A drug mixing device is disclosed. The drug mixing device comprises a movable actuator, wherein movement of the actuator causes mixing of a drug within the drug mixing device； and an elastic member coupled to the actuator. The elastic member is configured upon release to transition from an extended state to a non-extended state, the elastic member storing energy in the extended state. The movement of the actuator is driven by the release of the stored energy as the elastic member transitions from the extended state towards the non-extended state.
