Research on a Highly Sensitive SAW Strain Sensor Based on a Beam-Plate Structure

Real-time monitoring of component deformation under conditions of elevated temperature and high rotational speeds is essential for maintaining the structural integrity and operational safety of machinery. Conventional Surface Acoustic Wave (SAW) strain sensors exhibit limitations, including insufficient operating temperature capabilities and reduced measurement accuracy, which hinder their applicability under extreme conditions. This study developed a highly sensitive SAW strain sensor based on Langasite (LGS) and a beam-plate structure. The fabrication process employed a double-sided lithography wet etching technique to produce a beam-plate structure with a smooth surface, achieving a surface roughness of 0.945 nm — an 88.9% reduction from the roughness of 8.53 nm typically obtained using single-sided lithography. Interdigital electrode patterns were etched onto both the beam-plate and conventional LGS substrates using Micro-Electro-Mechanical Systems (MEMS) technology. The sensor was evaluated on a custom-designed high-temperature strain test platform. The results demonstrated that the beam-plate type SAW strain sensor operated stably across a temperature range of 25 °C-850 °C and a strain range of 0-1600 μƐ. The sensor exhibited a sensitivity of 550 Hz/μƐ at room temperature, which was approximately 3.14 times higher than that of conventional SAW sensors. Under the concurrent effects of temperature and strain at elevated temperatures, a temperature-strain decoupling algorithm was developed, yielding a maximum error between the decoupled and measured values ranging from -4.4% to +4.3%. The beam-plate type SAW strain sensor is characterized by its high sensitivity, excellent temperature resistance, rapid response time, and robust anti-interference properties. Thus, the proposed sensor is well-suited for applications in advanced fields such as aerospace, highend equipment, and other high-precision domains.