The sample preparation laboratory carries out preparation of biological and synthetic samples to make them suitable for electron microscopes. The laboratory hosts all facilities necessary for adapting them to the dimensions of microscopes and for analyzing them by scanning (SEM) and transmission electron microscopy (TEM): cutting, ultrathin sectioning, polishing, ion milling, embedding, staining, coating, fixation/dehydration, vitrification, etc. For specimen carbon decontamination a Fischione Plasma cleaner is available.
Flat and smooth surfaces are required for good quality images and chemical contrast in SEM. LMA has tuned up the automated grinder-polisher Buehler Phoenix Beta, specially designed to polish multiple samples embedded in resin. Conductive coating of samples are achieved by the vacuum coater Leica EM ACE200. A planetary drive stage is available for coating samples with irregular surfaces.
Mechanical thinning of cross-sections and planar views in a highly controlled way, with a diamond wire saw and a tripod polisher, in combination with low-angle and low-energy ion milling, produces a flat specimen of a few microns in thickness, with defect-free surfaces ready for TEM observation.
Ultramicrotomy is another technique to produce 50-70 nm thick slices of soft (biological, inorganic and composites) materials. Depending on the specific features of materials, samples can be sectioned between -180 °C (cryo-ultramicrotomy) and room temperature. In the case of biological samples, a previous treatment is necessary in which samples are fixed, dehydrated and embedded in epoxy resin before cutting.
Vitrification of samples and their analysis in cryogenic conditions are other outstanding techniques available in LMA. The vacuum coater LEICA EM ACE200 is equipped with a glow discharge option to make grids temporarily hydrophilic and allow aqueous solutions to spread easily.