The construction of a medical device having a disposable element is disclosed. Detachable elements comprising a body having a retention feature, an electrical contactor, and sensors are also disclosed. Further disclosed are detachable elements comprising a body having a hole and a retention pocket, an electrical contactor, and a printed circuit board assembly (PCB) in contact with the innermost surface of the body that forms the retention pocket. Further disclosed are detachable elements comprising a body having an opening and a printed film comprising conductive elements, where the conductive elements comprise a sensor configured to be aligned with the opening to expose the sensor. Further disclosed are reusable components having matching retention features.