Fabrication of a multiple-diameter branched network of microvascular channels with semi-circular cross-sections using xenon difluoride etching.

The majority of microfluidic devices employ networks of channels that have rectangular cross-sections. At the microvascular scale of 30 to 300 microm in diameter, however, the distribution of fluid mechanical stresses and the induced shape of cultured cells will be quite different in a rectangular channel from the near-circular cross-sections seen in vivo. While round-cross-section channels have been produced before by wet etching, fine control of feature size has not been demonstrated, and prior work has only produced channels of a single diameter on a given device. In this work, the xenon difluoride process for isotropic etching of silicon was optimized for production of channels with semicircular cross-sections. This process was then used to produce a network of microvessel-scale semicylindrical channels on a silicon chip, the diameter of which was decreased with each level of branching. Additionally, it was demonstrated that endothelial cells will adhere to both the bottom and sides of these channels, indicating that such chips may be useful in the future for culturing in vitro models of the microvasculature.