Dr. Syed Arshad Hussain Wellcomes You


Can we see the atom or something of nano dimension?

            Twenty five years ago, this question was often met with amazement by common people and with scepticism by the teaching community. The answer may be ‘atom is something which is not really visible’. But nowadays, it’s a common phenomenon to visualize the atom, even seeing them moving. Its not really a challenge to see the atom but to know and visualize how they are arranged within matter. This is because it’s the arrangement of that determines the properties of materials- their hardness, ductility, brittleness, strength and the catalytic properties.

             With our eyes we can see a fraction of a millimeter, let’s say one tenth of a millimeter or one hundred micrometers which is a little more than the diameter of a single hair. If we want to see at smaller scales than this, we use a lens. The lens bends the light rays or refracts and the object appears larger. Optical microscopes work on this principle. Lenses work well as long as we do not have to work at scales smaller than the wavelength of light which is about half a micrometer. This is because the smallest object that can be seen with waves of wavelength  is about  in dimension (the Rayleigh criterion). At this scale, we have to take into account the wave nature of light, so things are different. Optical microscopes help us to image about hundred times smaller than what we can see with our naked eyes. If we want to track a molecule or a particle that is still smaller, we can improve the resolution by labeling it with a fluorescent molecule. The fluorescence can be detected and we can follow the movement of the molecule or particles in liquids for example. If we need higher resolution, we can use electrons instead. Modern electron microscopes can let us see the arrangement of atom within the matter.  Thinking of electrons one might be puzzled as to how electrons, which are particles, can be used to image things at very small scales. At small scales things are different, drastically different. It’s the realm of quantum physics. Quantum particles propagate like waves and interact like particles. When the sample is thin enough and the electron comes in at high speed it can go through the sample. The path of the electron can be influenced by magnetic and electric fields and this effect is used in producing lenses for electrons. The advantage of electrons is that their wavelength is several orders of magnitude smaller than optical wavelengths and the microscope resolution is not limited by the wavelength but by the performance of the lenses. The wavelength of an electron is related to its velocity by  (de Broglie’s equation non-relativistic),  is the Planck’s constant,  and  are the mass and the velocity of the electron respectively. Now if  is greater than 80% of the speed of light, then  is less than  of the atomic dimension. With electron microscopes we can increase the resolution by more than a factor of thousand when compared to optical microscopes. We can see one tenth of a nanometer with a high resolution electron microscope, the length scale of the atom world. We can see planes of atoms. Electrons are also reflected off and in fact there is a type of electron microscope that works in reflection mode (SEM). SEM’s have about ten fold smaller resolution than TEMs. The drawback of electron microscopes is that electrons are charged and we need vacuum environment in order for the electrons to propagate freely. There are SEMs available today that do not need high vacuum and can function in a partial nitrogen or argon atmosphere with reduced resolution. This makes it particularly interesting to observe growth processes at the nanometer scale. Non conducting samples are more difficult to observe with electrons and often need to be coated with a conducting metal layer. The electron microscope also needs a high voltage generator (10kV to several 100kV) to accelerate the electrons. All together electron microscopes are rather large instruments.

For example, in silicon nitride ceramics the arrangement of lanthanum ( ) atoms (arrowed in figure 1) at the interface between a glassy film (top) and a silicon nitride crystal (bottom) is shown. The  atoms play a role in controlling the path of cracks as they pass through the silicon nitride ceramic.

     

Figure 1: The interface between a silicon nitride crystal (bottom) and a glass (top) in a silicon nitride ceramic. The bright atoms at the interface are La, used to engineer the strength of the interface.

            However it is the Atomic Force Microscope (AFM) (Nobel prize in 1986 for Binning and Rohrer for the fundamental Scanning Tunnelling Microscope) made revolutionary advancement towards the visualization of nanometer order and atomic dimension. The AFM works in the same way as our fingers which touch and probe the environment when we cannot see it. By using a finger to “visualize” an object, our brain is able to deduce its topography while touching it. The resolution we can get by this method is determined by the radius of the fingertip. To achieve atomic scale resolution, a sharp tip (radius ~1-2 nm) attached to a cantilever is used in the AFM to scan an object point by point and contouring it while a constant small force is applied to the tip. With the AFM the role of the brain is taken over by a computer, while scanning the tip is accomplished by a piezoelectric tube.

 Figure 2: The principle of Atomic Force Microscopy

 

The atomic force microscope got its name from the interactions between probe and sample on the atomic level The attractive Van-der-Waals-forces and repellent equal electric charges are described by the Lennard- Jones- potential. The AFM is based on a relatively simple mechanical principle: if you drag a very fine and flexible pointed needle (called a cantilever) over uneven surface, then the forces acting on the cantilever will be directly related to the displacements (deflections) of the cantilever. These deflections can be measured by shining an ultra sensitive laser on the tip of the cantilever and looking for changes in the reflected beam as the cantilever changes its position slightly. Under ideal conditions, this technique allows lateral resolution on the atomic level. The vertical resolution is below 0,1 nm.

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17 Comments so far
Leave a comment

i think that it is possible to see the atom. they dance and bounce and swirl a lot and it is amazing to watch. people tell me i’m crazy and that it is impossoble to actually see atoms moving with the naked eye. i can only see them in the air and then it’s mostly only on the blue sky background.

Comment by s.donovan

Hi – I can see atom like round circles with dots in each of them, connected together, all around us. Inside and outside. They appear to be transparent, my hand goes through them, heat (from the tip of a lit cigar) cannot push them away. You cant blow them away as well. It almost seems to me that we can see these “things” but they exist in a different dimension?? What is this that we are seeing??

