Shape memory alloy actuator assembly

An actuator assembly comprising:

• a first part and a second part, wherein a first axis is defined with reference to the second part;
• a shape memory alloy (SMA) wire connected to the first and second parts, the SMA wire for moving the first part relative to the second part in any of a set of directions that are at least partly perpendicular to the first axis, wherein the set of directions includes first and second directions;
• a set of arms, each of which is connected to the first and second parts and extends partly around the first axis, the set of arms configured to provide a biasing force that biases the first part towards a first position relative to the second part;
• wherein the set of arms has a first stiffness when the first part is moved away from the first position in the first direction and a second, lower stiffness when the first part is moved away from the first position in the second direction;
• wherein at least one of the set of arms comprises a portion that is configured to decrease the first stiffness by a larger amount relative to the amount that the portion decreases the second lower stiffness;
• and
• wherein the portion extends in a direction that is at least partly perpendicular to the first direction and at least partly parallel to the second direction, wherein the portion corresponds to at least one hairpin-shaped portion of the set of arms, wherein the hairpin-shaped portion comprises at least one pair of arm segments that extend alongside and generally parallel to each other and are connected to each other at one of the ends of the at least one pair of arm segments by a 180 degree turn.