And, for bonus points, how are they made?
These seem like an awfully important test piece. I’m pretty sure they’re just checking for glucose with some enzyme or something. But who knows, maybe its something simple or everyday? Are all brands using the same materials?
If you’re talking about strips that look like this:
I believe that most brands use Benedict’s reagent: copper sulphate, sodium citrate, sodium carbonate. It interacts with reducing sugars (like glucose) and the colour goes from blue to light green to green to brown-green to brown-red, depending on concentration.
I’ve use quite a few brands, but I’ve never come across one that changed colors. Is that blue despite the blood sample?
These almost look more like ph or ketone test strips…
I think this might be a “yes, but no” kind of thing.
Yes, these are test strips. Yes, they change color to indicate a reading. Yes, they use chemical reactions to cause that color change.
AFAIK: No, these aren’t for testing blood. No, these don’t seem to be for consumption by an electronic meter. And no, I don’t think this is what OP was asking about.
Like, there’s probably some good info, but not for this thread specifically :P
Source: Pulling it straight out of my ass, but it is informed by my limited experience with medical test equipment, and much less limited experience with electronics.
Those are used with urine, not blood. Urine is yellow-ish, but since it’s just a drop, it doesn’t stain the strip; instead, the blue tip changes colour as it reacts with the glucose in the urine. Then you compare that coloured tip with a chart, and you get an idea of the concentration of glucose in your body. Picture related:
I remember seeing those bottles in my bathroom all the time as a kid (my sister is diabetic).
It is roughly the same idea as the one behind the litmus test for pH, indeed. The difference is which substance you’re putting there (Benedict’s reagent vs. pH indicators) and which substance you’re testing for (glucose vs. H₃O⁺ / OH⁻).