Comment by Sudeep

hi sudeep i m parkash from punjab i wan tto share with u my experience.
i can also see some round small objects in air . when i told my friends then they said that i m joking. i can see them even when i close my eyes. tell me what is it?

Comment by parkash

hi every one if you and any person can see atom pleas contact me on my id shahfahadali@yahoo.co.in

Comment by Fahad Ali

those are floaters you are seeing, not atoms

Comment by Hunter

gyghfiuygdyedfhexiuisd g

Comment by dtuygxr

you’re seeing dead bacteria on your eye

Comment by some guy

um, they’re call floaters. everybody has them, and no, they’re not atoms. they are shriveled up blood cells that you get when you’re born.

Comment by wow people

NOT FLOATERS!!! I’ve seen atoms with naked eye since I was in kindergarten. I’m now 41 years old and I have had plenty of floaters. To the other people who see atoms when know the difference. Completely different. I kept trying to tell eye doctor and parents when I was little and finally let it go. We are special =o)

Comment by christine

im not sure what i see. when i look at the surface of just about anything i see billions of small lights of differant intensties flashing on and off and the less light in the room or outside the easier it becomes to see them

Comment by rabbit snatckh

I cannot believe I’m admitting this to strangers. But .. it’s all the same here. I have seen these dots since I was a kid and am looking for what this might be. I can only explain it as “seeing atoms.” Multi colored tiniest pixels across my vision always – it has added visual noise to everything. The pixels don’t move. They’re not floaters; I have those too. Also, I have always had strange wild flashing going on when I look at the small patterned tiles (vividly remember this on light/dark blue pattern bathroom tile patterns as a kid). Further, I have “matrix vision” ghost like images that chase real motion. I understand just as of tonight, a phenomenon called Purkinje images, different reflections on the cornea. I’m trying to categorize these wacko visual distractions. Anyway, great topic. I’m not sure if the author was looking for this kind of participation. But, the discussion has certainly helped me! It is great to hear others have the same experience — more power to us for having a super secret gift.

Comment by Col

Since a very young age I believed I could see atoms, but I was constantly teased about it and so I shunned that belief. I still can see what look like atoms, and I also can exaggerate the intensity of these “atoms” view by fiddling around with the focus of my eyes(My Dad thinks this is impossible). I also have extremely good eye sight and also occasionally suffer from random cuts of light flashing across my eyes, when closed and open.These cuts of light go away if I stop thinking about them but when I concentrate on them it intensifies to a point where I think I am blind but really can see perfectly fine just also another view appears in my brain. I know that these are entirely different to the “atoms” and have found through research that this tends to happen only to people with particularly good eye sight. I sure hope that these things are gifts and somewhat useful and that it is not some kind of dis-function.

Comment by crazydogkennel

I can see something that looks like atoms. If I look at a blank wall or a dull gray sky with both eyes are open, but one eye is covered, after a moment I can “see” star shapes that are moving incredibly fast. They appear to be spinning and they are touching and communicating with all the others around them. These shapes are like what you would see if you would take a your finger and draw something continuously on the surface of water; they are there only as long as you keep moving your finger moving. This is not the same thing as when you “see” stars, they are not shiny. By the way, I have no vision problems. It has taken me quite a while and practice to be able to do this, but worth the effort. Our eyes and brains are likely more sensitive than we imagined. Sharon

Comment by sharon csernak

I have been seeing this phenomena for a long time- since I was a child. I am now 29 years old. I do not know whether everyone can see them or just some of us. Maybey we are just more open minded..there are other unexplained things as well which i will not mention just yet- this is not eye floaters, and not dead bacteria as many will say. I dont know if it is atoms or some other form of energy collision- but it is real. I too have been called crazy or dismissed, so I dont discuss it with most people…I just want to find others out there like me so I dont feel alone.

Comment by Stephanie

Me too – I’ve noticed this since I was very small. I have no idea whether they are atoms or not – probably not, since it’s not as if I have perfect human vision let alone perfect unlimited vision :S Anyway, I think maybe it’s to do with the amount our brains can process sort of, like pixels, rather than actual individual atoms in reality, if that is even how they exist in reality. I think most people or everyone should be able to see them but just haven’t really thought about seeing them or looked in that way/focused in like that. For me, I can’t really tell if they’re moving – it’s like i can’t ditinguish one from another, but i know it’s lots of separate things, because otherwise they wouldn’t look like what i would imagine atoms to look like. They could be moving really fast or they could be stationary I have no idea. And they’re like completely transparent but then they can’t be otherwise they would just look like one continous thing.

Comment by Mia

I too can see atoms with my bare eyes, ever since I was eight or nine I found that I could do this trick where I focus at different magnifications and zoom levels. It sounds weird, but consider that eagles can do this so why can’t humans evolve a sort of super-vision? No one ever believes me when I tell them but it’s kinda hard to prove it on the spot. I always thought I was the only one with this ability but it seems there are others as well. That’s pretty cool and I’m glad to learn that, I don’t feel so odd now.

Comment by I thought I was crazy

I have always been able to see the weird pixel-looking things in the air. It looks like everything is made of them. At night I can see it the best. Sometimes they move in different streams of colors like red and gold. I use to watch them as a was falling asleep as a child. Has anyone had that experience before? Seeing the colorful pixels moving around the dark?

Comment by Sonya




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