A 2.45 GHz Low-Power Microwave Ablation-Assisted Drilling System with Tunable Impedance-Matching Structure

This study proposes a 2.45 GHz low-power microwave drilling system for precise bone drilling near sensitive organs with a tunable parallel metal impedance-matching sleeve. The system is based on a quarter-wavelength coaxial resonant cavity integrated with a movable parallel impedance tuning sleeve, which can mitigate impedance mismatch caused by dielectric variations in ablated tissue during drilling. To further ensure matching accuracy and stability, a solid-state source is employed to track the minimum reflection frequency within the operating bandwidth. Broadband electromagnetic and transient thermal simulations are conducted to evaluate the impedance response and thermal characteristics. A prototype microwave drilling system is fabricated and experimentally validated in fresh cartilage tissue, fresh cortical bone, and cooked bovine femur samples. The results demonstrate that the proposed tuning sleeve and adaptive source effectively regulate the response to the reflection coefficient. At 2.45 GHz and an input power of 20 W, the proposed system achieves a measured reflection coefficient below −12 dB and produces a localized drilled region within 10 s. Compared with previously reported microwave drilling systems operating at power levels of up to approximately 200 W and recent microwave drilling studies typically employing tens to hundreds of watts, the proposed system demonstrates bone drilling at a substantially reduced input power, while the integrated tunable sleeve provides structural impedance matching without relying solely on conventional external impedance tuners.