SRR-Based RF Sensor for Non-Invasive Detection of Static Bone Fracture States

This study presents the design and simulation of a metamaterial-based radio frequency (RF) sensor employing Split-Ring Resonator (SRR) structures for the non-invasive detection of static bone fracture states. Traditional imaging modalities such as X-ray, CT, and MRI, though widely used, often face limitations in accessibility, cost, radiation exposure, and sensitivity to micro-fractures. To address these gaps, the proposed sensor operates within the 1–3 GHz frequency range and leverages dual SRRs to enhance field confinement and sensitivity to dielectric changes caused by bone discontinuities. Full-wave simulations were conducted using CST Microwave Studio on a multilayer femur phantom comprising realistic anatomical layers, including skin, fat, muscle, cortical bone, and blood. The sensor demonstrated a strong response to variations in dielectric properties associated with fracture conditions, achieving detection of fracture features as small as 0.10 mm in width and 20 mm in depth beneath a 5.00 mm thick cortical layer. Reflection coefficient analysis (|S11|) revealed distinct resonance shifts between healthy, fractured, and healed bone states, with frequency deviations up to 47 MHz and quality factors exceeding 80. An iterative antenna design process led to an optimised SRR configuration (ANT 5), exhibiting high Q-factor, enhanced electromagnetic confinement, and excellent impedance matching. The findings highlight the sensor’s potential as a compact, non-ionising, and wearable diagnostic tool for orthopaedic applications.