Figure 1.

Complex substrates encoding large stiffness gradients with aligned extracellular matrix patterning. a) Simplified schematic of the primary components of the microfabricated system. Photopatterned KMPR forms the stiff backbone defining more rigid surface regions above it, while low Young’s modulus PDMS is spun to cover and planarize this structure. The thinner PDMS regions above the KMPR are designed to be stiffer than the neighboring thick PDMS films. b) Elastic modulus variation spanning the soft to stiff regions as determined from atomic force microscopy for a 1 μm thick PDMS layer over the stiff backbone. Thin PDMS regions have higher effective elastic modulus due to the presence of the underlying backbone. E₀ of our PDMS depends on cross-linker to base ratio (55:1 yield a modulus of around 16 kPa). c) Top and side view of the major elements showing a schematic of patterned cells. The cell contracts soft regions of the surface connected through focal adhesions, while those on stiff regions are accompanied by significantly reduced contraction. A confocal cross-section shows the planar nature of the substrate from stiff to soft. Scale bars are 5 μm.