This review paper provides a rigorous and comprehensive analysis and sets up a unified electromagnetic (EM) framework for planar microstrip resonant filters for two seemingly different but electromagnetically similar applications: non-invasive blood glucose monitoring and structural tension sensing. This work connects biochemical and mechanical tracking, studying the convergence of high-frequency planar technologies and complex material media. Four important microwave resonator topologies are analysed in detail, including Split Ring Resonators (SRR), Complementary Split Ring Resonators (CSRR), Hairpin Resonators, and Stub-Loaded Resonators (SLR). The underlying transduction physics is rigorously formulated, using the 3D vector cavity perturbation theory and conformal mapping expressions, coupled with modified first-order Cole-Cole dielectric relaxation equations. Mechanical strain deformation is explicitly linked to matrices of transmission lines to map physical elongation, Poisson’s ratio, and substrate elastomeric variations directly to resonance perturbations. Performance benchmarks are synthesized through a quantitative meta-analysis of literature covering the last five years, highlighting the basic trade-offs among near-field localization, quality factor (QL), and linear correlation coefficient (R2). In addition, we tackle some of the key engineering challenges, including the high loss tangent of human tissue, water absorption damping between 2-10 GHz, and thermal-mechanical drift cross-sensitivity. A multi-parameter calibration matrix framework, based on an isolated reference resonance peak, is described to overcome these multi-parameter interferences. Lastly, we discuss future directions for edge-computed machine learning calibration engines and passive, battery-free, chipless telemetry radio frequency identification (RFID) sensor tags for remote deployment.
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