Thermally responsive shape memory polymer actuator, prosthesis incorporating same, and fabrication method

A prosthetic device comprising:

• a plurality of thermally responsive shape memory actuators, wherein each thermally responsive shape memory actuator of the plurality of thermally responsive shape memory actuators comprises a body including a non-linear segment disposed between two body ends, and the body comprises a shape memory polymer material;
• a first structural member, a second structural member, and a movable joint connected between the first structural member and the second structural member, wherein the movable joint is configured to permit pivotal movement between the first structural member and the second structural member;
• a first anchor element and a second anchor element associated with the first structural member;
• a third anchor element and a fourth anchor element associated with the second structural member;
• wherein a first group of thermally responsive shape memory actuators is coupled between the first anchor element and the third anchor element, and is configured to promote pivotal movement between the first structural member and the second structural member in a first direction;
• and
• wherein a second group of thermally responsive shape memory actuators is coupled between the second anchor element and the fourth anchor element, and is configured to promote pivotal movement between the first structural member and the second structural member in a second direction that differs from the first direction.

A method of fabricating a thermally responsive shape memory actuator, the method comprising:

• forming a body by additive manufacturing, the body comprising a shape memory polymer material, a first end, a second end, and at least one non-linear segment disposed between the first end and the second end;
• following formation of the body, heating the body into a glass transition temperature range of the shape memory polymer material;
• applying tension to the body while the body is at an elevated temperature due to said heating of the body, wherein the tension is sufficient to elongate the body by at least partial straightening of the at least one non-linear segment;
• and
• cooling the body.