splitting hairs (and fibers): 4 methods of cross-sectioning
TRANSCRIPT
Splitting hairs (and fibers): 4 Methods of Cross-sectioning
Sandra Koch, Ph.D.Senior Research Microscopist
Cross-sections
• A cross-section is made by cutting a material at 90° to its main axis to study the morphology of the material you are analyzing
• Take care not to alter shape by the method you choose
What can a cross-section reveal?
How to determine the cross-section of hairs and fibers:
• Hot plate and polyethylene
• Cross-section plates
• Ultramicrotome
• Optical sectioning
Methods:1
How to determine the cross-section of hairs and fibers:
• Hot plate and polyethylene
• Cross-section plates
• Ultramicrotome
• Optical sectioning
Methods:1
2
How to determine the cross-section of hairs and fibers:
• Hot plate and polyethylene
• Cross-section plates
• Ultramicrotome
• Optical sectioning
Methods:1
2
3
How to determine the cross-section of hairs and fibers:
• Hot plate and polyethylene
• Cross-section plates
• Ultramicrotome
• Optical sectioning
Methods:1
2
3
4
Cross-Sectioning Method #1
Supplies:
• Disposable pipette (or sheets of
polyethylene film)
• Hot plate
• Two glass microscope slides
• Single-edge razor blade
• Double sided tape
Cross-Sectioning Method #1Method:• Cut a section of a disposable
polyethylene pipette• Thread hair/fiber inside pipette tube
Place between slides on hot plate till pipette melts – turns translucent
• Remove and slice sections with razor blade
• Double-sided tape helps to orient sections for viewing
• Can also use polyethylene sheets
Cross-Sectioning Method #1
• Polyethylene sheets
Cross-Sectioning Method #1
• Remove and slice sections with razor blade
Cross-Sectioning Method #1Double-sided tape can be useful to help orient sections for viewingBenefits:• Quick and easy method• Supplies typically on hand• Can observe internal microstructure
Limitations:• Material may not be oriented at 90° to fiber
length• Dull razor blade may alter hair/fiber
morphology
Moose hair cross-section
Cross-Sectioning Method #2Supplies:• Cross section plates• Thread• Packing material (suggest
different color than hair/fibers)• Razor bladeMethod:• wrap fiber packing around
material of interest• Pull bundle through hole with
loop of thread
Cross-Section Plate Demo
Cross-Sectioning Method #2Cross sectioning plates:• wrap fiber packing around
material of interest• Pull bundle through hole with
loop of thread• Cut flat along back surface with
razor blade• Coat with clear nail polish to
hold in place• Flip and cut top surface with
razor blade• Use as slide and place on
microscope stage to examine
Cross-section samples (fibers)
Cross-section examples (hairs)
Cross-Sectioning Method #2Benefits to cross-section plate:• Material prepared for direct analysis using
a microscope• Once coated with clear nail polish sections
are preservedLimitations:• If too much packing material is used
around hairs/fibers may not be able to pull through plate
• If too little packing material is used, sections may not stay in place
• Be careful of altering morphology
Cross-sectioning Method #3
Supplies:• Ultramicrotome• Glass or diamond boat to cut
sections• Resin and resin mold to hold
samples• Oven to cure resin
Cross-sectioning Method #3Ultramicrotome• Sample oriented in holder perpendicular to
cutting blade • Sections float off blade onto water
Cross-sectioning Method #3Ultramicrotome• If sections wrinkle, chloroform can
be used to help flatten sections• Staining can help reveal structure
Cross-sectioning method #3
Benefits:• Lower potential for distortion of
sample by cutting blade so measurements more precise
Limitations:• Must orient samples prior to
embedding and sectioning• Resource and equipment dependent
– Resin cures in oven– Glass or diamond boats to section
Cross-sectioning Method #4
Optical sectioning• Train your eye to recognize
different shapes by focusing up and down on a longitudinally prepared sample that you have images of the known cross-sectional shape
Cross-sectioning Method #4
• Microscopy training should involve examining known samples in longitudinal view and cross-section to be able to recognize features
Physical Cross-sectioning
• Direct observation of sample morphology
• Embedding methods differ in how samples are packed, oriented, and their potential for distortion
• Choice of sectioning method is dependent on equipment, time, sample size, and data needs
Thank You
Fiber Cross Sectioning Sheet-Pack of 50SKU: 315-PK50https://www.mccrone.com/product/fiber-cross-sectioning-sheet-pack-of-50/
Sandra Koch, Ph.D.Senior Research Microscopist
[email protected] • (630) 887-7100
Thank you for joining us.