In-Situ Tensile Testing of Hair Fibers in an Environmental Scanning Electron Microscope

The study conducted by the L'Oréal Institute for Ethnic Hair and Skin Research utilized an Environmental Scanning Electron Microscope (ESEM) with a specially designed tensile stage to investigate the hair breakage process. The researchers observed the dynamic changes in geometry and morphology of uncoated hair fibers under mechanical stress at 24°C and 18% relative humidity. They found that during extension, cuticle cells slipped, the hair cross-section restricted, cuticle fraying occurred, and finally, cracks appeared on the hair surface leading to complete fracture of the cuticle and cortex. The study confirmed the ESEM's capability to dynamically investigate hair's mechanical behavior and contributed to understanding the origins of hair fracture. The team planned to extend their research to study hair behavior under varying temperatures and relative humidities.