A bistable shape memory alloy (SMA) micro-switch includes a single continuous
SMA
element such as a nitinol wire that provides bi-directional motion for switching
functions. Bifunctional contact arms provide a mechanical force to maintain an
open state of the micro-switch in addition to conducting current through a circuit.
The SMA element includes first and second segments that are alternately heated
above a transition temperature to cause the SMA element to alternate between first
and second conformations. A cursor attached to the SMA element moves from a first
position to a second position as the SMA element moves from its first to its second
conformation. To close the SMA micro-switch, the contact arm is moved from an open
position to a closed position through sliding contact with the cursor as the cursor
moves from its second position to its first position. Friction generated by contact
between the cursor and the contact arm maintains the cursor in its first position
and the SMA micro-switch in its closed state.
