Anisotropic Fibers Under the Microscope

Anisotropic Fibers

This is part of a guide to the identification of particles seen in samples of free particles. This file includes all anisotropic particles that have approximately parallel sides and are at least five times as long as they are wide.

Smooth Fibers with no Internal or External Features

These particles are generally extruded polymers without rutile inclusions or Insect and Spider silks.

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Smooth Fibers with no External Features but with small (micrometer or less) filler (rutile).

These particles are generally extruded polymers with rutile particles added to enhance the color of the fiber.

Fibers with External Barbs or Scales

These fibers include mammalian hair, insect hair, feather barbules, and plant hair.

Mammals

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Insect Hair

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Feather Barbules

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Fibers with Internal Cells or internal Voids

These particles tend to be plant fibers, plant hairs, animal hairs, insect hairs, or fungal structures.

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Aspergillus Conidiophore

Fibers with Striations Parallel to Length

These particles tend to be mineral fibers, insect silks, or man-made plastic fibers though some plant fibers may also fall into this category.

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Aspergillus Conidiophore

Fibers with Striations at an Angle to Length

These structures may also be called nodes and occur in many plant fibers but may also occur in some man-made plastic fibers.

Fibers with Tapered Terminations

These fibers may grow tapered ends, like hairs of plants and animals, or may plastically deform and taper prior to final break. Paper fibers also tend to have tapered ends.

Fibers with Broomed Ends

These fibers tend to be fibers that consist of bundles of parallel finer fibers referred to as fibrils. They include some plant fibers, mammalian hair, some natural mineral fibers, and some soft polymers that form zones of stress-aligned fibrils when under load (i.e. polypropylene).

Fibers that Keep Dividing into Finer Fibers Parallel to Length

These fibers tend to be mineral fibers, including those identified as asbestos.

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