Mitigating response time of liquid crystal-based microwave devices by nanoparticles doping

Nanoparticle doping has emerged as an effective technique for tailoring the dynamic and dielectric properties of liquid crystal (LC)-based microwave devices. In this work, we investigate the influence of gold nanoparticle (GNP) doping on the microwave response and switching dynamics of nematic liquid crystals employed in reconfigurable phase shifters operating in the 1–6 GHz frequency range. LC mixtures containing different GNP concentrations were prepared and experimentally characterized in terms of dielectric tunability, insertion loss, threshold voltage, phase-shifting capability, and response time. Comparative measurements between undoped and doped LC systems reveal that nanoparticle incorporation significantly enhances the electro-optic response, leading to faster switching dynamics and improved phase-shift performance. An optimal doping concentration of approximately 1.5 wt. % was identified, at which the turn-off time was reduced by 50% for the phase shifter design, maintaining a high phase shift performance with the maximum differential phase shift of 76° in the operation band. Although higher nanoparticle concentrations introduce additional dielectric losses and aggregation effects, the overall microwave performance remains suitable for low-loss tunable applications. The observed improvements are attributed to nanoparticle-induced modifications of the local electric field distribution, dielectric anisotropy, and viscoelastic properties of the LC medium. These results demonstrate a potential prospect of applying nanoparticle-doped liquid crystals in compact, fast-response, and energy-efficient reconfigurable microwave and millimeter-wave devices for low latency requirements.