how to print on a microscopic scale

EscapeTheClassroom wrote:

As a teacher occasionally I would love to lock up mystudents. And I will. We are developing Escape the Classroom. Biology students will be locked up and through a series of puzzles they.might find a way to escape. On of the clues is that they find a microscopic slide. Under the microscope they can read a code on the slide.
But how to make this microscopic slide? How to print something which can't be read by the naked eye? But is has to be transparent/see through. Who has an idea?

Cool idea.

I would ask your nearest university very nicely. Most decent size universities will have a microscopy centre, that will include capabilities such as laser ablation for mass spectrometry. Laser ablation plinks lots of little, targeted holes into a sample - eg: samples = shells, rocks, all sorts of things.

There will be a bit of effort involved, but I suspect that someone at such a place would be interested in helping out.

I'll think about it and see if I can think of anything easier/better.

A much simpler solution may be to use a really good printer (perhaps a photo printer, for the detail) to print a really tiny message on a transparent sheet (or perhaps something like tracing paper, that light can shine through - I'm assuming you don't have reflected light microscopes, but instead the more traditional transmitted light microscopes), Then glue it to the slide with a clear glue.

Use film.

Print your text on paper, normal size, in white on a black background, so that it comes out black on clear on the negative.

Photograph the printed text on the finest grain black-and-white film you can find. B&H list a good selection, including Rollei Ortho and Adox CMS 20.

Any film camera with a good sharp prime lens will do. If it won't focus close enough, print your original bigger.

"How to print something which can't be read by the naked eye?"

Here is what I do.  I make test targets this way to test systems we build for machine vision.  Use Windows Paintbrush to make a file that has the text you want or any other pattern you may dream up.  Save the file as a bitmap or JPEG.  Send it to www.gammatech.com to have it printed as 35 mm slide film.

Dr Wilcox wrote:

Have you tested this out? Do you have film recommendations that are clear/ transparent so that the image can be seen under a brightfield microscope?

Photographic printing is used in the manufacture of computer chips with the right set-up it will certainly be able to give the resolution you'd need.

Any B&W film negative can be viewed via a brightfield microscope. The suggestion to use a slow film was to reduce grain size & so improve resolution. Colour negatives are not as good having a distinct orange cast in the background areas but would also be viewable on normal microscopes.