A metamaterial sensor that can be applied to detect water content in emulsified oil is proposed, which is reusable in experiment and nondestructive to the sample. Electric field of the original absorber is researched to guide the design of microfluidic. Also, its equivalent circuit model is proposed to validate its ability as a sensor. The calculated sensitivity of the sensor is 339 MHz/ε'r in the range of 11.26 GHz to 10.044 GHz, indicating its potential for detecting the emulsified oil. The experimental results reveal the reliable process of detection and the linear relationship between frequency shift and water content. This work provides a fast and convenient solution to check the quality of lubricant oil to some extent, which is relatively valuable to modern machinery.
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