Concept for a miniaturized cardiovascular multi sensor implant

Continuous monitoring of physiological parameters in cardiovascular areas allows early detection of critical conditions which may lead to clinical symptoms and hospitalization. Thereby early diagnostics, optimization of therapy and reduction of costs can be achieved. This abstract presents the concept of an implantable multi sensor system that utilizes, amongst others, a highly miniaturized capacitive pressure sensor and acceleration sensor. In medical applications it is recommended to achieve high-precision pressure measurements, e.g. for controlling of haemodynamic in pulmonary artery. The approach of a multi sensor system enables parallel monitoring of side effects. The patient's position is detected by the acceleration sensor which is developed at Fraunhofer ENAS. Further information about temperature or energy level deviations are used for the correction of measured pressure values. The core element of the implantable multi sensor system is a multi-functional Application Specific Integrated Circuit (ASIC), developed at Fraunhofer IMS, which is able to handle all measurements but also power management and communication. The complete system operates without any integrated energy sources and is simulated and designed to achieve low power consumption for telemetric operation distances up to 15 cm. The communication is according to the international standard for passive RFID item level identification for air interface communications at 13.56 MHz (ISO/IEC 18000-3). The required antenna is embedded within the circuit board. However, ensuring long-term stability, biocompatibility and integrity of implantable systems is necessary. The implementation requires new technologies and material combinations to fulfill these specifications. Most implantable and medically approved systems are encapsulated by materials like titanium or precious metals which lead to limitations regarding further miniaturization. The encapsulation should furthermore show suitable pressure transmission properties. These requirements can be achieved by a nanometer scale 3d-passivation of the sensor elements by Atomic Layer Deposition (ALD). Thus, hermetic sealing and high conformity is achieved.