In situ observation of surface deformation of polymer films by atomic force microscopy

The tensile X-Y stage, providing a load cell and a stretching device, has been constructed to observe the surface deformation of polymer film in situ by using an atomic force microscope (AFM). From the three-dimensional AFM images, the streak-like bumps were observed on a polyethylene terephalate (PET) film surface. By monitoring the change in the distance between them by the tensile load, the strain was evaluated in the direction both parallel and perpendicular to the tensile direction. The microscopic stress-strain relationship by AFM coincided with the macroscopic one, which indicates so-called affine deformation of PET film. Young's modulus was obtained as 2.3 GPa for PET from the initial slope of the stress-strain curve by AFM. The apparent Poisson ratio of the PET film surface could be also evaluated. (C) 2000 American Institute of Physics. [S0034-6748(00)01605-1].