This article introduces an open-source tool to experimentally compare blood residence time in biomedical devices using an image-based method. The experimental setup and the postprocessing workflow are comprehensively elucidated in a detailed report that conducts a thorough comparison of the residence times of a blood analog within three distinct blood oxygenator prototypes. 

Thrombosis is an inevitable complication for all blood-contacting devices, and it is particularly critical for devices with extensive contact surfaces. Its mitigation should be a primary consideration since the early design phases.

Microfluidic chambers are an established method to study blood coagulation under multiple biologic and flow variables in a controlled environment.^1,2 However, there are limitations on the kind of substrate that can be studied,³ and results cannot be translated to full-scale devices without undergoing extensive modeling of the coagulation pathways,⁴ decreasing their utility as a tool for rapid prototype screening. In the past decade, the increasing availability of computational power has led to the introduction of numerical simulations for full-scale models,^5–7 but they are resource intensive and rely on assumptions about the flow patterns.