Liquid Sensor/Detector Using an EBG Structure

This paper describes a novel procedure for detecting liquids with various permittivities using an electromagnetic bandgap (EBG) structure. The concept can also be used as a method for achieving antenna frequency tunability. The main sensor consists of an array of square patches on a square unit cell with a series of cuts and grooves in the dielectric material between the patches. These trenches allow for the deposition of the liquids to be detected. The variation in the dielectric characteristics of the liquids inserted produces a change in the reflected phase of the EBG. This change in the phase could be detected in various ways. In this paper, a planar antenna has been placed at a short distance from the EBG structure. The changes in the phase in the surface waves produce a change in the reflection coefficient of the antenna. Butan-1-ol, propan-2-ol, ethanol, and methanol have been inserted to demonstrate the tuning technique. In order to complete the experiments, the reflection coefficients and the radiation patterns were measured. Good agreement has been found between the simulated and measured results. The envisaged detector could be used in a laboratory or clean room where liquids may fall into the channels.