We had this conference in Chicago in 2016. As I was playing with the laser-cutter and making planetary motion devices see Here, I also was playing with the idea of circular slide rulers.
As the calculation of elution volumes and retention in CCC and CPC are using multiplications and divisions it is possible to do these on a circular slide ruler (or a normal one) by using logarithmic scales (because additions in that space correspond to multiplications in linear scale).
A bit of design, metallic-gold acrylic, flexible metallic with black background acrylic for the tag, and a piece of wood made by a colleague (Jim). I also found that simple M3 or M4 (can’t remember) screws with thin thread will lock perfectly two pieces of acrylic (with a hole cut slightly below the diameter of the screw). It takes a bit of tinkering with the parameters of the laser as the kerf tend to vary with the speed and power of the laser. But for that I made a simple svg file with circles of different diameters and colors. And each color had different settings in the laser driver. That way even with new materials, I can determine quickly what the settings should be.