Fig. 1

Mechanical characterization of PAA substrates. a Noted in the table are the percent concentrations of acrylamide (AAm) and bis-acrylamide (Bis) of the PAA substrates used in this study and the corresponding storage moduli G ^′, measured by rheometry from the series of substrates UV polymerized with different percent grayscale masks. b The graph plots the same data, with percent grayscale masks, mapped to their corresponding sequential positions found on radial gradient substrates. Red dashed lines show the best fit linear regressions of data for the steep gradient (r²=0.940) and shallow gradient (r²=0.974). Black dotted line represents the equation y=0 for visual reference