Additive manufacturing or three-dimensional (3D) printing technology is increasingly being employed in biochemical as well as clinical applications and more importantly in fabrication of microfluidic devices. However, the microfluidic community mainly relies on photolithography for fabrication of a defined mask, which is both tedious and expensive requiring clean room settings as well as limited to the generation of two-dimensional features. In this work, we 3D printed nanoclay-reinforced Pluronic ink as a sacrificial material, which exhibited shear thinning behavior and superior printability allowing the fabrication of unsupported or overhanging templates of channels with uniform diameter and circular cross-sections. To highlight the potential and effectiveness of the presented approach, we fabricated a human blood vessel-on-a-chip model with curved as well as straight channels. These channels were then lined up with human umbilical vein endothelial cells (HUVECs) and subjected to a dynamic culture for 10 d to explore the effect of shear stress on HUVEC morphology based on the location of HUVECs in the devices. Overall, we presented a highly affordable, practical and useful approach in manufacturing of polydimethylsiloxane-based devices with closed microfluidic channels, which holds great potential for a numerous applications, such as but not limited to organ-on-a-chip, microfluidics, point-of-care devices and drug screening platforms.