Side1

SamplepreparationforScanningelectronmicroscopy(SEM)SEMisprimarilyusefulforgivingathreedimensionalimageofthesurfaceofthespecimenandisforviewinglargeobjects.AswithTEM,specimensareimagedwithabeamofelectrons,butinsteadoftheelectronsbeingtransmittedthroughthespecimen,thebeamis"scanned"across,creatinganimageofthesurfaceofthesample,withexceptionaldepthoffield.Thisimageisachievedviathedetectionof"secondary"electronsthatarereleasedfromthespecimenasaresultofitbeingscannedbyveryhighenergy"primary"electrons(ie.thoseemittedfromtheelectron"gun"intheSEM).Asmostbiologicalspecimensaremadeupofnondensematerialtheamountofsecondaryelectronsproducedistoolowtobeofmuchuseincreatinganimageandthereforetheyareusuallycoatedwithaveryfinelayerofametalwhichreadilyproducessecondaryelectrons.Thelargedepthoffieldachievablecanproduceanimageofgreatvisualdepthwithathreedimensionalappearance.Theoperatingenvironmentofastandardscanningelectronmicroscopedictatesthatspecialistpreparationtechniquesareused.Typically,abiologicalspecimenischemicallyfixed,dehydratedthroughanacetoneorethanolseriesandthendriedatthecriticalpointamethodusedtominimizespecimendistortionduetodryingtensions.Fordrysamples,thisprocessisnotnecessary.SEMcanalsobeusedtoinvestigatesmoothsurfacesofindustrialsamples.Thesamplesaremountedonastubofmetalwithadhesive,coatedwith4060nmofmetalsuchasGold/Palladiumandthenobservedinthemicroscope.Everysampleisdifferent.PleaseconsultwiththeEMStaffbeforestartingaproject.

Epidermoidcarcinomacells.Bar:2m

Epidermoidcarcinomacells.Bar:2m

StaphylococcusAureus.Bar:2m

Side2

Smallintestine,villi.Bar:200m.

Smallintestine,microvillionthesurfaceofavillus.

Plastinatedglomerulusfromrat.Tissueisremoved.Bar:50m.

FlyBar:200m.

SpiderBar:300m.

Haironthesurface.Bar:10m.

SEMservicesinclude: Fixationanddehydration Criticalpointdrying Dryingwithhexamethyldisilazane(HMDS)andtButanol CoatingwithGold/PalladiumusingSputtercoater Imageprocessing(softwareScandium)