A Novel Air-Gap Enhanced Dual-Layer Metamaterial Biosensor for Real-Time Noninvasive Breast Cancer Detection: Design, Fabrication, and Clinical Validation

This research unveils a cutting-edge miniaturized metamaterial biosensor incorporating a strategically designed dual-substrate configuration, engineered to deliver exceptional sensitivity and selectivity for non-invasive breast cancer cell detection through high-resolution microwave dielectric analysis. The innovative sensor architecture employs a dual-layer FR4 substrate configuration with a strategically optimized 1.5 mm air gap, which significantly enhances electromagnetic field confinement and amplifies sensing sensitivity compared to conventional single-layer designs. The compact 40x40 mm2sensor demonstrates exceptional performance with a return loss of 23.43 dB at 2.44 GHz, achieving a remarkable sensitivity of 0.028 GHz/RIU while maintaining a miniaturized footprint of λ0/5. Unlike previous simulation-based studies, this work provides comprehensive experimental validation using real biological samples from both healthy individuals and breast cancer patients aged 44-66 years, including blood specimens and tissue sections for histopathological correlation. The sensor's discriminative capability is demonstrated through distinct frequency responses: healthy samples exhibit resonance frequencies between 1.6 and 1.8 GHz, while cancerous samples consistently resonate in the 1.8-2.1 GHz range, attributed to the higher permittivity of malignant cells. The air-gap enhancement mechanism concentrates electromagnetic fields at the sensing interface, resulting in superior analyte interaction and detection accuracy. Clinical validation involved CA 15-3 tumor marker analysis, where samples exceeding the 31.29 IU/mL threshold showed characteristic frequency shifts confirming the sensor's diagnostic reliability. This metamaterial-based approach offers significant advantages, including real-time label-free detection, cost-effective fabrication, and potential for point-of-care applications, positioning it as a transformative technology for early breast cancer screening and non-invasive biomedical diagnostics.