Galfenol resonant sensor for indirect wireless osteosynthesis plate bending measurements

The healing process of bone fractures can be monitored by a measurement of the osteosynthesis plate bending. An electrical resonant circuit consisting of a coil with a magnetostrictive Galfenol core and a capacitance enables an indirect wireless measurement of the plate bending. The Galfenol core is manufactured with a thin film technology using a Galfenol Fe 83 Ga 17 alloy. The sensor has a quit good linear resonant frequency-force characteristic. Both, time and frequency domain measurement techniques for the sensor, use an external measurement coil. In the frequency domain the transformed sensor impedance is evaluated and the resonance frequency is determined by a local extremum. In the time domain a short energizing sinus pulse is transmitted, the sensor response is received and a frequency counting, Fourier or Wavelet technique is used for resonance frequency detection.