Abstract: A microsystem switch (1, 20, 25, 30, 33) has a support (2) defining a recess (3), and a flexible bridge (6) is mounted on the support (2) bridging the recess (3). The bridge (6) is shaped so as to hold selectively a concave stable state, in which the bridge bulges into the recess (3), and a convex stable state in which the bridge bulges out of the recess (3). The switch includes an actuator (8, 9; 26, 27) for effecting flexing of the bridge (6) between the stable states, and a switching element (7, 31, 34) is mounted on the bridge (6) such that movement of the bridge between the stable states moves the switching element between an on position and an off position. According to another design, a microsystem switch (40, 55) has a support (41) defining a recess (42), and an elongate torsion member (44) is mounted on the support (41) bridging the recess (42). A flexible bridge (43, 56) is mounted on the support (41) bridging the recess (42) in a direction substantially perpendicular to the torsion member (44).