Described herein is Dielectric Constant Sensor (DDKS) comprising an EIT-based with two U-shaped structures and a transmission line that can compare dielectric constants (Dks) of two different materials that are placed at open stubs U-shaped structures. In at least one embodiment, DDKS generates fully tuned EIT resonance when a reference sample and a sample under test (SUT) have the same Dk. In at least one embodiment, a sharp resonant split is observed within EIT resonance band when a reference sample and sample under test have different Dks. In at least one embodiment, Dk sensor can detect biomarkers of infectious diseases in blood, urine, saliva, medicines, or any other biological sample.