User:Wiki78s/Serum-separating tube

The tubes have micronized silica particles which help clot the blood before centrifugation, and a gel at the bottom which separates whole blood cells from serum. Silica nanoparticles induce coagulation through contact activation of Hageman factor XII. The silica particles are desiccants, which adsorb and hold water vapor. This is used in the tubes so the blood adheres to the surface of the tiny silica particles and begins to clot.