Shape memory alloy-based device for controlling or monitoring pressure in a system

A device for a fluid system, the device comprising:

• a member composed of a shape memory alloy in an Austenitic phase state and including one end operatively connected to a fixed point;
• a movable element operatively connected to another end of the member;
• a housing operatively connected to the member;
• a cap adapted to cover an opening in the housing;
• a notch defined by the cap;
• wherein the member is configured to undergo a phase change from a high modulus Austenitic phase to a low modulus Martensitic phase in response to an activation stress;
• wherein the member is configured to reversibly stretch with the phase change, thereby moving the movable element relative to the fixed point;
• wherein the member is disposed in contact with a first region of the fluid system;
• wherein the movable element includes first and second faces such that the first face is in contact with the first region;
• wherein the activation stress is defined by a pressure differential across the first and second faces of the movable element exceeding a first critical value;
• and
• wherein the movable element is configured to engage with the notch when the pressure differential exceeds the first critical value, thereby selectively preventing removal of the cap from the housing.