(a) Microfluidic device for 3D-cell culture. Reprinted with permission from Kim et al., Biomed. Microdevices 9, 25 (2007). Copyright 2007 Springer. (b) Cell-embedded Matrigel (hydrogel) in a μCCA device. Reprinted with permission from Sung and Shuler, Lab Chip 9, 1385 (2009). Copyright 2009 The Royal Society of Chemistry. (c) 1 × 3 PIRE designed to uniformly pattern cells via DCP. Reprinted with permission from Hsiung et al., Lab Chip 11, 2333 (2011). Copyright 2011 The Royal Society of Chemistry. (d) HμREL biochip. Reprinted with permission from Chao et al., Biochem. Pharmacol. 78, 625 (2009). Copyright 2009 Elsevier.