http://www.actuonix.com
Linear actuators for LEGO can be found here: http://www.actuonix.com/category-s/1929.htm
Lego Mindstorms*, EV3*, Power Functions*, and Technic* compatible linear actuators. These linear actuators are self contained units which include an electric motor. They will push up to 25N and move at 12mm/s unloaded. The maximum movement of this model is 100mm (~4 Inches).
For use with your NXT* or EV3* Brick, you will need one of the standard motor connection cables that are included in the Mindstorms* kit. The L12-NXT Software Block can be downloaded from L12-NXT Block , and the L12-EV3 block can be downloaded from L12 EV3 Block
Please note: The Lego Group does not endorse these products.