Hi Everyone,
Just wanted to update you all on what we have been up to this semester at Grinnell. We are working on a spray method for producing the films rather than using a printer. We bought a Paasche® airbrush to spray the solutions (turns out it is exactly the width of a 2x Lego block). The airbrush can be easily deconstructed (I have been at a liberal arts college too long), cleaned, and parts readily replaced if necessary. So far we get the best films by using a spray pyrolysis method adding ~10% ethanol to reduce the droplet size and spraying onto heated substrates (~200 C). There is a good review article for this written by Pramod Patil in "Materials Chemistry and Physics", 59 (1999) 185-198. He reports the use of several chlorides and acetates which may also work for printing in addition to the nitrate salts. We found when we coated a glass substrate at room temperature the original smooth coating dried into islands of material on the glass.
Our original idea was to create a gradient by accelerating the airbrush in a half circle spin using a mask to define the triangles. The Lego motor was not very good at accelerating fast enough or reproducible enough to produce a gradient. When I was looking through my students results (Michael Hargadine, new this semester) I notice one that that had a very nice gradient over the triangle. It turned for that the airbrush was not aimed correctly at the triangle mask. So now we are building a new apparatus to take advantage of the natural gradient ones gets with an airbrush and target the triangles just a bit off center. We are building a Lego trolley driven by the Lego motor that will carry the airbrush over the heated substrate horizontally (waiting for parts to finish building it, Precious Princess Palace is one vacation until Nov. 13). The substrate is mounted on a hotplate that can be adjusted vertically on another trolley so we can aim at the desired triangle. This trolley is an old wood 3-metal wheeled “skate board” looking apparatus from our physics department that was use to demonstrate elastic collisions (has a spring bumper on one side). The hotplate sits on the “skateboard” and its position is adjusted by pushing it with a labjack up and down a 3 slotted track. The process will require several passes of the airbrush to complete a 4 metal-3at-a-time pattern but we can use simpler solutions and avoid the precipitation issues we had with the ink base. I will keep you posted.

Lee Sharpe
Grinnell College