Anyone else playing with electron/ion microscopes?

[Nathan McCorkle]

Been attending a workshop and they're just so cool! Wondering if there's anyone out there that does electron microscopy or FIB (focused ion beam) work for milling/sectioning or depositing material. There was a cool demo that used FreeCAD and a slicing script to generate milling or deposition patterns, basically what the 3D printer folks are doing. There was even a guy doing sectioning and imaging of cells which had been treated with nanoparticles, then frozen with cryo to allow sectioning. He was using the omniprobe to weld to the cells with water vapor, to pick them up and transfer them to a TEM grid (I think). The ice would eventually sublimate so the weld slop would go away to be able to get nice images. I could almost imagine the opposite, using this kind of thing to place frozen cells in some particle 3D/rotation arrangement.

Anyway, fun stuff!

--
-Nathan

[John Griessen]

On 10/09/2014 02:26 AM, Nathan McCorkle wrote:
> There was even a guy doing sectioning and imaging of cells which had been treated with nanoparticles, then frozen with cryo to
> allow sectioning.

How did sectioning work?

guess 1. Ablating layers and leaving the rest?
Was the focused beam able to get a smooth level surface, or depended
on time burning and then view and decide where to burn off more?

guess 2. Slicing through all and
using the flat surface left after rotating it 90 deg to view?

[Nathan McCorkle]

On Thu, Oct 9, 2014 at 7:05 AM, John Griessen <jo...@industromatic.com> wrote:

On 10/09/2014 02:26 AM, Nathan McCorkle wrote:

There was even a guy doing sectioning and imaging of cells which had been treated with nanoparticles, then frozen with cryo to
allow sectioning.

How did sectioning work?

guess 1.  Ablating layers and leaving the rest?
Was the focused beam able to get a smooth level surface, or depended
on time burning and then view and decide where to burn off more?

They pretty much raster the beam left and right in a line or thin but wide rectangle, and use it like a belt sander on the face of the substrate-to-be-imaged. Sometimes this creates 'curtains' which appear in 'belt sanded'-face image looking like scratches. This can be from variations in the material properties (i.e. a vein of carbon or some impurity in steel) which can then propagate. A different workshop demonstrated a prototype polishing process where they'd rotate the item being 'belt sanded' maintaining the plane being worked on, so if scratches form in one direction, you just start 'sanding' from a different direction to try and stop the scratches. Here's a quick online drawing:

http://sketchtoy.com/63285604

 

(idk if this site is crappy or not, first time using it after searching online draw share)

guess 2.  Slicing through all and
using the flat surface left after rotating it 90 deg to view?

I think this is what I described, except that in their case they actually have an ion beam and an electron beam separated by 52 degrees, so they don't have to tilt it 90 degrees to view (if you can deal with image transformation resolution loss, I think they don't even need to rotate the item at all, just de-skew it in software later... I could be wrong about this though, but I think I'm right).

They do this since the electron beam is usually less damaging/impactful on the material, and you can do things like give the sample a negative voltage bias to decelerate the incoming electrons just as they get close or touch the sample, which can improve imaging and/or reduce impact on the sample.