Fig. 1. A constricted channel simulates spatial gradients in WSS found at sites of lymphatic valve formation.

a We developed PDMS channels that have a sharp constriction from a uniform width (w = 5 mm) to a minimum width (w_min = 1.84 mm). The length of the channel (L) is 48.20 mm and the height 0.25 mm. b Superimposition of the WSS profile surrounding the constriction and a live-cell image showing HLMVECs adhering to the bottom surface of the channel. HLMVECs experience a sharp WSSG near the site of maximum constriction. Finite element simulation (COMSOL) shows the WSS profile for HLMVECs located near the constriction region. The flow is unidirectional in the y-direction. The WSS profile is symmetric across the x midline. Based on the flow direction in y, we binned data from the area around the constriction into four regions (400 × 400 μm): (Left) 18.5–30 dyn cm⁻², (Tip) 9–50 dyn cm⁻², (Right) 9–14.5 dyn cm⁻², and (Middle) 22 dyn cm⁻². Scale bar = 100 μm.