The design of two of the components which comprise a smart structure is described. A smart structure is a system that has a sensor, control, and actuator. The two aspects that are discussed are the sensor and actuator. There have been numerous changes made to the basic design of the smart structure components to improve their simplicity and cost efficiency. The novel design of the sensor of ammonia based on a planar optical waveguide made of thin fi lm of polymer polyimide doped with indicat or dye bromocresol purple is explained . This particular sensor is designed to detect the presence of ammonia in ambient air. The film of dye -doped polyimide demonstrated reversible increase of absorption with a pea k near 600 nm in response to presence of ammonia in ambient air. Two advantages of the polymer is that it works at elevated temperatures as high as 300 o C and it can be saturated with water vapor in such a way that our sensor will not be affected by the cha nge in humidity of ambient air. To improve the sensitivity of the sensor the concentration of dye dopant was increased. This gave more than a ten times better sensitivity (1 ppm) . The coupling of input and output optic fibers with the waveguide was done by means of coupling prisms or coupling grooves. The latter configuration has the advantage of low cost, less sensitivity to temperature variation, and the possibility of coupling from both sides of the waveguide . Exposing the sensor to more than 5000 ppm of ammonia led to saturation of the sensitive film which causes an increase in response time and a decrease in sensitivity. Also a description of an actuator that uses the principle of the photomechanical effect in polyvinylidene fluoride is detailed. To ach ieve the photothermal bending of strips of polyvinylidene fluoride a laser beam with a few milliwatts of power was used. The force generated by the bending strip of polymer was 10 -4 N, which propelled a 1 g oscillating wheel of a mechanical clock. The freq uency of photomechanical resonance at pulsed illumination was inversely proportional to the length of the strip.
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