Bi-directional, single material thermal actuator

A thermal actuator comprising:

• a first arm having a proximal end and a distal end;
• a second arm, parallel to the first arm, and having a proximal end and a distal end;
• a third arm arranged between and parallel to the first and second arms, the third arm having a proximal end and a distal end, the first, second and third arms are made of a single material;
• the distal ends of the first, second and third aims are coupled together to form a distal end of the thermal actuator wherein:
• (a) when the proximal end of the third arm is coupled to ground and current is applied to the proximal end of the first arm, the first arm thermally expands by an amount that is greater than an amount by which the third arm thermally expands whereby the distal end of the thermal actuator moves and applies force in a first direction, and (b) when the proximal end of the third arm is coupled to ground and current is applied to the proximal end of the second arm, the second arm thermally expands by an amount that is greater than an amount by which the third arm thermally expands, whereby the distal end of the thermal actuator moves and applies force in a direction opposite the first direction, and wherein the distal end of the thermal actuator moves in a plane containing the first, second and third arms.

A method of applying force in at least two opposite directions, comprising:

• supplying current to a first arm of a thermal actuator such that the first arm heats up and longitudinally expands relative to a cold arm of the thermal actuator such that a distal end of the thermal actuator moves and applies a force to an object in a first direction;
• and
• alternatively, supplying current to a second arm of a thermal actuator such that the second arm heats up and longitudinally expands relative to the cold arm such that the distal end of the thermal actuator moves and applies a force to the object in a direction opposite to the first direction, wherein
• the distal end of the thermal actuator moves in a plane containing the first, second and cold aims.