Variable pressure and environmental scanning electron microscopy: imaging of biological samples

Area of Science:

• Electron Microscopy
• Biological Imaging
• Materials Science

Background:

• Routine scanning electron microscopy (SEM) requires extensive sample preparation.
• Variable pressure SEM (VPSEM) utilizes elevated gas pressures and specialized detectors.
• Environmental SEM (ESEM) offers sample cooling capabilities.

Purpose of the Study:

• To describe the capabilities of VPSEM for biological sample analysis.
• To highlight the advantages of VPSEM over traditional SEM.
• To detail the imaging parameters and resolutions achievable with VPSEM.

Main Methods:

• Employing elevated gas pressures in the SEM sample chamber.
• Utilizing specialized electron detectors for imaging.
• Combining elevated pressures with sample cooling for hydrated samples.
• Operating with field emission electron sources for high resolution.

Main Results:

• VPSEM allows direct examination of biological samples without preparation.
• Hydrated samples can be maintained in a pristine state under specific VPSEM conditions.
• Dynamic biological processes are observable with VPSEM.
• High-resolution imaging (2-4 nm) is achievable at low beam voltages (1.0 kV) under extreme VPSEM conditions.
• Charge contrast imaging provides unique information related to sample luminescence.

Conclusions:

• VPSEM offers a powerful, non-destructive method for studying biological samples.
• The technique facilitates the observation of dynamic processes and hydrated states.
• VPSEM provides unique charge contrast imaging capabilities comparable to confocal microscopy's luminescence imaging.