Fig. 2.

Characterization of shape and microtopography of the PDMS microwell devices. A) High-resolution flat (HRF) device. Top and cross-sectional views of CAD models (upper) and corresponding SEM micrographs (lower) are shown. White dash lines were used to outline a single microwell culturing space. B) High-resolution curve (HRC) device. Top and cross-sectional views of CAD models (upper) and corresponding SEM micrographs (lower) are shown. White dash lines were used to outline a single microwell culturing space. C) Low-resolution curved (LRC) devices showed distorted morphology (SEM micrographs, upper), and anisotropic shape in the x- and y-directions (inspection microscopy sectional views, lower). D) Representative top-view high-magnification SEM images and corresponding microtopography analysis of a microwell for HRF (left two), HRC (middle two), and LRC (right two) devices. SEM images of the microwell bottom revealed microtopography, contours of which were analyzed and annotated in red lines. The microtopography was measured as a distance between two adjacent contours along the white lines. The contour analysis in HRC and HRF showed a regularly-spaced grid and concentric circles, whereas that in LRC showed irregular concentric circles. E) Distribution of microtopography periodicity as a function of the device. Periodicity was measured as a distance between two adjacent contours along the white lines, which are the vertical/horizontal axis for HRF and diagonal axis for LRC and HRC. Statistical analysis: One-way ANOVA with Tukey's post-hoc analysis. Scale bars: (A, B and C): 1 mm; (D) 100 μm.