First kneel in respect...
although I have seen a lot of very powerful DIY videos before, I knelt instantly when I saw this.
an engineer named Ben Krasnow made a scanning electron microscope himself! This is an electron microscope. It's definitely not something you can do with a few glass lenses. It's the hardest DIY project ever.
you know, in the laboratory, scanning electron microscope is also the existence of high-end atmosphere, one is hundreds of thousands or even millions, students have to register if they want to use it. And you said you made one yourself? (and it was made in 2011. )
the following is the author, and his own electron microscope:
the glass cover is the core components, and the other big things are vacuum pumps and power supplies, and because the pumps overheat at work, so he added cooling.
it looks like something.
it took him about 100 hours, and all the weekends during production were devoted to making an electron microscope. As for the cost, it's about $1500, which seems to be very cheap.
so, how on earth is this electron microscope made?
first of all, we will see a bell-shaped glass cover on the picture, which is used to isolate the air. The electron microscope works in a vacuum, so Krasnow uses this cover to cover all the key components and then connects the pump to vacuum the interior.
what's in the hood? First of all, we will see an upright copper tube, above which is his own "electron gun", which is the source of the emission of electrons.
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the key component of the electron gun is a slender tungsten wire, which can emit electrons when it is electrically heated to a high temperature (about 2800K).
these electrons will replace the light beam of the optical microscope for imaging, but they cannot be used directly to illuminate the sample. At present, the electron beam is still relatively scattered, while the scanning electron microscope needs a very concentrated electron beam. So the next part to go through is the "lens" that converges the electron beam. It can be simply understood as similar to an optical lens, but of course the principle is different. In fact, a magnetic lens is used to converge the electron beam.
in this DIY electron microscope, the place where the sample is placed is as follows:
next, it is time to collect the signal of the sample, and the block on the right shown in the following figure is a detector. First of all, it needs to attract the electrons that need to be detected with a high voltage, bombard the scintillator to produce flash, and pass through the light tube, photomultiplier tube, and finally become an amplified electrical signal.
finally, he displayed these signals on the screen of the oscilloscope.
so, what's the end result? This is what it looks like:
and so on:
(this piece is said to be a necklace)
and the electron microscope photos we usually see are like this:
_ (∠) _
well, the author himself admits that this DIY electron microscope, whether in terms of resolution or magnification, is far from being compared with the products on the market. What he shows on the oscilloscope is only some simple images.
but to be honest, he can successfully make it and still use it, which is already very good! After all, the technology of electron microscopy on the market is much more mature.
in his tubing channel Applied Science, he used a total of five videos to introduce the DIY project (you can see how complicated it is. If you are interested, you can come and have a look.
by the way, this person usually uses an electron microscope (this time is a mature product, of course) to shoot some interesting things. For example, the following motion picture of a vinyl record and stylus is his work:
(this is my knee, please take it away! )
schematic Source: http://www.jeol.co.jp/cn/words/semterms/sem_cn-a_z.pdf