Device to deliver an alarm signal upon detection of a gravitational wave generated by a body falling into a swimming pool, using a differential detector that includes a comparison device for comparing a sensitivity threshold value to the value of the electrical signal received, and to deliver an alarm signal when the received electrical signal exceeds the sensitivity threshold value. The antenna can be used to receive signals from a patient via a matching layer that is positioned at the open end of the enclosure. Moreover, by carrying out the silicidation at an early stage in the fabrication, the choice of material for the second gate is not limited by any high-temperature processes. An inclined portion of the second semiconductor layer extends in the second direction. Thereby, the drug molecules are uniformly distributed in the contact lens and can be gradually and locally released to the eye of the user wearing the contact lens.