Assessing Hair’s Internal Porosity Using Scanning Electron Microscopy.

Author: Angela Cristina Vargas Calle*; Viviane Albarici; Cristina Moreira; Leslie Laquieze; Adriano Pinheiro.

Published at: January 01, 2025

https://kosmoscience.com/pdf/assessing-hairs-internal-porosity-using-scanning-electron-microscopy.pdf

IFSCC 2025 Congress 2025, Full Paper ( Abstract Reference Number) IFSCC 2025 Congress 2025, Full Paper ( Abstract Reference Number) 2 of 8 whether the strands floated on the surface or sank. Based on this observation, they classified the strands as: Low porosity for those that floated; Normal porosity for those in which part of the strand floated and part sank; High porosity for those in which all strands sank [1]. This type of indirect measurement is used by consumers because it is easy to perform and does not require expensive measuring instruments, however it does not provide numerical measurements of porosity or information about the shape of the pores, that are important data in the study of the interaction between the hair strand and cosmetic products. However, advancements in image analysis and SEM (Scanning Electron Microscopy) now offer promising alternatives for directly evaluating hair porosity. Scanning Electron Microscopy (SEM) is a technique that uses ionizing radiation to generate images of surfaces. Although the technique requires a high vacuum and coating of the hair sample, it is much more cost-effective than X-ray microtomography, SAXS, or BET. SEM is a widely used technique, and many laboratories are equipped with the necessary instruments and offer analyses at an affordable price. With this technique, it is possible to obtain high-resolution, highly magnified images, which allows for direct visualization of hair pores when the strand is cut transversely. Some microscopes even come with software that enables direct pore measurement from the image; however, this software is sold separately and is usually expensive, often not justifying the investment. The only drawback of using SEM to measure porosity is that it assumes the distribution of pores is the same throughout the hair strand, which is not always true [11]. However, this limitation can be reduced by performing evaluations at multiple points along the same strand. On this context, this study aimed to develop a reliable, cost-effective methodology to measure hair porosity by quantifying the number and size of internal pores using SEM cross-sectional images. The approach involved two phases. In the first phase, we optimized the preparation of hair cross-sections by testing combinations of embedding media and cutting tools to preserve internal hair morphology. Three embedding media and three cutting tools were evaluated. In the second phase, the methodology was validated for reproducibility and sensitivity to cosmetic treatments. Four groups of Caucasian hair swatches were used: one untreated control and three double-bleached groups treated with different products. Cross-sections of these samples were analyzed via SEM, and images were processed using a plugin developed during phase one. This plugin quantified the number and area of internal pores.