TESTING
analysis techniques available have allowed the interrogation of hair surfaces and have provided an understanding of the chemical and physical changes associated with treatment products, thereby enabling the development of new and more effective hair care treatments.
Surface characterisation methods for hair 3D scanning electron microscopy Available software provides the capability to convert pairs of stereoscopic digital SEM images into a 3D representation of the area sampled. The resultant calibrated image contains z (height) information, allowing metrology of macro and micro areas. The main benefit of this is that the metrology of materials which are difficult to determine by other methods (such as rough surfaces, angular metals, cutting tools, fibres) can be easily resolved. Furthermore, compared to white light
interferometric methods, the lateral resolution in x and y is significantly superior. The use of 3D SEM allows us to quantify subtle structural changes on hair fibres that may not be visible through conventional imaging. This data can then be leveraged to support R&D decisions, optimise active ingredient delivery, and provide evidence for scientifically robust claims.
White light interferometry White light interferometry (WLI) is an optical metrology technique that provides measurement of the physical characteristics
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Figure 4: ToFSIMS image of human hair with false colour overlay of alkyl sulphate (pink) on keratin (green)
of a material including micro-topography, form and texture surface topography, roughness, dimensional metrology, and layer thickness measurement. The resolution of the measurements is <1 µm in the x and y axes and <1 nm in the z-axis, allowing for micro-features and topographic variations to be monitored in detail. Processing of the raw data allows for the
generation of a range of data formats including: ■ Pseudo-colour height maps: The colour scale is calibrated in nanometres, microns, or millimetres. This allows a 3D graphical
Figure 5: Optical image of cross sectioned human hair
representation of surface topography. Derived amplitude parameters allow classification of various aspects of topography - for example, Sa - the arithmetic mean of the deviations from the mean (the statistical average area surface roughness parameter). ■ Profilometry: Enables the generation of line scans across any user-defined XY locus of the sample. This is particularly useful for measuring the magnitude of specific surface features with high accuracy (nm). ■ Contour map plots (axonometric plots: Regions of equivalent height are connected by
www.personalcaremagazine.com
November 2025 PERSONAL CARE
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