A matrix protein microarray was developed to study blood coagulation with spatially controlled surface biochemistry, thus allowing numerous conditions to be studied in a single flow experiment. This microarray used collagen and increasing levels of lipidated tissue factor to assay simultaneous platelet deposition and fibrin formation. Fibrillar collagen (1 mg/ml) with varying surface concentrations of tissue factor (1 pM to 1 nM) was microarrayed (1 nL spots) via robotic contact printing onto cleaned plain glass slides (200 micron diameter features). Recalcified citrated whole blood supplemented with Corn Trypsin Inhibitor (CTI; 50 µg/ml to inhibit coagulation Factor XIIa) was perfused for 5 min at shear rates of 100, 500, and 1000 s^-1. After perfusion, the slides were immunostained with platelet glycoprotein Ib-alpha (GP Ib-alpha) and fibrinogen (Alexa Fluor 647 and FITC, respectively) and imaged. With respect to fibrin build-up at 5 min, TF displayed a switch-like regulatory function over a very narrow concentration range allowing a determination of the surface EC50 of 3.63, 8.40, and 10.2 TF-molecules/µm² at 100, 500, 1000 s^-1, respectively. As expected, higher shear rates helped suppress fibrin formation. To further investigate the role of very low sub-picomolar soluble levels of TF (i.e. blood-borne TF), whole blood (with and without exogeneously supplemented 100 fM TF) was used in this system under static and flow conditions. The addition of TF had no significant effect under static conditions. However under flow, the addition of this small amount of TF caused and significant increase in the coagulation response. We conclude that sub-pM TF in the blood may synergize with the TF on the array surface to evoke this response under flow. This is one of the first in vitro systems that can incorporate the major components of the in vivo hemostasis system: flow, focal surface chemistry, and combinations of matrix proteins.