Piezoresistive effect of carbon nanotube films was investigated by athree-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapordeposition. The experimental results showed that the carbon nanotubes have a striking piezoresistiveeffect. The relative resistance was changed from 0 to 10.5 X 10^(-2) and 3. 25 X 10^(-2) for dopedand undoped films respectively at room temperature when the microstrain under stress from 0 to 500.The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35℃.The origin of the resistance changes in the films may be attributed to a strain-induced change inthe band gap for the doped tubes and the defects for the undoped tubes.
