Specimen Preparation for Scanning Electron Microscopy

• Conductive Specimens (such as metallic objects):
  Usually, these specimens do not have to be sputter coated. Simply mount the specimen on a SEM stub using conductive paint or putty.

• Non-conductive Dry Specimens (ex: ceramics, polymers):
  Mount on specimen stub with glue spots, double-stick tape, conductive paint or putty. These will need to be sputter coated.

• Tough Non-conductive Wet Specimens (ex: arthropods and mollusks but not plant cuticles ):
  These should be dehydrated before mounting. It may be possible to simply air-dry the specimen. Normally, these specimens are dehydrated by immersion in increasing concentrations of ethanol up to 100% ethanol. The specimen may be air dried from a transitional solvent that has a lower surface tension than ethanol. Common transitional solvents include acetone and HMDS. Dried specimens are very fragile and must be handled with care.

  Mount dried specimens on SEM specimen stub as with Non-conductive Dry Specimens above. These specimens will need to be sputter coated.

• Soft Non-conductive Wet Specimens (ex: protists, algae, tissue culture cells, plant cuticles, internal cell structures):
  
  1. Fix specimens in buffered glutaraldehyde or formaldehyde using procedures appropriate for transmission electron microscopy. Rinse as appropriate.
  2. Dehydrate through the ethanol series up to 100% ethanol and critically point dry from ethanol. See lab director for instructions for using the critical point dryer.
  3. Handle fragile dried specimens with care.
  4. Mount on stub as with Non-conductive Dry Specimens above. Specimens must be sputter coated.