Embolic ischemia and pulmonary embolism are
health emergencies that arise when a particle such as a blood
clot occludes a smaller blood vessel in the brain or the lungs,
and restricts flow of blood downstream of the vessel. In this
work, the reflow technique (Wang et al. Biomed. Microdevices
2007, 9, 657) was adapted to produce a microchannel network
that mimics the occlusion process. The technique was first
revisited and a simple geometrical model was developed to
quantitatively explain the shapes of the resulting
microchannels for different reflow parameters. A critical mod-
ification was introduced to the reflow protocol to fabricate
nearly circular microchannels of different diameters from the
same master, which is not possible with the traditional reflow
technique. To simulate the phenomenon of occlusion by clots,
a microchannel network with three generations of branches
with different diameters and branching angles was fabricated,
into which fibrin clots were introduced. At low constant pres-
sure drop (ΔP), a clot blocked a branch entrance only partial-
ly, while at higher ΔP, the branch was completely blocked.
Instances of simultaneous blocking of multiple channels by
clots, and the consequent changes in the flow rates in the
unblocked branches of the network, were also monitored.
This work provides the framework for a systematic study of

• An exploration of the reflow technique for the fabrication of an in vitro microvascular system to study occlusive clots