Skip to main content

A Liquid Sensor based on Frequency Selective Surfaces

Njogu, Peter M., Sanz Izquierdo, Benito, Parker, E.A. (2022) A Liquid Sensor based on Frequency Selective Surfaces. IEEE Transactions on Antennas and Propagation, . ISSN 1558-2221. (In press) (doi:10.1109/tap.2022.3219540) (KAR id:98144)

PDF Author's Accepted Manuscript
Language: English

Download (885kB) Preview
[thumbnail of A_Liquid_Sensor_based_on_Frequency_Selective_Surfaces - P. Njogu - AAM.pdf]
This file may not be suitable for users of assistive technology.
Request an accessible format
Official URL:


A novel, simple and easy-to-fabricate liquid sensor using frequency selective surfaces (FSS) is proposed. The new sensor concept is based on modifying the capacitance between adjacent FSS elements when materials of different electrical characteristics are inserted. The change in capacitance produces a change in resonant frequency. The FSS design consists of a 9 x 9 array of square loops on 0.31λ x 0.31λ square unit cells with trenches between the loops. The trenches are filled with liquids under test (LTU). The structure operates at 4.6 GHz without any liquid. When liquids are inserted in the trenches, the resonance frequency varies in relation to the dielectric constant of the liquid. This is observed by measuring the transmission coefficient (S 21 ). Butan-1-ol, ethanol, methanol, propan-2-ol, and Xylene are used to demonstrate the sensing function. A maximum sensitivity of 8.65 % for Xylene was achieved. Further, very low differences were observed between the measured and expected dielectric constant and loss tangent, thus validating the design. The device is inexpensive, compact, and easy to make and scalable for large area operations in liquid detection for microwave sensing applications. This technique has potential applications in reconfigurable FSS.

Item Type: Article
DOI/Identification number: 10.1109/tap.2022.3219540
Additional information: ** Article version: VoR ** From Crossref journal articles via Jisc Publications Router ** Licence for VoR version of this article starting on 01-01-2022:
Uncontrolled keywords: Dielectric, frequency selective surface (FSS), liquid, material characterization, permittivity, sensor
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Engineering and Digital Arts
Funders: Engineering and Physical Sciences Research Council (
SWORD Depositor: JISC Publications Router
Depositing User: JISC Publications Router
Date Deposited: 30 Nov 2022 16:49 UTC
Last Modified: 06 Dec 2022 13:55 UTC
Resource URI: (The current URI for this page, for reference purposes)
Njogu, Peter M.:
Sanz Izquierdo, Benito:
Parker, E.A.:
  • Depositors only (login required):


Downloads per month over past year