Monday, July 25, 2011

Let's See What We've Got

I wrote recently about how my research has hit a bit of a snag - I am able to put ink on a stamp, but I'm not able to transfer the pattern of ink to a glass slide.

But what exactly is going wrong? I feel a bit dumb showing up to a weekly meeting, and just stammering "But... but... it's not working!?" I need to have more helpful information than that. WHAT is not working? Is some of the pattern transferring, but not all of it? Is the ink puddling on the slide? Is the ink not coming off the stamp at all? WHAT'S GOING ON?


I need to see what I've got. I need to apply eyeballs to the situation. So I spent an afternoon taking pictures of all the various ways my stamp is, well, not stamping.

First of all, what is it supposed to look like? Well, I'm trying to stamp a pattern of lines. A couple good lines would look like this:

Figure: Very simple. 50 um lines, spaced 100 um apart.

And what am I getting instead? Oh, lots of things. Sometimes when I peel the slide off the stamp, I can feel the slide stick to the stamp. And when I look at a "stuck" slide, you can see little pieces of stamp where they ripped off and stuck to the slide.

Figure: Bits of stamp. Stuck to slide. Very sad.

I think what is happening there, is that I didn't get the ink to coat the stamp very well. And the places where there was no ink, the stamp just bonded directly to the slide. Need ink, need ink...

Sometimes I can feel that when I press the stamp down onto the slide, I smudge it a little bit (apparently, my fingers are not calibrated down to microns...). And on the "smudged" slides, the lines look like this:

Looks pretty smudged, a fairly obvious conclusion. Most likely the ink was liquid, and beaded up into droplets when it shifted before it was dry.

I also get some funny areas where I see "clear" lines. It's supposed to be solid light-blue colored lines, but here you can just faintly see the outlines where the lines are supposed to be.

Let's zoom in, shall we?

Yep, looks pretty much like nothing is there. So what's going on? Turns out, if you color over those "clear" lines with Sharpie, it looks like SOMETHING is there.

Figure: Sharpie reveals all.

Huh. So when you paint over the slide with marker, it bleeds into lines - but it looks like there is nothing on the slide. The nothing must be something, right? Let's look at another Sharpied part of the slide.

Here we see a lot going on. We see the Sharpie bleeding into the clear lines, and then we see a couple solid lines that almost look like they are supposed to. And then we see these little wiggly things.

For the slides that I think should be "good results," (meaning no smudging, I didn't feel it stick, nothing else obvious went wrong), most of the slide is filled with these wiggly lines.

Wiggles, wiggles. You wouldn't know this unless I told you (which I am now doing), but those lines are way thinner than they are supposed to be. About 10 microns wide, instead of 50 microns wide.

And they are everywhere! Let's zoom in:

Hmm. Hard to focus.

In fact, the reason it's hard to focus is because those little wiggles are very tall. 10 microns tall, instead of a thin layer of 80 nanometers.

And what is this? Now this wiggles aren't even in lines anymore!

Wait - wait - let's think about this. Instead of flat, wide, thin lines in a logical order, we are getting tall, skinny, wiggly things that move around.

Aha! I think I know! The ink has become a FILM, instead of a LIQUID, and it's rolling into strings. We're making very tiny ropes! Ropes that then detach and wiggle around the slide. And in fact, we can catch one in the process of rolling:

Yep, yep. My nice pattern of liquid ink drops is not that at all. I'm getting film transfer, and the film is curling up under induced stresses. I'm making strings!

Well THAT'S fun.

All of the literature background research on transfer mechanisms that I did was involved with liquid transfer. But now that I know it's a film, that's a whole different ballgame.

Back to the drawing board...


  1. Oof. Good luck with that, eesh.

  2. Perhaps the liquid has to wet the slide better, so it doesn't pull into a string under surface tension?

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