Hemostasis is the complex biochemical network that controls blood clotting. We previously described a chemical model that mimicked the dynamics of hemostasis based on a simple regulatory mechanisma threshold response due to the competition between production and removal of activators. Here, we used human blood plasma in phospholipid-coated microfluidic channels to test predictions based on this mechanism. We demonstrated that, for a given geometry of channels, clot propagation from an obstructed channel into a channel with flowing blood plasma is dependent on the shear rate in the channel with flowing blood plasma. If confirmed in vivo, these results may explain clot propagation from a small vessel to a larger, clinically relevant vessel. In addition, these results would further validate the use of modular mechanisms, simplified chemical models, and microfluidics to study complex biochemical networks.