-off, but actively triggering them across different geometries remains an open challenge: the material’s actuation output must be precisely matched to each structure’s geometry-dependent instability threshold. Here, we present a material–geometry coupling strategy that meets this challenge using liquid crystal elastomer (LCE) actuator layers integrated into three architectures of increasing constraint: a pre-compressed composite beam, an open curved frame, and a closed curved triangular frame. By tuning the LCE network composition against the geometric resistance of each architecture, localized near-infrared irradiation drives a slow photothermal loading stage that culminates in rapid, instability-driven switching. For the representative constrained beam, NIR heating triggers switching within approximately 11.7 s, whereas the instability-driven configuration reversal itself occurs within approximately 25 ms. Integrating a flexible copper radiator with the triangular frame yields a bistable antenna whose two states hold their resonance near 3.65 GHz while redirecting the main beam by 100° state-to-state, demonstrating bistable beam redirection with potential relevance to attitude-changing aerial platforms. These results establish a material–geometry coupling strategy for remotely reconfigurable bistable soft structures and flexible functional devices.