Method, device and system for converting the kinetic energy of randomly moving particles into a usable form of mechanical energy. The device (74) includes a cylinder (75) which supports selectively permeable membranes (76) covered on one side with molecular gates. The cylinder (75) is encircled by another body (c) having stationary blocking surfaces (d) interposed between the selectively permeable membranes (76) to restrict the motion of particles contained between the cylinder (75) and the body (c). In a different embodiment, the device (74) may include a magnet for effecting ion separation. The method comprising the steps of selectively blocking particles moving in one general direction within the device while permitting the passage of particles in the opposite direction such that a vectorial force acting on the apparatus is generated.