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Microtensile Tests and in situ Atomic Force Microscopy (AFM)Aims
Microtensile TestsA new setup based on measuring the forces and the deformations by means of an optical microscope was designed and built. Microfabrication technologies such as dry etching were used to prepare freestanding polymer tensile samples with thicknesses of around one micorn. The substrate material was polyimide (PI 2723 from HD Microsystems). On top of it PEDOT:PSS was deposited and patterned. These PEDOT:PSS films and a thickness down to even 100 nm. Finally, the Young's modulus of polyimide and PEDOT:PSS could be measured. A value of 3.3 GPs could thus be obtained for PI 2723 and of 4.5 GPa for PEDOT:PSS. These values are different from bulk values and could therefore hint at different material properties at thicknesses below one micron.
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In Situ Atomic Force MicroscopyA similar setup was used to integrate an AFM into the microtensile setup. Controlled loads could be applied to a notched specimen and the corresponding crack growth originating from the notch could be observed at very high resolution. This approach might help determine fracture toughnesses and might finally even allow to observe cracks at a molecular level.
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References
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