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In this paper, a new operating principle for a tactile sensor for medical diagnostics is proposed based on the measurement of three-dimensional magnetic fields. A permanent magnet and the newly developed 3D-Hall sensor AS54xx of the Fraunhofer Institute for Integrated Circuits (IIS) in Erlangen, Germany, are embedded in one silicone pad. An external force changes the position of the magnet in relation to the AS54xx, thus changing the measured magnetic field in three dimensions. In contrast to conventional tactile sensors, one sensor cell provides three dimensional information about external forces, thus making it potentially possible to detect tumors by palpation with only this one sensor cell. Three prototypes of the tactile sensor with different silicones and permanent magnets have been fabricated, and the feasibility of the operating principle has been proven for axial forces with laboratory experiments. Hysteresis effects of the tactile sensor have turned out to be negligible.
Ledermann et al. (Sat,) studied this question.