Temperature-Decoupled Multimodal Surface Acoustic Wave Strain Sensors Using Z-Cut Lithium Niobate on Insulator Substrate

Surface acoustic wave (SAW) strain sensors have attracted widespread attention in recent years due to their wireless, passive operation and excellent stability in complex environments. In this work, a multimodal SAW strain sensor based on Z-cut lithium niobate on insulator (LNOI) substrate is proposed and fabricated. Five distinct acoustic modes are identified, each exhibiting significantly different responses to strain and temperature. Among them, the 0th-order antisymmetric Rayleigh mode shows the highest positive strain sensitivity (92 Hz/$\mu \varepsilon $), while the 1st-order symmetric Rayleigh mode exhibits a negative strain sensitivity (−64 Hz/$\mu \varepsilon $). To eliminate the interference of temperature in strain measurements, an effective decoupling method is proposed based on the sensitivity differences of these two modes, using a frequency response sensitivity matrix to achieve the separation of temperature and strain signals. Experimental results demonstrate excellent decoupling performance, with root-mean-square errors of$0.13~^{\circ }$C for temperature and$15.88~\mu \varepsilon $for strain. These findings confirm the great potential of the proposed sensor for high-performance, wireless, and multiparameter sensing applications.