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Yes, look at all that squashed DNA, lol. Seriously though, how do we know that is DNA? It just looks like wiggly worms. And the DNA pic is black and white, but the picture of graphite is in colour. How is it in colour? Is it 'enhanced' with photoshop or something?
More here: https://www.sciencelearn.org.nz/resources/2036-dna-extractio...
This project is great. Last semester at university lab, our group tried to rebuild it in our lab. Through our spectacular fail, we learned how amazing this project actually is. It is harder than it seems. One can learn very much about piezo electronics, especially about OPamp circuits. And do not underrate the damping!
And the amplification circuitry, that's not trivial. I was actually surprised he got away with having the wiring out in the open without shielding it for EMI.
Yes, look at all that squashed DNA, lol. Seriously though, how do we know that is DNA? It just looks like wiggly worms. And the DNA pic is black and white, but the picture of graphite is in colour. How is it in colour? Is it 'enhanced' with photoshop or something?
False colour is pretty much standard for many imaging techniques including STM.
Earlier quoted context omitted.
And the amplification circuitry, that's not trivial. I was actually surprised he got away with having the wiring out in the open without shielding it for EMI.
In the section for "Electronics" is this line "I place a metal can over the STM during scanning to shield the tip and preamp. Without the shield, the images produced by the STM are dominated by 60 Hz noise pickup."
Earlier quoted context omitted.
False colour is pretty much standard for many imaging techniques including STM.
Its not even really false color, its just a look up table applied to the data, which is some equi-tunneling current or height map, don't know exactly how this is done, bit out of my field.
Yes, look at all that squashed DNA, lol. Seriously though, how do we know that is DNA? It just looks like wiggly worms. And the DNA pic is black and white, but the picture of graphite is in colour. How is it in colour? Is it 'enhanced' with photoshop or something?
So how then are the images generated?
It uses a technique called Fluorescence Microscopy: https://en.wikipedia.org/wiki/Fluorescence_microscope
You essentially stick some special molecules on the DNA that absorb light in one frequency and then they emit light in another frequency. So you blast the molecules with light of one frequency and then use a dichroic mirror to filter that light out and you only see the emissions and thus you see where the DNA is, but you don't "see" the DNA itself.
Like STM itself what we mean when we "see" something at those length scales is interesting. Scanning Tunnelling Microscopy is like a blind man reading braille - not really "seeing" anything but getting enough info to describe the picture.
source: I used to work in the same lab as Dan. Hi Dan!
I think I'm going to build this with my kids. What better way to show them atoms than to actually make them build a microscope that shows you the things directly?
I'm sure its a cool project. But its not showing things directly, is it? Its interpreting a frequency and converting that to an image. Is it really that different to a music visualiser?
I think I'm going to build this with my kids. What better way to show them atoms than to actually make them build a microscope that shows you the things directly?
I'm sure its a cool project. But its not showing things directly, is it? Its interpreting a frequency and converting that to an image. Is it really that different to a music visualiser?
I don't understand the downvotes. That's an honest fundamental question.
It's not "showing things directly" because it can't. The limit of what you can see with light is proportional to the wavelength of the light (this is called the diffraction limit). For visible light and lens-based optics that's around 1/2 micron.
The distance between the atoms in that graphite is ~3 angstroms, that about 2000 times smaller than the diffraction limit for visible light.
You CAN get atomic resolution with a transmission electron microscope. Instead of light it uses electrons and has a far finer diffraction limit that visible light. Instead of lenses it uses electrostatic deflection.
Earlier quoted context omitted.
I'm sure its a cool project. But its not showing things directly, is it? Its interpreting a frequency and converting that to an image. Is it really that different to a music visualiser?
> But its not showing things directly, is it? I don't understand the downvotes. That's an honest fundamental question. It's not "showing things directly" because it can't. The limit of what you can see with light is proportional to the wavelength of the light (this is called the diffraction limit). For visible light and lens-based optics that's around 1/2 micron. The distance between the atoms in that graphite is ~3…
Because the comment is factually wrong. Because it tries to argue something in bad faith.
> That's an honest fundamental question.
But it wasn't a question, it was a statement, and a faulty one at that.
Best case interpretation would require substituting 'current' for 'frequency' and even then it would be inaccurate because the current is a proxy for the Z-distance to the tip which is then used to convert to a 3D map, which in turn can be visualized.
It is fairly obvious that this is an indirect process so clear the word 'directly' wasn't about 'seeing atoms' but all about the fact that you can make the observations yourself.
Whether you are measuring a current or looking through an eyepiece both are observations. And looking at the resulting image is also an observation.
As opposed to reading about STMs and looking at pretty pictures online or in books.
It's a shallow comment masquerading as an insightful one, the worst way to derail any conversation.
We cut a piece of ordinary steel wire diagonally with an ordinary wire cutter. Somehow we did it right - the first one worked. It was all somewhat fiddly and sometimes the image was noisy. But we did get images of atoms.