Atoms are small. Really small. You just won’t believe how minusculely microscopically mindbogglingly small they are. I mean you may think it’s a short way down the road to the chemist’s, but that’s just peanuts to atoms.
Atoms really are small. The atomic radius of a carbon atom is on the order of 0.1 nanometers, that’s 0.0000001 millimeters. It’s hard to grasp how fantastically small this is compared to objects we generally encounter, but as a starting point I’d recommend looking at the “Powers of Ten” video found below whose ability to convey the concept has been unrivaled since it was published in 1977.
The term nanometer might be most familiar from the semiconductor industry, and its seemingly unstoppable march to smaller feature sizes. Feature sizes currently hover somewhere around the 10 nanometer mark. So while these multi-billion dollar facilities can achieve 10nm precision it’s somewhat surprising that sub-nanometer feature size positioning, and fabrication techniques are available at relatively low cost to the hacker hobbyist.
In this article we’re going to review some of the amazing work demonstrated by hobbyists in the area of the very very small through use of cutting edge, but low cost techniques.
Continue reading “Teeny Tiny Very Small – Atomic Resolution And The Home Hobbyist”
LEGO2NANO, are building an open hardware AFM (Atomic Force Microscope).
AFMs are a kind of probe microscope. Unlike an optical microscope, a probe is used to “feel” the topology of a surface. An atomic force microscope uses a flexible cantilever with a nanometer scale tip on the end. As the tip scans across the surface it will be deflected by its interaction with the surface. A laser spot is usually reflected off the back of the cantilever, and captured by a photodiode array. The angle of the reflected beam, and therefore which photodiodes are excited lets you know how much the cantilever was deflected by the surface.
One of the challenges of building an AFM is developing an actuator that can move with nanoscale precision. We recently reported on [Dan Berard]s awesome capacitor actuator, and have previously reported on his STM build which uses a piezo buzzer. LEGO2NANO are experimenting with a number of different configurations, including using Piezo buzzers, but in a different configuration to [Dan]s system.
The LEGO2NANO project runs as a yearly summer school to encourage high school students to take part in the ambitious task of building an AFM for a few hundred dollars (commercial instruments cost about 100,000USD). While the project isn’t yet complete, whatever the outcome the students have clearly learned a lot, and gained an exciting insight into this cutting edge microscopy technique.
[Dan Berard] has been using capacitors as actuators.
We’ve featured Dan’s awesome self built STM (scanning tunneling microscope) before. These microscopes work by moving a tip with nanometer precision across a surface. While the images he acquired are great, one disadvantage of the actuator he used is its poor rigidity. This limits the system to faster scan speeds.
In his search for a better actuator [Dan] thought he’d try using MLCC capacitors! While not known for their electromechanical properties, you may have encountered capacitors that appear to “sing” (PDF), emitting an audible tone. This is due to the piezoelectric properties of BaTiO3. Effectively the capacitor acts as a weak piezo electric speaker.
Using a 100V drive voltage [Dan] was able to get 300nm of deflection using the capacitor. To extend the range of the actuator he decided to ‘pole the ceramic dielectric’ this involved heating the capacitor above its Curie temperature of 120C. For this he used a transistor to heat the part as an ad-hoc hotplate. This increased the range of the actuator to 800nm, ideal for many STM (and other SPM) systems.
[Dan] is still weighing up his options for his next build, but MLCC capacitors are certainly a cheap and interesting choice.