Devices formed by two triple layer artificial muscles of polypyrrole, working face to face in aqueous solution, producing longitudinal and valve movements are presented. Linear movements describing up to a 60% the length of the device were attained. Both, rate and sense of the movement are under control of the driving current. The position of the device is under control of the consumed charge. Any attained position is maintained after switching off the device. The device works simultaneously as an actuator and as a sensor of: the electrolyte concentration, the current flowing by the device, or the trailed weight. (c) 2007 Elsevier Ltd. All rights reserved.