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Gas Injection Flow Splitter for Focal Charge Compensation with Serial Block-face Scanning Electron Microscopy (SBEM)

Objectives

Scanning electron microscopes create images by scanning an electron beam across a sample. Samples encased in nonconductive resin build up charge, which creates black spots on the image. This can be mitigated by using a nozzle to spray nitrogen gas over the sample. The gas ionizes, which neutralizes the charge. There currently exists a prototype gas injection mechanism, designed by our sponsors at the National Center for Microscopy and Imaging Research (NCMIR) which has been shown to work. Our goal is to design a better and more robust mechanism that works for any sample size.

Figure above can show the improvement of charge reduction by injecting nitrogen gas

Prototype CAD

The two-layer flow splitter design:

The new design combines the carbon fiber needle and angled mount into one manifold that splits the gas into two exit holes, surround the specimen surface more completely.

Installed Manifold on SEM

NCMIR's existing design:

The old prototype uses a single carbon fiber nozzle on a custom angled mounting solution. Not pictured is the silicone tube that attaches the carbon fiber nozzle to the gas tank.

Results

*click on pictures to see in detail

Effects of charging with no gas (left) vs. charge reduction with gas injection manifold (right) at 80x zoom

Effects of charging with no gas (left) vs. charge reduction with gas injection manifold (right) at 400x zoom