Topics Covered
Background
The Composition of Human Hair
Means to Generate High Resolution
Surface Images of Hair
Investigation of Different Human
Hair Samples using WITec AFM
Factors Which Governs the Surface
Topography of Human Hair
Background
WITec is a
manufacturer of high-performance instrumentation for scientific and
industrial applications focused on new solutions for Optical and Scanning
Probe Microscopy.
The
Composition of Human Hair
Human hair is composed of three elements. The cuticule is the outer
surface of the hair shaft; it is a very hard keratinous substance.
The next element is the cortex which is a more fiberous keratin. The
third element is the medulla, a soft keratin-rich material.
Means
to Generate High Resolution Surface Images of Hair
To investigate the reaction of the
hair surface to chemical or cosmetic treatment, a tool is needed to
image the surface with high resolution. Offering easy sample preparation
and high resolution imaging possibilities, the Mercury 100 AFM
is a well suited instrument for such studies.
The integrated scientific-grade optical microscope provides superior optical
access, easy cantilever alignment, and high resolution cantilever survey. An
integrated video camera supports precise positioning of the cantilever on the
sample area of interest. The cantilever be can easily placed on the hair.
The diameter of the hair is approximately
50 µm and the width of the cantilever is 25 µm. The aim of these studies
is to show, the surface structures of different coloured hair. The
difference between untreated and bleached blonde hair should also
be demonstrated, which will be very interesting as it shows how the
different hair will respond to cosmetic treatments.
Investigation of Different Human Hair Samples using WITec AFM
Different human hair was fixed to microscopic slides coated with double-sided
adhesive tape. On the left is a brown untreated hair with crenulated cuticule
borders (scan range: 30 µm x 30 µm). On the right a natural white hair is imaged
(scan range: 40 µm x 40 µm). Clearly visible are the platelets of the keratin,
which are wrapped around the hair shaft in several layers.
On the left, an untreated blonde
hair (scan range: 35 µm x 35 µm), on the right, a bleached one (scan
range: 15 µm x 15 µm). Clearly visible is the complete loss of the
scale-like structure after the bleaching process.
Factors
Which Governs the Surface Topography of Human Hair
The thickness of the cuticle cells varies with the different colours: 300 nm
to 400 nm for the brown hair, between 300 nm and 500 nm for the blonde hair,
while the cuticle cells of the white hair are approximately 700 nm thick. Chemical
treatment (bleaching) or the preparation of the hair with hair care products
lead to significant differences in the surface topography.
Combining the Mercury
100 AFM with the Digital Pulsed Force Mode provides additional information about
the sample surface such as adhesion, stiffness or viscosity. Line
A shows completely untreated hair. Line B shows hair after shampooing
and line C after being treated with conditioner.
In the topography of the unwashed
hair, the borders of the cuticule seem to be frayed and some particles
are visible. The washed hair shows a smoother result but the hair
treated with conditioner is even more so and the platelets of keratin
are wrapped closely around the hair shaft.
There is a remarkable change in
adhesion. The untreated hair shows different areas with more adhesion
(bright) and less adhesion. These are the regions with the accumulation
of contaminants.
In the washed hair, only the regions
at the borders of the crenelated follicle show more adhesion. The
hair treated with conditioner shows a nearly uniform surface. Differences
in stiffness are only visible on the untreated hair in contaminated
areas.
Only the untreated
hair shows significant differences in viscosity. The brighter areas
which also show particles are more viscous. The washed hair and the
hair with conditioner seem to show nearly the same results with respect
to viscosity.
Source: Mercury 100 AFM Human Hair by WITec
For more information on this source please visit Witec