Dynamic indentation of polymers using the atomic force microscope

The applications of Atomic Force Microscope (AFM) on study of surface property of polymeric materials have been demonstrated. The surface microstructure of the material was characterized by the so called dynamic indentation technique. Being penetrated by the AFM tip, the sample surface was simultaneously undergoing an oscillation at smaller amplitude (3-5 nm) by a piezoelectric actuator. The merit of the developed dynamic indentation technique is to characterize the material's modulus as a function of indentation depth using one cycle of the depth sensing indentation force data. The results have shown that the technique is a powerful method for polymer characterization with nanometer spatial resolution. The obtained photo-detector signals from AFM were numerically processed by Fourier series to analyze the storage modulus of the sample. The PDMS polymer materials were tested and results were compared with MTS Nano Indenter data. It is believed that the technique can be readily applied for indentation study of thin film, coating materials and nano-structures.