3D-Printed Fluidically Tunable Frequency Selective Surface with Microcontroller-Driven Pumping

Frequency selective surfaces (FSS) are widely recognized for their ability to manipulate electromagnetic waves by filtering specific frequency bands. Traditionally, FSS consists of a periodic array of conductive patterns on a dielectric substrate and operates at fixed frequency ranges. However, the static nature of these designs limits their adaptability in dynamic environments. This study introduces an additively manufactured tunable FSS featuring integrated fluidic channels. The conductive patterns are created using a copper aerosol spray with a negative masking technique. By injecting dielectric fluids with varying permittivity into fluidic channels, the effective permittivity of the substrate is altered, enabling dynamic tuning of the frequency band. The proposed FSS demonstrates tunable resonance, operating between 4.28 GHz (with empty channels) and 3.52 GHz (with channels filled with distilled water), enabling adaptive filtering capabilities. A microcontroller-driven micropump ensures precise fluid delivery, minimizing shear stress and enhancing repeatability. Additionally, the ESP32 microcontroller provides wireless control of the pump, enabling remote tuning. Experimental results demonstrate that the proposed FSS performs closely to simulated responses with minor deviations, exhibits polarization insensitivity, and maintains stability up to a 60° incidence angle. This tunable FSS offers a practical solution for real-time frequency tuning, with potential applications in adaptive communication systems and electronic warfare.