Photomechanical effect in films of polyvinylidene fluoride

Photothermal bending of strips of polyvinylidene fluoride was initiated by a laser beam with a power of a few milliwatts. A bending strip generated a force of 10−4N that propelled a 1 g oscillating wheel of a mechanical clock. The frequency of photomechanical resonance at pulsed illumination was inversely proportional to the length of the strip. The proposed model explained bending as a result of uneven thermal expansion on opposite sides of the strip. The model predicted, in agreement with experiment, that the force is proportional to beam power and does not depend on the shape or position of the beam in the strip.