Cirrhosis of the liver is an extremely serious condition that requires extensive medical monitoring and often intervention. Progression of the condition can be fatal, so even if caught early it must be monitored closely. But, like most things in medicine, that gets expensive. That’s why Marb built his own DIY “micro lab” to analyze ammonia levels in blood and urine.

Disclaimer: Don’t rely on YouTube videos for your medical needs!

The severity of Marb’s condition correlates with increased ammonia production, which is common for cirrhosis of the liver. More ammonia in the blood and urine indicates progression of the disease and a need for immediate medical intervention. Marb’s micro lab lets him monitor his own ammonia levels at home.

The central detection mechanism of this micro lab relies on Berthelot’s reagent, which becomes a blue-green color in the presence of ammonia. To make use of that, the micro lab needs to properly expose the sample to Berthelot’s reagent and look at the resulting color change.

An Arduino Nano board controls the whole process through a custom PCB. That starts with heating the sample in a vial to release the ammonia vapor. The vapor travels via a tube through a gas diffuser into another vial containing Berthelot’s reagent. A magnetic stirrer beneath mixes the gas into the reagent. A 660nm (deep red) laser shines through that vial into a photo diode on the other side, and the Arduino monitors that through a pre-amp.

If a lot of the red light passes through, then the Berthelot’s reagent didn’t turn very blue and there is little to no ammonia present. If hardly any red light passes through, then reagent is very blue and that indicates a high level of ammonia.

The amount of light detected, between those two extremes, provides a reasonably accurate measure of Marb’s ammonia levels, so he can keep track of his condition’s progression.

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