Fabrication of multiwell substrates and mechanical characterization of tunable PDMS elastomer. Multiwell PDMS devices for TFM are fabricated by (A) optionally coating a layer of fluorescent microspheres (for de-drifting images) on the custom glass slide, (B) spin-coating a ∼100-μm-thick layer of compliant PDMS, (C) spin-coating a ∼1-μm-thick layer of compliant PDMS mixed with custom-synthesized beads with different fluorescence emission for measuring cell-induced deformation of the PDMS, (D) bonding a multiwell partitioning strip to the top, and (E) ligating and culturing cells. (F) A graph of PDMS moduli as determined by shear rheology (n = 4 independent preparations per data point) is shown. (G) A table of same-mean PDMS moduli ± SD is shown. To see this figure in color, go online.