Incredible, a home made scanning tunneling microscope by Dan Berard

[William Gaatjes]

Amazing, what an incredible feature, a home build scanning tunneling microscope. Built by Daniel Berard, a phd physics student at McGill university. Amazing feature to build such a device in hardware and write the software for it.

https://www.eeweb.com/project/home-built-stm/

The project was built by Daniel, a Physics PhD student at McGill University. It is made of cheap piezo buzzer element. He was able to image highly-oriented pyrolytic graphite (HOPG) with atomic resolution. The image below shows the hexagonal lattice structure of graphite.
The STM electronics works using a microcontroller (Teensy 3.1) which scans the tip in a raster pattern by generating X and Y scanning signals using a DAC. A DC bias voltage, also generated by a DAC, is applied to a conductive sample, causing electrons to tunnel across the gap between the tip and the sample when they are brought close enough together (<1 nm). This current is measured by a preamplifier, which outputs a voltage proportional to the tunneling current. This signal is digitized and fed into a PI control loop, the output of which is sent to a DAC and used to drive the scanner’s Z-axis, causing the tip to track the sample topography. What’s truly amazing is that this actually works really well! The tunneling current increases exponentially (by around a factor of 10 per Angstrom) as the tip gets closer to the sample surface, and this is what makes the STM so sensitive, to the point of being able to resolve individual atoms under ambient conditions.

https://en.wikipedia.org/wiki/Scanning_tunneling_microscope

The website from Dan Berard.
https://dberard.com/home-built-stm/

 

[William Gaatjes]

I wonder how he made the head. The piëzo crystal is electrically driven and it physically deforms when a voltage is applied, creating a movement. Interesting how he mapped the relationship between voltage and physical movement. I am sure there is some neat mathematics for this but that is way over my head.

 

[William Gaatjes]

More information.
http://web.archive.org/web/20121107205242/http://www.geocities.com/spm_stm/Project.html

 

[BarkingGhostar]

Considering when STMs first came to light in the popular realm (c.1989), my response to this is, "About freaking time!"

 

[agent00f]

I wonder how he made the head. The piëzo crystal is electrically driven and it physically deforms when a voltage is applied, creating a movement. Interesting how he mapped the relationship between voltage and physical movement. I am sure there is some neat mathematics for this but that is way over my head.

The head is actually a really clever design from that second page you linked. He cuts a cheapo disk piezo speaker into 4, and when voltage is applied to opposing quarters the center will tend to "rotate" to some proportionate angle. The rotation is physically restricted by a rod he mounts to the center of the disk, but since the degree of rotation is pretty small, the resulting sinusoid is approximately linear so there isn't much math to it.

 

[MongGrel]

You would be surprised what some people can do with simple mocks ups, I've refined MIMU's and a few things in the past to refine them from what some engineers throw together at home and mail it in and I cleaned it up a lot and refined it.

Some things were a bit cardboard and duct tape.

 

[William Gaatjes]

You would be surprised what some people can do with simple mocks ups, I've refined MIMU's and a few things in the past to refine them from what some engineers throw together at home and mail it in and I cleaned it up a lot and refined it.

Some things were a bit cardboard and duct tape.

What is a MIMU ?

 

[sdifox]

What is a MIMU ?

Magnetic and Inertial Movement Unit is my guess

 

[William Gaatjes]

Magnetic and Inertial Movemebt Unit is my guess

Ah thank you. Mems acceleration/guroscope sensors combined with magnetic sensors like the MPU9250 from Invensense.
I even have a little extension board with such a sensor. I have not had time to play with it yet.
We use them often in designs at work.