Tuesday, February 04, 2025
Preparing Glass Slides For RepRapMicron Micro-Deposition
The RepRapMicron currently works by depositing dots of UV resin approximately 10μm-20μm diameter on a prepared glass microscope slide using a very fine probe. The reservoir for the resin is a piece of carefully folded aluminium foil stuck to one end of the slide. This also serves as a ground contact for calibrating the height of the probe before printing.
Materials
You might as well make a few in one go so you will need:
- Clean glass microscope slides
- Aluminium cooking foil
- 3D UV Printer resin (I have clear standard eSun)
- Metal probe or wire
- Cotton swabs
- Jar lid with smooth corners
- Sheet of printer paper (not shown)
- UV Light to cure resin in some kind of stand
- Tissues to clean any mess
- Scissors, depending on how well you can tear foil
Procedure
First, wash and dry your hands (or wear gloves, your call). Start by tearing or cutting a strip of aluminium foil as wide as your slide. I do this by placing a slide on top of the foil and tearing along the square edge of the glass. If you can't manage that, use scissors.
Using a cotton swab, smooth out the end of the foil strip using a glass slide as a base as best you can, paying particular attention to the short edge.
Carefully place 0.5mm of the short edge of the foil over the side of a microscope slide and hold it firmly in place. Use a swab to fold this tiny free edge over the side of the slide at a right angle.
Turn the foil over and carefully fold the edge right over with the swab. When it is folded along the entire length, press more firmly to ensure it is folded flat.
Looking through a microscope at the foil, this is what we are trying to achieve:
Put a slide on top of the foil, and tear off the excess to leave a nice square with one folded edge.
Using a metal probe or piece of wire, place a tiny drop - I wipe the excess off the tip on the edge of the bottle and use what's left - at one end of the slide.
This is the droplet spread out a bit with the probe. A little goes a very long way as you will be turning it into a layer only a micron or two thick shortly.
Wrap some foil around the end of a swab, and use it to spread the resin over a square area at one end of the slide. Do not go further than this square, as all the resin must be under the aluminium foil.
Put the square of foil smoothly and carefully onto the resin area. The folded edge should be uppermost and on the side of the square facing the middle of the slide.
Place a piece of printer paper over the foil. Cover it completely, with at least 5mm overhang. This paper protects the foil from being scraped, but also absorbs any excess resin that will be squeezed out during burnishing. Rub with a firm, rounded object such as a jar lid or the back of an exceptionally stout fingernail. Pay special attention to the folded edge. It is important to hold the paper firmly in place.
Finally, cure the resin by placing the slide over a UV lamp, illuminating the resin under the foil. Curing time depends on your resin and lamp, I just leave mine there for a minute on a 4W lamp which is definitely overkill.
Store the finished slides in a clean protective container. Should last indefinitely.
Use
In use a tiny droplet of resin is placed on the foil away from the folded edge, and then carefully smeared towards it until the resin just contacts the edge. This ensures that a very thin layer of resin is presented to the probe, and prevents the resin from flooding the slide.
