Active material based fasteners including cable ties and twist ties

A fastener for securing an object, the fastener comprising:

• a flexible elongated member including a first end and a second end spaced opposite the first end;
• wherein the first end and the second end are configured for twisting together so that the first end overlaps and contacts the second end to thereby fasten the first end to the second end and form a continuous band configured for contracting around the object;
• wherein the flexible elongated member includes a shape-memory alloy transitionable between a martensite phase and an austenite phase in response to an activation source;
• wherein the shape-memory alloy has a memorized shape when the shape-memory alloy has the austenite phase, and wherein the shape-memory alloy has a temporary shape when the shape-memory alloy has the martensite phase;
• wherein the shape-memory alloy has an austenite start temperature at which the shape-memory alloy transitions from the martensite phase to the austenite phase;
• and
• a flexible sheath disposed on the flexible elongated member and formed from a shape memory polymer transitionable between a softened state and a hardened state at an activation temperature that is greater than the austenite start temperature;
• wherein the flexible elongated member transitions from the temporary shape to the memorized shape upon heating of the shape-memory alloy to a temperature greater than the austenite start temperature to thereby automatically twist the first end and the second end together.

A fastener for securing an object, the fastener comprising:

• a flexible elongated member including a first end and a second end spaced opposite the first end;
• wherein the first end and the second end are configured for twisting together so that the first end overlaps and contracts the second end to thereby fasten the first end to the second end and form a continuous band configured for contracting around the object;
• wherein the flexible elongated member includes a shape-memory alloy transitionable between a martensite phase and an austenite phase in response to an activation source;
• wherein the shape-memory alloy has a memorized shape when the shape-memory alloy has the austenite phase, and wherein the shape-memory alloy has a temporary shape when the shape-memory alloy has the martensite phase;
• wherein the shape-memory alloy has an austenite start temperature at which the shape-memory alloy transitions from the martensite phase to the austenite phase;
• and
• a flexible sheath disposed on the flexible elongated member and formed from a shape memory polymer transitionable between a softened state and a hardened state at an activation temperature that is greater than the austenite start temperature;
• wherein the flexible elongated member transitions from the temporary shape to the memorized shape upon heating of the shape-memory alloy to a temperature greater than the austenite start temperature to thereby automatically untwist the first end from the second end.