Doing science at house is a problem, as a result of analysis devices and lab tools are usually very costly. They’re area of interest merchandise marketed in direction of industrial labs, universities, and analysis hospitals which have big budgets, so affordability is never a precedence. Nonetheless, you may get fortunate and discover used tools at a worth that’s accessible to citizen scientists. However what about consumables? If scanning tunneling microscopy is your aim, then take a look at Baird Bankovic’s DIY etcher that’s able to producing atomically sharp suggestions.
A scanning tunneling microscope (STM) can picture particular person atoms, which is much past the aptitude of an optical microscope. STM works by transferring a conducting probe throughout the floor of the fabric in a vacuum. By making a voltage bias between the fabric and the probe, electrons tunnel by way of the vacuum from the fabric to the probe. Measuring the present offers information on the bodily construction of the atoms within the materials. That information can then be analyzed to create a picture. STM can “see” options smaller than 0.1 nanometers and might detect depth with a decision of 0.01 nanometers.
However all of that requires a probe with a particularly sharp tip that has a degree on the identical scale because the measured atoms. That tip additionally must be conductive. Machining such suggestions by conventional mechanical means is out of the query — such fabrication can’t produce a degree tremendous sufficient. As a substitute, STM suggestions are etched by dipping a wire “clean” into an etchant and passing a present by way of. When managed correctly, this course of causes the wire to dissolve till it snaps off, leaving an atomically sharp tip.
Bankovic construct a machine to manage this course of. An Arduino Mega board handles all the fabrication in accordance with the enter parameters. The person simply must trim the tungsten wire to size and place the container of etchant. The Arduino, which mounts onto a customized PCB with a number of keys and an LCD, controls the rotation of a stepper motor and displays the present passing by way of the wire. The stepper mounts to a 3D-printed body and drives a lead screw that lowers and raises the wire feeder, which rides on a linear rail.
To keep away from blunting the tip, the wire have to be faraway from the etchant as quickly because it snaps off. To carry the wire at precisely that second, the Arduino seems on the electrical present and acts when it sees a dip. It makes use of the same approach to find the floor of the etchant in order that it submerges the tip to the right depth.
If in case you have an STM and want some suggestions, Bankovic uploaded all the information and code for this DIY etcher to GitHub.