Fabrication of Flexible ALN Thin Film-Based Piezoelectric Pressure Sensor for Integration Into an Implantable Artificial Pancreas

This works reports about the fabrication and the characterization of AlN-based flexible piezoelectric pressure sensor, to be integrated into an implantable artificial pancreas. The artificial organ comprises an intestine wall-interfaced refilling module, able to dock an ingestible insulin capsule. A linearly actuated needle punches the capsule to transfer the insulin to an implanted reservoir. The pressure sensor, located at the connection of the needle with the linear actuator, is designed to sense the occurred capsule punching. Polycrystalline AlN thin film was successfully sputtered at room temperature on Kapton substrate with a preferential orientation along c-axis, as peremptorily required for the intrinsic piezoelectric response of the nitride layer. The characterization, aimed to verify the sensor capability to convert the local stress into electrical charge, confirms the linear proportionality of the generated charges with the applied force within the range of the interest values (0.3–3.3 N) and at very low frequency (lower than 5 Hz) for the specific application of the ingestible capsule punching and insulin transfer.