Cost-Effective Flexible CSRR-Based Sensor for Noninvasive Measurement of Permittivity of Biomaterials †

Abstract

A novel, cost-effective, flexible microwave sensor is proposed to facilitate point-of-care testing (POCT) methods for medical diagnosis. The sensor is based on the complementary split-ring resonator (CSRR) to accurately measure the permittivity of biomaterials over a wide range of frequencies. This ability can be used to characterize various materials under test (MUT) such as blood, saliva, tissue samples, etc. The flexibility of the proposed sensor means that it can be used when the accessibility of the sample has technical difficulties, such as on curved surfaces. Firstly, the optimized structure and coupling to the readout transmission line are evaluated using finite element method (FEM) simulations. Then, the prototype of the optimized structure is fabricated on a thin polydimethylsiloxane (PDMS) substrate as a biocompatible economical polymer, and aluminium is carefully chosen for the fabrication of CSRR and readout parts. The proposed flexible sensor is tested and compared to conventional rigid CSRR sensors. The proposed structure withstood the different bending positions well, and also showed an improvement in the results for curved MUT.