Flexure Probe Holder & Kit For OpenFlexure Microscope Illumination Stage

This is a flexure device that uses flexible sections of the print as hinges and springs. It holds a hypodermic needle to an OpenFlexure stage so that it can be used as a probe. It was designed for the RepRapMicron Project https://reprap.org/wiki/RepRapMicron but may have other uses in biology. There is also a probe socket tip to add your own probes to.

Parts

In addition to the 3 printed parts you will need:

• 2 x M3 50mm screws
• 5 x M3 16mm screws
• 4 x M3 nuts
• 6 x M3 washers
• 2 x M3 wing nuts

The wing nuts are optional and can be replaced with your choice of 3D printed M3 thumbscrews, or ordinary nuts at a pinch.

Printing

Print the Substage separately as you may well find it needs a brim (It does on my Prusa Mk4). Then print the arm/clamp file. I use ordinary PLA - you don't need anything super flexible.

Assembly

Drive a M3 x 50 screw fully into a wingnut (or thumbscrew) and secure in place with a nut.

Insert a nut into the rectangular cavity in the clamp. Screw the wingnut-equipped screw through the hole in the side of the clamp so that it just captures the nut.

Fasten the arm to one of the holes in the sloping side of the Substage - the top one is probably best with a nut (goes in a cavity underneath), 16mm screw, and washer on top. Ensure that you attach the arm so that the little spigot on it is spaced away from the Substage. This gap is needed for the hypodermic needle cap. Probably best not to fit the needle just yet…

Insert a 50mm screw into the underside of the Substage beam so that a few mm protruded through the beam, and put a nut on it. Drive the screw all the way in, and tighten the nut to hold the screw firmly to the lower beam on the Substage.

Compress the Substage so that a few mm of the 50mm screw protrudes. Put on a washer and a wingnut (or thumbscrew/nut).

Put the clamp through the Substage and fasten down with 4 screws and washers, as shown in the main picture. The Substage should be able to slide back and forth a bit.

Probe

For many purposes a standard hypodermic needle will do. For those wishing to make their own probe tips, a probe socket is supplied that will take wire probes from 0.8mm to 0.4mm in diameter. Simply push the shaft of the probe into the slot on the probe socket. If necessary glue or melt it into place. This was developed to stiffen the shaft of thinner probes.

Probe Storage

As probes are delicate things, there is a probe storage spigot. This can be hot-glued to the inside of the lid of, for example, a pill container. The probe tip can then be fitted to the spigot, and the container screwed on to protect the tip.

Use

Position the Substage by sliding it back and forth in the clamp. Do up the wingnut on the side of the clamp until it exerts pressure on the Substage and locks it in place.

Screw down the top wingnut approximately 12mm onto the screw shaft. This will compress the mechanism.

Slightly slacken the screw on the arm. This can now be slid up and down, and swivelled to make fitting the hypodermic needle on the spigot easier. Position it so that the probe is just above where you want it, then tighten the screw to hold the arm there. No need to go over-tight here.

You may need to loosen the side wingnut and reposition the Substage to get the probe point in the right place.

Tightening the top wingnut will raise the probe, loosening will lower it. You've probably got it from here.

Note

This design supersedes the Mk 1 as it is far more stable and easily adjusted.