According to one embodiment, a cannula assembly may include a cannula module and an inserter module. In the pre-operational state the cannula is retracted with respect to the skin-contacting surface. In operational state the cannula projects beyond the skin-contacting surface. The inserter module may include an energy store and an activation mechanism. When the energy store is at least partially discharged, the stored potential energy is transformed to kinetic energy that moves the cannula from the pre-operational state to the operational state. The activation mechanism is triggerable from outside the cannula assembly with a trigger device. The activation mechanism prevents the energy store from being discharged before it is triggered by the trigger device, and enables the energy store to be discharge after it is triggered by the trigger device to force the cannula from the pre-operational state into the operational state.
