For looking at really small stuff, an optical microscope will only go so far. Looking at things at the nanometer level, though, usually requires some sort of electron microscope, with all the hassle of vacuum chambers and high voltages. There is another way to investigate the domain of the very small: an atomic force microscope. Unlike their electron spewing brothers, they don’t require high voltages or hard vacuums. They can also be built for about $1000, as [whoand] over on the Instructables shows us.
Instead of shooting light or electrons at an object and picking up the reflections, an atomic force microscope drags a very, very tiny stylus across an object. This stylus is attached to a probe that will reflect laser light off of it into a photosensor, eventually rendering an image on a display. [whoand] is using a laser diode and pickup unit from a DVD-ROM drive for the optical pickup unit, a frame made from soldered together PCBs, and a few piezos to vibrate the probe.
The probes themselves are incredible pieces of engineering with a tip size of a few nanometers. They’re consumable, and expensive, ranging from $20 to $500 per probe. Still, with these probes, [whoand] can look at the pits in a CD or DVD, measure the surface of an eraser, or check out the particulate matter floating around in the atmosphere in Beijing.
Thanks [Rob] for the tip.
18 thoughts on “A DIY Atomic Force Microscope”
maybe built for even less
1. the cd player deck you can get from any junk cd player (unless you need new laser) even then the players are very cheap usually double digits.
2. unless you need specific value for piezo disks you can take them from today’s telephones most of today’s cheap land line phone sets use piezo elements for the ringers.
3. tv cable connectors can be salvaged from any tv, vcr, tv dvd recorder, cable box.
4. the frame plates look like circuit board stock (etching services may charge more to etch and cut the frame pieces since they are not standard order).
seeing that a sample is a piece of blu ray media it looks possible to just take the lens out of the laser assembly of a blu ray drive and attach it to an optical microscope in such a way to boost the zoom.
Using a zoom lens is fundamentally impossible here. The microscope used a POINTED TIP to measure surface features, and the resolution is dependant on the sharpness of the point. The optical bit is only used to measure the movement of the tip/arm as it is moved over the surface.
On an unrelated note, I’ve seen universities take quartz crystal oscillators, take the can off, and mount a very fine tip (to measure the intermolecular forces in materials) on the end of the crystal wafer. As the atomically sharp tip is run over the sample, forces between the sample and the tip will affect the frequency the crystal vibrates at, which can be measured using sensitive frequency equipment. This might provide a picture which is more sensitive and detailed, assuming you can find a tip sharp enough to make it worthwhile.
Or try http://www.geocities.com/spm_stm/Project.html
I found a language anomaly with the eraser.
A bunch of students in Taiwan made a working AFM from off-the-shelf parts, yet you’re concerned about an error in English article usage? Something something fun at parties.
Hmm. You sound very troubled my friend.
I just find it amusing that they have Korean eraser rather than Taiwanese.
And what do you mean by “something fun at parties.”?
Do you mean that is what I should say to people at parties?
I won’t do that because I would sound like an uptight party pooper just like you :P
while I understand it doesn’t return actual measurement figure, but an atomic force microscope is basically a high precision measuring device? At this cost this should find it’s way into the science department of any high school that actually cares. Although the cost of the consumable component is a bummer, and is going to limit looking at objects just for the hell of it.
That, and the author of the instructable happened to have the driver electronics on hand.
There’s also the problem of durability. Equipment used by high school students needs to endure being handled by a large number of people, many of whom don’t want to be there or are some combination of malicious and stupid. Anything hacked together is going to become unusable very, very quickly, so everything needs to be either so cheap it’s disposable or so tough you basically can’t break it.
I wish they had more detail on the DVD pickup interface and the controlling hardware. This is a great project!
How diamond styli were originally made for the first AFM’s was quite low tech. Buy some cheap diamonds then smash them. Sift through the rubble with a high powered optical microscope to look for really pointy shards. Mount a likely looking one in the AFM and if you got a blurry scan the shard wasn’t sharp enough so try another one.
I bet with synthetic diamond film it’d be possible to grow an AFM stylus right onto the sensor.
Has this been featured before?
Am I missing somthing here? It works by dragging the stylus over the object being examined. How do they detect the DVD tracks when as you know they are sandwiched between the plastic on the one side and the printed artwork on the other???
Ok ignore my comment, after reading it again I see that they mention removing the protection layer :)
Whoa! That’s really impressive. Any chance of spelling their initials out with xenon atoms?
Awesome hack well worth the read.
For the diamond you could also try sifting through diamond abrasive powder, which is relatively low cost.
This sort of stuff might also yield a few suitable shards..
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