are affixed at either end of the sma element and provide means for transmitting linear forces to the environment only one anchor bar is shown for clarity as in a conventional helical spring the overall 34 strain 34 or lengthening of the serpentine spring is much greater than the local strain of the spring material at any point for example a local strain of 5 might translate into a 100 change in overall length of the actuator by utilizing a long continuous path of material 400 the ohmic heating resistance of the spring can be made very high adjacent portions of the spring must be electrically isolated from one another one approach might be to cast the entire device in a very compliant elastomer factors such as thickness and height of the serpentine spring will affect strain limits and hence the elongation potential a very slender aspect ratio will limit the device to a contraction mode of operation due to buckling constraints this provides a compact planar configuration for mechanically transforming the high force low strain output of smas to provide a more useful high strain low force output a compact high strain high force actuator can be made by combining a number of serpentine actuators in parallel a serpentine planar spring actuator according to this aspect of the invention provides significant advantages over conventional sma actuators a serpentine actuator comprising a planar.