• air bubble detector
• artificial pancreas
• diabetes
• infra-red sensing technique
• insulin delivery

In the design of any medical device, safety is fundamental since the implications of an improper functioning could lead to serious consequences. Specifically, in a fully implantable artificial pancreas, it is essential to avoid the presence of air inside the implanted reservoir to avoid the risk of administering an erroneous dosage of insulin to the patient causing hyperglycemicia and changes of therapeutic function of the insulin due to a prolonged air/insulin contact. In this thesis, we targeted a fully implanted AP prototype that is able to refill the reservoir by swallowable insulin capsules and inject the insulin in intraperitoneal cavity. We focus on the realization of a micro-fluidic sensor positioned on the suction line to understand when the refilling operation of the implanted tank is completed. After an analysis of the various techniques for sensing two-phase flows, a non-intrusive infrared sensing technique has been chosen. The discrimination between different flow regimes is based on the fact that IR rays are attenuated differently when they penetrate gases and liquids, so the acquired voltage depends on the light intensity passed by each medium. The circuit of the sensor has been designed and several tests have been performed to determine the minimum size of the bubble measurable by the sensor, the maximum flow rate at which it is still possible to detect the bubbles and the response time of the sensor. During the tests, the signals for different dimensions of bubble have been compared, the sensor has been tested also in closed environment and finally with insulin. Lastly, the sensor has been coupled with the reservoir and electronic board of the AP to ensure its proper functioning to stop the reservoir actuator in a simulated aspiration event. These experiments proved the functionality of the proposed sensor to enhance the safety in the AP.