Abstract: A method for testing a drug delivery device including a piezoelectric transducer, a microcontroller, and a DC power source, with the piezoelectric transducer having an operative state and inoperative state. The method includes providing a drive signal to the piezoelectric transducer of the drug delivery device, determining an actuation voltage value or an actuation current value, and comparing the actuation voltage value or the actuation current value to a baseline value to determine whether the piezoelectric transducer is in the operative state or the inoperative state.

Abstract: Capillary-based pressure threshold sensors are provided for liquids that exploit the properties of hydrophobic, superhydrophobic, oleophobic and amphiphobic porous membranes to detect when fluid passes through the membrane in the event of the pressure across the membrane rising above the breakthrough pressure of a fluid. Example implementations are provided of different configurations for a capillary-based pressure threshold sensor, and of how a capillary-based pressure threshold sensor is used in a medication delivery device or other fluid delivery devices to detect occlusion or other fluid flow condition.