A linear actuator assembly (100) has a linear actuator including a motor shaft (104) extending from a base (24) with a piezoelectric component (28) which oscillates the shaft (104). The shaft (104) has a faceted surface. A movable carriage (16) has a notch (40) with at least one flat surface that receives the shaft (104) of the linear actuator. The carriage (16) is in direct and continuous contact with the motor shaft (104) at the notch (40) such that the motor shaft's facet is in contact with the flat surface of the notch (40) when the carriage (16) moves linearly along a travel axis (20). A spring (42) is coupled to the carriage (16) to urge the motor shaft (104) into contact with the notch (40) of the carriage (16) so as to maintain contact between the motor shaft's facet and the flat surface of the notch (40) to inhibit rotation of the motor shaft (104).