From square to circular polymeric microchannels by spin coating technology: a low cost platform for endothelial cell culture.

Square microchannels are easy to fabricate by means of micromachining or lithographic techniques. However, in vitro vascular microcapillaries--as well as plug production and microparticle alignment--require mainly circular microchannels that can be used also in applications based on open microchannels. Nowadays, a simple, low cost, and versatile method to fabricate circular microchannels is still missing. Here, we report on a fast, inexpensive, flexible and reproducible method to fabricate circular microchannels by coupling spin coating with micromilled square microchannels. The proposed method is based on the balance between the displacement of liquid PDMS induced by centrifugal forces and the surface tension that tends to keep the liquid accumulated especially in the corners, which become therefore rounded. To show the versatility of the described experimental study we prepared a variety of rounded microchannels, including branched and PMMA-PDMS hybrid configuration microchannels. Finally, an endothelial cell layer was formed by culturing brain endothelial bEnd.3 cells inside the proposed circular microchannels. Results demonstrated a more successful adhesion, growth, and homogeneous distribution of the cells along the circular microchannel than those observed in the square microchannel used as a control.