Frequently asked questions
Why would I use the katana microtome?
If you currently do serial section TEM (ssTEM) but find that it is too time/labour intensive
If you currently use FIB but need to image larger volumes in a short time
Any biological question where you need to see the ultrastructure of a specimen
What samples can I study?
The most common application is for biological samples, which are generally stained and embedded in resin
Anything that can be cut with a diamond and show contrast in an SEM
How thin can katana microtome cut?
Short answer: Around 15nm under certain optimised conditions. For a more typical scenario with a well stained resin-embedded biological sample, you can expect to hit a lower limit of approx. 25nm. Some other materials (e.g. aluminium) can cut cleanly down to 10nm
Detailed answer: There is a complex trade-off between electron dose on the sample (and hence image quality) and cutting performance. To illustrate with some of extreme examples:
If you use very low electron dose (<1e/nm2) then you can cut cleanly at 10nm. However, this approach has diminishing returns since the resolution will then be limited by image noise
If you are taking multiple images per cut, or a very high signal-to-noise ratio (SNR) image, or using very small pixel size, then you may need to cut thicker (e.g. 100 nm) to maintain clean and uniform cutting
If you use a more sensitive BSE detector, you can get the same SNR from lower electron dose, so you can cut thinner
The SBFSEM technique usually has a sweet-spot where it is easy to operate and get good results: Accelerating voltage 2kV, 15e/nm2 (dose at sample), Modern BSE detector giving SNR >4:1 at above conditions, Pixel size 10x10x30nm
What are the optimum working conditions for katana?
This will depend on the SEM, detector, type of sample, and how you wish to balance trade-offs (e.g. do you prefer high SNR over thin cutting)
What happens if I use the incorrect operating conditions?
This won’t result in damage, but your data will be sub-optimal. Pushing the dose too high, or cutting too thin will result in failure to cut cleanly. The knife will chatter over the surface, or will take alternating thick/thin cuts. The end effect of this is a reduction in Z resolution.
Using too high an accelerating voltage will result in signal originating below the next cut. Again, this limits your actual Z resolution.