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The possible use of polycrystalline diamond (poly-C) as a piezoresistive position sensor in a cochlear prosthesis is being investigated for the first time. The fabrication process of the poly-C thin film was optimized for compatibility and integration with the Si-based bulk micromachining technology of the cochlear probe. In-situ doped poly-C, films, with a thickness of 1 μm, were grown on insulating substrates using MPCVD and patterned by ECR-assisted plasma etching. The piezoresistors can be used as position sensors to detect the curvature and position of the probe during implant surgery. The film quality, electrical properties, contact resistance and piezoresistivity of the poly-C sensors were characterized, which demonstrated a successful integration of diamond technology with the microsystem technology. A gauge factor of 28 was achieved for the poly-C sensors on the probe.