Quasi two-way shape-memory alloy-excited reconfigurable cavity for in-pipe water monitoring

OpenAlex İngilizce

Abstract This study presents a passively reconfigurable microwave cavity-based measurement system for in-pipe water monitoring. The system features quasi two-way actuation, made possible by a spring-biased shape memory alloy. A preloaded one-way shape memory alloy element serves both as a temperature-responsive actuator and as the cavity’s excitation probe. Temperature variations induce a change in the probe’s geometry, which in turn affects the cavity’s coupling factor and resonance behavior, allowing the system to differentiate between hot and cold water conditions. Unlike conventional one-way shape memory alloys that stay deformed after cooling, the proposed configuration uses a spring to restore the actuator’s shape. This enables reversible phase transitions and the switching between distinct electromagnetic modes. The system can also detect water quality anomalies by responding to changes in dielectric properties through mode-specific resonance. Since similar dielectric shifts may result from either temperature changes or contamination, conventional systems suffer from a uniqueness problem. By linking distinct shape memory alloy phase states to specific electromagnetic modes, the proposed method introduces an additional physical variable that helps to reduce this ambiguity, particularly across the 45 ∘ C transition boundary. Unlike traditional microwave systems, this design is fully passive and structurally adaptive mode selection through smart material actuation. The proposed design achieves a high normalized sensitivity of 0.0073, supported by a comprehensive uncertainty analysis and validated through long-term stability tests, ultimately providing a compact and maintenance-free solution for multi-parameter water quality monitoring.