Zeiss spinning disc confocal
Hitachi S-570 LaB6 SEM
Hitachi S-900 Field-emission SEM
Colloidal metals & conjugates
Instrument & training fees
Practical Microscopy course
Scanning electron microscopy is typically done in a high vacuum, as gas molecules interfer with the electron beam and with the emitted secondary and backscattered electrons used for imaging. There are particular instances when a low-vacuum or environmental SEM can be used, or is required, but these instruments necessarily trade off resolution to be able to work with gas in the sample chamber.
Specimens for SEM must then be prepared for the high-vacuum imaging environment. The preparation procedures depend upon both the samples being examined and the aim of the study. Biological specimens, such as cells and tissues or tissue components, must first be fixed to preserve their native structure. Some samples, such as hard tissues like bone or teeth, and organisms with a tough exoskeleton, such as some arthropods, can be studied without any preparation, but these are the exception.
Fixation is done either by chemical or physical means. Chemical fixation is the standard with which most people are familiar, and typically uses formalin or glutaraldehyde of varying per cent concentrations in a buffer of a specific pH and osmolarity. Physical fixation may be by heat (such as boiling an egg), but is more commonly done by freezing. Freeze-fixation (=cryofixation) is done in several different ways, but the best ways are by plunging the specimen into slush nitrogen -- liquid nitrogen cooled to its freezing point -- or by high-pressure freezing.
Hydrated samples, like most biological and some materials specimens, must first be dehydrated before placing the specimen in the SEM sample chamber. This is typically done by passing the specimens through a graded series of ethanol-water mixtures to 100% EtOH, and then drying the samples by the critical-point method. Freeze-fixed samples may also be freeze-dried (but not in a lyophilizer).
The details of the different fixation, dehydration, and drying procedures, how big the samples shoud be, and so on, are all dependent on the samples and the questions being asked. Please feel free to make an appointment with BBPIC staff for a no-charge consultation on specimen preparation before beginning your study
The BBPIC has several instruments for preparing samples for SEM. These are service instruments for use by any group that needs them. Sample preparation can be done by BBPIC staff, or investigators may be trained for independent use.
Bal-Tec HPF-010 high-pressure freezer
Slush-nitrogen plunge freezing
Bal-Tec MED-010 cryocoater
Lab-built freeze dryer
Tousimis Samdri 780 and lab-built critical point dryers (CPD)
SeeVac Auto conductavac IV sputter coater
VCR IBS/TM200S ion-beam coater