Cold-stage microscopy system for fast-frozen liquids.

Area of Science:

• Materials Science
• Electron Microscopy
• Colloid Science

Background:

• Examining microstructured liquids like colloidal suspensions and microemulsions in electron microscopes requires minimizing artifacts.
• Traditional fixation methods can introduce structural alterations, hindering accurate observation.

Purpose of the Study:

• To present thermal fixation (ultrafast freezing) as a superior technique for electron microscopy of microstructured liquids.
• To detail a novel method for preparing thin liquid samples for cryo-electron microscopy.

Main Methods:

• Trapping a thin layer (approx. 100 nm) of liquid between two thin polyimide films (approx. 40 nm) mounted on copper grids.
• Rapidly freezing the liquid sandwich by immersing it in liquid nitrogen at its melting point.
• Utilizing a new transfer module for a JEOL JEM-100CX microscope to maintain a cold stage and prevent frost formation during sample transfer.

Main Results:

• Demonstrated that thermal fixation significantly reduces artifacts compared to other methods.
• Showcased the effectiveness of polyimide films for water-containing samples, highlighting their resistance to electron beam damage.
• Presented successful sample observations using the developed fast-freeze, cold-stage microscopy system.

Conclusions:

• Ultrafast freezing is the least artifact-laden fixation technique for microstructured liquids in electron microscopy.
• The described sample preparation and transfer method enables high-quality cryo-electron microscopy of sensitive liquid systems.
• This approach is crucial for accurate structural analysis of colloidal suspensions, microemulsions, and similar materials.