Development of a specialized diamond knife for controlled notch introduction in ultrathin polymer films for in situ tensile transmission electron microscopy

In situ tensile testing in a transmission electron microscope (TEM) is a powerful tool for investigating polymer fracture at the nanoscale, but the stochastic nature of crack initiation has long hindered systematic observation. We report a specialized diamond knife, co-developed with Syntek Co., Ltd., that introduces a controlled V-shaped notch into a trimmed specimen block prior to cryo-ultramicrotomy. Ultrathin films (∼100 nm) of a copolymer film containing a well-defined notch were prepared and observed using in situ tensile TEM. Cracks initiated reproducibly from the notch tip and propagated predictably, providing new experimental control for nanoscale fracture studies.