**6. Conclusion**

A telemetry system using a capacitive strain sensor has been developed for the detection of spinal fusion monitoring. The strain sensor was made using MEMS process with high sensitivity and reduced size that serves the purpose for strain detection on the spinal fusion rod. The cantilever structure of the sensor is composed of two parallel plates, galss and silicon, respectively, with a narrow gap D0 (3 μm) and a conjoint end. The bending strain sensor has the characteristics of high nominal capacitance (20 pF), high sensitivity, and compact dimensions (2 mm x 7 mm x 0.8 mm). It utilizes a variable gap configuration comprised of silicon and glass beams that are bonded at one end and open at the opposing end. This type of structure has been tested to withstand a strain range of 0 to 1000 με. The inductive link between the implant circuit and the reader was sufficient for supplying power to the implant circuit and extracting data at 10 cm distance. A specific sensor has a linear gauge factor of 252 in the capacitive domain and 249 in the frequency domain. Measurements made through air and water with a corpectomy model produced a linear response consistent with a metal foil reference gauge. The strain measurement system was also tested with the corpectomy model designed as a simplified mechanical analog of a spine section and was then tested using a human spine. For the biomechanics application, the sensor is expected to be in a fluidic environment. The tests of the corpectomy model placed in water tank were successful in showing that measurements were possible in conditions present in-vivo. The read range was limited to 10 cm due to the reader design used and the sensor coil design constraints. Finally, a test performed using a human spine showed the wireless implant detected strain roughly one third of the load were shared by the intact spine after the spine is fused.
