Evaluation of the surface properties of hair with acoustic emission analysis

Abstract

Objective The tactile sensation of hair is an important consumer‐perceivable attribute. There are limited instrumental options to measure the haptic properties of hair. In this study, we introduce a novel technique using the acoustic emissions produced when skin comes in contact with dry hair in a stroking motion. Methods Using a free‐field microphone with a frequency response of 8–12,500 Hz, we recorded acoustic emission data of the interaction of skin with hair. Data were captured with Electroacoustics Toolbox software and analysed with Matlab. Acoustic emission profiles were generated allowing us to monitor the acoustic response at distinct frequencies. Results Various experiments were conducted to develop this novel technique as a suitable measure to monitor the surface properties of hair. Increasing the normal force and velocity of the interaction led to an increase in acoustic emissions. We also examined the acoustic profile of hair that underwent chemical treatment. For example, bleached hair produced a much higher magnitude acoustic response than the corresponding virgin hair. On the other hand, hair conditioner systems mitigated the acoustic response. Finally, investigations of textured hair revealed that the three‐dimensional structure of the hair fibre assembly and its ability to return to its original state when perturbed produce the most dominant acoustic response for this type of hair. Conclusion We introduce a cutting‐edge method to reproducibly evaluate the surface properties of hair. Different types of hair geometry produce unique acoustic profiles as do hair types that experience harsh damaging treatments. This is also a very practical and efficient way to evaluate the degree of protection or conditioning of the fibre.

Exploring the Effects of Wetting and Free Fatty Acid Deposition on an Atomistic Hair Fiber Surface Model Incorporating Keratin-Associated Protein 5-1

“…Historically, the hair surface was thought to act as a hydrophobic barrier to foreign agents and a boundary lubricant between hair fibers . When hair is damaged, it was hypothesized that exposure of a hydrophilic surface would promote water adsorption .…”

“…Historically, the hair surface was thought to act as a hydrophobic barrier to foreign agents and a boundary lubricant between hair fibers. 51 When hair is damaged, it was hypothesized that exposure of a hydrophilic surface would promote water adsorption. 16 It is now known that this is not true, as undamaged hair fibers have been shown to absorb moisture, in excess of 20% wt, when exposed to humid conditions.…”

Hair Aging in Different Races and Ethnicities

“…Caucasians and Asians typically experience chemical hair damage to the distal hair shaft, whereas African Americans experience chemical hair damage near the hair root (Monselise et al, 2017). Thermal treatments, including hair drying, straightening, and curling, degrade hair keratin and create damage to the hair similar to that caused by chemicals (McMullen et al, 2015). Smoking can also increase the rate at which hair ages, leading to early-onset alopecia and graying (Jo et al, 2012; Mirmirani, 2015).…”

“…Hair dyes often contain ammonia, which allows the entry of peroxides and dye into the hair cortex, causing oxidative damage to the hair fiber, splitting, drying, and dulling the hair, especially after cumulative treatments (Saitta et al, 2013). Chemical relaxers remove lipids from the cuticle, leading to a hair fiber that is porous to water, damaging the cell membrane and decreasing tensile strength (Khumalo et al, 2000; McMullen et al, 2015).…”

“…The diameter and pigmentation of the hair change from childhood to puberty and adulthood to old age (McMullen et al, 2015). The density of the hair (i.e., the number of hair fibers per cm 2 ) is determined by the hair growth cycle (Maymone et al, 2021).…”