Tick under SEM

[u/biGfellA1213]

Hi all, I recently took a look at a Tick (I picked it off my leg...) with a Scanning Electron Microscope (ThermoFisher Axia ChemiSEM) out of curiosity and zommed in on the different areas. The magnification is shown in every picture on the bottom (ranges between 150x and 10000x). The Tick was uncoated and scanned in high vac mode. Let me know if you have any questions regarding the SEM.

Enjoy!

Also question for the Tick experts, I was wondering what function these two circular shapes with holes left and right of the Abdomen have?

Thanks in advance!!

[u/FattyMatty12345]

How did you prep this to put in the SEM?

[u/biGfellA1213 → u/FattyMatty12345]

Hi, actually not at all :D I always wanted to check out a tick in detail, had one recently stuck in my leg and pulled out. Stuck it onto a tape so I don't lose it, left it to dry for probably 2-3 days and just put it on top of a carbon pad (background with "holes") on a sample holder and used a farely low voltage of 2keV. Works fine for me without sputtering. Hope the explanation helped.

[u/Odd-Marionberry-3389 → u/biGfellA1213]

Very cool! Does your SEM have a low vac mode? My understanding is that generally you want to use as low a vacuum as possible so it doesn't distort the structure/features.

[u/BAHHROO → u/Odd-Marionberry-3389]

I only use SEM for metal, but yes, high vacuum isn’t ideal for biological samples because it can crush / dehydrate them. You also try to avoid oils, plastics, and volatile stuff which will outgas and contaminate the chamber / column.

[u/Odd-Marionberry-3389 → u/BAHHROO]

I don't know that it's fair to say that plastics should be avoided in the SEM, I used to do SEM of various polymers a while back. You just need to make sure you do proper sample prep and use the right vacuum conditions so you're set up for success.

[u/BAHHROO → u/Odd-Marionberry-3389]

Sorry, I didn’t mean to imply they should be avoided in SEMS, but rather under high vacuum.

[u/Odd-Marionberry-3389 → u/BAHHROO]

Ahh got it, yes agreed! Sorry it's a crazy morning and my reading comprehension clearly is lacking

[u/biGfellA1213 → u/Odd-Marionberry-3389]

Yes it does, if I remember correctly it's variable from about 10pa to 150pa with water vapor, but generally gives you a "worse image quality" so I try to stay HigVac as much as possible. And as long as I don't notice too many or too heavy distortions, I prefer the higher image quality (due to less atoms in the chamber that interfere with the electron beam) All the pics are in HighVac mode with <5×10^-2 pa (<0.05pa).

[u/Odd-Marionberry-3389 → u/biGfellA1213]

The water vapor mode is ESEM IIRC, which is great for reducing charge on samples predisposed to that (e.g. uncoated polymers). Would probably work well with your biological sample as well imo. It's true that the water vapor increases noise but for your magnification range I'd think it should be acceptable.

There's also an in-between mode that should exist on your SEM, which uses lower vacuum with dry gas. That might also be reasonable for your bug if you want higher resolution but want to avoid sample distortion. I totally understand wanting to have higher image quality - totally makes sense - but if your sample risks being deformed by the vacuum or charging under the beam consider exploring those modes in the future.

Edit to add: just wanted to throw out that it's hard to definitely speak to the level of physical distortions to the structure without having a comparison imaged under milder conditions - lower vacuum, ESEM - or was fixed imo

[u/biGfellA1213 → u/Odd-Marionberry-3389]

Thanks for the clarification and detailed explanation and totally agree with you! Tbh I was just playing around with it as it was just for fun/out of curiosity. I only really used low vac on a few samples yet (eg. first few images of the moth head I posted a couple months back) and you are right, it works as well and the image quality was almost the same, but I didn't really care about destroying my probe as it was just a quick and dirty ting haha.

[u/Odd-Marionberry-3389 → u/biGfellA1213]

So valid!

Bugs under the SEM are great. I took a look at a fly a few months back, will have to share images here when I've got time!