Demonstration of scalable units made of biomaterial elastomers. (A–C) SEM images of 4L devices viewed (A) from above or (B,C) in cross-sections taken perpendicular and parallel to the microvessels (*), respectively, and showing sinusoidal internal pore architectures of the heart cell scaffolds. Scale bars 500 μm. (D–F) SEM images of interfaces viewed (D) from above or (E,F) in cross-section. Arrow (F) points to spin-coated PGS. Scale bars (D,F) 50 μm; (E) 100 μm. (G–J) Confocal images and 3D renderings of actin-stained heart cells cultured on 4L devices with perfusion for 4 days (G,I) at surface; (H,J) at intersection between the two layers of the heart cell scaffold. Scale bars 100 μm; cells appear green; scaffold appears blue. (K) Perfusion culture of an 8L device; (L,M) SEM images of 8L devices viewed from different angles to which faux coloration was added to distinguish APS μfluidic base and heart cell components (purple) from PGS vascular-parenchymal interfaces (tan). Scale bars 1.0 mm.